Complex Hollow Nanostructures: Synthesis and Energy-Related Applications

"Crystallinity Wave"-Driven Synthesis of Hollow Multi-Shell Covalent Organic Frameworks for Enhanced Supercapacitors

Hollow multi-shell covalent organic frameworks (COFs) with abundant modular interfaces, high loading capacity, and various microenvironments are expected to hold great potential for chemical separation, heterogeneous catalysis, and energy storage/conversion. However, the synthetic methodology of COF hollow multi-shell nanoarchitectures has not been established. Herein, we demonstrate an ingenious "crystallinity wave"-induced regional difference ripening strategy to synthesize a series of hollow multi-shell COF particles with controllable shell numbers and shell thickness. The methodology relies on the isolation effect of the local crystalline COF thin layer inserted between the two layers of amorphous covalent organic polymer by the short-time Ostwald ripening, so that different regions of the particles exhibit distinct reaction stages before reaching chemical equilibrium in the subsequent dynamic imine exchange reaction, and then regions that tend to hydrolyze dissolve during the complete ripening process to form a hollow multi-shell structure. Remarkably, this strategy can be extended to prepare other hollow multi-shell COFs by altering monomers. As a proof-of-concept application, the obtained hollow multi-shell COFs are used as the electrode materials for supercapacitor. Benefiting from the short mass transfer path of the hollow multi-shell structure, ordered channels of the COF, and their high surface area, the as-prepared particles exhibit remarkably enhanced specific capacitance.

Defect-rich Co,N-doped Ti3C2Tx/C/poly (3,4-ethylenedioxy thiophene) molecularly imprinted sensor for ultrasensitive electrochemical detection of gatifloxacin

The molecular imprinting electrochemical sensors (MIECS) currently face issues such as low sensitivity and stability to be improved. This study innovatively combines ZIF-67/Ti3C2Tx, treated at high temperature, with molecular imprinting technology to construct a MIECS with excellent stability and high sensitivity. First, size-controllable ZIF-67 was grown in situ on Ti3C2Tx, and after high-temperature treatment, Co,N-Ti3C2Tx/C was obtained. This was combined with proton-conductive poly(3,4-ethylenedioxythiophene) (PEDOT) to build the MIECS (Co,N-Ti3C2Tx/C/PEDOT/MIP/GCE). A series of structural characterization and electrochemical tests revealed that the synergistic effect of the abundant defect structures and the excellent proton conductivity of PEDOT significantly enhanced the electrochemical redox activity. The modified electrode demonstrated outstanding electrochemical performance, including an ultra-high electrochemical active surface area and selective recognition of gatifloxacin (GAT) through the imprinted cavities. Further investigation of the sensor's electrochemical detection performance for GAT showed that the fabricated sensor has high sensitivity, good stability, and excellent selectivity. Experimental results indicated that the sensor has a wide linear response range (0.005-50 μM), a low detection limit (2 nM), and test RSD values are all less than 5 % in honey, milk and lake water, and reliable recoveries were achieved in comparison with standard chromatographic methods. Highlight its potential for practical antibiotic monitoring applications.

Progress of 0D Biomass-Derived Porous Carbon Materials Produced by Hydrothermal Assisted Synthesis for Advanced Supercapacitors

Supercapacitors are garnering considerable interest owing to their high-power density, rapid charge-discharge capability, and long cycle life. Among the various materials explored, biomass-derived carbon nanomaterials stands out as a sustainable and cost-effective choice, thanks to its natural abundance and eco-friendly characteristics. This review delineates recent advances in the synthesis of zero-dimensional (0D) carbon nanomateirlas from various biomass precursors via hydrothermal assisted synthesis. It offers a comprehensive discussion on the factors affecting the synthesis of 0D carbon nanomaterials, including precursor type, concentration, reaction temperature, and time. Furthermore, the review underscores the impact of different activation methods on the morphology and electrochemical performance of 0D carbon nanomaterials. Finally, we outline the challenges and future prospects of utilizing biomass-derived carbon nanomaterials in supercapacitor applications, emphasizing the importance of optimizing synthesis parameters to attain the desired material properties.

Strengthened d-p orbital hybridization and hydrogen diffusion in a hollow N-doped porous carbon/Ru cluster catalyst system for hydrogen evolution reactions

Developing advanced catalysts with rapid hydrogen evolution reaction (HER) kinetics in alkaline media is vital for hydrogen production. Through the d-p orbital hybridization effect, the electronic structure and H* adsorption can be optimized on metal species. Herein, a N-doped hollow carbon (H-NPC)-supported Ru cluster (c-Ru@H-NPC) catalyst was constructed via carbonization of well-defined hollow metal-organic frameworks, followed by etching and anchoring of Ru clusters. The hollow structure could not alter the coordination number of Ru while exhibiting higher-level electron transfer, thereby strengthening the orbital hybridization. Additionally, finite element simulations indicated the acceleration of H2 diffusion for hollow structures. Furthermore, the N-doping strengthened the electron interaction of Ru-C by the d-p hybridization effect, which was confirmed by theoretical calculations and in situ Raman spectroscopy. Therefore, in alkaline/alkaline seawater media, c-Ru@H-NPC needed only 10/12 mV overpotentials and 1.52/1.55 V cell voltages to drive the HER and overall water splitting, respectively, at a current density of 10 mA cm-2, exhibiting outstanding catalytic activity. Meanwhile, the attenuation of current density was very small towards successive stability tests for >55 h at 10 mA cm-2. This work permits new insights into the design of high-performance metal cluster catalysts for the HER and other conversion reactions.

Pioneering Built-In Interfacial Electric Field for Enhanced Anion Exchange Membrane Water Electrolysis

As a half-reaction in anion exchange membrane water electrolysis (AEMWE) technology, the hydrogen evolution reaction (HER) at the cathode is severely hindered by the sluggish reaction kinetics involved in additional water dissociation step, which results in large overpotentials and low energy conversion efficiency. Here, we develop a nano-heterostructure composed of ultra-thin W5N4 shells over Ni3N nanoparticles (Ni3N@W5N4) as efficient catalysts, in which built-in interfacial electric field (BIEF) is created owing to the distinct lattice arrangements and work functions of biphasic metal nitrides. The BIEF facilitates the electron localization around the interface and enables high valence W and more exposed binding sites in the surface W5N4 shell for accelerating the water dissociation step, ultimately leading to a remarkable reduction in the energy barriers of RDS from 1.40 eV to 0.26 eV. Theoretical calculations and operando X-ray absorption spectroscopy analysis results demonstrated that surface W5N4 serves as the active species for HER. Moreover, the ultra-thin shell characteristics enable the optimized W5N4 with enhanced intrinsic catalytic activity to be fully exposed as active sites. Consequently, the Ni3N@W5N4 exhibits exceptional performance in alkaline HER (60 mV@10 mA cm-2) and remarkable long-term stability (500 mA cm-2 for 100 hours). When employed as the cathode in the AEMWE device, the synthesized Ni3N@W5N4 demonstrates stable performance for 90 hours at a current density of 1 A cm-2.

Fe/Fe3C particles encapsulated in hollow carbon nanoboxes for high performance zinc-air batteries

Zinc-air batteries are recognized for their environmental friendliness and high energy density; however, the slow kinetics of the oxygen reduction reaction (ORR) at the air electrode hinder their commercial viability. The research focuses on synthesizing cubic hollow carbon structures derived from Metal-Organic Frameworks (MOFs), which enhance catalytic performance through improved conductivity and mass transfer. The resulting Fe/Fe3C/HCNB catalyst demonstrates a half-wave potential of 0.826 V for ORR and achieves a peak power density of 274 mW cm-2 in zinc-air batteries, surpassing commercial Pt/C catalysts. Electrochemical impedance spectroscopy reveals that the hollow structure enhances hydrophilicity and reduces solution resistance, facilitating greater active site engagement in electrochemical reactions. The study concludes that the unique structural features of Fe/Fe3C/HCNB significantly improve discharge performance and stability, positioning it as a promising alternative for zinc-air battery applications.

Polythiophene-coated carbon nano boxes for efficient platinum-based catalysts for methanol electrooxidation

To improve the efficiency of the methanol oxidation reaction (MOR) in direct methanol fuel cells (DMFCs), it is essential to develop catalysts with high catalytic activity. However, constructing polyatomic doped carbon nanomaterials and understanding the interaction mechanisms between dopant elements remain significant challenges. In this study, we propose nitrogen-doped carbon nanobox (CNB) derived from Zeolitic Imidazolate Framework-67 (ZIF-67) crystals as precursors to serve as carriers for highly efficient platinum nanoparticles (Pt NPs). We synthesized platinum/poly(3,4-propylenedioxythiophene)/carbon nanobox (Pt/PProDOT/CNB) composites by wrapping CNB around PProDOT films via in situ oxidative polymerization. This unique structural design provides several advantages to the catalyst, including a large active surface area, numerous accessible electrocatalytic active centers, an optimized electronic structure, and good electronic conductivity. The Pt/PProDOT/CNB composites demonstrated excellent methanol oxidation performance, with a remarkable mass activity (MA) of 1639.9 mA mg-1Pt and a high electrochemical active surface area (ECSA) of 160.8 m2/g. Furthermore, the catalyst exhibited good CO resistance and outstanding durability.

Development of a Machine Learning Potential to Study the Structure and Thermodynamics of Nickel Nanoclusters

Machine learning (ML) potentials such as the Gaussian approximation potential (GAP) have demonstrated impressive capabilities in mapping structure to properties across diverse systems. Here, we introduce a GAP model for low-dimensional Ni nanoclusters and demonstrate its flexibility and effectiveness in capturing the energetics, structural diversity, and thermodynamic properties of Ni nanoclusters across a broad size range. Through a systematic approach encompassing model development, validation, and application, we evaluate the model's efficacy in representing energetics and configurational features in low-dimensional regimes while also examining its extrapolative nature to vastly different spatiotemporal regimes. Our analysis and discussion shed light on the data quality required to effectively train such models. Trajectories from large-scale MD simulations using the GAP model analyzed with data-driven models like graph neural networks reveal intriguing insights into the size-dependent phase behavior and thermomechanical stability characteristics of porous Ni nanoparticles. Overall, our work underscores the potential of ML models, which coupled with data-driven approaches serve as versatile tools for studying low-dimensional systems and complex material dynamics.

Unveiling the Dynamic Pathways of Metal-Organic Framework Crystallization and Nanoparticle Incorporation for Li-S Batteries

Metal-organic frameworks (MOFs) present diverse building blocks for high-performance materials across industries, yet their crystallization mechanisms remain incompletely understood due to gaps in nucleation and growth knowledge. In this study, MOF structural evolution is probed using in situ liquid phase transmission electron microscopy (TEM) and cryo-TEM, unveiling a blend of classical and nonclassical pathways involving liquid-liquid phase separation, particle attachment-coalescence, and surface layer deposition. Additionally, ultrafast high-temperature sintering (UHS) is employed to dope ultrasmall Cobalt nanoparticles (Co NPs) uniformly within nitrogen-doped hard carbon nanocages confirmed by 3D electron tomography. Lithium-sulfur battery tests demonstrate the nanocage-Co NP structure's exceptional capacity and cycling stability, attributed to Co NP catalytic effects due to its small size, uniform dispersion, and nanocage confinement. The findings propose a holistic framework for MOF crystallization understanding and Co NP tunability through ultrafast sintering, promising advancements in materials science and informing future MOF synthesis strategies and applications.

Hierarchical Ni3V2O8@N-Doped Carbon Hollow Double-Shell Microspheres for High-Performance Lithium-Ion Storage

Transition metal oxides (TMOs) are highly dense in energy and considered as promising anode materials for a new generation of alkaline ion batteries. However, their electrode structure is disrupted due to significant volume changes during charging and discharging, resulting in the short cycle life of batteries. In this paper, the hierarchical Ni3V2O8@N-doped carbon (Ni3V2O8@NC) hollow double-shell microspheres were prepared and used as electrode materials for lithium-ion batteries (LIBs). The utilization efficiency and ion transfer rate of Ni3V2O8 were improved by the hollow microsphere structure formed through nanoparticle self-assembly. Furthermore, the uniform N-doped carbon layer not only enhanced the structural stability of Ni3V2O8, but also improved the overall electrical conductivity of the composite. The Ni3V2O8@NC electrode has an initial discharge capacity of up to 1167.3 mAh g-1 at a current density of 0.3 A g-1, a reversible capacity of up to 726.5 mAh g-1 after 200 cycles, and still has a capacity of 567.6 mAh g-1 after 500 cycles at a current density of 1 A g-1, indicating that the material has good cycle stability and high-rate capability. This work presents new findings on the design and fabrication of complex porous double-shell nanostructures.

Colloidal Templating in Catalyst Design for Thermocatalysis

Conventional catalyst preparative methods commonly entail the impregnation, precipitation, and/or immobilization of nanoparticles on their supports. While convenient, such methods do not readily afford the ability to control collective ensemble-like nanoparticle properties, such as nanoparticle proximity, placement, and compartmentalization. In this Perspective, we illustrate how incorporating colloidal templating into catalyst design for thermocatalysis confers synthetic advantages to facilitate new catalytic investigations and augment catalytic performance, focusing on three colloid-templated catalyst structures: 3D macroporous structures, hierarchical macro-mesoporous structures, and discrete hollow nanoreactors. We outline how colloidal templating decouples the nanoparticle and support formation steps to devise modular catalyst platforms that can be flexibly tuned at different length scales. Of particular interest is the raspberry colloid templating (RCT) method which confers high thermomechanical stability by partially embedding nanoparticles within its support, while retaining high levels of reactant accessibility. We illustrate how the high modularity of the RCT approach allows one to independently control collective nanoparticle properties, such as nanoparticle proximity and localization, without concomitant changes to other catalytic descriptors that would otherwise confound analyses of their catalytic performance. We next discuss how colloidal templating can be employed to achieve spatially disparate active site functionalization while directing reactant transport within the catalyst structure to enhance selectivity in multistep catalytic cascades. Throughout this Perspective, we highlight developments in advanced characterization that interrogate transport phenomena and/or derive new insights into these catalyst structures. Finally, we offer our outlook on the future roles, applications, and challenges of colloidal templating in catalyst design for thermocatalysis.

Hf-Doped CoP Hollow Nanocubes as High-Performance Electrocatalyst for Oxygen Evolution Reaction

Designing and synthesizing hollow frame structures with unique three-dimensional open structures in electrocatalysis remain a challenge. Etching is an effective method to synthesize metal-organic frameworks (MOFs) with a hollow structure and rich function. Herein, we report the design and synthesis of Hf-doped CoP hollow nanocubes by selective etching and ion exchange. Different from the traditional etching method, we used acid xylenol orange solution to etch typically the (211) crystal face of ZIF-67, obtaining the unique bell-like structure, named XO-ZIF-67. Subsequently, Hf-doped CoP hollow nanocubes were formed by Hf4+ doping and simple phosphating treatment. Electrochemical tests showed that the overpotential of the obtained catalyst is only 291 mV at the current density of 10 mA cm-2 when applied in catalyzing the oxygen evolution reaction (OER). Furthermore, the catalyst shows excellent stability when running in 1 M KOH solution for 25 h.

Revealing the Dynamic Lithiation Process of Copper Disulfide by in Situ TEM

Transition metal oxides, fluorides, and sulfides are extensively studied as candidate electrode materials for lithium-ion batteries driven by the urgency of developing next-generation higher energy density lithium batteries. These conversion-type electrode materials often require nanosized active materials to enable a "smooth" lithiation and de-lithiation process during charge/discharge cycles, determined by their size, structure, and phase. Herein, the structural and chemical changes of Copper Disulfide (CuS2) hollow nanoparticles during the lithiation process through an in situ transmission electron microscopy (TEM) method are investigated. The study finds the hollow structure of CuS2 facilitates the quick formation of fluidic Li2S "drops," accompanied by a de-sulfurization to the Cu7S4 phase. Meanwhile, the metallic Cu phase emerges as fine nanoparticles and grows into nano-strips, which are embedded in the Li2S/Cu7S4 matrix. These complex nanostructured phases and their spatial distribution can lead to a low de-lithiation barrier, enabling fast reaction kinetics.

Unveiling Confinement Engineering for Achieving High-Performance Rechargeable Batteries

The confinement effect, restricting materials within nano/sub-nano spaces, has emerged as an innovative approach for fundamental research in diverse application fields, including chemical engineering, membrane separation, and catalysis. This confinement principle recently presents fresh perspectives on addressing critical challenges in rechargeable batteries. Within spatial confinement, novel microstructures and physiochemical properties have been raised to promote the battery performance. Nevertheless, few clear definitions and specific reviews are available to offer a comprehensive understanding and guide for utilizing the confinement effect in batteries. This review aims to fill this gap by primarily summarizing the categorization of confinement effects across various scales and dimensions within battery systems. Subsequently, the strategic design of confinement environments is proposed to address existing challenges in rechargeable batteries. These solutions involve the manipulation of the physicochemical properties of electrolytes, the regulation of electrochemical activity, and stability of electrodes, and insights into ion transfer mechanisms. Furthermore, specific perspectives are provided to deepen the foundational understanding of the confinement effect for achieving high-performance rechargeable batteries. Overall, this review emphasizes the transformative potential of confinement effects in tailoring the microstructure and physiochemical properties of electrode materials, highlighting their crucial role in designing novel energy storage devices.

An integrated smartphone-based electrochemical detection system for highly sensitive and on-site detection of chemical oxygen demand by copper-cobalt bimetallic oxide-modified electrode

A portable and integrated electrochemical detection system has been constructed for on-site and real-time detection of chemical oxygen demand (COD). The system mainly consists of four parts: (i) sensing electrode with a copper-cobalt bimetallic oxide (CuCoOx)-modified screen-printed electrode; (ii) an integrated electrochemical detector for the conversion, amplification, and transmission of weak signals; (iii) a smartphone installed with a self-developed Android application (APP) for issuing commands, receiving, and displaying detection results; and (iv) a 3D-printed microfluidic cell for the continuous input of water samples. Benefiting from the superior catalytic capability of CuCoOx, the developed system shows a high detection sensitivity with 0.335 μA/(mg/L) and a low detection limit of 5.957 mg/L for COD determination and possessing high anti-interference ability to chloride ions. Moreover, this system presents good consistency with the traditional dichromate method in COD detection of actual water samples. Due to the advantages of cost effectiveness, portability, and point-of-care testing, the system shows great potential for water quality monitoring, especially in resource-limited remote areas.

Stable Structure and Fast Ion Diffusion: A Flexible MoO2@Carbon Hollow Nanofiber Film as a Binder-Free Anode for Sodium-Ion Batteries with Superior Kinetics and Excellent Rate Capability

Designing innovative anode materials that exhibit excellent ion diffusion kinetics, enhanced structural stability, and superior electrical conductivity is imperative for advancing the rapid charge-discharge performance and widespread application of sodium-ion batteries. Hollow-structured materials have received significant attention in electrode design due to their rapid ion diffusion kinetics. Building upon this, we present a high-performance, free-standing MoO2@hollow carbon nanofiber (MoO2@HCNF) electrode, fabricated through facile coaxial electrospinning and subsequent heat treatment. In comparison to MoO2@carbon nanofibers (MoO2@CNFs), the MoO2@HCNF electrode demonstrates superior rate capability, attributed to its larger specific surface area, its higher pseudocapacitance contribution, and the enhanced diffusion kinetics of sodium ions. The discharge capacities of the MoO2@HCNF (MoO2@CNF) electrode at current densities of 0.1, 0.2, 0.5, 1.0, 2.0 and 5.0 A g-1 are 195.55 (155.49), 180.98 (135.20), 163.81 (109.71), 144.05 (90.46), 121.16 (71.21) and 88.90 (44.68) mAh g-1, respectively. Additionally, the diffusion coefficients of sodium ions in the MoO2@HCNFs are 8.74 × 10-12 to 1.37 × 10-12 cm2 s-1, which surpass those of the MoO2@CNFs (6.49 × 10-12 to 9.30 × 10-13 cm2 s-1) during the discharging process. In addition, these prepared electrode materials exhibit outstanding flexibility, which is crucial to the power storage industry and smart wearable devices.

Confined Synthesis of Dual-Atoms Within Pores of Covalent Organic Frameworks for Oxygen Reduction Reaction

Dual-atom catalysts exhibit higher reactivity and selectivity than the single-atom catalysts. The pyrolysis of bimetal salt precursors is the most typical method for synthesizing dual-atomic catalysts; however, the finiteness of bimetal salts limits the variety of dual-atomic catalysts. In this study, a confined synthesis strategy for synthesizing dual-atomic catalysts is developed. Owing to the in situ synthesis of zeolitic imidazolate frameworks in the pores of covalent organic frameworks (COFs), the migration and aggregation of metal atoms are suppressed adequately during the pyrolysis process. The resultant catalyst contains abundant Zn─Co dual atomic sites with 2.8 wt.% Zn and 0.5 wt.% Co. The catalyst exhibits high reactivity toward oxygen reduction reaction with a half-wave potential of 0.86 V, which is superior to that of the commercial Pt/C catalyst. Theoretical calculations reveal that the Zn atoms in the Zn─Co dual atomic sites promote the formation of intermediate OOH*, and thus contribute to high catalytic performance. This study provides new insights into the design of dual-atom catalysts using COFs.

Nanosized Prussian blue and its analogs for bioimaging and cancer theranostics

Prussian blue (PB) nanoparticles (NPs) and Prussian blue analogs (PBAs) can form metal-organic frameworks through the programmable coordination of ferrous ions with cyanide. PB and PBAs represent a burgeoning class of hybrid functional nano-systems with a wide-ranging application spectrum encompassing biomedicine, cancer diagnosis, and therapy. A comprehensive overview of recent advancements is crucial for gaining insights for future research. In this context, we reviewed the synthesis techniques and surface modification strategies employed to tailor the dimensions, morphology, and attributes of PB NPs. Subsequently, we explored advanced biomedical utilities of PB NPs, encompassing photoacoustic imaging, magnetic resonance imaging, ultrasound (US) imaging, and multimodal imaging. In particular, the application of PB NPs-mediated photothermal therapy, photodynamic therapy, and chemodynamic therapy to cancer treatment was reviewed. Based on the literature, we envision an evolving trajectory wherein the future of Prussian blue-driven biological applications converge into an integrated theranostic platform, seamlessly amalgamating bioimaging and cancer therapy. STATEMENT OF SIGNIFICANCE: Prussian blue, an FDA-approved coordinative pigment with a centuries-long legacy, has paved the way for Prussian blue nanoparticles (PB NPs), renowned for their remarkable biocompatibility and biosafety. These PB NPs have found their niche in biomedicine, playing crucial roles in both diagnostics and therapeutic applications. The comprehensive review goes beyond PB NP-based cancer therapy. Alongside in-depth coverage of PB NP synthesis and surface modifications, the review delves into their cutting-edge applications in the realm of biomedical imaging, encompassing techniques such as photoacoustic imaging, magnetic resonance imaging, ultrasound imaging, and multimodal imaging.

Boosted hydrogen evolution kinetics of heteroatom-doped carbons with isolated Zn as an accelerant

Carbon-based single-atom catalysts, a promising candidate in electrocatalysis, offer insights into electron-donating effects of metal center on adjacent atoms. Herein, we present a practical strategy to rationally design a model catalyst with a single zinc (Zn) atom coordinated with nitrogen and sulfur atoms in a multilevel carbon matrix. The Zn site exhibits an atomic interface configuration of ZnN4S1, where Zn's electron injection effect enables thermal-neutral hydrogen adsorption on neighboring atoms, pushing the activity boundaries of carbon electrocatalysts toward electrochemical hydrogen evolution to an unprecedented level. Experimental and theoretical analyses confirm the low-barrier Volmer-Tafel mechanism of proton reduction, while the multishell hollow structures facilitate the hydrogen evolution even at high current intensities. This work provides insights for understanding the actual active species during hydrogen evolution reaction and paves the way for designing high-performance electrocatalysts.

Integrated PtxCoy-Hierarchical Carbon Matrix Electrocatalyst for Efficient Hydrogen Evolution Reaction

Pt-based catalysts are regarded as state-of-the-art electrocatalysts for producing clean hydrogen energy; however, their wide application is restricted by their low abundance, high cost, and poor stability. Herein, we report an integrated PtxCoy-hierarchical carbon matrix electrocatalyst (Pt/Co@NCNTs, Pt3Co@NCNTs, PtCo@NCNTs, and PtCo3@NCNTs) that is developed using a thermally driven Co migration strategy forming alloy nanoparticles to achieve efficient hydrogen evolution reaction (HER). Benefiting from its electronic regulation effect and unique hierarchical hollow structure, the Pt3Co@NCNTs catalyst loaded with 11.5 wt % Pt exhibits superior catalytic performance and durability for HER compared with commercial 20 wt % Pt/C. Under both alkaline and acidic conditions, Pt3Co@NCNTs exhibits excellent HER activity with overpotentials of 21 and 45 mV at 10 mA cm-2, respectively. Density functional theory (DFT) results further verify that the interaction between Pt and Co in Pt3Co@NCNTs can modulate electronic rearrangement, optimize the d-band center, and accelerate water dissociation and *H desorption, thereby enhancing HER activity.

Rational Design of Hollow Structural Materials for Sodium-Ion Battery Anodes

The development of sodium-ion battery (SIB) anodes is still hindered by their rapid capacity decay and poor rate capabilities. Although there have been some new materials that can be used to fabricate stable anodes, SIBs are still far from wide applications. Strategies like nanostructure construction and material modification have been used to prepare more robust SIB anodes. Among all the design strategies, the hollow structure design is a promising method in the development of advanced anode materials. In the past decade, research efforts have been devoted to modifying the synthetic route, the type of templates, and the interior structure of hollow structures with high capacity and stability. A brief introduction is made to the main material systems and classifications of hollow structural materials first. Then different morphologies of hollow structural materials for SIB anodes from the latest reports are discussed, including nanoboxes, nanospheres, yolk shells, nanotubes, and other more complex shapes. The most used templates for the synthesis of hollow structrual materials are covered and the perspectives are highlighted at the end. This review offers a comprehensive discussion of the synthesis of hollow structural materials for SIB anodes, which could be potentially of use to research areas involving hollow materials design for batteries.

Rational design of one-dimensional skin-core multilayer structure for electrospun carbon nanofibers with bicontinuous electron/ion transport toward high-performance supercapacitors

The fast transport of electrons and ions within electrodes is crucial to the final electrochemical properties. Herein, we have developed a unique ultra-long one-dimensional (1D) skin-core multilayer structure based on electrospun carbon nanofibers mainly through a facile Stöber method combined with resorcinol-formaldehyde resin, which not only achieves bicontinuous electron/ion transport during the charge/discharge process, but also provides large surface area for ion adsorption. Particularly, controlling the number of active layers as well as regulating the active sites in layer both can obviously improve capacitive properties. Benefiting from the synergistic effects of the desirable architecture, such the rational-designed skin-core structural carbon nanofibers as supercapacitor electrode can deliver a high specific capacitance up to 255 F g-1 at 0.5 A g-1, favorable rate capability with 89% capacitance retention of initial capacitance at 8 A g-1, and excellent cycling stability with nearly 93% capacity retention after 10,000 cycles at 2 A g-1. Furthermore, the as-assembled symmetric supercapacitor devices also present a maximum energy density of 8.77 Wh kg-1 at 0.25 kW kg-1 and a maximum power density of 3.70 kW kg-1 at 6.74 Wh kg-1. Such skin-core carbon nanofibers provide an effective strategy to design high-performance supercapacitor electrode for the next-generation energy storage devices.

Flexible ultrathin Nitrogen-Doped carbon mediates the surface charge redistribution of a hierarchical tin disulfide nanoflake electrode for efficient capacitive deionization

Constructing pseudocapacitive electrodes with high specific capacities is indispensable for increasing the large-scale application of capacitive deionization (CDI). However, the insufficient CDI rate and cycling performance of pseudocapacitive-based electrodes have led to a decline in their use due to the corresponding volumetric expansion and contraction that occurs during long-term CDI processes. Herein, hierarchical porous SnS2 nanoflakes are encapsulated inside an N-doped carbon (NC) matrix to achieve efficient CDI. Benefiting from the synergistic properties of the pseudocapacitive SnS2 nanoflakes and few-layered N-doped carbon, the heterogeneous interface simultaneously provides more available vigorous sites and demonstrates rapid charge-transfer kinetics, resulting in a superior desalination capability (49.86 mg g-1 at 1.2 V), rapid desalination rate (1.66 mg g-1 min-1) and better cyclic stability. Computational research reveals a work function-induced surface charge redistribution of the SnS2@NC heterojunction, which can lead to an auspicious surface electronic structure that reduces the adsorption energy to improve the diffusion kinetics toward sodium adsorption. This work contributes to providing a thoughtful understanding of the interface engineering between transition metal dichalcogenides and NC to construct high-performance CDI electrode materials for further industrialization.

Periodic arrays of structurally complex oxide nanoshells and their use as substrate-confined nanoreactors

Sacrificial templates present an effective pathway for gaining high-level control over nanoscale reaction products. Atomic layer deposition (ALD) is ideally suited for such approaches due to its ability to replicate the surface topography of a template material through the deposition of an ultrathin conformal layer. Herein, metal nanostructures are demonstrated as sacrificial templates for the formation of architecturally complex and deterministically positioned oxide nanoshells, open-topped nanobowls, vertically standing half-shells, and nanorings. The three-step process sees metal nanocrystals formed in periodic arrays, coated with an ALD-deposited oxide, and hollowed out with a selective etch through nanopores formed in the oxide shell. The procedure is further augmented through the use of a directional ion beam that is used to sculpt the oxide shells into bowl- and ring-like configurations. The functionality of the so-formed materials is demonstrated through their use as substrate-confined nanoreactors able to promote the growth and confinement of nanomaterials. Taken together, the work expands the design space for substrate-based nanomaterials, creates a platform for advancing functional surfaces and devices and, from a broader perspective, advances the use of ALD in forming complex nanomaterials.

Advancements and Prospects of Graphite Anode for Potassium-Ion Batteries

Potassium-ion batteries (KIBs) have recently attracted considerable attention owing to their resource abundance, low cost and environmental friendliness. Graphite as a mature commercial anode material for lithium-ion batteries, has been proved as a promising anode candidate for KIBs by reversible forming potassium-graphite intercalation compounds. However, large volume expansion and sluggish K+ kinetics caused by the incompatibility between large radius of K+ and the small interlayer spacing of graphite, result in the poor cycle stability and rate performances, hindering its practical application. Extensive research efforts have focused on improving the potassium storage performance of graphite anodes. This review provides an overview of recent advances in addressing these challenges and optimizing the electrochemical performance of graphite anodes for KIBs. Various strategies to improve the electrochemical performance of graphite and graphitic carbon anodes, such as microcrystalline regulation, heteroatom doping, morphological adjustment, and coating modification, are discussed, while the critical issues and challenges associated with graphite anodes and the prospects for their advancement in KIBs are highlighted. The review offers valuable guidelines for rational structural design and promotes the commercial development of high-performance graphite anode materials for KIBs.

Tandem-biocatalysis reactors constructed by topological evolution of CaCO3 particles into hollow metal hydroxide spheres

Despite remarkable advances in the design and synthesis of hollow inorganic spheres (HISs), the harsh synthetic conditions have precluded the applications of HISs to biochemical and biological fields. Herein we report a biocompatible strategy for synthesizing metal hydroxide HISs (MH-HISs) by simply mixing CaCO3 particles with metal ions in water. The ion-exchange reaction between Ca2+ and metal ions leads to the structural and chemical evolution from solid CaCO3 particles to hollow MH-HISs via core-shell and yolk-shell structures, while enabling the encapsulation of enzymes to the shells without loss of catalytic activities. The biocompatible protocol makes multienzymatic cascade reactions achievable, with great recyclability due to mechanical durability of MH-HISs.

Molecular Diffusion in Nanoreactors' Pore Channel System: Measurement Techniques, Structural Regulation, and Catalytic Effects

Nanoreactors, as a new class of materials with highly enriched and ordered pore channel structures, can achieve special catalytic effects by precisely identifying and controlling the molecular diffusion behavior within the ordered pore channel system. Nanoreactors-driven molecular diffusion within the ordered pore channels can be highly dependent on the local microenvironment in the nanoreactors' pore channel system. Although the diffusion process of molecules within the ordered pore channels of nanoreactors is crucial for the regulation of catalytic behaviors, it has not yet been as clearly elucidated as it deserves to be in this study. In this review, fundamental theory and measurement techniques for molecular diffusion in the pore channel system of nanoreactors are presented, structural regulation strategies of pore channel parameters for controlling molecular diffusion are discussed, and the effects of molecular diffusion in the pore channel system on catalytic reactivity and selectivity are further analyzed. This article attempts to further develop the underlying theory of molecular diffusion within the theoretical framework of nanoreactor-driven catalysis, and the proposed perspectives may contribute to the rational design of advanced catalytic materials and the precise control of complex catalytic kinetics.

Understanding ZIF particle chemical etching dynamics and morphology manipulation: in situ liquid phase electron microscopy and 3D electron tomography application

In situ liquid phase transmission electron microscopy (TEM) and three-dimensional electron tomography are powerful tools for investigating the growth mechanism of MOFs and understanding the factors that influence their particle morphology. However, their combined application to the study of MOF etching dynamics is limited due to the challenges of the technique such as sample preparation, limited field of view, low electron density, and data analysis complexity. In this research, we present a study employing in situ liquid phase TEM to investigate the etching mechanism of colloidal zeolitic imidazolate framework (ZIF) nanoparticles. The etching process involves two distinct stages, resulting in the development of porous structures as well as partially and fully hollow morphologies. The etching process is induced by exposure to an acid solution, and both in situ and ex situ experiments demonstrate that the outer layer etches faster leading to overall volume shrinking (stage I) while the inner layer etches faster giving a hollow morphology (stage II), although both the outer layer and inner layer have been etched in the whole process. 3D electron tomography was used to quantify the properties of the hollow structures which show that the ZIF-67 crystal etching rate is larger than that of the ZIF-8 crystal at the same pH value. This study provides valuable insights into MOF particle morphology control and can lead to the development of novel MOF-based materials with tailored properties for various applications.

Fabrication of dual heteroatom-doped graphitic carbon from waste sponge with "killing two birds with one stone" strategy for advanced aqueous zinc-ion hybrid capacitors

Emerging aqueous zinc-ion hybrid capacitors (AZICs) are considered a promising energy storage because of their superior electrochemical performance. The pore structure, suitable heteroatom content, and graphitization degree (GD) of carbon-based cathodes significantly influence the electrochemical performance of AZICs. The N, S dual-doped porous graphitic carbon materials (LC-750) with the combined characteristics of high GD (1.11) and large specific surface area (1678.38 m² g^-1) are successfully developed by a facile "killing two birds with one stone" strategy using K₃Fe(C₂O₄)₃·3H₂O as the activating and graphitizing agent, and waste sponge (WS) and coal tar pitch (CTP) as the heteroatom and carbon resource, respectively. Results show that the LC-750 cathode displays high capacities of 185.3 and 95.2 mAh g^-1 at 0.2 and 10 A g^-1. Specifically, the assembled LC-750//Zn capacitor can offer a maximal energy density of 119.5 Wh kg^-1, a power density of 20.3 kW kg^-1, and a capacity retention of 87.8% after 15,000 cycles at 10 A g^-1. Density functional theory simulations demonstrate that N and S dual-doping can promote the adsorption kinetics of Zn ions. This design strategy is a feasible and cost-effective method for the preparation of dual heteroatom-doped graphitic carbon electrodes, which enables recycling of WS and CTP into high-valued products.

Synthesis and Nanostructure Investigation of Hybrid β-Ga2 O3 /ZnGa2 O4 Nanocomposite Networks with Narrow-Band Green Luminescence and High Initial Electrochemical Capacity

The material design of functional "aero"-networks offers a facile approach to optical, catalytical, or and electrochemical applications based on multiscale morphologies, high large reactive area, and prominent material diversity. Here in this paper, the synthesis and structural characterization of a hybrid β-Ga₂ O₃ /ZnGa₂ O₄ nanocomposite aero-network are presented. The nanocomposite networks are studied on multiscale with respect to their micro- and nanostructure by X-ray diffraction (XRD) and transmission electron microscopy (TEM) and are characterized for their photoluminescent response to UV light excitation and their electrochemical performance with Li-ion conversion reaction. The structural investigations reveal the simultaneous transformation of the precursor aero-GaN(ZnO) network into hollow architectures composed of β-Ga₂ O₃ and ZnGa₂ O₄ nanocrystals with a phase ratio of ≈1:2. The photoluminescence of hybrid aero-β-Ga₂ O₃ /ZnGa₂ O₄ nanocomposite networks demonstrates narrow band (λ_em  = 504 nm) green light emission of ZnGa₂ O₄ under UV light excitation (λ_ex  = 300 nm). The evaluation of the metal-oxide network performance for electrochemical application for Li-ion batteries shows high initial capacities of ≈714 mAh g^-1 at 100 mA g^-1 paired with exceptional rate performance even at high current densities of 4 A g^-1 with 347 mAh g^-1 . This study provides is an exciting showcase example of novel networked materials and demonstrates the opportunities of tailored micro-/nanostructures for diverse applications a diversity of possible applications.

Structure and oxygen vacancy engineered CuCo-layered double oxide nanotube arrays as advanced bifunctional electrocatalysts for overall water splitting

In recent years, as a green renewable energy production technology, electrochemical water splitting has demonstrated high development potential. Many materials have been reported as successful catalysts in the water-splitting field. However, it is still a huge challenge to produce bifunctional electrocatalysts for the efficient and sustainable generation of hydrogen and oxygen simultaneously. Herein, we successfully developed oxygen vacancies abundant CuCo layered double oxide (O_v-CuCo-LDO) hollow nanotube arrays (HNTAs) loaded on nickel foam as advanced electrocatalysts for total water splitting. When the current density was 10 mA cm^-2, the O_v-CuCo-LDO HNTAs exhibited outstanding onset overpotentials of 53.9 and 72.5 mV for the hydrogen evolution and oxygen evolution reactions (HER and OER) in alkaline medium, respectively, because of the bimetallic synergistic effect between the cobalt and copper and the unique hollow porous structure. In addition, an as-assembled O_v-CuCo-LDO||O_v-CuCo-LDO electrolytic cell showed a small potential of 1.55 V to deliver a current density of 10 mA cm^-2. Moreover, it also showed remarkable durability after long-term overall water splitting for more than 20 h. The research results in this paper are of great interest to practical applications of the water decomposition process, providing clear and in-depth insights into preliminary robust and efficient multifunctional electrocatalysts for overall water splitting.

Stepwise Monomicelle Assembly for Highly Ordered Mesoporous TiO2 Membranes with Precisely Tailored Mesophase and Porosity

Mesoporous materials with crystalline frameworks have been acknowledged as very attractive materials in various applications. Nevertheless, due to the cracking issue during crystallization and incompatible hydrolysis and assembly, the precise control for crystalline mesoscale membranes is quite infertile. Herein, we presented an ingenious stepwise monomicelle assembly route for the syntheses of highly ordered mesoporous crystalline TiO₂ membranes with delicately controlled mesophase, mesoporosity, and thickness. Such a process involves the preparation of monomicelle hydrogels and follows self-assembly by stepwise solvent evaporation, which enables the sensitive hydrolysis of TiO₂ oligomers and dilatory micelle assembly to be united. In consequence, the fabricated mesoporous TiO₂ membranes exhibit a broad flexibility, including tunable ordered mesophases (worm-like, hexagonal p6mm to body-centered cubic Im3̅m), controlled mesopore sizes (3.0-8.0 nm), and anatase grain sizes (2.3-8.4 nm). Besides, such mesostructured crystalline TiO₂ membranes can be extended to diverse substrates (Ti, Ag, Si, FTO) with tailored thickness. The great mesoporosity of the in situ fabricated mesoscopic membranes also affords excellent pseudocapacitive behavior for sodium ion storage. This study underscores a novel pathway for balancing the interaction of precursors and micelles, which could have implications for synthesizing crystalline mesostructures in higher controllability.

A corpus of CO2 electrocatalytic reduction process extracted from the scientific literature

The electrocatalytic CO₂ reduction process has gained enormous attention for both environmental protection and chemicals production. Thereinto, the design of new electrocatalysts with high activity and selectivity can draw inspiration from the abundant scientific literature. An annotated and verified corpus made from massive literature can assist the development of natural language processing (NLP) models, which can offer insight to help guide the understanding of these underlying mechanisms. To facilitate data mining in this direction, we present a benchmark corpus of 6,086 records manually extracted from 835 electrocatalytic publications, along with an extended corpus with 145,179 records in this article. In this corpus, nine types of knowledge such as material, regulation method, product, faradaic efficiency, cell setup, electrolyte, synthesis method, current density, and voltage are provided by either annotating or extracting. Machine learning algorithms can be applied to the corpus to help scientists find new and effective electrocatalysts. Furthermore, researchers familiar with NLP can use this corpus to design domain-specific named entity recognition (NER) models.

Bowl-Shaped Bispyrrole-Fused Perylene-diimide and Its Anions

Incorporating two pyrrole subunits at the bay positions of perylene-diimide has been a long-pursued goal since 2009, but it has not been achieved due to high strain. Herein, via one step Buchwald-Hartwig reaction, PDI-2N was successfully generated with a bowl depth of 1.52 Å. Though with electron-rich pyrrole embedding, PDI-2N's radical anion and dianion were facilely prepared and were investigated both experimentally and theoretically. Moreover, PDI-2N crystallized in different manners under distinct conditions, and it formed tubular crystals with infinite two-directional columnar stacking under DMF conditions. This finding develops a dream bowl-shaped PDI derivative that holds great promise in organoelectronics.

Morphology Engineering in Multicomponent Hollow Metal Chalcogenide Nanoparticles

Hollow metal chalcogenide nanoparticles are widely applicable in environmental and energy-related processes. Herein, we synthesized such particles with large compositional and morphological diversity by combining scanning probe block copolymer lithography with a Kirkendall effect-based sulfidation process. We explored the influence of temperature-dependent diffusion kinetics, elemental composition and miscibility, and phase boundaries on the resulting particle morphologies. Specifically, CoNi alloys form single-shell sulfides for the synthetic conditions explored because Co and Ni exhibit similar diffusion rates, while CuNi alloys form sulfides with various types of morphologies (yolk-shell, double-shell, and single-shell) because Cu and Ni have different diffusion rates. In contrast, Co-Cu heterodimers form hollow heterostructured sulfides with varying void numbers and locations depending on synthesis temperature and phase boundary. At higher temperatures, the increased miscibility of CoS₂ and CuS makes it energetically favorable for the heterostructure to adopt a single alloy shell morphology, which is rationalized using density functional theory-based calculations.

Kinetics Driven by Hollow Nanoreactors: An Opportunity for Controllable Catalysis

As a novel class of catalytic materials, hollow nanoreactors offer new opportunities for improving catalytic performance owing to their higher controllability on molecular kinetic behavior. Nevertheless, to achieve controllable catalysis with specific purposes, the catalytic mechanism occurring inside hollow nanoreactors remains to be further understood. In this context, this Review presents a focused discussion about the basic concept of hollow nanoreactors, the underlying theory for hollow nanoreactor-driven kinetics, and the intrinsic correlation between key structural parameters of hollow nanoreactors and molecular kinetic behaviors. We aim to provide in-depth insights into understanding kinetics occurred within typical hollow nanoreactors. The perspectives proposed in this paper may contribute to the development of the fundamental theoretical framework of hollow nanoreactor-driven catalysis.

Metal-organic frameworks and their derivatives for metal-ion (Li, Na, K and Zn) hybrid capacitors

Metal-ion hybrid capacitors (MIHCs) hold particular promise for next-generation energy storage technologies, which bridge the gap between the high energy density of conventional batteries and the high power density and long lifespan of supercapacitors (SCs). However, the achieved electrochemical performance of available MIHCs is still far from practical requirements. This is primarily attributed to the mismatch in capacity and reaction kinetics between the cathode and anode. In this regard, metal-organic frameworks (MOFs) and their derivatives offer great opportunities for high-performance MIHCs due to their high specific surface area, high porosity, topological diversity, and designable functional sites. In this review, instead of simply enumerating, we critically summarize the recent progress of MOFs and their derivatives in MIHCs (Li, Na, K, and Zn), while emphasizing the relationship between the structure/composition and electrochemical performance. In addition, existing issues and some representative design strategies are highlighted to inspire breaking through existing limitations. Finally, a brief conclusion and outlook are presented, along with current challenges and future opportunities for MOFs and their derivatives in MIHCs.

Mechanisms for self-templating design of micro/nanostructures toward efficient energy storage

The ever-growing demand in modern power systems calls for the innovation in electrochemical energy storage devices so as to achieve both supercapacitor-like high power density and battery-like high energy density. Rational design of the micro/nanostructures of energy storage materials offers a pathway to finely tailor their electrochemical properties thereby enabling significant improvements in device performances and enormous strategies have been developed for synthesizing hierarchically structured active materials. Among all strategies, the direct conversion of precursor templates into target micro/nanostructures through physical and/or chemical processes is facile, controllable, and scalable. Yet the mechanistic understanding of the self-templating method is lacking and the synthetic versatility for constructing complex architectures is inadequately demonstrated. This review starts with the introduction of five main self-templating synthetic mechanisms and the corresponding constructed hierarchical micro/nanostructures. Subsequently, the structural merits provided by the well-defined architectures for energy storage are elaborately discussed. At last, a summary of current challenges and future development of the self-templating method for synthesizing high-performance electrode materials is also presented.

Construction of Bimetallic Metal-Organic Frameworks with the Nanosheet-Assembled Hierarchical Hollow Structure for CO2 Fixation

Incorporating secondary metal nodes with functionality into organic ligand nodes to form a bimetallic metal-organic frameworks (MOFs) would facilitate an enhancement in properties and broaden applied areas of MOFs. Hierarchical tubular Cu/Zn-MOF-74 assembled by nanosheet arrays is synthesized at ambient temperature and pressure by phase transformation of Cu-based precursor MOF in immersion solution with Zn²⁺. The content of Zn in Cu/Zn-MOF-74 can be controlled by adjusting the concentration of Zn²⁺ in immersion solution, and it can reach a maximum of 36.4%. Moreover, the catalytic activity toward cycloaddition of CO₂ with styrene oxide of Cu/Zn-MOF-74 is improved significantly compared with that of monometallic Cu-MOF-74. Meanwhile, the advanced hierarchical tubular structure contributing to enhancement in catalytic activity enables Cu/Zn-MOF-74 to present higher conversion toward this cycloaddition of CO₂ than traditional rod-like Cu/Zn-MOF-74. This templated synthesis would provide an opportunity for designing various bimetallic MOFs or MOF-based compounds with improved performances in multiple applications.

In-Built Fabrication of MOF Assimilated Porous Hollow Carbon from Pre-Hydrolysate for Supercapacitor

With the fast consumption of traditional fossil fuels and the urgent requirement for a low-carbon economy and sustainable development, supercapacitors are gaining more and more attention as a clean energy storage and conversion device. The research on electrode materials for supercapacitors has become a hot topic nowadays. An electrode material for a supercapacitor, comprising the ZIF-67 in-built carbon-based material, was prepared from a biomass pre-hydrolysate via a hydrothermal process. As a by-product of dissolving slurry, the pre-hydrolysate is rich in carbon, which is an excellent biomass resource. The utilization of pre-hydrolysate to prepare carbon energy materials could realize the high value utilization of pre-hydrolysate and the efficient energy conversion of biomass. Meanwhile, the cobalt-based MOF (such as ZIF-67), as a porous crystalline material, has the advantages of having a regular order, high specific surface area and controllable pore size, as well as good thermal and chemical stability. The addition of ZIF-67 modified the morphology and pore structure of the carbon, and the obtained samples showed outstanding electrochemical performance. One- and two-step synthetic processes generated specimens with a coral-like cross-linked structure and a new type of rough, hollow, dandelion-like structure, respectively, and the pore size was in the range of 2.0–5.0 nm, which is conducive to ion transport and charge transfer. In C2-ZIF-67, the hollow structures could effectively prevent the accumulation of the electrochemical active center, which could provide enough space for the shrinkage and expansion of particles to protect them from the interference of electrolytes and the formation of solid electrolyte interphase film layers. Additionally, the plush tentacle structure with low density and a large specific surface area could expose more active sites and a large electrolyte electrode contact area, and short electron and charge transport paths. Importantly, active, free electrons of small amounts of Co-MOF (1 wt%) could be stored and released through the redox reaction, further improving the electrical conductivity of Carbon-ZIF-67 materials in this work. Consequently, C2-ZIF-67 exhibited superior specific capacitance (400 F g⁻¹, at 0.5 A g⁻¹) and stability (90%, after 10,000 cycles).

Effects of ultrafiltration on Co-Metal Organic Framework/pre-hydrolysis solution carbon materials for supercapacitor energy storage

Here, a Co-Metal Organic Framework/pre-hydrolysis (Co-MOF/pre-hydrolysis) solution carbon material is prepared by a mild and environmentally-friendly hydrothermal carbonization technique using a pulping pre-hydrolysis solution as the raw material and Co-MOF as the metal dopant. The stable hollow structure provide sufficient space for particle shrinkage and expansion, while the low density and large specific surface area of the long, hairy tentacle structure provide a greater contact area for ions, which shorten the transmission path of electrons and charges. The materials exhibit excellent specific capacitance (400 F/g, 0.5 A/g) and stability (90%, 10,000 cycles). The Change of different concentration ratios in the structures significantly affect the electrochemical performance. The specific surface area of the carbon materials prepared by ultra-filtration increased, but the specific surface area decrease as ultrafiltration concentration increase. The specific capacitance decrease from 336 F/g for C-ZIF-67-1/3 volume ultrafiltration to 258 F/g for C-ZIF-67-1/5 ultrafiltration. The results indicate that energy storage by the carbon materials relied on a synergistic effect between their microporous and mesoporous structures. The micropores provide storage space for the transmission of ions, while the mesopores provide ion transport channels. The separation of large and small molecules after ultrafiltration concentration limit the ion transmission and energy storage of the pores.

Research progress on ZnSe and ZnTe anodes for rechargeable batteries

Transition-metal chalcogenides (TMCs) with tunable direct bandgaps and interlayer spacing are attractive for energy-related applications. Semiconducting zinc chalcogenides, especially their selenides (ZnSe) and tellurides (ZnTe), with enhanced conductivity, high theoretical capacity, low operation voltage and abundance, have appeared on the horizon and receive increasing interest in terms of electrochemical energy storage and conversion. Despite the existing typical obstruction owing to the large volume change, relatively low electrical conductivity and sluggish ion diffusion kinetics into the bulk phase, several effective strategies such as compositing, doping, nanostructuring, and electrode/cell design have exhibited promising applications. We herein provide a timely and systematic overview of recent research and significant advances regarding ZnSe, ZnTe and their hybrids/composites, covering synthesis to electrode design and to applications, especially in advanced Li/Na/K-ion batteries, as well as the reaction mechanisms thereof. It is hoped that the overview will shed new light on the development of ZnSe and ZnTe for next-generation rechargeable batteries.

In Situ Chalcogen Leaching Manipulates Reactant Interface toward Efficient Amine Electrooxidation

Engineering the reaction interface is necessary for advancing various electrocatalytic processes. However, most designed catalysts tend to be ineffective due to the inevitable structural reconstruction. Here we utilize that operando electrocatalysis variations (i.e., chalcogen leaching) manipulate the reactant interface toward amine electrooxidation. Taking chalcogen-doped Ni(OH)₂ as an example, operando techniques uncover that chalcogens leach from the matrix and then adsorb on the surface of NiOOH as chalcogenates during the electrooxidation process. The charged chalcogenates will induce the local electric field that pushes the polar amines through the inner Helmholtz plane to enrich on the catalyst surface. Meanwhile, the polarization effect of chalcogenates and amines boost amino C-N bond activation for dehydrogenation into nitrile C≡N bonds. Under the promotion effect of surface-adsorbed chalcogenate ions, our catalysts display over 99.5% propionitrile selectivity at the low potential of 1.317 V with an ultrahigh current density. This finding highlights the use of operando changes of catalysts to rationally design efficient catalysts and further clarifies the underlying role of chalcogen atoms in the electrooxidation process.