Dual Metal-Loaded Porous Carbon Materials Derived from Silk Fibroin as Bifunctional Electrocatalysts for Hydrogen Evolution Reaction and Oxygen Evolution Reaction

Porous carbon nanosheets integrated with graphene-wrapped CoO and CoNx as efficient bifunctional oxygen electrocatalysts for rechargeable zinc-air batteries

The development of advanced bifunctional oxygen electrocatalysts for the oxygen reduction reactions (ORR) and oxygen evolution reactions (OER) is crucial for the practical application of zinc-air batteries (ZABs). Herein, porous carbon nanosheets integrated with abundant graphene-wrapped CoO and CoNx (CoO/CoNx-C) were successfully fabricated through a simple one-step pyrolysis. With convenient porous channel and large accessible surface, abundant CoO/CoNx species and graphene wrapping structure, CoO/CoNx-C exhibited a half-wave potential of 0.844 V in ORR and an overpotential of 384 mV (@10 mA cm-2) in OER in the alkaline environment and presented a negative shift of 9 mV in ORR after 8000 cycles and positive shift of 19 mV in OER after 2000 cycles. Electrochemical acid-washing and comparison analysis revealed that the ORR activity mainly originated from CoO nanoparticles, while CoNx species were greatly responsible for OER catalysis. Furthermore, the as-prepared CoO/CoNx-C endowed the rechargeable liquid and solid ZABs with superior power density (161 mW cm-2 for liquid ZABs and 137 mW cm-2 for solid ZABs) and long-term stability (stable in 1000 h charge/discharge tests) compared to commercial catalysts. This work provides a feasible strategy for cobalt/carbon hybrid materials as advanced bifunctional electrocatalysts for ZABs.

Silk Nanofibers/Carbon Nanotube Conductive Aerogel

Natural silk nanofibers (SNF) are attractive conductive substrates due to their high aspect ratio, outstanding mechanical strength, excellent biocompatibility, and controllable degradability. However, the inherently non-conductivity severely restricts the potential sensor application of SNF-based aerogels. In this work, the conductive nanofibrous aerogels with low-density achieved through freeze-drying by dispersing carbon nanotubes (CNT) into SNF suspension. The addition of CNT significantly increases the conductivity with improved mechanical properties of composite aerogels. SEM results reveal that the distinct hierarchical structure comprising micropores and nanofibrous networks within the pores is formed when CNT content reached 30%. Furthermore, increased cell viability suggested the excellent biocompatibility of SNF-CNT-based conductive aerogel for tissue-engineering applications. Subsequently, the elastic water-borne polyurethane (WPU) is incorporated to SNF-CNT system to construct aerogel with good sensing properties. The introduction of WPU demonstrates enhanced compressive performances and an exceptionally high elastic recovery ratio of 99.8%, thereby exhibiting a stable and lossless strain-sensing signal output at 5% strain. This study provides a feasible choice and strategy for exploring the potential application of SNF in functional aerogels.

Efficient Host Materials for Lithium-Sulfur Batteries: Ultrafine CoP Nanoparticles in Black Phosphorus-Carbon Composite

The pursuit of efficient host materials to address the sluggish redox kinetics of sulfur species has been a longstanding challenge in advancing the practical application of lithium-sulfur batteries. In this study, amorphous carbon layer loaded with ultrafine CoP nanoparticles prepared by a one-step in situ carbonization/phosphating method to enhance the inhibition of 2D black phosphorus (BP) on LiPSs shuttle. The carbon coating layer facilitates accelerated electron/ion transport, enabling the active involvement of BP in the conversion of soluble lithium polysulfides (LiPSs). Concurrently, the ultra-fine CoP nanoparticles enhance the chemical anchoring ability and introduce additional catalytic sites. As a result, S@BP@C-CoP electrodes demonstrate exemplary cycling stability (with a minimal capacity decay of 0.054 % over 500 cycles at 1 C) and superior rate performance (607.1 mAh g-1 at 5 C). Moreover, at a sulfur loading of 5.5 mg cm-2, the electrode maintains an impressive reversible areal capacity of 5.45 mAh cm-2 after 50 cycles at 0.1 C. This research establishes a promising approach, leveraging black phosphorus-based materials, for developing high-efficiency Li-S batteries.

Self-supporting hierarchical Co3O4-nanowires@NiO-nanosheets core-shell nanostructure on carbon foam to form efficient bifunctional electrocatalyst for overall water splitting

Designing cost-effective and robust bifunctional electrocatalysts for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) is highly desired in hydrogen production from overall water splitting, but still suffers great challenges due to the sluggish catalytic OER/HER kinetics. In this paper, a surface/defect engineering strategy is developed to synthesize three-dimensional (3D) carbon foam (CF)-supported unique hierarchical Co3O4 nanowires@NiO nanosheets core-shell nanostructured catalyst (NiO@Co3O4/CF) with rich oxygen-vacancies as a novel bifunctional catalyst for alkaline water splitting electrolysis. Benefited from the synergy of the 3D hierarchical core-shell structure and rich oxygen vacancies, the as-obtained NiO@Co3O4/CF shows both excellent OER (η200 = 325 mV, η500 = 374 mV) and HER (η10 = 104 mV) activities with low Tafel slopes (64.26 mV dec-1 for OER and 109.14 mV dec-1 for HER, respectively) and outstanding stability. A simple overall water splitting electrolysis cell assembled by this bifunctional NiO@Co3O4/CF as both OER and HER catalysts requires only a cell voltage of 1.53 V to obtain the current density of 10 mA cm-2 and displays a long-term stability. This work has successfully developed an approach for rational design and novel synthesis of metal oxide hybrids as bifunctional electrocatalysts with high activity and stability for overall water splitting.

RuSe2-CoTe Heterogeneous Surfaces Coated with NC Layer for Excellent HER Performance under Alkaline Condition

Electrocatalytic hydrogen production has been a promising high-purity hydrogen production technology, attracting a large number of researchers' research interest. Ru has a hydrogen binding capacity similar to Pt, but its price is far lower than Pt, making it a promising alternative to Pt. However, a single Se electronic structure modulation is not sufficient to enable RuSe2 to be used for practical applications on a large scale due to the lack of electrons. Therefore, choosing a suitable way to electronically modulate the Ru atoms in RuSe2 can effectively improve the activity of the catalyst. Cobalt telluride (CoTe) can significantly enhance electrocatalytic performance due to tellurium's low electronegativity and excellent metal properties. In this work, the NC layer possesses excellent electrical conductivity and CoTe acts as an electron donor to optimize the electronic structure locally and trigger electron transfer efficiently. The RuSe2-CoTe/NC electrode requires an overpotential of only 25.4 mV (10 mA cm-2), which is superior to that of RuSe2/NF (65 mV) and CoTe/NC (115 mV). Meanwhile, the Tafel slope of RuSe2-CoTe/NC (67.8 mV dec-1) was better than that of RuSe2/NF (113.6 mV dec-1) and CoTe/NC (209.5 mV dec-1), showing that the build-up of the superior heterojunction makes the RuSe2-CoTe/NC with better hydrogen evolution reaction (HER) reaction kinetics. In addition, after 30 h of long-term stability testing, no significant decrease in catalytic activity was observed, proving the good stability of the RuSe2-CoTe/NC catalyst.

Advances in Preparation and Properties of Regenerated Silk Fibroin

Over the years, silk fibroin (SF) has gained significant attention in various fields, such as biomedicine, tissue engineering, food processing, photochemistry, and biosensing, owing to its remarkable biocompatibility, machinability, and chemical modifiability. The process of obtaining regenerated silk fibroin (RSF) involves degumming, dissolving, dialysis, and centrifugation. RSF can be further fabricated into films, sponges, microspheres, gels, nanofibers, and other forms. It is now understood that the dissolution method selected greatly impacts the molecular weight distribution and structure of RSF, consequently influencing its subsequent processing and application. This study comprehensively explores and summarizes different dissolution methods of SF while examining their effects on the structure and performance of RSF. The findings presented herein aim to provide valuable insights and references for researchers and practitioners interested in utilizing RSF in diverse fields.

Functional Carbon from Nature: Biomass-Derived Carbon Materials and the Recent Progress of Their Applications

Biomass is considered as a promising source to fabricate functional carbon materials for its sustainability, low cost, and high carbon content. Biomass-derived-carbon materials (BCMs) have been a thriving research field. Novel structures, diverse synthesis methods, and versatile applications of BCMs have been reported. However, there has been no recent review of the numerous studies of different aspects of BCMs-related research. Therefore, this paper presents a comprehensive review that summarizes the progress of BCMs related research. Herein, typical types of biomass used to prepare BCMs are introduced. Variable structures of BCMs are summarized as the performance and properties of BCMs are closely related to their structures. Representative synthesis strategies, including both their merits and drawbacks are reviewed comprehensively. Moreover, the influence of synthetic conditions on the structure of as-prepared carbon products is discussed, providing important information for the rational design of the fabrication process of BCMs. Recent progress in versatile applications of BCMs based on their morphologies and physicochemical properties is reported. Finally, the remaining challenges of BCMs, are highlighted. Overall, this review provides a valuable overview of current knowledge and recent progress of BCMs, and it outlines directions for future research development of BCMs.

Liquid nitrogen quenching inducing lattice tensile strain to endow nitrogen/fluorine co-doping Fe3O4 nanocubes assembled on porous carbon with optimizing hydrogen evolution reaction

In this work, the lattice tensile strain of nitrogen/fluorine co-doping ferroferric oxide (Fe₃O₄) nanocubes assembled on chrysanthemum tea-derived porous carbon is induced through a novel liquid nitrogen quenching treatment (named as TS-NF-FO/PC_X-Y, TS: Tensile strain, NF: Nitrogen/Fluorine co-doping, FO: Fe₃O₄, PC: Porous carbon, X: The weight ratio of KOH/carbon, Y: The adding amount of porous carbon). Besides, the electrocatalytic activity influenced by the adding amount of porous carbon, the type of dopant, and the introduction of lattice tensile strain is systematically studied and explored. The interconnected porous carbon could improve electrical conductivity and prevent Fe₃O₄ nanocubes from aggregating. The induced nitrogen/fluorine could cause extrinsic defects and tailor the intrinsic electron state of the host materials. Lattice tensile strain could tailor the surface electronic structure of Fe₃O₄ via changing the dispersion of surface atoms and their bond lengths. Impressively, the designed TS-NF-FO/PC₅-0.25 delivers a low overpotential of 207.3 ± 0.4 mV at 10 mA/cm² and demonstrates desirable reaction dynamics. Density functional theory calculations illustrate that the electron structure and hydrogen adsorption free energy (ΔG_*H) are optimized by the synergistic effect among porous carbon, nitrogen/fluorine co-doping and lattice tensile strain, thus promoting hydrogen evolution reaction (HER) catalytic activity. Overall, this work paves the way to unravel the enhancement mechanism of HER on transition metal oxide-based materials by electronic structure and phase composition modulation strategy.

Silk-derived nitrogen-doped porous carbon electrodes with enhanced ionic conductivity for high-performance supercapacitors

Supercapacitors are attracting extensive attention in energy storage fields thanks to their high safety, cost-effectiveness, and environmental friendliness. The carbon materials, especially for the porous carbon materials derived from renewable biomass materials, are important electrode materials with cost-effective feature for supercapacitors. However, the inferior ionic conductivity of biomass materials inhibits their electrochemical performance in energy storage devices. Herein, an immiscible liquid-mediated method is provided to improve the ionic conductivity of silk-derived nitrogen-doped porous carbon (NPC) electrodes. Natural Bombyx mori (silkworm) silk is used as a carbon source for the preparation of electrode of supercapacitor. Further introducing immiscible organic liquid into the NPCs promotes the ion transport in the inner pores of the electrodes. With the assistance of organic liquid, the supercapacitor presents a specific capacitance of 565.3 F g^-1 at a current density of 1 A g^-1. The supercapacitor shows the maximum specific energy and power density of 26.2 Wh kg^-1 and 263.9 W kg^-1, and holds a capacitance retention of approximately 93.3% after 10 000 cycles. This work provides a facile method for the rational design of carbon material derived from biomass material to fabricate electrode with high ionic conductivity, and the strategy will be extendable to other biomass materials for a wide range of applications.

Collagen and Silk Fibroin as Promising Candidates for Constructing Catalysts

A catalyst determines the mechanism of an organic chemical reaction, thus enabling the commercially viable formation of desired material products. Biopolymers offer new opportunities for the construction of catalysts by virtue of their biocompatibility, environmental benignity, and sustainability, as well as their low cost. Biopolymers are especially useful as carriers and precursors in catalysis application. The employment of biocompatible and biosustainable collagen and silk fibroin materials will revolutionize state-of-the-art electronic devices and systems that currently rely on conventional technologies. In this review, we first consider the ordered hierarchical structure, origin, and processing methods of collagen and silk fibroin. Then, the unique advantages and applicability of collagen and silk fibroin for constructing catalysts are summarized. Moreover, a summary of the state-of-the-art design, fabrication, and application of collagen- and silk fibroin-based catalysts, as well as the application of collagen- and silk-based catalysts, is presented by focusing on their roles as carriers and precursors, respectively. Finally, challenges and prospects are assessed for the construction and development of collagen and silk fibroin-based catalysts.