Defect engineered ternary metal spinel-type Ni-Fe-Co oxide as bifunctional electrocatalyst for overall electrochemical water splitting

Transition metal spinel oxides were engineered with active elements as bifunctional water splitting electrocatalysts to deliver superior intrinsic activity, stability, and improved conductivity to support green hydrogen production. In this study, we reported the ternary metal Ni-Fe-Co spinel oxide electrocatalysts prepared by defect engineering strategy with rich and deficient Na+ ions, termed NFCO-Na and NFCO, which suggest the formation of defects with Na+ forming tensile strain. The Na-rich NiFeCoO4 spinel oxide reveals lattice expansion, resulting in the formation of a defective crystal structure, suggesting higher electrocatalytic active sites. The spherical NFCO-Na electrocatalysts exhibit lower OER and HER overpotentials of 248 mV and 153 mV at 10 mA cm-2 and smaller Tafel slope values of about 78 mV dec-1 and 129 mV dec-1, respectively. Notably, the bifunctional NFCO-Na electrocatalyst requires a minimum cell voltage of about 1.67 V to drive a current density of 10 mA cm-2. The present work highlights the significant electrochemical activity of defect-engineered ternary metal oxides, which can be further upgraded as highly active electrocatalysts for water splitting applications.

Highly-exposed copper and ZIF-8 interface enables synthesis of hydrocarbons by electrocatalytic reduction of CO2

Electrochemical reduction of CO2 (CO2RR) to fuels and chemicals is a promising route to close the anthropogenic carbon cycle for sustainable society. The Cu-based catalysts in producing high-value hydrocarbons feature unique superiorities, yet challenges remain in achieving high selectivity. In this work, Cu@ZIF-8 NWs with highly-exposed Cu nanowires (Cu NWs) and ZIF-8 interface are synthesized via a surfactant-assisted method. Impressively, Cu@ZIF-8 NWs exhibit excellent stability and a high Faradaic efficiency of 57.5% toward hydrocarbons (CH4 and C2H4) at a potential of -0.7 V versus reversible hydrogen electrode. Computational calculations combining with experiments reveal the formation of Cu and ZIF-8 interface optimizes the adsorption of reaction intermediates, particularly stabilizing the formation of *CHO, thereby enabling efficient preference for hydrocarbons. This work highlights the potential of constructing metals and MOFs heterogeneous interfaces to enhance catalytic properties and offers valuable insights for the design of highly efficient CO2RR catalysts.

Morphological and structural characteristics of the elytra reduce impact damage to ladybird beetles

Beetle elytra act as natural protective covers and effectively shield their flexible abdomens and fragile hindwings from damage. The existing studies have attributed this contribution of the elytra to its honeycomb structures. In this combined experimental and theoretical study, we used the seven-spotted ladybird beetle to demonstrate that both biological morphology and the hollow structure of the dome-like elytra combined to reduce damage during falling. The falling ladybird beetles had a high probability (59.52%) of hitting the ground with the costal edge of the elytra. This strategy could assist with converting the translational energy into rotational kinetic energy, resulting in the reduction of the impulse during falling. In addition, the hollow structures on the elytra could further absorb the residual impact energy. In the future, this biological paradigm could be used as a basis for the development of falling/landing techniques for advanced robots.

Floating photocatalysts as promising materials for environmental detoxification and energy production: A review

The oxygenation process of the catalyst surface, the incident-light harvesting capability, and facile recycling of utilized photocatalysts play key role in the outstanding photocatalytic performances. The typical existing photocatalysts in powder form have many drawbacks, such as difficult separation from the treated water, insufficient surface oxygenation, poor active surface area, low incident-light harvesting ability, and secondary pollution of the environment. A great number of scientific works introduced novel and fresh ideas related to designing floating photocatalytic systems by immobilizing highly active photocatalysts onto a floatable substrate. Thanks to direct contact with the illuminated light and oxygen molecules in the interface of water/air, the photocatalytic performance is maximized through production of more reactive species, employed in the photocatalytic reactions. Furthermore, facile recovering of the utilized photocatalysts for next processes avoids secondary pollution as well as diminishes the process's price. This review highlights the performance of developed floating photocatalysts for diverse applications. Furthermore, different floating substrates and possible mechanisms in floating photocatalysts are briefly mentioned. In addition, several emerging self-floating photocatalytic systems are taken attention and discussed. Specially, coupling photo-thermal and photocatalytic effects seems to be a good strategy for introducing a new class of floating photocatalyst to utilize the free, abundant, and green sunlight energy for the aims of water desalination and purification. Despite of a large number of attempts about the floating photocatalysts, there are still plenty of rooms for more in-depth research to be carried out for attaining the required characteristics of the large scale utilizations of these materials.

An adapted model predictive control MPPT for validation of optimum GMPP tracking under partial shading conditions

The energy generation efficiency of photovoltaic (PV) systems is compromised by partial shading conditions (PSCs) of solar irradiance with many maximum power points (MPPs) while tracking output power. Addressing this challenge in the PV system, this article proposes an adapted hybrid control algorithm that tracks the global maximum power point (GMPP) by preventing it from settling at different local maximum power points (LMPPs). The proposed scheme involves the deployment of a 3 × 3 multi-string PV array with a single modified boost converter model and an adapted perturb and observe-based model predictive control (APO-MPC) algorithm. In contrast to traditional strategies, this technique effectively extracts and stabilizes the output power by predicting upcoming future states through the computation of reference current. The boost converter regulates voltage and current levels of the whole PV array, while the proposed algorithm dynamically adjusts the converter's operation to track the GMPP by minimizing the cost function of MPC. Additionally, it reduces hardware costs by eliminating the need for an output current sensor, all while ensuring effective tracking across a variety of climatic profiles. The research illustrates the efficient validation of the proposed method with accurate and stable convergence towards the GMPP with minimal sensors, consequently reducing overall hardware expenses. Simulation and hardware-based outcomes reveal that this approach outperforms classical techniques in terms of both cost-effectiveness and power extraction efficiency, even under PSCs of constant, rapidly changing, and linearly changing irradiances.

Upcycling harmful algal blooms into short-chain organic matters assisted with cellulose-based flocculant

Upcycling harmful algal blooms (HABs) into short-chain organic matters (SCOMs) presents a significantly underexplored opportunity for addressing environmental concerns and achieving circular economy. But there are challenges of low HABs harvesting and SCOMs conversion efficiencies. To address these issues, a novel cellulose-based flocculant derived from abundant agricultural waste (wheat straw) was developed. This flocculant possesses high surface positive charge to aggregate negatively charged microalgae cells via charge neutralization mechanism, resulting in HABs harvesting efficiency of 97 %. Moreover, the flocculant can serve as a carbon to nitrogen (C/N) regulator to optimize the harvested slurry properties for downstream fermentation. Following hydrothermal pretreatment for one hour, the HABs-flocculant slurry was effectively converted into SCOMs with a total energy output of 64.3 kJ/L and energy conversion efficiency of 67 %, in which SCOMs was major contributor (92 %). This work may inspire eco-friendly and cost-effective approach for HABs disposal with extra benefits of SCOMs production.

Recent Advances in Flexible Wearable Technology: From Textile Fibers to Devices

Smart textile fabrics have been widely investigated and used in flexible wearable electronics because of their unique structure, flexibility and breathability, which are highly desirable with integrated multifunctionality. Recent years have witnessed the rapid development of textile fiber-based flexible wearable devices. However, the pristine textile fibers still can't meet the high standards for practical flexible wearable devices, which calls for the development of some effective modification strategies. In this review, we summarize the recent advances in the flexible wearable devices based on the textile fibers, putting special emphasis on the design and modifications of textile fibers. In addition, the applications of textile fibers in various fields and the critical role of textile fibers are also systematically discussed, which include the supercapacitors, sensors, triboelectric nanogenerators, thermoelectrics, and other self-powered electronic devices. Finally, the main challenges that should be overcome and some effective solutions are also manifested, which will guide the future development of more effective textile fiber-based flexible wearable devices.

Current significance and future perspective of 3D-printed bio-based polymers for applications in energy conversion and storage system

The increasing global population has led to a surge in energy demand and the production of environmentally harmful products, highlighting the urgent need for renewable and clean energy sources. In this context, sustainable and eco-friendly energy production strategies have been explored to mitigate the adverse effects of fossil fuel consumption to the environment. Additionally, efficient energy storage devices with a long lifespan are also crucial. Tailoring the components of energy conversion and storage devices can improve overall performance. Three-dimensional (3D) printing provides the flexibility to create and optimize geometrical structure in order to obtain preferable features to elevate energy conversion yield and storage capacitance. It also serves the potential for rapid and cost-efficient manufacturing. Besides that, bio-based polymers with potential mechanical and rheological properties have been exploited as material feedstocks for 3D printing. The use of these polymers promoted carbon neutrality and environmentally benign processes. In this perspective, this review provides an overview of various 3D printing techniques and processing parameters for bio-based polymers applicable for energy-relevant applications. It also explores the advances and current significance on the integration of 3D-printed bio-based polymers in several energy conversion and storage components from the recently published studies. Finally, the future perspective is elaborated for the development of bio-based polymers via 3D printing techniques as powerful tools for clean energy supplies towards the sustainable development goals (SDGs) with respect to environmental protection and green energy conversion.

Tuning Carbon Dioxide Reduction Reaction Selectivity of Bi Single-Atom Electrocatalysts with Controlled Coordination Environments

Control over product selectivity of the electrocatalytic CO2 reduction reaction (CO2 RR) is a crucial challenge for the sustainable production of carbon-based chemical feedstocks. In this regard, single-atom catalysts (SACs) are promising materials due to their tunable coordination environments, which could enable tailored catalytic activities and selectivities, as well as new insights into structure-activity relationships. However, direct evidence for selectivity control via systematic tuning of the SAC coordination environment is scarce. In this work, we have synthesized two differently coordinated Bi SACs anchored to the same host material (carbon black) and characterized their CO2 RR activities and selectivities. We find that oxophilic, oxygen-coordinated Bi atoms produce HCOOH, while nitrogen-coordinated Bi atoms generate CO. Importantly, use of the same support material assured that alternation of the coordination environment is the dominant factor for controlling the CO2 RR product selectivity. Overall, this work demonstrates the structure-activity relationship of Bi SACs, which can be utilized to establish control over CO2 RR product distributions, and highlights the promise for engineering atomic coordination environments of SACs to tune reaction pathways.

Superstretchable Liquid-Metal Electrodes for Dielectric Elastomer Transducers and Flexible Circuits

Dielectric elastomer transducers (DETs), with a dielectric elastomer (DE) film sandwiched between two compliant electrodes, are highly sought after in the fields of soft robotics, energy harvesting, and human-machine interaction. To achieve a high-performance DET, it is essential to develop electrodes with high conductivity, strain-insensitive resistance, and adaptability. Herein, we design an electrode (Supra-LMNs) based on multiple dynamic bond cross-linked supramolecular networks (Ns) and liquid metal (LM), which realizes high conductivity (up to 16,000 S cm-1), negligible resistance changes at high strain (1.3-fold increase at 1000% strain), instantaneous self-healability at ambient temperature, and rapid recycling. The conductive pathway can be activated through simple friction by transmitting stress through the silver nanowires (AgNWs) and cross-linking sites of LM particles. This method is especially attractive for printing circuits on flexible substrates, especially DE films. Utilized as dielectric elastomer generator (DEG) electrodes, it reduces the charge loss by 3 orders of magnitude and achieves high generating energy density and energy conversion efficiency on a low-resistance load. Additionally, serving as sensor (DES) and actuator (DEA) electrodes, it enables a highly sensitive sensing capability and complex interaction.

2D MXenes Nanosheets for Advanced Energy Conversion and Storage Devices: Recent Advances and Future Prospects

Since the initial MXenes were discovered in 2011, several MXene compositions constructed using combinations of various transition metals have been developed. MXenes are ideal candidates for different applications in energy conversion and storage, because of their unique and interesting characteristics, which included good electrical conductivity, hydrophilicity, and simplicity of large-scale synthesis. Herein, we study the current developments in two-dimensional (2D) MXene nanosheets for energy storage and conversion technologies. First, we discuss the introduction to energy storage and conversion devices. Later, we emphasized on 2D MXenes and some specific properties of MXenes. Subsequently, research advances in MXene-based electrode materials for energy storage such as supercapacitors and rechargeable batteries is summarized. We provide the relevant energy storage processes, common challenges, and potential approaches to an acceptable solution for 2D MXene-based energy storage. In addition, recent advances for MXenes used in energy conversion devices like solar cells, fuel cells and catalysis is also summarized. Finally, the future prospective of growing MXene-based energy conversion and storage are highlighted.

Recent advances of modification effect in Co3O4-based catalyst towards highly efficient photocatalysis

Tricobalt tetroxide (Co3O4) has been developed as a promising photocatalyst material for various applications. Several reports have been published on the self-modification of Co3O4 to achieve optimal photocatalytic performance. The pristine Co3O4 alone is inadequate for photocatalysis due to the rapid recombination process of photogenerated (PG) charge carriers. The modification of Co3O4 can be extended through the introduction of doping elements, incorporation of supporting materials, surface functionalization, metal loading, and combination with other photocatalysts. The addition of doping elements and support materials may enhance the photocatalysis process, although these modifications have a slight effect on decreasing the recombination process of PG charge carriers. On the other hand, combining Co3O4 with other semiconductors results in a different PG charge carrier mechanism, leading to a decrease in the recombination process and an increase in photocatalytic activity. Therefore, this work discusses recent modifications of Co3O4 and their effects on its photocatalytic performance. Additionally, the modification effects, such as enhanced surface area, generation of oxygen vacancies, tuning the band gap, and formation of heterojunctions, are reviewed to demonstrate the feasibility of separating PG charge carriers. Finally, the formation and mechanism of these modification effects are also reviewed based on theoretical and experimental approaches to validate their formation and the transfer process of charge carriers.

The Renaissance of Ferrocene-Based Electrocatalysts: Properties, Synthesis Strategies, and Applications

The fascinating electrochemical properties of the redox-active compound ferrocene have inspired researchers across the globe to develop ferrocene-based electrocatalysts for a wide variety of applications. Advantages including excellent chemical and thermal stability, solubility in organic solvents, a pair of stable redox states, rapid electron transfer, and nontoxic nature improve its utility in various electrochemical applications. The use of ferrocene-based electrocatalysts enables control over the intrinsic properties and electroactive sites at the surface of the electrode to achieve specific electrochemical activities. Ferrocene and its derivatives can function as a potential redox medium that promotes electron transfer rates, thereby enhancing the reaction kinetics and electrochemical responses of the device. The outstanding electrocatalytic activity of ferrocene-based compounds at lower operating potentials enhances the specificity and sensitivity of reactions and also amplifies the response signals. Owing to their versatile redox chemistry and catalytic activities, ferrocene-based electrocatalysts are widely employed in various energy-related systems, molecular machines, and agricultural, biological, medicinal, and sensing applications. This review highlights the importance of ferrocene-based electrocatalysts, with emphasis on their properties, synthesis strategies for obtaining different ferrocene-based compounds, and their electrochemical applications.

Low-Dimensional High-Entropy Alloys for Advanced Electrocatalytic Reactions

Low-dimensional high-entropy alloy (HEA) nanomaterials are widely employed as electrocatalysts for energy conversion reactions, due to their inherent advantages, including high electron mobility, rich catalytically active site, optimal electronic structure. Moreover, the high-entropy, lattice distortion, and sluggish diffusion effects also enable them to be promising electrocatalysts. A thorough understanding on the structure-activity relationships of low-dimensional HEA catalyst play a huge role in the future pursuit of more efficient electrocatalysts. In this review, we summarize the recent progress of low-dimensional HEA nanomaterials for efficient catalytic energy conversion. By systematically discussing the fundamentals of HEA and properties of low-dimensional nanostructures, we highlight the advantages of low-dimensional HEAs. Subsequently, we also present many low-dimensional HEA catalysts for electrocatalytic reactions, aiming to gain a better understanding on the structure-activity relationship. Finally, a series of upcoming challenges and issues are also thoroughly proposed as well as their future directions.

Recent advances on surface mounted metal-organic frameworks for energy storage and conversion applications: Trends, challenges, and opportunities

Establishing green and reliable energy resources is very important to counteract the carbon footprints and negative impact of non-renewable energy resources. Metal-organic frameworks (MOFs) are a class of porous material finding numerous applications due to their exceptional qualities, such as high surface area, low density, superior structural flexibility, and stability. Recently, increased attention has been paid to surface mounted MOFs (SURMOFs), which is nothing but thin film of MOF, as a new category in nanotechnology having unique properties compared to bulk MOFs. With the advancement of material growth and synthesis technologies, the fine tunability of film thickness, consistency, size, and geometry with a wide range of MOF complexes is possible. In this review, we recapitulate various synthesis approaches of SURMOFs including epitaxial synthesis approach, direct solvothermal method, Langmuir-Blodgett LBL deposition, Inkjet printing technique and others and then correlated the synthesis-structure-property relationship in terms of energy storage and conversion applications. Further the critical assessment and current problems of SURMOFs have been briefly discussed to explore the future opportunities in SURMOFs for energy storage and conversion applications.

Amorphous and defective Co-P-O@NC ball-in-ball hollow structure for highly efficient electrocatalytic overall water splitting

Electrochemical water splitting using hollow and defect-rich catalysts has emerged as a promising strategy for efficient hydrogen production. However, the rational design and controllable synthesis of such catalysts with intricate morphology and composition present significant challenges. Herein, we propose a template-engaged approach to fabricate a novel ball-in-ball hollow structure of Co-P-O@N-doped carbon with abundant oxygen vacancies. The synthesis process involves the preparation of uniform cobalt-glycerate (Co-gly) polymer microspheres as precursors, followed by surface coating with ZIF-67 layer, adjustable chemical etching by phytic acid, and controllable pyrolysis at high temperature. The resulting ball-in-ball structure offers a large number of accessible active sites and high redox reaction centers, facilitating efficient charge transport, mass transfer, and gas evolution, which are beneficial for the acceleration of electrocatalytic reaction. Additionally, density functional theory (DFT) calculations indicate that the incorporation of oxygen and the presence of Co-P dangling bonds in CoP significantly enhance the adsorption of oxygenated species, leading to improved intrinsic electroactivity at the single-site level. As a sequence, the titled catalyst exhibits remarkable electrocatalytic activity and stability for water splitting in alkaline media. Notably, it only requires a low overpotential of 283 mV to achieve a current density of 10 mA cm^-2 for the oxygen evolution reaction. This work may provide some new insights into the design of complex hollow structures of phosphides with abundant defects for energy conversion.

Manipulating multi-spectral slow photons in bilayer inverse opal TiO2@BiVO4 composites for highly enhanced visible light photocatalysis

Manipulation of light has been proved to be a promising strategy to increase light harvesting in solar-to-chemical energy conversion, especially in photocatalysis. Inverse opal (IO) photonic structures are highly promising for light manipulation as their periodic dielectric structures enable them to slow down light and localize it within the structure, thereby improving light harvesting and photocatalytic efficiency. However, slow photons are confined to narrow wavelength ranges and hence limit the amount of energy that can be captured through light manipulation. To address this challenge, we synthesized bilayer IO TiO₂@BiVO₄ structures that manifested two distinct stop band gap (SBG) peaks, arising from different pore sizes in each layer, with slow photons available at either edge of each SBG. In addition, we achieved precise control over the frequencies of these multi-spectral slow photons through pore size and incidence angle variations, that enabled us to tune their wavelengths to the electronic absorption of the photocatalyst for optimal light utilization in aqueous phase visible light photocatalysis. This first proof of concept involving multi-spectral slow photon utilization enabled us to achieve up to 8.5 times and 2.2 times higher photocatalytic efficiencies than the corresponding non-structured and monolayer IO photocatalysts respectively. Through this work, we have successfully and significantly improved light harvesting efficiency in slow photon-assisted photocatalysis, the principles of which can be extended to other light harvesting applications.

Long afterglow particle enables spectral and temporal light management to boost photosynthetic efficiency

Herein, we develop a strategy of matched spectral and temporal light management to improve photosynthetic efficiency by co-assembling natural thylakoid membrane (TM) with artificial long afterglow particle (LAP). To be specific, LAP with excellent stability and biocompatibility possesses the capabilities of light conversion and storage, optically-matched with the absorption of TM. These favorable features permit LAP as an additional well-functioned light source of photosynthesis performed by TM. As a consequence, enhanced photosynthesis is achieved after co-assembly, compared with pure TM. Under light, the rates of electron transfer, oxygen yield and adenosine triphosphate (ATP) production in this biohybrid architecture are boosted owing to down-conversion fluorescence emission from LAP. Under dark, persistent phosphorescence emission in charged LAP facilitates continual photosynthesis of TM, while that of pure TM almost stops immediately. This proof-of-concept work opens a new route to augment the photosynthetic efficiency of green plants by utilizing precise light-managed materials.

How does mandatory energy conversion affect sustainable development: Perspectives of regional heterogeneity and efficiency decomposition

Clean energy conversion is a core approach and development trend to tackle climate change, while the severe drawbacks such as supply deficiency and cost increase restrict regional sustainable development. This paper employs a natural experiment of coal-to-gas conversion of the Chinese government to study the effect of such policy on regional sustainable development, as well as the underlying mechanism. Based on a city-level dataset from 2006 to 2019, this paper measure green total factor productivity (GTFP) using data envelopment analysis (DEA) combined with the Malmquist‒Luenberger productivity index. Then, this paper evaluates the impact of the CTG policy in pilot cities using the Difference-in-Difference (DID) with Propensity Score Matching (PSM) approach. This paper finds that the CTG policy increased the GTFP of the pilot cities by 2.25% (0.0229/1.02). A series of robustness tests confirmed the findings. Subsequent mechanism analysis shows that the CTG policy increases the GTFP of pilot cities mainly by increasing technical efficiency. In addition, the mechanism of the CTG policy's impact differs between central and noncentral cities. In particular, the CTG policy increases the technological innovation indicator (TC) of provincial capital cities by 2.35% while it increases the technical efficiency indicator (EC) of other cities by 1.89%, which proves the Porter effect in provincial capital cities. Finally, several implications are provided for policymakers to promote other types of renewable energy.

Enhanced osmotic energy conversion through bacterial cellulose based double-network hydrogel with 3D interconnected nanochannels

Hydrogel with 3D networks have shown great potential for ion transportation and energy conversion. However, the micron size pores of hydrogel greatly limit the ion selectivity and energy conversion performance. Here, we report a bacterial cellulose (BC) derived hydrogel membrane with double-network (DN) and tailored ion transport channels by rationally filling acrylic acid (AAc)-co-acrylamide (AAm)-co-methyl methacrylate (MMA) polymers into BC hydrogel micropores. Fabricated AAM/BC DN hydrogel membrane displays a unique hierarchical interconnected porous structure and 3D cation transport channels. From the results, the maximum power density reached up to 7.63 W·m^-2 at 50-fold salinity gradient under alkaline conditions (pH 11). Interestingly, the power density of 45.5 W·m^-2 was achieved through acid-base neutralization reaction. Furthermore, hydrogel successfully obtained a power density of 28.4 W·m^-2 from a mixed system of paper black liquor wastewater/seawater. The results of this investigation suggested the enormous potential of BC-based nanofluidic membrane in sustainable osmotic energy conversion.

Selective and Generic Photocatalytic Oxidation of Alcohol with Pd-TiO2 Thin Films: Butanols to Butanal/Butanone with Different Morphologies of Pd and 0.5θPt -Pd Counterparts

The present study reports on the photocatalytic oxidation of butanols to butanal/butanone using thin film form of facet-dependent nano-Pd supported on commercial TiO₂ under one-sun condition and demonstrates the generic nature. Pd-nanocube (Pd_NC (100)), Pd-truncated octahedron (Pd_TO (100) and (111)), polycrystalline (Pd_PC ), and their counterparts with half-a-monolayer Pt-coated on Pd (0.5θ_Pt -Pd)) have been used as co-catalyst. A potentially scalable thin film form of Pd/TiO₂ photocatalyst, prepared by drop-casting method, has been employed to study oxidation of n-butanol, 2-butanol, and iso-butanol to corresponding aldehyde/ketone. 100% selectivity is demonstrated to respective aldehyde/ketone with any catalyst used in the present study with varying degree of butanols conversion by NMR. 0.5θ_Pt -Pd_TO /TiO₂ shows the highest conversion of 2-butanol to butanone (13.6% in 4 h). Continuous 10 h of reaction with the most active 0.5θ_Pt -Pd_TO /P25 catalyst demonstrates 31% conversion of 2-butanol to butanone, and catalyst recyclability has been demonstrated. The present protocol can be scalable to large scales to maximize the conversion in direct sunlight. Due to its generic nature, the current method can also be applied to many other alcohols and substrate molecules.

Towards powerful magnetocaloric devices with static electro-permanent magnets

INTRODUCTION

Magnetocaloric energy conversion represents an alternative to existing refrigeration, heat pump and energy harvesting technologies. A crucial part of a magnetocaloric device concerns the magnetic field source. It uses mainly rare-earth materials and consists of moving parts and a drive system while displaying a limited energy efficiency and unavailability of fast and variable control of the magnetic field. Recent advances in efficient heat transfer for high-frequency magnetic cooling call for new developments of magnetic field sources that can operate with high efficiency at high frequencies.

OBJECTIVES

We report the concept of an electro-permanent magnetic (EPM) field source that efficiently recovers magnetic energy. In contrast to existing magnets, it allows very well-controlled operation without any moving parts. The main objective of this paper is to present a numerical and experimental study in which such an EPM was designed, built and tested.

METHODS

An extensive numerical investigation of the proposed design was carried out in terms of various geometrical and operating parameters. One of the design variations was built and experimentally evaluated for its energy efficiency and temperature increase at various operating frequencies.

RESULTS

We demonstrate an energy efficiency of these magnets of over 80% and operation with frequencies up to 50 Hz, which is crucial for future high-power-density and high-frequency magnetocaloric devices.

CONCLUSIONS

Considering high energy efficiency at high operating frequencies, such EPMs would allow for miniaturization, making them a viable option for future compact magnetocaloric devices.

A novel cascaded energy conversion system inducing efficient and precise cancer therapy

Cancer therapies based on energy conversion, such as photothermal therapy (PTT, light-to-thermal energy conversion) and photodynamic therapy (PDT, light-to-chemical energy conversion) have attracted extensive attention in preclinical research. However, the PTT-related hyperthermia damage to surrounding tissues and shallow penetration of PDT-applied light prevent further advanced clinical practices. Here, we developed a thermoelectric therapy (TET) based on thermoelectric materials constructed p-n heterojunction (SrTiO₃/Cu₂Se nanoplates) on the principle of light-thermal-electricity-chemical energy conversion. Upon irradiation and natural cooling-induced the temperature gradient (35–45 ^oC), a self-build-in electric field was constructed and thereby facilitated charges separation in bulk SrTiO₃ and Cu₂Se. Importantly, the contact between SrTiO₃ (n type) and Cu₂Se (p type) constructed another interfacial electric field, further guiding the separated charges to re-locate onto the surfaces of SrTiO₃ and Cu₂Se. The formation of two electric fields minimized probability of charges recombination. Of note, high-performance superoxide radicals and hydroxyl radicals’ generation from O₂ and H₂O under catalyzation by separated electrons and holes, led to intracellular ROS burst and cancer cells apoptosis without apparent damage to surrounding tissues. Construction of bulk and interfacial electric fields in heterojunction for improving charges separation and transfer is also expected to provide a robust strategy for diverse applications.

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A thermoelectric therapy based on the principle of light-heat-electricity-chemical energy conversion has been provided.

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Two self-build-in electric fields guide electron-hole pairs directional and ordered separation.

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Thermoelectric therapy under mild temperature gradient induces cancer cells apoptosis without damage to normal tissues.

E-waste recycled materials as efficient catalysts for renewable energy technologies and better environmental sustainability

Waste from electrical and electronic equipment exponentially increased due to the innovation and the ever-increasing demand for electronic products in our life. The quantities of electronic waste (e-waste) produced are expected to reach 44.4 million metric tons over the next five years. Consequently, the global market for electronics recycling is expected to reach $65.8 billion by 2026. However, electronic waste management in developing countries is not appropriately handled, as only 17.4% has been collected and recycled. The inadequate electronic waste treatment causes significant environmental and health issues and a systematic depletion of natural resources in secondary material recycling and extracting valuable materials. Electronic waste contains numerous valuable materials that can be recovered and reused to create renewable energy technologies to overcome the shortage of raw materials and the adverse effects of using non-renewable energy resources. Several approaches were devoted to mitigate the impact of climate change. The cooperate social responsibilities supported integrating informal collection and recycling agencies into a well-structured management program. Moreover, the emission reductions resulting from recycling and proper management systems significantly impact climate change solutions. This emission reduction will create a channel in carbon market mechanisms by trading the CO2 emission reductions. This review provides an up-to-date overview and discussion of the different categories of electronic waste, the recycling methods, and the use of high recycled value-added (HAV) materials from various e-waste components in green renewable energy technologies.

Construction and characterization of organic photovoltaic cells sensitized by Chrysanthemum based natural dye

In this work, natural dyes from three different species of the same flower family (Chrysanthemum), which containing anthocyanin were extracted and properly prepared to be used as photosensitizers in DSSCs construction. The cells were fabricated with titanium dioxide nanoparticles (TiO₂) for the photoanodes, whereas platinum electrodes were used for the photocathodes. To understand the behavior of light absorption in addition to the coloring components present in the dyes and the molecular functional groups present in the samples, the UV-Vis absorption spectroscopy and FTIR spectroscopy were used respectively. The performance and efficiency of solar cells were evaluated to establish the photovoltaic criteria for each DSSC built. Through electrochemical characterizations, it was possible to notice that the highest photovoltaic conversion efficiency was obtained with the Chrysanthemum Violet (CV) cell, with efficiency (η) of 1.348%, compared to 1.229% and 0.485% for the Chrysanthemum Green (CG) and Chrysanthemum Blue (CB) cells, respectively. The CV cell also has the highest open circuit voltage (V_OC) at 0.58 V. The results corroborate to present the organic solar cells as a viable option for the electric energy generation.

Photoactivation and conformational gating for manganese binding and oxidation in bacterial reaction centers

The influence of illumination history of native bacterial reaction centers (BRCs) on the ability of binding and photo-induced oxidation of manganous ions was investigated in the pH range between 8.0 and 9.4. Binding of manganous ions to a buried site required 6 to 11-fold longer incubation periods, depending on the pH, in dark-adapted BRCs than in BRCs that were previously illuminated prior to manganese binding. The intrinsic electron transfer from the bound manganese ion to the photo-oxidized primary electron donor was found to be limited by a 2 to 5-fold slower precursor conformational step in the dark-adapted samples for the same pH range. The conformational gating could be eliminated by photoactivation, namely if the BRCs were illuminated prior to binding. Unlike in Photosystem II, photoactivation in BRCs did not involve cluster assembly. Photoactivation with manganese already bound was only possible at elevated detergent concentration. In addition, also exclusively in dark-adapted BRCs, a marked breaking point in the Arrhenius-plot was discovered around 15 °C at pH 9.4 indicating a change in the reaction mechanism, most likely caused by the change of orientation of the 2-acetyl group of the inactive bacteriochlorophyll monomer located near the manganese binding site.

Recent Advancement in Rational Design Modulation of MXene: A Voyage from Environmental Remediation to Energy Conversion and Storage

Use of MXenes (Ti₃ C₂ T_x ), which belongs to the family of two-dimensional transition metal nitrides and carbides by encompassing unique combination of metallic conductivity and hydrophilicity, is receiving tremendous attention, since its discovery as energy material in 2011. Owing to its precursor selective chemical etching, and unique intrinsic characteristics, the MXene surface properties are further classified into highly chemically active compound, which further produced different surface functional groups i. e., oxygen, fluorine or hydroxyl groups. However, the role of surface functional groups doesn't not only have a significant impact onto its electrochemical and hydrophilic characteristics (i. e., ion adsorption/diffusion), but also imparting a noteworthy effect onto its conductivity, work function, electronic structure and properties. Henceforth, such kind of inherent chemical nature, robust electrochemistry and high hydrophilicity ultimately increasing the MXene application as a most propitious material for overall environment-remediation, electrocatalytic sensors, energy conversion and storage application. Moreover, it is well documented that the role of MXenes in all kinds of research fields is still on a progress stage for their further improvement, which is not sufficiently summarized in literature till now. The present review article is intended to critically discuss the different chemical aptitudes and the diversity of MXenes and its derivates (i. e., hybrid composites) in all aforesaid application with special emphasis onto the improvement of its surface characteristics for the multidimensional application. However, this review article is anticipated to endorse MXenes and its derivates hybrid configuration, which is discussed in detail for emerging environmental decontamination, electrochemical use, and pollutant detection via electrocatalytic sensors, photocatalysis, along with membrane distillation and the adsorption application. Finally, it is expected, that this review article will open up new window for the effective use of MXene in a broad range of environmental remediation, energy conversion and storage application as a novel, robust, multidimensional and more proficient materials.

Degradation of mixed typical odour gases via non-thermal plasma catalysis

The simultaneous treatment of H₂S and NH₃ typical odours by plasma was investigated and the co-treatment of both was found to have a facilitating effect the conversion. The degradation efficiency and by-product emissions of single plasma technology and plasma co-catalytic two-stage technology were compared and the degradation mechanism was further analyzed. The results show that in the single plasma technology conversion experiment, the conversion rate of the treated odours mixture is higher than that of the treated single odours, and the by-product emissions of SO₂ and NO_x are also reduced due to the reaction of intermediate products and by-products during the reaction process. The absolute removal of the odours mixture is optimal when treating at a gas flow rate of 6 L/min, a voltage of 16 kV and a frequency of 200 Hz. The M(Ce,Cu)-Mn/13X loaded catalyst was synthesized by co-precipitation method. Under the conditions of gas flow rate of 3-7 L/min, the efficiency of H₂S and NH₃ removal and the reduction of by-product emission were ranked as: uncatalyzed > Cu-Mn/13X > Ce-Mn/13X, which proved that Ce-Mn/13X showed better catalytic activity and application value.

Catalytic radiosensitization: Insights from materials physicochemistry

Radiotherapy is indispensable in clinical cancer treatment, but because both tumor and normal tissues have similar sensitivity to X-rays, their clinical curative effect is intrinsically limited. Advanced nanomaterials and nanotechnologies have been developed for radiotherapy sensitization, typically employing high atomic number (high-Z) materials to enhance the energy deposition of X-rays in tumor tissues, but the efficiency is largely limited by the toxicity of heavy metals. A new and promising approach for radiosensitization is catalytic radiosensitization, which takes advantage of the catalytic activity of nanomaterials triggered by radiation. The efficiency of catalytic radiosensitization can be greatly enhanced by electron modulation and energy conversion of nanocatalysts upon X-ray irradiation, further enhancing the clinical curative effect. In this review, we highlight the challenges and opportunities in cancer radiosensitization, discuss novel approaches to catalytic radiosensitization, and finally describe the development of catalytic radiosensitization based on an in-depth understanding of radio-nano interactions and catalysis-biological interactions.

Role of nitrogen transport for efficient energy conversion potential in low carbon and high nitrogen/phosphorus wastewater by microalgal-bacterial system

Microalgal-bacterial system (MBS) is potential biotechnology in wastewater treatment because it can remedy defects of conventional processes (e.g., insufficient carbon source and imbalanced elements ratio). However, the mechanisms of nitrogen (N) transport and removal in MBS are still unclear. In this study, it was discovered that MBS was conducive to adsorb NH₄⁺-N and NO₃^--N through electrical neutralization, while extracellular polymeric substances (EPS) could provide binding sites (e.g., -OH and -CH₃) for enhancing N transport and removal. The microalgae-bacteria interaction could accelerate N transport and removal from aqueous solution to cell. More importantly, the microalgal starch biosynthetic metabolism exhibited demonstrating the energy production potential could be boosted via MBS. Overall, the NO₃^--N and NH₄⁺-N removal efficiencies, and energy yield were 82.28%, 94.15%, and 86.81 kJ/L, respectively, which are better than other relevant studies. Altogether, it is meaningful for revealing the applicability of MBS for treating wastewater and producing energy.

MXenes based nano-heterojunctions and composites for advanced photocatalytic environmental detoxification and energy conversion: A review

Extensive research is being done to develop multifunctional advanced new materials for high performance photocatalytic applications in the field of energy production and environmental detoxification, MXenes have emerged as promising materials for enhancing photocatalytic performance owing to their excellent mechanical properties, appropriate Fermi levels, and adjustability of chemical composition. Numerous experimental and theoretical research works implied that the dimensions of MXenes have a significant impact on their performance. For photocatalysis to thrive in the future, we must understand the current state of the art for MXene in different dimensions. Using MXene co-catalysts in widely used in photocatalytic applications such as CO₂ reduction, hydrogen production and organic pollutant oxidation, this study focuses on the most recent developments in MXenes based materials, structural modifications, innovations in reaction and material engineering. It has been reported that using 5 mg of CdS-MoS₂-MXene researchers were able to generate as high as 9679 μmol/g/h hydrogen under visible light. The MXenes based heterojunction photocatalyst Co₃O₄/MXene was utilized to degrade 95% bisphenol A micro-pollutant in just 7 min. Numerous novel materials, their preparations and performances have been discussed. Depending upon the nature of MXene-based materials, the synthesis techniques and photocatalytic mechanism of MXenes as co-catalyst are also summarized. Finally, some final thoughts and prospects for developing highly efficient MXene-based photocatalysts are provided which will indeed motivate researchers to design novel hybrid materials based on MXenes for sustainable solutions to energy and pollution issues.

Review of resource and recycling of silicon powder from diamond-wire sawing silicon waste

The installed capacity of solar photovoltaic power generation has grown rapidly in the last decades. With the rapid development of the photovoltaic industry, the demand for Si wafers, which are integral to solar cells, has grown dramatically. In the manufacture of Si wafers, the traditional loose abrasive sawing method (LAS) has gradually been replaced by the diamond-wire sawing method (DWS). However, during the diamond-wire wafer sawing process, approximately 35%-40% of the crystalline Si becomes diamond-wire sawing silicon waste (DSSW). Therefore, DSSW represents a resource worth recycling due to its low levels of impurities and high silicon content. Furthermore, recycling prevents DSSW from becoming environmental pollution and eliminates disposal costs. This review provides an overview of the recycling and reutilization of DSSW based on an extensive literature survey. In view of the rapid increase in DSSW production and current purification bottleneck of < 5 N, in-situ utilizations may be more feasible, such as the preparation of silicon containing alloys and functional ceramic materials, which not only frees from the complex purification process, but has a huge demand. Finally, based on the review, future prospects are proposed, aiming to identify research directions with significant potential in the resource utilization of DSSW and other silicon wastes.

Fundamental understanding of microbial fuel cell technology: Recent development and challenges

The research on microbial fuel cells (MFCs) is rising tremendously but its commercialization is restricted by several microbiological, material, and economic constraints. Hence, a systematic assessment of the research articles published previously focusing on potential upcoming directions in this field is necessary. A detailed multi-perspective analysis of various techniques for enhancing the efficiency of MFC in terms of electric power production is presented in this paper. A brief discussion on the central aspects of different issues are preceded by an extensive analysis of the strategies that can be introduced to optimize power generation and reduce energy losses. Various applications of MFCs in a broad spectrum ranging from biomedical to underwater monitoring rather than electricity production and wastewater treatment are also presented followed by relevant possible case studies. Mathematical modeling is used to understand the concepts that cannot be understood experimentally. These methods relate electrode geometries to microbiological reactions occurring inside the MFC chamber, which explains the system's behavior and can be improved. Finally, directions for future research in the field of MFCs have been suggested. This article can be beneficial for engineers and researchers concerned about the challenges faced in the application of MFC.

Microbial fuel cell scale-up options: Performance evaluation of membrane (c-MFC) and membrane-less (s-MFC) systems under different feeding regimes

In recent years, bioelectrochemical systems have advanced towards upscaling applications and tested during field trials, primarily for wastewater treatment. Amongst reported trials, two designs of urine-fed microbial fuel cells (MFCs) were tested successfully on a pilot scale as autonomous sanitation systems for decentralised area. These designs, known as ceramic MFCs ( c -MFCs) and self-stratifying MFCs ( s -MFC), have never been calibrated under similar conditions. Here, the most advanced versions of both designs were assembled and tested under similar feeding conditions. The performance and efficiency were evaluated under different hydraulic retention times (HRT), through chemical oxygen demand measures and polarisation experiments. Results show that c -MFCs displayed constant performance independently from the HRT (32.2 ± 3.9 W m-3) whilst displaying high energy conversion efficiency at longer HRT (NER COD  = 2.092 ± 0.119 KWh.Kg COD -1, at 24h HRT). The s -MFC showed a correlation between performance and HRT. The highest performance was reached under short HRT (69.7 ± 0.4 W m-3 at 3h HRT), but the energy conversion efficiency was constant independently from the HRT (0.338 ± 0.029 KWh.Kg COD -1). The c -MFCs and s -MFCs similarly showed the highest volumetric efficiency under long HRT (65h) with NER V of 0.747 ± 0.010 KWh.m-3 and 0.825 ± 0.086 KWh.m-3, respectively. Overall, c -MFCs seems more appropriate for longer HRT and s -MFCs for shorter HRT.

A review of advances in multifunctional XTiO3 perovskite-type oxides as piezo-photocatalysts for environmental remediation and energy production

Over more than three decades, the field of engineering of photocatalytic materials with unique properties and enhanced performance has received a huge attention. In this regard, different classes of materials were fabricated and used for different photocatalytic applications. Among these materials, recently multifunctional XTiO₃ perovskites have drawn outstanding interest towards environmental remediation and energy conversion thanks to their unique structural, optical, physiochemical, electrical and thermal characteristics. XTiO₃ perovskites are able to initiate different surface catalytic reactions. Under ultrasonic vibration or heating, XTiO₃ perovskites can induce piezo-catalytic reactions due to the titling of their conduction and valence bands, resulting in the formation of separated charge carriers in the medium. In addition, under light irradiation, XTiO₃ perovskites are considered as a new class of photocatalysts for environmental and energy related applications. Herein, we addressed the recent advances on variously synthesized, doped and formulated XTiO₃ perovskite-type oxides showing piezo- and/or photocatalytic exploitation in environmental remediation and energy conversion. The control of structural crystallite size and phase, conductivity, morphology, oxygen vacancy control, doping agents and ratio has a significant role on the photocatalytic and piezocatalytic activities. The different piezo or/and photocatalytic processes mechanistic pathways towards varying applications were discussed. The current challenges facing these materials and future trends were addressed at the end of the review.

Microbial fuel cells for bioelectricity production from waste as sustainable prospect of future energy sector

Microbial fuel cell (MFC) is lauded for its potentials to solve both energy crisis and environmental pollution. Technologically, it offers the capability to harness electricity from the chemical energy stored in the organic substrate with no intermediate steps, thereby minimizes the entropic loss due to the inter-conversion of energy. The sciences underneath such MFCs include the electron and proton generation from the metabolic decomposition of the substrate by microbes at the anode, followed by the shuttling of these charges to cathode for electricity generation. While its promising prospects were mutually evinced in the past investigations, the upscaling of MFC in sustaining global energy demands and waste treatments is yet to be put into practice. In this context, the current review summarizes the important knowledge and applications of MFCs, concurrently identifies the technological bottlenecks that restricted its vast implementation. In addition, economic analysis was also performed to provide multiangle perspectives to readers. Succinctly, MFCs are mainly hindered by the slow metabolic kinetics, sluggish transfer of charged particles, and low economic competitiveness when compared to conventional technologies. From these hindering factors, insightful strategies for improved practicality of MFCs were formulated, with potential future research direction being identified too. With proper planning, we are delighted to see the industrialization of MFCs in the near future, which would benefit the entire human race with cleaner energy and the environment.

One-dimensional metal-organic frameworks for electrochemical applications

Metal-organic frameworks (MOFs) are as a category of crystalline porous materials. Extensive interest has been devoted to energy storage and energy conversion applications owing to their unique advantages of periodic architecture, high specific surface area, high adsorption, high conductivity, high specific capacitance, and high porosity. One-dimensional (1D) nanostructures have unique surface effects, easily regulated size, good agglutination of the substrate, and other distinct properties amenable to the field of energy storage and conversion. Therefore, 1D nanostructures could further improve the characteristic properties of MOFs, and it is of great importance for practical applications to control the size and morphological characteristics of MOFs. The electrochemical application of 1D MOFs is mainly discussed in this review, including energy storage applications in supercapacitors and batteries and energy conversion applications in catalysis. In addition, various synthesis strategies for 1D MOFs and their architectures are presented.

2D Graphdiyne: A Rising Star on the Horizon of Energy Conversion

Two-dimensional (2D) graphdiyne (GDY), a rapidly rising star on the horizon of carbon materials, is a new carbon allotrope featuring sp- and sp² -cohybridized carbon atoms and 2D one-atom-thick network. Since the first successful synthesis of GDY by Professor Li's group in 2010, GDY has attached great interests from both scientific and industrial viewpoints based on its unique structure and physicochemical properties, which provides a fertile ground for applications in various fields including electrocatalysis, energy conversion, energy storage and optoelectronic devices. In this work, various potential properties of the GDY-based electrocatalysts and their recent advances in energy conversion are reviewed, including atomic catalysts, heterogeneous catalysts, and metal-free catalysts. The critical role of GDY in improving catalytic activity and stability is analyzed. The perspectives of the challenges and opportunities faced by GDY-based materials for energy conversion are also outlined.

Conserved spinal cord bioenergetics in experimental autoimmune encephalomyelitis in C57BL6 mice, measured using phosphorescence oxygen analyzer

Background

We have previously reported that spinal cord respiration (cellular mitochondrial oxygen consumption) and ATP content are conserved in the studied model of experimental autoimmune encephalomyelitis (EAE), foreseeing a recovery of the diseased rats. This exemplary lesion of multiple sclerosis is used here to measure spinal cord bioenergetics in C57BL6 mice. Our hypothesis is that, despite the well-known focal axonal mitochondrial pathology, bioenergetics of the CNS is reasonably preserved in this disease.

Methods

EAE was induced with an immunodominant myelin oligodendrocyte glycoprotein epitope in complete Freund's adjuvant, appended by injections of pertussis toxin. A low- and high-dose of the encephalitogen, administered into base of tail or hind-flank, were investigated. Control mice received only the incomplete adjuvant into tail. Oxygen measurements were based on quenching the phosphorescence of Pd(II) meso-tetra (sulfophenyl) tetrabenzoporphyrin by molecular oxygen. Cellular ATP was measured using the luciferin/luciferase system.

Results

The kinetics of spinal cord oxygen consumption was zero-order (linear with time) and inhibited by cyanide, confirming oxygen was reduced by cytochrome oxidase. The rate of respiration (in μM O₂.min⁻¹.mg⁻¹; measured on Days 13–28) in control mice was (mean ± SD) 0.086 ± 0.024 (n = 8) and in immunized mice was 0.079 ± 0.020 (n = 15, P = 0.265, Mann-Whitney test). Consistently, cellular ATP (in μmol mg⁻¹ dry pellet weight; measured on Days 13–28) in control mice was 0.068 ± 0.079 (n = 11) and in immunized mice was 0.063 ± 0.061 (n = 24, P = 0.887, Mann-Whitney U test).

Conclusions

In vitro measurements of spinal cord bioenergetics show conservation of the mitochondrial function in mice with EAE. These results suggest the previously documented reduced mitochondrial electrochemical potential in this disease is alterable, and likely reflects the adverse events of neuroinflammation.

Harnessing energy from the waste produced in Bangladesh: evaluating potential technologies

With the increasing trend of the urban population in Bangladesh, waste generation is also increasing. With 70% organic solid waste, the urban areas generate 23,688 tonnes of waste per day. This rapid enhancement in waste production has an adverse effect onlandfill resources and the day-to-day lifestyle. In this regard adopting waste to energy techniques can be considered good idea to overcome the current waste management problem. This WtE conversion technique solves the landfill resources problem and produces electricity and heat to be supplied. This study aims to investigate the current status of MSW management in Bangladesh and identify the major problems. Here, five fundamental methods such as pyrolysis, incineration, anaerobic digestion (AD), gasification, hydrothermal carbonization (HTC) are reviewed critically and discussed the feasibilities in Bangladesh to generate power. The analysis is done considering different types of parameters like moisture content, calorific value, and residence time. These analyses pertaining to MSW management may be fruitful for encouraging researchers and authorities to improve further.

Pyrolysis: An effective technique for degradation of COVID-19 medical wastes

COVID-19 has led to the enormous rise of medical wastes throughout the world, and these have mainly been generated from hospitals, clinics, and other healthcare establishments. This creates an additional challenge in medical waste management, particularly in developing countries. Improper managing of medical waste may have serious public health issues and a significant impact on the environment. There are currently three disinfection technologies, namely incineration, chemical and physical processes, that are available to treat COVID-19 medical waste (CMW). This study focuses on thermochemical process, particularly pyrolysis process to treat the medical waste. Pyrolysis is a process that utilizes the thermal instability of organic components in medical waste to convert them into valuable products. Besides, the technique is environmentally friendly, more efficient and cost-effective, requires less landfill capacity, and causes lower pollution. The current pandemic situation generates a large amount of plastic medical wastes, which mainly consists of polyethylene, polypropylene, polystyrene, polyethylene terephthalate, and nylon. These plastic wastes can be converted into valuable energy products like oil, gas and char through pyrolysis process. This review provides detailed information about CMW handling, treatment, valuable product generation, and proper discharge into the open environment.

Mitophagy in plants

Mitochondria play a central role in primary metabolism in plants as well as in heterotrophic eukaryotes. Plants must control the quality and number of mitochondria in response to a changing environment, across cell types and developmental stages. Mitophagy is defined as the degradation of mitochondria by autophagy, an evolutionarily conserved system for the removal and recycling of intracellular components. Recent studies have highlighted the importance of mitophagy in plant stress responses. This review article summarizes our current knowledge of plant mitophagy and discusses the underlying mechanisms. In plants, chloroplasts cooperate with mitochondria for energy production, and autophagy also targets chloroplasts through a process known as chlorophagy. Advances in plant autophagy studies now allow a comparative analysis of the autophagic turnover of mitochondria and chloroplasts, via the selective degradation of their soluble proteins, fragments, or entire organelles.

Nanoporous Gold for Energy Applications

Research activities using nanoporous gold (NPG) were reviewed in the field of energy applications in three categories: fuel cells, supercapacitors, and batteries. First, applications to fuel cells are reviewed with the subsections of proof-of-concept studies, studies on fuel oxidations at anode, and studies on oxygen reduction reactions at cathode. Second, applications to supercapacitors are reviewed from research activities on active materials/NPG composites to demonstrations of all-solid-state flexible supercapacitors using NPG electrodes. Third, research activities using NPG for battery applications are reviewed, mainly about fundamental studies on Li-air and Na-air batteries and some model studies on improving Li ion battery anodes. Although NPG based studies are the main subject of this review, some of meaningful studies using nanoporous metals are also discussed where relevant. Finally, summary and future outlook are given based on the survey on the research activities.

Natural Cellulose Substance Based Energy Materials

Natural cellulose substances have been proven to be ideal structural templates and scaffolds for the fabrication of artificial functional materials with designed structures, psychochemical properties and functionalities. They possess unique hierarchically porous network structures with flexible, biocompatible, and environmental characteristics, exhibiting great potentials in the preparation of energy-related materials. This minireview summarizes natural cellulose-based materials that are used in batteries, supercapacitors, photocatalytic hydrogen generation, photoelectrochemical cells, and solar cells. When natural cellulose substances are employed as the structural template or carbon sources of energy materials, the three-dimensional porous interwoven structures are perfectly replicated, leading to the enhanced performances of the resultant materials. Benefiting from the mechanical strengths of natural cellulose substances, wearable, portable, free-standing, and flexible materials for energy storage and conversion are easily obtained by using natural cellulose substances as the substrates.

Investigations on a mathematical model for optimum impedance compensation of a giant magnetostrictive ultrasonic transducer and its resonance characteristics

Giant magnetostrictive materials (GMMs) have been widely used to fabricate transducers with high-energy output because of their excellent properties. However, there are few reports on mathematical models to optimize the impedance compensation and resonance characteristics of giant magnetostrictive transducers. In this study, a giant magnetostrictive ultrasonic transducer (GMUT) suitable for rotary ultrasonic machining systems is proposed. A mathematical model for optimum impedance compensation that considers the loss in energy conversion is established to maximize the use of ultrasonic energy. The frequency characteristics of the electrical feedback signal in the resonance state are investigated, and the resonance zone found is used for frequency tracking. An impedance analyzer is used to determine the parameters of the mathematical model, and the validity of the optimum compensation capacitance is verified by experiments. The frequency characteristics of the minimum current, active power, and amplitude are obtained to obtain the resonance zone in the GMUT with the lowest energy consumption. The results of this study provide a reference for frequency tracking.

Fermentation-pyrolysis of fibre waste from a paper recycling mill for the production of fuel products

A range of energy fuels (ethanol, char, oil/wax and gas) was produced from fibre waste contaminated with plastic through the application of a fermentation-pyrolysis route. The fibre component was first converted to ethanol by simultaneous saccharification and fermentation (SSF), achieving an ethanol concentration of 39.8 g/L. The residue, enriched in lignin and plastics, was subjected to fast pyrolysis at temperatures between 350 and 550 °C. A wax product with a higher heating value (HHV) higher than 28 MJ/kg was obtained for temperatures higher than 450 °C, while values lower than 15 MJ/kg were observed for the oils produced from the untreated waste stream. Pyrolysis at 550 °C produced a wax with an HHV as high as 32.1 MJ/kg, where 51.8% of the energy content of the fermentation residue was transferred. The attractive energy contents of the pyrolysis products were enabled by oxygen removal from the feedstock during fermentation to ethanol.

Tuning the redox potential of the primary electron donor in bacterial reaction centers by manganese binding and light-induced structural changes

The influence of transition metal binding on the charge storage ability of native bacterial reaction centers (BRCs) was investigated. Binding of manganous ions uniquely prevented the light-induced conformational changes that would yield to long lifetimes of the charge separated state and the drop of the redox potential of the primary electron donor (P). The lifetimes of the stable charge pair in the terminal conformations were shortened by 50-fold and 7-fold upon manganous and cupric ion binding, respectively. Nickel and zinc binding had only marginal effects. Binding of manganese not only prevented the drop of the potential of P/P⁺ but also elevated it by up to 117 mV depending on where the metal was binding. With variable conditions, facilitating either manganese binding or light-induced structural changes a controlled tuning of the potential of P/P⁺ in multiple steps was demonstrated in a range of ~200 mV without the need of a mutation or synthesis. Under the selected conditions, manganese binding was achieved without its photochemical oxidation thus, the energized but still native BRCs can be utilized in photochemistry that is not reachable with regular BRCs. A 42 Å long hydrophobic tunnel was identified that became obstructed upon manganese binding and its likely role is to deliver protons from the hydrophobic core to the surface during conformational changes.

Defect Compensation Weakening Induced Mobility Enhancement in Thermoelectric BiTeI by Iodine Deficiency

Carrier mobility (weighted mobility more specifically) of thermoelectrics fundamentally determines its power factor, representing a new cut-in point to optimize the thermoelectric performance. However, researches on enhancing the carrier mobility to improve power factor has been overlooked. In present work, we highlight a significant mobility enhancement in BiTeI by introducing I deficiency, which improves the power factor and final ZT value. A defect compensation weakening mechanism is adopted that the induced I vacancies reduce the concentration of intrinsic I Te • and Te I ' antisite defects, which weakens the donor-acceptor defect compensation and suppresses the defects-induced carrier scattering. As a result, the carrier mobility is obviously enhanced in I-deficient samples, which ensures an effectively improved power factor and final ZT. A maximum ZT of 0.57 is achieved at 570 K perpendicular to the pressing direction, which is superior to pristine BiTeI and among the highest values reported for bulk BiTeI-based thermoelectric materials. Present work opens up a new avenue for thermoelectric optimization mainly by mobility enhancement.

Combustion in the future: The importance of chemistry

Combustion involves chemical reactions that are often highly exothermic. Combustion systems utilize the energy of chemical compounds released during this reactive process for transportation, to generate electric power, or to provide heat for various applications. Chemistry and combustion are interlinked in several ways. The outcome of a combustion process in terms of its energy and material balance, regarding the delivery of useful work as well as the generation of harmful emissions, depends sensitively on the molecular nature of the respective fuel. The design of efficient, low-emission combustion processes in compliance with air quality and climate goals suggests a closer inspection of the molecular properties and reactions of conventional, bio-derived, and synthetic fuels. Information about flammability, reaction intensity, and potentially hazardous combustion by-products is important also for safety considerations. Moreover, some of the compounds that serve as fuels can assume important roles in chemical energy storage and conversion. Combustion processes can furthermore be used to synthesize materials with attractive properties. A systematic understanding of the combustion behavior thus demands chemical knowledge. Desirable information includes properties of the thermodynamic states before and after the combustion reactions and relevant details about the dynamic processes that occur during the reactive transformations from the fuel and oxidizer to the products under the given boundary conditions. Combustion systems can be described, tailored, and improved by taking chemical knowledge into account. Combining theory, experiment, model development, simulation, and a systematic analysis of uncertainties enables qualitative or even quantitative predictions for many combustion situations of practical relevance. This article can highlight only a few of the numerous investigations on chemical processes for combustion and combustion-related science and applications, with a main focus on gas-phase reaction systems. It attempts to provide a snapshot of recent progress and a guide to exciting opportunities that drive such research beyond fossil combustion.

Defect-Rich Copper-doped Ruthenium Hollow Nanoparticles for Efficient Hydrogen Evolution Electrocatalysis in Alkaline Electrolyte

It is of great importance to develop highly efficient and stable Pt-free catalysts for electrochemical hydrogen generation from water electrolysis. Here, monodisperse 7.5 nm copper-doped ruthenium hollow nanoparticles (NPs) with abundant defects and amorphous/crystalline hetero-phases were prepared and employed as efficient hydrogen evolution electrocatalysts in alkaline electrolyte. Specifically, these NPs only require a low overpotential of 25 mV to achieve a current density of 10 mA cm^-2 in 1.0 M KOH and show acceptable stability after 2000 potential cycles, which represents one of the best Ru-based electrocatalysts for hydrogen evolution. Mechanism analysis indicates that Cu incorporation can modify the electronic structure of Ru shell, thereby optimizing the energy barrier for water adsorption and dissociation processes or H adsorption/desorption. Cu doping paired with the defect-rich and highly open hollow structure of the NPs greatly enhances hydrogen evolution activity.