Atomically Dispersed Mo Sites Anchored on Multichannel Carbon Nanofibers toward Superior Electrocatalytic Hydrogen Evolution

Interfacial Design of Ti3C2Tx MXene/Graphene Heterostructures Boosted Ru Nanoclusters with High Activity Toward Hydrogen Evolution Reaction

The development of a cost-competitive and efficient electrocatalyst is both attractive and challenging for hydrogen production by hydrogen evolution reaction (HER). Herein, a facile glycol reduction method to construct Ru nanoclusters coupled with hierarchical exfoliated-MXene/reduced graphene oxide architectures (Ru-E-MXene/rGA) is reported. The hierarchical structure, formed by the self-assembly of graphene oxides, can effectively prohibit the self-stacking of MXene nanosheets. Meanwhile, the formation of the MXene/rGA interface can strongly trap the Ru3+ ions, resulting in the uniform distribution of Ru nanoclusters within Ru-E-MXene/rGA. The boosted catalytic activity and underlying catalytic mechanism during the HER process are proved by density functional theory. Ru-E-MXene/rGA exhibits overpotentials of 42 and 62 mV at 10 mA cm-2 in alkaline and acidic electrolytes, respectively. The small Tafel slope and charge transfer resistance (Rct) values elucidate its fast dynamic behavior. The cyclic voltammetry (CV) curves and chronoamperometry test confirm the high stability of Ru-E-MXene/rGA. These results demonstrate that coupling Ru nanoclusters with the MXene/rGA heterostructure represents an efficient strategy for constructing MXene-based catalysts with enhanced HER activity.

Atomic Molybdenum Nanomaterials for Electrocatalysis

As a sustainable energy technology, electrocatalytic energy conversion requires electrocatalysts, which greatly motivates the exploitation of high-performance electrocatalysts based on nonprecious metals. Molybdenum-based nanomaterials have demonstrated promise as electrocatalysts because of their unique physiochemical and electronic properties. Among them, atomic Mo catalysts, also called Mo-based single-atom catalysts (Mo-SACs), have the most accessible active sites and tunable microenvironments and are thrivingly explored in various electrochemical conversion reactions. A timely review of such rapidly developing topics is necessary to provide guidance for further exploration of optimized Mo-SACs toward electrochemical energy technologies. In this review, recent advances in the synthetic strategies for Mo-SACs are highlighted, focusing on the microenvironment engineering of Mo atoms. Then, the representative achievements of their applications in various electrocatalytic reactions involving the N2, H2O, and CO2 cycles are summarized by combining experimental and computational results. Finally, prospects for the future development of Mo-SACs in electrocatalysis are provided and the key challenges that require further investigation and optimization are highlighted.

Molybdenum single-atoms decorated multi-channel carbon nanofibers for advanced lithium-selenium batteries

The cathode in lithium-selenium (Li-Se) batteries has garnered extensive attention owing to its superior specific capacity and enhanced conductivity compared to sulfur. Nonetheless, the adoption and advancement of Li-Se batteries face significant challenges due to selenium's low reactivity, substantial volume fluctuations, and the shuttle effect associated with polyselenides. Single-atom catalysts (SACs) are under the spotlight for their outstanding catalytic efficiency and optimal atomic utilization. To address the challenges of selenium's low chemical activity and volume expansion in Li-Se batteries, through electrospun, we have developed a lotus root-inspired carbon nanofiber (CNF) material, featured internal multi-channels and anchored with molybdenum (Mo) single atoms (Mo@CNFs). Mo single atoms significantly enhance the conversion kinetics of selenium (Se), facilitating rapid formation of Li2Se. The internally structured multi-channel CNF serves as an effective host matrix for Se, mitigating its volume expansion during the electrochemical process. The resulting cathode, Se/Mo@CNF composite, exhibits a high discharge specific capacity, superior rate performance, and impressive cycle stability in Li-Se batteries. After 500 cycles at a current density of 1 C, it maintains a capacity retention rate of 82% and nearly 100% coulombic efficiency (CE). This research offers a new avenue for the application of single-atom materials in enhancing advanced Li-Se battery performance.

Hydrogen Production via Electrolysis of Wastewater

The high energy consumption of traditional water splitting to produce hydrogen is mainly due to complex oxygen evolution reaction (OER), where low-economic-value O2 gas is generated. Meanwhile, cogeneration of H2 and O2 may result in the formation of an explosive H2/O2 gas mixture due to gas crossover. Considering these factors, a favorable anodic oxidation reaction is employed to replace OER, which not only reduces the voltage for H2 production at the cathode and avoids H2/O2 gas mixture but also generates value-added products at the anode. In recent years, this innovative strategy that combines anodic oxidation for H2 production has received intensive attention in the field of electrocatalysis. In this review, the latest research progress of a coupled hydrogen production system with pollutant degradation/upgrading is systematically introduced. Firstly, wastewater purification via anodic reaction, which produces free radicals instead of OER for pollutant degradation, is systematically presented. Then, the coupled system that allows for pollutant refining into high-value-added products combined with hydrogen production is displayed. Thirdly, the photoelectrical system for pollutant degradation and upgrade are briefly introduced. Finally, this review also discusses the challenges and future perspectives of this coupled system.

Boosting electrocatalytic performance via electronic structure regulation for acidic oxygen evolution

High-purity hydrogen produced by water electrolysis has become a sustainable energy carrier. Due to the corrosive environments and strong oxidizing working conditions, the main challenge faced by acidic water oxidation is the decrease in the activity and stability of anodic electrocatalysts. To address this issue, efficient strategies have been developed to design electrocatalysts toward acidic OER with excellent intrinsic performance. Electronic structure modification achieved through defect engineering, doping, alloying, atomic arrangement, surface reconstruction, and constructing metal-support interactions provides an effective means to boost OER. Based on introducing OER mechanism commonly present in acidic environments, this review comprehensively summarizes the effective strategies for regulating the electronic structure to boost the activity and stability of catalytic materials. Finally, several promising research directions are discussed to inspire the design and synthesis of high-performance acidic OER electrocatalysts.

HER catalytic activity and regulation of a transition metal atom-anchored BC3 monolayer: a first-principles study

An atomic-level understanding of the hydrogen evolution reaction (HER) on a transition metal (TM) atom-anchored 2D monolayer is vital to explore highly efficient catalysts for hydrogen production. Here, the catalytic activities and modulation of TM atom (Ti, Fe, Cu, Zn, Mo, Ag, Au)-doped BC3 monolayers are investigated by first-principles calculations. Au@BC3 and Fe@BC3 are proven to be potentially excellent HER catalysts. Partial oxidation engineering on Zn@BC3 could improve its performance. Au@BC3 and Ti, Cu and Mo-anchored BC3 with the support of a NbB2 (0001) surface are expected to replace Pt due to the Gibbs free energy changes extremely close to zero. It is revealed that the catalytic activity of the adsorption site is highly related to the degree of charge transfer between the adsorption site and substrate.

Review of Carbon Support Coordination Environments for Single Metal Atom Electrocatalysts (SACS)

This topical review focuses on the distinct role of carbon support coordination environment of single-atom catalysts (SACs) for electrocatalysis. The article begins with an overview of atomic coordination configurations in SACs, including a discussion of the advanced characterization techniques and simulation used for understanding the active sites. A summary of key electrocatalysis applications is then provided. These processes are oxygen reduction reaction (ORR), oxygen evolution reaction (OER), hydrogen evolution reaction (HER), nitrogen reduction reaction (NRR), and carbon dioxide reduction reaction (CO2 RR). The review then shifts to modulation of the metal atom-carbon coordination environments, focusing on nitrogen and other non-metal coordination through modulation at the first coordination shell and modulation in the second and higher coordination shells. Representative case studies are provided, starting with the classic four-nitrogen-coordinated single metal atom (MN4 ) based SACs. Bimetallic coordination models including homo-paired and hetero-paired active sites are also discussed, being categorized as emerging approaches. The theme of the discussions is the correlation between synthesis methods for selective doping, the carbon structure-electron configuration changes associated with the doping, the analytical techniques used to ascertain these changes, and the resultant electrocatalysis performance. Critical unanswered questions as well as promising underexplored research directions are identified.

Correlating Single-Atomic Ruthenium Interdistance with Long-Range Interaction Boosts Hydrogen Evolution Reaction Kinetics

Correlated single-atom catalysts (c-SACs) with tailored intersite metal-metal interactions are superior to conventional catalysts with isolated metal sites. However, precise quantification of the single-atomic interdistance (SAD) in c-SACs is not yet achieved, which is essential for a crucial understanding and remarkable improvement of the correlated metal-site-governed catalytic reaction kinetics. Here, three Ru c-SACs are fabricated with precise SAD using a planar organometallic molecular design and π-π molecule-carbon nanotube confinement. This strategy results in graded SAD from 2.4 to 9.3 Å in the Ru c-SACs, wherein tailoring the Ru SAD into 7.0 Å generates an exceptionally high turnover frequency of 17.92 H2 s-1 and a remarkable mass activity of 100.4 A mg-1 under 50 and 100 mV overpotentials, respectively, which is superior to all the Ru-based catalysts reported previously. Furthermore, density functional theory calculations confirm that Ru SAD has a negative correlation with its d-band center owing to the long-range interactions induced by distinct local atomic geometries, resulting in an appropriate electrostatic potential and the highest catalytic activity on c-SACs with 7.0 Å Ru SAD. The present study promises an attractive methodology for experimentally quantifying the metal SAD to provide valuable insights into the catalytic mechanism of c-SACs.

A Versatile Extended Stöber Approach to Monodisperse Sub-40 nm Carbon Nanospheres for Stabilizing Atomically Dispersed Fe─N4 Sites Toward Efficient Oxygen Reduction Electrocatalysis

The development of atomically dispersed iron-nitrogen-carbon (Fe─N─C) catalysts as an alternative to precious platinum holds great potential for the substantial progress of a variety of oxygen reduction reaction (ORR)-associated energy conversion technologies. Nevertheless, the precise synthesis of Fe─N─C single atomic catalysts (SACs) with a high density of accessible active sites and pronounced electrocatalytic performance still remains an enormous challenge. Herein, an innovative extended Stöber method is designed for the controllable preparation of monodisperse small-sized N-doped carbon colloidal nanospheres (≈40 nm) anchoring atomically isolated Fe─N4 sites (abbreviated as Fe-SA@N-CNSs hereafter) with a narrow size distribution and high uniformity. Benefiting from the single Fe─N4 moieties and the unique spherical carbon substrate, the resultant Fe-SA@N-CNSs exhibit excellent ORR activity, outstanding long-term durability, and methanol tolerance in KOH electrolyte. More impressively, when further assembled into a flexible solid-state rechargeable zinc-air battery (ZAB), the Fe-SA@N-CNSs-driven ZAB delivers a higher open circuit voltage, a larger power density, and robust cycling/mechanical stability, outperforming the state-of-the-art Pt/C-based counterpart and further testifying the great potential of the as-prepared Fe-SA@N-CNSs in diverse ORR-related practical energy devices. The developed extended Stöber method provides an efficient and versatile avenue toward the preparation of a series of well-defined SACs for diverse electrocatalytic systems.

Tuning the Coordination Environment of Carbon-Based Single-Atom Catalysts via Doping with Multiple Heteroatoms and Their Applications in Electrocatalysis

Carbon-based single-atom catalysts (SACs) are considered to be a perfect platform for studying the structure-activity relationship of different reactions due to the adjustability of their coordination environment. Multi-heteroatom doping has been demonstrated as an effective strategy for tuning the coordination environment of carbon-based SACs and enhancing catalytic performance in electrochemical reactions. Herein, recently developed strategies for multi-heteroatom doping, focusing on the regulation of single-atom active sites by heteroatoms in different coordination shells, are summarized. In addition, the correlation between the coordination environment and the catalytic activity of carbon-based SACs are investigated through representative experiments and theoretical calculations for various electrochemical reactions. Finally, concerning certain shortcomings of the current strategies of doping multi-heteroatoms, some suggestions are put forward to promote the development of carbon-based SACs in the field of electrocatalysis.

Template-assisted Fabrication of O-doped CoP Microflowers with Optimal Electronic Modulation for Electrochemical Hydrogen Evolution

Exploring efficient, affordable and stable electrocatalyst toward hydrogen evolution reaction (HER) is of great scientific significance for the practical implementation of the water splitting. The heteroatom doping represents a serviceable strategy to further elevate the catalytic performance for a transition metal-based electrocatalyst because of the electronic regulation effect. Herein, a reliable self-sacrificial template-engaged approach is proposed to synthesize O-doped CoP (denoted as O-CoP) microflowers, which simultaneously considers the regualtion of electronic configuration via anion doping and sufficient exposure of active sites via nanostructure engineering. The suitable O incorporation content in CoP matrix could tremendously modify the electronic configuration, accelerate the charge transfer, promote the exposure of active sites, strengthen the electrical conductivity, and adjust the adsorption state of H*. Consequently, the optimized O-CoP microflowers with optimal O concentration display a remarkable HER property with a small overpotential of 125 mV to afford a current density of 10 mA cm-2 , a low Tafel slope of 68 mV dec-1 and long-term durability for 32 h under alkaline electrolyte, manifesting a considerable potential application for hydrogen production at large scale. The integration of anion incorporation and architecture engineering in this work will bring in a depth insight for the design of low-cost and effective electrocatalysts in energy conversion and storage systems.

One-dimensional carbon based nanoreactor fabrication by electrospinning for sustainable catalysis

An efficient and economical electrocatalyst as kinetic support is key to electrochemical reactions. For this reason, chemists have been working to investigate the basic changing of chemical principles when the system is confined in limited space with nanometer-scale dimensions or sub-microliter volumes. Inspired by biological research, the design and construction of a closed reaction environment, namely the reactor, has attracted more and more interest in chemistry, biology, and materials science. In particular, nanoreactors became a high-profile rising star and different types of nanoreactors have been fabricated. Compared with the traditional particle nanoreactor, the one-dimensional (1D) carbon-based nanoreactor prepared by the electrospinning process has better electrolyte diffusion, charge transfer capabilities, and outstanding catalytic activity and selectivity than the traditional particle catalyst which has great application potential in various electrochemical catalytic reactions.

Interfacial Engineering of CoN/Co3 O4 Heterostructured Hollow Nanoparticles Embedded in N-Doped Carbon Nanowires as a Bifunctional Oxygen Electrocatalyst for Rechargeable Liquid and Flexible all-Solid-State Zn-Air Batteries

The design of economical, efficient, and robust bifunctional oxygen electrocatalysts is greatly imperative for the large-scale commercialization of rechargeable Zn-air battery (ZAB) technology. Herein, the neoteric design of an advanced bifunctional electrocatalyst composed of CoN/Co₃ O₄ heterojunction hollow nanoparticles in situ encapsulated in porous N-doped carbon nanowires (denoted as CoN/Co₃ O₄ HNPs@NCNWs hereafter) is reported. The simultaneous implementation of interfacial engineering, nanoscale hollowing design, and carbon-support hybridization renders the synthesized CoN/Co₃ O₄ HNPs@NCNWs with modified electronic structure, improved electric conductivity, enriched active sites, and shortened electron/reactant transport pathways. Density functional theory computations further demonstrate that the construction of a CoN/Co₃ O₄ heterojunction can optimize the reaction pathways and reduce the overall reaction barriers. Thanks to the composition and architectural superiorities, the CoN/Co₃ O₄ HNPs@NCNWs exhibit distinguished oxygen reduction reaction and oxygen evolution reaction performance with a low reversible overpotential of 0.725 V and outstanding stability in KOH medium. More encouragingly, the homemade rechargeable liquid and flexible all-solid-state ZABs utilizing CoN/Co₃ O₄ HNPs@NCNWs as the air-cathode deliver higher peak power densities, larger specific capacities, and robust cycling stability, exceeding the commercial Pt/C + RuO₂ benchmark counterparts. The concept of heterostructure-induced electronic modification herein may shed light on the rational design of advanced electrocatalysts for sustainable energy applications.

Manipulating the Rectifying Contact between Ultrafine Ru Nanoclusters and N-Doped Carbon Nanofibers for High-Efficiency pH-Universal Electrocatalytic Hydrogen Evolution

The rational design of ingenious strategies to boost the intrinsic activity and stability of ruthenium (Ru) is of great importance for the substantial progression of water electrolysis technology. Based on Mott-Schottky effect, electronic regulation within a metal/semiconductor hybrid electrocatalyst represents a versatile strategy to boost the electrochemical performance. Herein, a typical Mott-Schottky hydrogen evolution reaction (HER) electrocatalyst composed of uniform ultrafine Ru nanoclusters in situ anchored on N-doped carbon nanofibers (abbreviated as Ru@N-CNFs hereafter) through a feasible and scalable "phenolic resin-bridged" strategy is reported. Both spectroscopy analyses and density functional theory calculations manifest that such rectifying contact can induce the spontaneous electron transfer from Ru to N-doped carbon nanofibers to generate a built-in electric field, thus enormously promoting the charge transfer efficiency and HER intrinsic activity. Moreover, the seamless immobilization of Ru nanoclusters on the substrate can prevent the active sites from unfavorable migration, coarsening, and detachment, rendering the excellent structural stability. Consequently, the well-designed Ru@N-CNFs afford prominent pH-universal HER performances with small overpotentials of 16 and 17 mV at 10 mA cm^-2 and low Tafel slopes of 31.8 and 28.5 mV dec^-1 in acidic and alkaline electrolytes, respectively, which are superior to the state-of-the-art commercial Pt/C and Ru/C benchmarks.

Embedding Atomically Dispersed Iron Sites in Nitrogen-Doped Carbon Frameworks-Wrapped Silicon Suboxide for Superior Lithium Storage

Silicon suboxide (SiO_x ) has attracted widespread interest as Li-ion battery (LIB) anodes. However, its undesirable electronic conductivity and apparent volume effect during cycling impede its practical applications. Herein, sustainable rice husks (RHs)-derived SiO₂ are chosen as a feedstock to design SiO_x /iron-nitrogen co-doped carbon (Fe-N-C) materials. Using a facile electrospray-carbonization strategy, SiO_x nanoparticles (NPs) are encapsulated in the nitrogen-doped carbon (N-C) frameworks decorating atomically dispersed iron sites. Systematic characterizations including high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) and X-ray absorption fine structure (XAFS) verify the existence of Fe single atoms and typical coordination environment. Benefiting from its structural and compositional merits, the SiO_x /Fe-N-C anode delivers significantly improved discharge capacity of 799.1 mAh g^-1 , rate capability, and exceptional durability, compared with pure SiO₂ and SiO_x /N-C, which has been revealed by the density functional theory (DFT) calculations. Additionally, the electrochemical tests and in situ X-ray diffraction (XRD) analysis reveal the oxidation of Li_x Si phase and the storage mechanism. The synthetic strategy is universal for the design and synthesis of metal single atoms/clusters dispersed N-C frameworks encapsulated SiO_x NPs. Meanwhile, this work provides impressive insights into developing various LIB anode materials suffering from inferior conductivity and huge volume fluctuations.

Designing a Built-In Electric Field for Efficient Energy Electrocatalysis

To utilize intermittent renewable energy as well as achieve the goals of peak carbon dioxide emissions and carbon neutrality, various electrocatalytic devices have been developed. However, the electrocatalytic reactions, e.g., hydrogen evolution reaction/oxygen evolution reaction in overall water splitting, polysulfide conversion in lithium-sulfur batteries, formation/decomposition of lithium peroxide in lithium-oxygen batteries, and nitrate reduction reaction to degrade sewage, suffer from sluggish kinetics caused by multielectron transfer processes. Owing to the merits of accelerated charge transport, optimized adsorption/desorption of intermediates, raised conductivity, regulation of the reaction microenvironment, as well as ease to combine with geometric characteristics, the built-in electric field (BIEF) is expected to overcome the above problems. Here, we give a Review about the very recent progress of BIEF for efficient energy electrocatalysis. First, the construction strategies and the characterization methods (qualitative and quantitative analysis) of BIEF are summarized. Then, the up-to-date overviews of BIEF engineering in electrocatalysis, with attention on the electron structure optimization and reaction microenvironment modulation, are analyzed and discussed in detail. In the end, the challenges and perspectives of BIEF engineering are proposed. This Review gives a deep understanding on the design of electrocatalysts with BIEF for next-generation energy storage and electrocatalytic devices.

Macro/Micro-Environment Regulating Carbon-Supported Single-Atom Catalysts for Hydrogen/Oxygen Conversion Reactions

Single-atom catalysts (SACs) have attracted tremendous research interest due to their unique atomic structure, maximized atom utilization, and remarkable catalytic performance. Among the SACs, the carbon-supported SACs have been widely investigated due to their easily controlled properties of the carbon substrates, such as the tunable morphologies, ordered porosity, and abundant anchoring sites. The electrochemical performance of carbon-supported SACs is highly related to the morphological structure of carbon substrates (macro-environment) and the local coordination environments of center metals (micro-environment). This review aims to provide a comprehensive summary on the macro/micro-environment regulating carbon-supported SACs for highly efficient hydrogen/oxygen conversion reactions. The authors first summarize the macro-environment engineering strategies of carbon-supported SACs with altered specific surface areas and porous properties of the carbon substrates, facilitating the mass diffusion kinetics and structural stability. Then the micro-environment engineering strategies of carbon-supported SACs are discussed with the regulated atomic structure and electronic structure of metal centers, boosting the catalytic performance. Insights into the correlation between the co-boosted effect from the macro/micro-environments and catalytic activity for hydrogen/oxygen conversion reactions are summarized and discussed. Finally, the challenges and perspectives are addressed in building highly efficient carbon-supported SACs for practical applications.

Tailoring Bond Microenvironments and Reaction Pathways of Single-Atom Catalysts for Efficient Water Electrolysis

Single-Atom Sites (SASs) are commonly stabilized and influenced by neighboring atoms in the host; disclosing the structure-reactivity relationships of SASs in water electrolysis are the grand challenges originating from the enormous support materials with complex structures. Through a multidisciplinary view of the design principles, synthesis strategies, characterization techniques, and theoretical analysis of structure-performance correlations, this timely review is dedicated to summarizing the most recent progress in tailoring bond microenvironments on different supports and discussing the reaction pathways and performance advantages of different SAS structures for water electrolysis . The essences and mechanisms of how SAS structures influence their electrocatalysis and the critical needs for their future developments are discussed. Finally, the challenges and perspectives are also provided to stimulate their practically widespread utilization in water-splitting electrolyzers.

Silver decorated nickel-cobalt (oxy)hydroxides fabricated via surface reconstruction engineering for boosted electrocatalytic oxygen evolution and urea oxidation

Electrochemical water splitting is considered to be a promising renewable hydrogen generation technology but is significantly limited by the kinetically sluggish oxygen evolution reaction (OER) at the anode. Herein, a silver nanoparticle decorated nickel-cobalt (oxy)hydroxide composite is fabricated on nickel foam (Ag@NiCo(OH)_x/NF) via electrodeposition followed by spontaneous redox reaction. Benefitting from the synergetic contributions of an amorphous/crystalline phase, abundant artificial heterointerfaces, and a 3D porous architecture, the as-designed Ag@NiCo(OH)_x/NF shows substantially enhanced electrocatalytic performance toward the OER and urea oxidation reaction. Impressively, in the urea-assisted alkaline electrolyzer (coupled with commercial Pt/C on NF as the cathode) for hydrogen production, a cell voltage of only 1.49 V is required to deliver a current density of 50 mA cm^-2, much lower than that of traditional water splitting (1.69 V). Importantly, this work represents a facile and feasible method to exploit efficient self-supported electrocatalysts toward overall water splitting and urea-rich wastewater purification.

Cobalt nanoparticles embedded into nitrogen-doped graphene with abundant macropores as a bifunctional electrocatalyst for rechargeable zinc-air batteries

Nitrogen doped carbon materials containing transition metal nanoparticles have attracted much attention as bifunctional oxygen electrocatalysts. In this paper, the template etching method is used to obtain the nitrogen-doped graphene with abundant macropores embedded with cobalt nanoparticles (Co@N-C). The prepared Co@NC-800 catalyst has a half-wave potential (E 1/2= 0.835V) close to Pt/C and good stability in excess of Pt/C for oxygen reduction reaction (ORR). At the same time, the catalyst has good oxygen evolution reaction (OER) performance. In addition, zinc-air batteries (ZABs) based on the Co@NC-800 catalyst show good cycle stability of up to 200000 s and high power density of 73.5 mW cm -2 . The synergistic effect of the integrated component between nitrogen-doped graphene and cobalt nanoparticles as well as the macroporous structure endow Co@NC-800 with abundant exposed active sites and mass/electron transfer capacity, thus leading to the high electrocatalytic activity. This work shows potential for practical applications in electrochemistry.

Manipulation of Mott-Schottky Ni/CeO2 Heterojunctions into N-Doped Carbon Nanofibers for High-Efficiency Electrochemical Water Splitting

Designing affordable and efficient bifunctional electrocatalysts for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) has remained a long-lasting target for the progressing hydrogen economy. Utilization of metal/semiconductor interface effect has been lately established as a viable implementation to realize the favorable electrocatalytic performance due to the built-in electric field. Herein, a typical Mott-Schottky electrocatalyst by immobilizing Ni/CeO₂ hetero-nanoparticles onto N-doped carbon nanofibers (abbreviated as Ni/CeO₂ @N-CNFs hereafter) has been developed via a feasible electrospinning-carbonization tactic. Experimental findings and theoretic calculations substantiate that the elaborated constructed Ni/CeO₂ heterojunction effectively triggers the self-driven charge transfer on heterointerfaces, leading to the promoted charge transfer rate, the optimized chemisorption energies for reaction intermediates and ultimately the expedited reaction kinetics. Therefore, the well-designed Ni/CeO₂ @N-CNFs deliver superior HER and OER catalytic activities with overpotentials of 100 and 230 mV at 10 mA cm^-2 , respectively, in alkaline solution. Furthermore, the Ni/CeO₂ @N-CNFs-equipped electrolyzer also exhibits a low cell voltage of 1.56 V to attain 10 mA cm^-2 and impressive long-term durability over 55 h. The innovative manipulation of electronic modulation via Mott-Schottky establishment may inspire the future development of economical electrocatalysts for diverse sustainable energy systems.

One-dimensional amorphous cobalt(ii) metal–organic framework nanowire for efficient hydrogen evolution reaction

The CoCH@Co-MOF-30 nanowire shows outstanding activity in HER for water splitting.