Organic/Inorganic Hybrid Fibers: Controllable Architectures for Electrochemical Energy Applications

Self-Healable Multifunctional Fibers via Thermal Drawing

The development of soft electronics and soft fiber devices has significantly advanced flexible and wearable technology. However, they still face the risk of damage when exposed to sharp objects in real-life applications. Taking inspiration from nature, self-healable materials that can restore their physical properties after external damage offer a solution to this problem. Nevertheless, large-scale production of self-healable fibers is currently constrained. To address this limitation, this study leverages the thermal drawing technique to create elastic and stretchable self-healable thermoplastic polyurethane (STPU) fibers, enabling cost-effective mass production of such functional fibers. Furthermore, despite substantial research into the mechanisms of self-healable materials, quantifying their healing speed and time poses a persistent challenge. Thus, transmission spectra are employed as a monitoring tool to observe the real-time self-healing process, facilitating an in-depth investigation into the healing kinetics and efficiency. The versatility of the fabricated self-healable fiber extends to its ability to be doped with a wide range of functional materials, including dye molecules and magnetic microparticles, which enables modular assembly to develop distributed strain sensors and soft actuators. These achievements highlight the potential applications of self-healable fibers that seamlessly integrate with daily lives and open up new possibilities in various industries.

Recent advances in food waste-derived nanoporous carbon for energy storage

Affordable and environmentally friendly electrochemically active raw energy storage materials are in high demand to switch to mass-scale renewable energy. One particularly promising avenue is the feasibility of utilizing food waste-derived nanoporous carbon. This material holds significance due to its widespread availability, affordability, ease of processing, and, notably, its cost-free nature. Over the years, various strategies have been developed to convert different food wastes into nanoporous carbon materials with enhanced electrochemical properties. The electrochemical performance of these materials is influenced by both intrinsic factors, such as the composition of elements derived from the original food sources and recipes, and extrinsic factors, including the conditions during pyrolysis and activation. While current efforts are dedicated to optimizing process parameters to achieve superior performance in electrochemical energy storage devices, it is timely to take stock of the current state of research in this emerging field. This review provides a comprehensive overview of recent developments in the fabrication and surface characterisation of porous carbons from different food wastes. A special focus is given on the applications of these food waste derived porous carbons for energy storage applications including batteries and supercapacitors.

Interfacial Assembly of Nanocrystals on Nanofibers with Strong Interaction for Electrocatalytic Nitrate Reduction

One-dimensional fiber architecture serves as an excellent catalyst support. The orderly arrangement of active materials on such a fiber substrate can enhance catalytic performance by exposing more active sites and facilitating mass diffusion; however, this remains a challenge. We developed an interfacial assembly strategy for the orderly distribution of metal nanocrystals on different fiber substrates to optimize their electrocatalytic performance. Using electrochemical nitrate reduction reaction (NO3 - RR) as a representative reaction, the iron-based nanofibers (Fe/NFs) assembly structure achieved an excellent nitrate removal capacity of 2317 mg N/g Fe and N2 selectivity up to 97.2 %. This strategy could promote the rational design and synthesis of fiber-based electrocatalysts.

Recent advances of bifunctional catalysts for zinc air batteries with stability considerations: from selecting materials to reconstruction

With the growing depletion of traditional fossil energy resources and ongoing enhanced awareness of environmental protection, research on electrochemical energy storage techniques like zinc-air batteries is receiving close attention. A significant amount of work on bifunctional catalysts is devoted to improving OER and ORR reaction performance to pave the way for the commercialization of new batteries. Although most traditional energy storage systems perform very well, their durability in practical applications is receiving less attention, with issues such as carbon corrosion, reconstruction during the OER process, and degradation, which can seriously impact long-term use. To be able to design bifunctional materials in a bottom-up approach, a summary of different kinds of carbon materials and transition metal-based materials will be of assistance in selecting a suitable and highly active catalyst from the extensive existing non-precious materials database. Also, the modulation of current carbon materials, aimed at increasing defects and vacancies in carbon and electron distribution in metal-N-C is introduced to attain improved ORR performance of porous materials with fast mass and air transfer. Finally, the reconstruction of catalysts is introduced. The review concludes with comprehensive recommendations for obtaining high-performance and highly-durable catalysts.

Iron-Based Nanocatalysts for Electrochemical Nitrate Reduction

Nitrate has a high level of stability and persistence in water, endangering human health and aquatic ecosystems. Due to its high reliability and efficiency, the electrochemical nitrate reduction reaction (NO₃ RR) is regarded as the best available option for mitigating excess nitrate in water and wastewater, especially for the removal of trace levels of nitrate. One of the most critical factors in the electrochemical reduction are the catalysts, which directly affect the reaction efficiency of nitrate removal. Iron-based nanocatalysts, which have the advantages of nontoxicity, wide availability, and low cost, have emerged as a promising electrochemical NO₃ RR material in recent years. This review covers major aspects of iron-based nanocatalysts for electrochemical NO₃ RR, including synthetic methods, structural design, performance enhancement, electrocatalytic nitrate reduction test, and reduction mechanism. The recent progress of iron-based nanocatalysts for electrochemical NO₃ RR and the mechanism of functional advantages for modified structures are reviewed from the perspectives of loading, doping, and assembly strategies, in order to realize the conversion from pollutant nitrate to harmless nitrogen or ammonia and other sustainable products. Finally, challenges and future directions for the development of low-cost and highly-efficient iron-based nanocatalysts are explored.

ZIF-67-Derived (NiCo)S2@NC Nanosheet Arrays Hybrid for Efficient Overall Water Splitting

Electrocatalytic water splitting is considered a promising approach to obtain clean and sustainable hydrogen energy. The integration of optimal nanoarchitecture and multicomponent synergy has been a significant factor for designing a bifunctional electrocatalyst to promote the cathodic hydrogen evolution reaction (HER) and anodic oxygen evolution reaction (OER). In particular, the charge migration, mass transfer, and gas release rate in the catalyzing process are closely correlated with the architecture of the catalyst. Here, ZIF-67-derived N-doped carbon nanofiber-supported (NiCo)S₂ nanosheet [(NiCo)S₂/NCNF] as a bifunctional electrocatalyst was synthesized using electrospinning, template etching, and subsequent gas sulfidation method. The hierarchical hybrid nanofiber with inner hollow cubes and outer nanosheets provides easy electron penetration, high charge/mass transportation efficiency, and robust structure stability. Furthermore, the MOF-derived carbon-encapsuled bimetal-sulfide and the synergistic effect of double active centers are conducive to an exceptional performance, showing low overpotentials of 177 and 203 mV to drive a current density of 10 mA cm^-2 and robust stability for the HER and OER, respectively. Meanwhile, the (NiCo)S₂/NCNF electrodes exhibit a small voltage of 1.61 V for overall water splitting activity with an electrolyzer cell at current densities of 10 mA cm^-2 over 12 h. This work presents novel insights into the bifunctional catalyst for promoting the overall water splitting via a MOF-derived nanoarchitecture and multicomponent synergy.

Enhanced Structural Stability and Volumetric Capacity of a 3D Pyknotic Graphene Conductive Network via a Pillar Effect of Sn Nanoparticles for Sodium-Ion Batteries

High volumetric capacity and durability anode materials for sodium ion batteries have been urgently required for practical applications. Herein, we reported a Sn-pillared pyknotic graphene conductive network with high-level N-doping. This densely stacked block offers high volumetric Na-ion storage capacity, rapid electrochemical reaction kinetics, and robust structural stability during cycling owing to the high capacity component (metallic Sn ≈847 mAh g^-1), high tap density (≈2.63 g cm^-3), high conductivity (N doping ≈5 at. %), and strong spatially confined and pillared structure. Moreover, theoretical simulations have indicated that the charge accumulation around the N-doped region is more pronounced compared to the pristine one, and electrons accumulate around the N atom while loss occurs at the Na atom. These studies also suggest that it might possibly contribute to higher conductivity and stronger electrophilic reactivity, thereby resulting in enhanced Na-ion storage performance. As a result, the as-obtained electrode material exhibits competitive volumetric capacity (1462 mAh cm^-3 at 0.1 A g^-1), cycling performance (1207 mAh cm^-3 after 100 cycles), and promising rate behavior simultaneously.

How to Build a Microplastics-Free Environment: Strategies for Microplastics Degradation and Plastics Recycling

Microplastics are an emergent yet critical issue for the environment because of high degradation resistance and bioaccumulation. Unfortunately, the current technologies to remove, recycle, or degrade microplastics are insufficient for complete elimination. In addition, the fragmentation and degradation of mismanaged plastic wastes in environment have recently been identified as a significant source of microplastics. Thus, the developments of effective microplastics removal methods, as well as, plastics recycling strategies are crucial to build a microplastics-free environment. Herein, this review comprehensively summarizes the current technologies for eliminating microplastics from the environment and highlights two key aspects to achieve this goal: 1) Catalytic degradation of microplastics into environmentally friendly organics (carbon dioxide and water); 2) catalytic recycling and upcycling plastic wastes into monomers, fuels, and valorized chemicals. The mechanisms, catalysts, feasibility, and challenges of these methods are also discussed. Novel catalytic methods such as, photocatalysis, advanced oxidation process, and biotechnology are promising and eco-friendly candidates to transform microplastics and plastic wastes into environmentally benign and valuable products. In the future, more effort is encouraged to develop eco-friendly methods for the catalytic conversion of plastics into valuable products with high efficiency, high product selectivity, and low cost under mild conditions.

Polypyrrole-Coated K2Mn[Fe(CN)6] Stabilizing Its Interfaces and Inhibiting Irreversible Phase Transition during the Zinc Storage Process in Aqueous Batteries

Prussian blue analogues (PBAs) have been considered as promising cathodes for aqueous zinc-ion batteries because of their open framework for accommodating large ions, tunable valence state, and facile synthesis. Among PBAs, potassium manganese hexacyanoferrate (KMHCF) is favored due to its high working voltage, high specific capacity, and low cost. However, it suffers from severe capacity decay and poor rate capability, which are mainly a result of poor intrinsic conductivity, irreversible phase transition, transition metal dissolution, and structural collapse during charge/discharge cycling. These issues extremely limit its practical application. In order to solve these problems, conductive polypyrrole (PPy) was used to coat KMHCF microcubes to form KMHCF@PPy composites to achieve superior rate capability and prolonged cycle life. With the PPy coating, the KMHCF@PPy composite delivers a discharge capacity of 107.6 mA h g^-1 after 100 cycles at 100 mA g^-1, and even at 500 mA g^-1 after 500 cycles, 64.2 mA h g^-1 still remained. The excellent electrochemical performance can be attributed to the effects from PPy. On the one hand, PPy supplies an effective electronic transmission network for KMHCF to enhance the electronic conductivity. On the other hand, it plays the role of a protective layer to effectively inhibit the dissolution of Mn and the phase transition during the cycling.