Surface functionalized highly porous date seed derived activated carbon and MoS2 nanocomposites for hydrogenation of CO2 into formic acid

Catalytically Active Carbon for Oxygen Reduction Reaction in Energy Conversion: Recent Advances and Future Perspectives

The shortage and unevenness of fossil energy sources are affecting the development and progress of human civilization. The technology of efficiently converting material resources into energy for utilization and storage is attracting the attention of researchers. Environmentally friendly biomass materials are a treasure to drive the development of new-generation energy sources. Electrochemical theory is used to efficiently convert the chemical energy of chemical substances into electrical energy. In recent years, significant progress has been made in the development of green and economical electrocatalysts for oxygen reduction reaction (ORR). Although many reviews have been reported around the application of biomass-derived catalytically active carbon (CAC) catalysts in ORR, these reviews have only selected a single/partial topic (including synthesis and preparation of catalysts from different sources, structural optimization, or performance enhancement methods based on CAC catalysts, and application of biomass-derived CACs) for discussion. There is no review that systematically addresses the latest progress in the synthesis, performance enhancement, and applications related to biomass-derived CAC-based oxygen reduction electrocatalysts synchronously. This review fills the gap by providing a timely and comprehensive review and summary from the following sections: the exposition of the basic catalytic principles of ORR, the summary of the chemical composition and structural properties of various types of biomass, the analysis of traditional and the latest popular biomass-derived CAC synthesis methods and optimization strategies, and the summary of the practical applications of biomass-derived CAC-based oxidative reduction electrocatalysts. This review provides a comprehensive summary of the latest advances to provide research directions and design ideas for the development of catalyst synthesis/optimization and contributes to the industrialization of biomass-derived CAC electrocatalysis and electric energy storage.

Morphology engineering of defective graphene for microwave absorption

Graphene with abundant defects has been considered as the most lightweight electromagnetic functional materials. Although important, the dominant electromagnetic response of defective graphene with diverse morphologies is rarely the focus of existing research. Herein, the defective graphene with two-dimensional planar structure (2D-ps) and three-dimensional continuous network (3D-cn) morphologies were dexterously designed with 2D mixing and 3D filled systems of polymeric matrix. A comparison between the topologies of defective graphene-based nanofillers and the microwave attenuation behaviors was examined. Defective graphene with 3D-cn morphology can achieve ultralow filling content and broadband absorption, which is attributed to the presence of numerous pore structures that promote impedance matching, induce continuous conduction loss and provide multiple reflection and scattering sites for electromagnetic wave attenuation. Comparatively, by virtue of the increased filling content of 2D-ps, the dielectric losses primarily originate from the dielectric genes, including aggregation-induced-charge transport, abundant defect and dipole polarization, resulting in good microwave absorption at low thickness and low frequency. Therefore, this work provides a pioneering insight into morphology engineering of defective graphene microwave absorbers, and it will guide future exploration of customizing high-performance microwave absorption materials based on graphene-based low-dimensional building blocks.

Carbon-doped defect MoS2 co-catalytic Fe3+/peroxymonosulfate process for efficient sulfadiazine degradation: Accelerating Fe3+/Fe2+ cycle and 1O2 dominated oxidation

In order to accelerate Fe³⁺/Fe²⁺ cycle and boost singlet oxygen (¹O₂) generation in peroxymonosulfate (PMS) Fenton-like system, a co-catalyst of defect MoS₂ was prepared by C doping and C2-MoS₂/Fe³⁺/PMS system was structured. The removal efficiency of sulfadiazine (SDZ) antibiotics was nearly 100 % in 10 min in the system under the appropriate conditions ([co-catalysts] = 0.2 g/L, [PMS] = 0.1 mM, [Fe³⁺] = 0.4 mM, pH 3.5), and the reaction rate constant was 4.6 times that of Fe³⁺/PMS system. C doping MoS₂ could induce phase transition, yield more sulfur defects, and expedite electron transfer. Besides, exposed Mo⁴⁺ sites on C2-MoS₂ could significantly enhance the regeneration and stability of Fe²⁺ and further promote the activation of PMS. ·OH, SO₄·^-, and ¹O₂ were responsible for SDZ degradation in the system. Notably, ¹O₂ generation was efficiently promoted by sulfur defects and CO sites on C2-MoS₂, and ¹O₂ played the main role in SDZ degradation. Therefore, this co-catalytic system exhibited great anti-interference and stability, and organic contaminants could be efficiently and stably degraded in a 14-day long-term experiment. This work provides a new approach for improving the co-catalytic performance of MoS₂ for Fe³⁺ mediated Fenton-like technology, and offers a promising antibiotic pollutant removal strategy.

Green, zero-waste pathway to fabricate supported nanocatalysts and anti-kinetoplastid agents from sugarcane bagasse

The conversion processes of sugarcane into direct-consumption sugar and juice are generating a tremendous amount of waste, the so-called sugarcane bagasse (SCB). Biochar preparation is among the practical solutions aiming to manage and valorize SCB into high added-value functional material (FM). Herein, we propose a novel zero-waste pathway to fabricate two FMs from one biomass. The SCB was first macerated and ultrasonicated to obtain the natural extract that served as bio-reducing medium. Then, the H₂O/EtOH-extracted SCB was in-situ impregnated with a bimetallic solution of copper and silver nitrates. The process produced an intermediate composite (FM₀), Ag/Cu-Ag⁺/Cu²⁺-loaded SCB which was carbonized to elaborate Ag/Cu-Biochar (FM₁), free Ag/Cu nanoparticles (FM₂) were obtained by microwaving the residual liquid waste. FM₁ exhibited high catalytic activity for the total Fenton-like degradation of methylene blue. The experimental data followed the pseudo-first and the pseudo-second order rate laws with apparent degradation rate constants K₁ 45 10^-3 min^-1 and K₂ 0.115 g.mg^-1.min^-1, respectively. FM₀, FM₁ and FM₂ were tested as new anti-kinetoplastid materials against two flagellated protozoans namely the Leishmania spp and the Trypanosoma cruzi. Notably, Ag/Cu (FM₂) showed exceptional leishmanicidal and trypanocidal effects with IC₅₀ values of 2.909 ± 0.051, 3.580 ± 0.016 and 3.020 ± 0.372 ppm for L.donovani, L. amazonensis and Trypanosoma cruzi, respectively. In this way, we combine green chemistry and agrowaste valorization in a full zero-waste process, to address the 3rd (indicator 3.3.5) and 6th (indicator 6.3.1) United Nations sustainable development goals, ″Good Health and Well-Being″ and ″Clean Water and Sanitation″.

A review on sensing and catalytic activity of nano-catalyst for synthesis of one-step ammonia and urea: Challenges and perspectives

One of the most significant chemical operations in the past century was the Haber-Bosch catalytic synthesis of ammonia, a fertilizer vital to human life. Many catalysts are developed for effective route of ammonia synthesis. The major challenges are to reduce temperature and pressure of process and to improve conversion of reactants produce green ammonia. The present review, briefly discusses the evolution of ammonia synthesis and current advances in nanocatalyst development. There are promising new ammonia synthesis catalysts of different morphology as well as magnetic nanoparticles and nanowires that could replace conventional Fused-Fe and Promoted-Ru catalysts in existing ammonia synthesis plants. These magnetic nanocatalyst could be basis for the production of magnetically induced one-step green ammonia and urea synthesis processes in future.

Nano-activated carbon derived from date palm coir waste for efficient sequestration of noxious 2,4-dichlorophenoxyacetic acid herbicide

Alarming water contamination rates by toxic herbicides have drawn attention to treat these pollutants using efficient, easy, and economic techniques. In this work, date-palm coir (DPC) waste-based nano-activated carbon (DPC-AC) was successfully prepared and examined for adsorptive removal of toxic 2,4-dichlorophenoxyacetic acid (2,4-DPA) herbicide from synthetic wastewater. The DPC-AC was synthesized via a single-step carbonization-KOH activation approach. The nanosorbent displayed a flaky morphology with graphitic structure and oxygen-rich surface functionalities. The nanocarbon with a mean particle size of 163 nm possessed a high specific surface area of 947 m²/g with an average pore size of 2.28 nm. High 2,4-DPA removal efficiency of 98.6% was obtained for the optimal adsorption conditions of pH 2, dosage 0.15 g, rotational speed 100 rpm, time 90 min, and initial 2,4-DPA concentration of 100 mg/L. Langmuir isotherm best described the equilibrium behavior with a theoretical maximum of 50.25 mg/g adsorption capacity for the system. Pseudo-second order model was more appropriate in quantifying the kinetics for all initial feed concentrations. Thermodynamically, the adsorption process was spontaneous, endothermic, and involved low activation energy. A plausible mechanism for the adsorption-desorption of 2,4-DPA onto DPC-AC is also discussed. Cost analysis and regenerability studies proved the economic value ($3/kg) and reusable nature of DPC-AC without any significant loss in its performance. Overall, this study highlights the advantages of DPC waste valorization into efficient nanoadsorbent and the sequestration of noxious 2,4-DPA herbicide from its aqueous streams using this nanosorbent.

Solvent-mediated synthesis of BiOI with a tunable surface structure for effective visible light active photocatalytic removal of Cr(VI) from wastewater

The present study investigated the effect of various solvents on the tunable surface morphology and photocatalytic activity (PCA) of bismuth oxyiodide (BiOI), which could be used for the reduction of Cr(VI) under visible light irradiation (VLI). BiOI samples exhibiting different morphologies, i.e., two-dimensional square-like nanosheet and three-dimensional hierarchical flower-like morphology, were synthesized by a hydro/solvothermal process using different solvents, namely H₂O, MeOH, EtOH, and ethylene glycol (EG). The crystal structure, surface morphology, surface area, light-absorption capability, and recombination rate of the photogenerated charge carriers were examined by X-ray diffraction, scanning electron microscopy, Brunauer-Emmett-Teller analysis, UV-vis diffuse reflectance spectroscopy, photoluminescence, and transient photocurrent analyses, respectively. The BiOI sample fabricated in EG showed excellent photocatalytic efficiency (~99%) for the reduction of Cr(VI) after 90 min under VLI. The enhanced PCA demonstrated that the high surface area and well-structured surface characteristics of flower-like 3D BiOI microspheres played important roles in the photoreduction process. Moreover, a plausible mechanism for the reduction of Cr(VI) over the EG-BiOI photocatalyst was proposed. The results of the PCA evaluation and recycle test revealed that 3D EG-BiOI microspheres could serve as promising materials for the efficient removal of Cr(VI) from wastewater. Additionally, EG-BiOI could be utilized in other environmental remediation processes.

Hybrid capacitive deionization of NaCl and toxic heavy metal ions using faradic electrodes of silver nanospheres decorated pomegranate peel-derived activated carbon

Capacitive deionization (CDI) is an evolving technology for eradicating salt and toxic heavy metal ions from brackish wastewater. However, traditional CDI electrodes have lower salt adsorption capacity and inadequate adsorption of selective metal ions for long-term operations. Herein, Ag nanospheres incorporated pomegranate peel-derived activated carbon (Ag/P-AC) was prepared and implied to the CDI process for removing NaCl, toxic mono-, di-, and trivalent metal ions. Morphological analysis revealed that the 80-100 nm-sized Ag nanospheres were uniformly decorated on the surfaces of P-AC nanosheets. The Ag/P-AC has a higher specific surface area (640 m² g^-1), superior specific capacitance (180 F g^-1 at 50 mV s^-1) and a lower charge transfer resistance (0.5 Ω cm²). CDI device was fabricated by Ag/P-AC as an anode, which adsorbed anions and P-AC as cathode for adsorption of positively charged ions at 1.2 V in an initial salt concentration of 1000 mg L^-1. An asymmetric Ag/P-AC//P-AC exhibited a maximum NaCl adsorption capacity of 36 mg g^-1 than symmetric P-AC//P-AC electrodes (22.7 mg g^-1). Furthermore, Pb(II), Cd(II), F^-, and As(III) ions were successfully removed from simulated wastewater by using Ag/P-AC//P-AC based CDI system. These asymmetric CDI-electrodes have an excellent prospect for the removal of salt and toxic contaminants in industrial wastewater.

Impact of structure, doping and defect-engineering in 2D materials on CO2 capture and conversion

2D material based strategies for adsorption and conversion of CO2 to value-added products.

The role of deep eutectic solvents and carrageenan in synthesizing biocompatible anisotropic metal nanoparticles

Plasmonic metal nanoparticles are widely used for many applications due to their unique optical and chemical properties. Over the past decade, anisotropic metal nanoparticles have been explored for imaging, sensing, and diagnostic applications. The variations and flexibility of tuning the size and shape of the metal nanoparticles at the nanoscale made them promising candidates for biomedical applications such as therapeutics, diagnostics, and drug delivery. However, safety and risk assessment of the nanomaterials for clinical purposes are yet to be made owing to their cytotoxicity. The toxicity concern is primarily due to the conventional synthesis route that involves surfactants as a structure-directing agent and as a capping agent for nanoparticles. Wet chemical methods employ toxic auxiliary chemicals. However, the approach yields monodispersed nanoparticles, an essential criterion for their intended application and a limitation of the green synthesis of nanoparticles using plant extracts. Several biocompatible counterparts such as polymers, lipids, and chitosan-based nanoparticles have been successfully used in the synthesis of safe nanomaterials, but there were issues regarding reproducibility and yield. Enzymatic degradation was one of the factors responsible for limiting the efficacy. Hence, it is necessary to develop a safer and nontoxic route towards synthesizing biocompatible nanomaterials while retaining morphology, high yield, and monodispersity. In this regard, deep eutectic solvents (DESs) and carrageenan as capping agent for nanoparticles can ensure the safety. Carrageenan has the potential to act as antibacterial and antiviral agent, and adds enhanced stability to the nanoparticles. This leads to a multidimensional approach for utilizing safe nanomaterials for advanced biomedical and clinical applications.