Self-supported bimodal-pore structured nitrogen-doped carbon fiber aerogel as electrocatalyst for oxygen reduction reaction

A novel and facile synthesis strategy for highly stable cesium lead halide nanowires

As promising low-dimensional semiconductor materials, cesium lead halide (CsPbX₃, X = Cl, Br, I) perovskite-like nanowires (NWs) can be widely applied to the field of semiconductor devices and integrated optoelectronics. Therefore, developing a facile and efficient synthesis method of cesium lead halide perovskite-like NWs can bring both fundamental and practical impacts to the field of optoelectronics. Here, we developed a synthesis strategy of all-inorganic cesium lead halide CsPbI₃ perovskite-like NWs under catalyst-free, solution-phase, and low-temperature conditions. The synthesis strategy was designed such that no inert gas is required and thus enables the synthesis to be carried out in air, which significantly reduces temperature, steps, time, and cost required for the reaction. The as-synthesized NWs were 7 μm in length and 80–100 nm in diameter with ideal morphology. Most of the CsPbI₃ NWs were crystallized in orthorhombic phases that were arranged orderly with a uniform growth direction. In addition, the CsPbI₃ NWs showed a photoluminescence peak near 610 nm and the fluorescence lifetime was 7.34 ns. The photoluminescence mechanism of CsPbI₃ NWs involves the self-trapping behaviour in the radiative recombination process. The composition of CsPbI₃ NWs is highly related to the synthesis temperature. The facile synthesis strategy has opened up a novel path for the synthesis of perovskite-like NWs, laying the foundation for the application of nano-optoelectronic devices, fluorescent anti-counterfeiting, and fluorescent composite materials.

Under air ambient, low temperature, and short reaction time conditions, a facile operation step is proposed to synthesize CsPbI₃ nanowires.

High-performance nanostructured bio-based carbon electrodes for energy storage applications

Polyacrylonitrile (PAN)-based carbon precursor is a well-established and researched material for electrodes in energy storage applications due to its good physical properties and excellent electrochemical performance. However, in the fight of preserving the environment and pioneering renewable energy sources, environmentally sustainable carbon precursors with superior electrochemical performance are needed. Therefore, bio-based materials are excellent candidates to replace PAN as a carbon precursor. Depending on the design requirement (e.g. carbon morphology, doping level, specific surface area, pore size and volume, and electrochemical performance), the appropriate selection of carbon precursors can be made from a variety of biomass and biowaste materials. This review provides a summary and discussion on the preparation and characterization of the emerging and recent bio-based carbon precursors that can be used as electrodes in energy storage applications. The review is outlined based on the morphology of nanostructures and the precursor's type. Furthermore, the review discusses and summarizes the excellent electrochemical performance of these recent carbon precursors in storage energy applications. Finally, a summary and outlook are also given. All this together portrays the promising role of bio-based carbon electrodes in energy storage applications.

N-Doped porous biocarbon materials derived from soya peptone as efficient electrocatalysts for the ORR

A non-noble metal oxygen reduction catalyst was designed and fabricated via a facile carbonization of soya peptone and ZnCl₂.

Optimization Strategies of Preparation of Biomass-Derived Carbon Electrocatalyst for Boosting Oxygen Reduction Reaction: A Minireview

Oxygen reduction reaction (ORR) has attracted considerable attention for clean energy conversion technologies to reduce traditional fossil fuel consumption and greenhouse gas emissions. Although platinum (Pt) metal is currently used as an electrocatalyst to accelerate sluggish ORR kinetics, the scarce resource and high cost still restrict its further scale-up applications. In this regard, biomass-derived carbon electrocatalysts have been widely adopted for ORR electrocatalysis in recent years owing to their tunable physical/chemical properties and cost-effective precursors. In this minireview, recent advances of the optimization strategies in biomass-derived carbon electrocatalysts towards ORR have been summarized, mainly focusing on the optimization of pore structure and active site. Besides, some current challenges and future perspectives of biomass-derived carbon as high-performance electrocatalysts for ORR have been also discussed in detail. Hopefully, this minireview will afford a guideline for better design of biomass-derived carbon electrocatalysts for ORR-related applications.

Carbon Anode in Carbon History

This study examines how the several major industries, associated with a carbon artifact production, essentially belong to one, closely knit family. The common parents are the geological fossils called petroleum and coal. The study also reviews the major developments in carbon nanotechnology and electrocatalysis over the last 30 years or so. In this context, the development of various carbon materials with size, dopants, shape, and structure designed to achieve high catalytic electroactivity is reported, and among them recent carbon electrodes with many important features are presented together with their relevant applications in chemical technology, neurochemical monitoring, electrode kinetics, direct carbon fuel cells, lithium ion batteries, electrochemical capacitors, and supercapattery.

Interplay between porous texture and surface-active sites for efficient oxygen reduction reactions in N-inherited carbon

Nitrogen-doped porous carbon materials have excellent ORR activities due to their synergistic effects caused by the electron-accepting ability of the adjacent sp² bonded carbon atoms leading to the redistribution of charge density.

Promoting Electrocatalysis upon Aerogels

Electrocatalysis plays a prominent role in renewable energy conversion and storage, enabling a number of sustainable processes for future technologies. There are generally three strategies to improve the efficiency (or activity) of the electrocatalysts: i) increasing the intrinsic activity of the catalyst itself, ii) improving the exposure of active sites, and iii) accelerating mass transfer during catalysis (both reactants and products). These strategies are not mutually exclusive and can ideally be addressed simultaneously, leading to the largest improvements in activity. Aerogels, as featured by large surface area, high porosity, and self-supportability, provide a platform that matches all the aforementioned criteria for the design of efficient electrocatalysts. The field of aerogel synthesis has seen much progress in recent years, mainly thanks to the rapid development of nanotechnology. Employing precursors with different properties enables the resulting aerogel with targeted catalytic properties and improved performances. Here, the design strategies of aerogel catalysts are demonstrated, and their performance for several electrochemical reactions is reviewed. The common principles that govern electrocatalysis are further discussed for each category of reactions, thus serving as a guide to the development of future aerogel electrocatalysts.

Sustainable Carbonaceous Materials Derived from Biomass as Metal-Free Electrocatalysts

Although carbon is the second most abundant element in the biosphere, a large proportion of the available carbon resources in biomass from agriculture, stock farming, ocean fisheries, and other human activities is currently wasted. The use of sustainable carbonaceous materials as an alternative to precious metals in electrocatalysis is a promising pathway for transforming sustainable biomass resources into sustainable energy-conversion systems. The development of rational syntheses of metal-free carbonaceous catalysts derived from sustainable biomass has therefore become a topic of significant interest in materials chemistry. However, great efforts are still required to develop methods that are low cost, scalable, and environmentally friendly and which afford carbonaceous materials having an electrocatalytic performance comparable to, or even better than, existing precious metal catalysts. Herein, recent achievements in developing metal-free carbonaceous catalysts based on biomass are reviewed and discussed and the critical issues which still need to be addressed are highlighted. The focus is on representative synthesis and optimization strategies applicable to different kinds of biomass, as well as studies of the physicochemical structure and electrochemical performance of the resulting metal-free carbonaceous catalysts. Finally, some guidelines for the future development of this important area are provided.

Biopolymer nanofibrils: structure, modeling, preparation, and applications

Biopolymer nanofibrils exhibit exceptional mechanical properties with a unique combination of strength and toughness, while also presenting biological functions that interact with the surrounding environment. These features of biopolymer nanofibrils profit from their hierarchical structures that spun angstrom to hundreds of nanometer scales. To maintain these unique structural features and to directly utilize these natural supramolecular assemblies, a variety of new methods have been developed to produce biopolymer nanofibrils. In particular, cellulose nanofibrils (CNFs), chitin nanofibrils (ChNFs), silk nanofibrils (SNFs) and collagen nanofibrils (CoNFs), as the four most abundant biopolymer nanofibrils on earth, have been the focus of research in recent years due to their renewable features, wide availability, low-cost, biocompatibility, and biodegradability. A series of top-down and bottom-up strategies have been accessed to exfoliate and regenerate these nanofibrils for versatile advanced applications. In this review, we first summarize the structures of biopolymer nanofibrils in nature and outline their related computational models with the aim of disclosing fundamental structure-property relationships in biological materials. Then, we discuss the underlying methods used for the preparation of CNFs, ChNFs, SNF and CoNFs, and discuss emerging applications for these biopolymer nanofibrils.

Advanced Biomass-Derived Electrocatalysts for the Oxygen Reduction Reaction

Recent progress in advanced nanostructures synthesized from biomass resources for the oxygen reduction reaction (ORR) is reviewed. The ORR plays a significant role in the performance of numerous energy-conversion devices, including low-temperature hydrogen and alcohol fuel cells, microbial fuel cells, as well as metal-air batteries. The viability of such fuel cells is strongly related to the cost of the electrodes, especially the cathodic ORR electrocatalyst. Hence, inexpensive and abundant plant and animal biomass have become attractive options to obtain electrocatalysts upon conversion into active carbon. Bioresource selection and processing criteria are discussed in light of their influence on the physicochemical properties of the ORR nanostructures. The resulting electrocatalytic activity and durability are introduced and compared to those from conventional Pt/C-based electrocatalysts. These ORR catalysts are also active for oxygen or hydrogen evolution reactions.

Carbon-Based Functional Materials Derived from Waste for Water Remediation and Energy Storage

Carbon-based functional materials hold the key for solving global challenges in the areas of water scarcity and the energy crisis. Although carbon nanotubes (CNTs) and graphene have shown promising results in various fields of application, their high preparation cost and low production yield still dramatically hinder their wide practical applications. Therefore, there is an urgent call for preparing carbon-based functional materials from low-cost, abundant, and sustainable sources. Recent innovative strategies have been developed to convert various waste materials into valuable carbon-based functional materials. These waste-derived carbon-based functional materials have shown great potential in many applications, especially as sorbents for water remediation and electrodes for energy storage. Here, the research progress in the preparation of waste-derived carbon-based functional materials is summarized, along with their applications in water remediation and energy storage; challenges and future research directions in this emerging research field are also discussed.

Cotton Wool Derived Carbon Fiber Aerogel Supported Few-Layered MoSe2 Nanosheets As Efficient Electrocatalysts for Hydrogen Evolution

Recent studies have proven that newly emerging two-dimensional molybdenum diselenide (MoSe2) is a promising noble-metal-free electrocatalyst for hydrogen evolution reaction (HER). Increasing the exposures of the active edges of MoSe2 nanostructures is a key issue to fully realize the excellent electrochemical properties of MoSe2. In this work, a few-layered MoSe2/carbon fiber aerogel (CFA) hybrids have been facilely obtained through the combination of high-temperature carbonization and one-pot solvothermal reaction. CFA derived from cotton wool is used as a three-dimensional conductive network for construction of hierarchical MoSe2/CFA hybrids, where few-layered MoSe2 nanosheets are uniformly and perpendicularly decorated on the surfaces of CFA. In the designed and prepared hybrids, CFA effectively increases the exposures of the active edges of MoSe2 nanosheets as well as provides reduced lengths for both electron transportation and ion diffusion. Therefore, the obtained optimal MoSe2/CFA hybrid exhibits excellent electrochemical activity as HER electrocatalyst with a small onset potential of -0.104 V vs reversible hydrogen electrode and a small Tafel slope of 62 mV per decade, showing its great potential as a next-generation Pt-free electrocatalyst for HER.

Towards high-efficiency nanoelectrocatalysts for oxygen reduction through engineering advanced carbon nanomaterials

We summarize and discuss recent developments of different-dimensional advanced carbon nanomaterial-based noble-metal-free high-efficiency oxygen reduction electrocatalysts, including heteroatom-doped, transition metal-based nanoparticle-based, and especially iron carbide (Fe₃C)-based carbon nanomaterial composites.

Transforming waste biomass with an intrinsically porous network structure into porous nitrogen-doped graphene for highly efficient oxygen reduction

Porous nitrogen-doped graphene with a very high surface area (1152 m² g⁻¹) is synthesized by a novel strategy using intrinsically porous biomass (soybean shells) as a carbon and nitrogen source via calcination and KOH activation with outstanding oxygen reduction performance.

Shrimp-shell derived carbon nanodots as carbon and nitrogen sources to fabricate three-dimensional N-doped porous carbon electrocatalysts for the oxygen reduction reaction

3D N-doped porous carbon material was successfully fabricated by a simple template-assisted pyrolysis method, exhibiting superior ORR catalytic performance.

A low-cost cementite (Fe3C) nanocrystal@N-doped graphitic carbon electrocatalyst for efficient oxygen reduction

A core–shell structure Fe₃C nanocrystal@N-doped graphitic carbon (Fe₃C@NGC) nanocomposite was successfully fabricated, and used as an electrocatalyst with large surface area, exhibiting great potential for oxygen reduction reaction (ORR).