Vanadium-Doped Heterointerfaced Ni3N-MoOx Nanosheets with Optimized H and H2O Adsorption for Effective Alkaline Hydrogen Electrocatalysis.

Nickel (Ni)-based materials represent a compelling avenue as platinum alternatives in the realm of alkaline hydrogen electrocatalysis. However, conventional nickel nitrides (Ni3N) have long been hindered by sluggish hydrogen evolution kinetics in alkaline environments, owing to inadequate adsorption strengths of both hydrogen and water molecules. Herein, a novel approach is presented involving the design of vanadium (V)-doped Ni3N/MoOx heterogeneous nanosheets (V-Ni3N@MoOx), engineered to achieve optimized adsorption strengths for hydrogen evolution and oxidation reactions (HER/HOR). Theoretical insights underscore the superior catalytic performance of this composite, attributed to a synergistic interplay between unique V doping and the heterointerfaced structure. This synergistic effect not only fine-tunes the electronic structure, establishing an optimal d band center to mitigate proton over-bonding, but also ameliorates the energy barrier through enhanced H2O dissociation capability. Consequently, V-Ni3N@MoOx manifests remarkable catalytic activities, evincing an overpotential of 56 mV at 10 mA cm-2 for HER and an exchange current density of 1.91 mA cm-2 for HOR in alkaline media. Notably, the stability assessment reveals the enduring performance of V-Ni3N@MoOx for HER/HOR, exhibiting no activity decay over extended operational durations. This study underscores the efficacy of heterogeneous interface modulation as a transformative strategy in designing Ni-based materials for alkaline hydrogen electrocatalysis.

Taking Advantage of Potential Coincidence Region: Insights into Gas Production Behavior in Advanced Self-Activated Hydrazine-Assisted Alkaline Seawater Electrolysis.

Water electrolysis assisted by hydrazine has emerged as a prospective energy conversion method for achieving efficient hydrogen generation. Due to the potential coincidence region (PCR) between the hydrogen evolution reaction (HER) and the electro-oxidation of hydrazine, the hydrazine oxidation reaction (HzOR) offers distinct advantages in terms of strategy amalgamation, device architecture, and the broadening of application horizons. Herein, we report a bifunctional electrocatalyst of interfacial heterogeneous Fe2P/Co2P microspheres supported on Ni foam (FeCoP/NF). Benefiting from the strong interfacial coupling effect between Fe2P and Co2P and the three-dimensional microsphere structure, FeCoP/NF exhibits outstanding bifunctional electrocatalytic performance, achieving 10 mA cm-2 with low overpotentials of 10 and 203 mV for HER and HzOR, respectively. Utilizing FeCoP/NF for both electrodes in HzOR-assisted water electrolysis results in significantly reduced potentials of 820 mV for 1 A cm-2 in contrast to the electro-oxidation of alternative chemical substrates. The presence of a potential coincidence region makes the application of self-activated seawater electrolysis realistic. The gas production behavior at different current densities in this interesting hydrogen production system is discussed, and some rules that are distinguished from conventional water electrolysis are summarized. Furthermore, a new self-powered hydrogen production system with a direct hydrazine fuel cell, rechargeable Zn-hydrazine battery, and hydrazine-assisted seawater electrolysis is proposed, emphasizing the distinct benefits of HzOR and its potential role in electrochemical energy conversion technologies powered by renewable sources.

Changes in α-Dicarbonyl Compound Contents during Storage of Various Fruits and Juices.

α-Dicarbonyl compounds (α-DCs) are commonly present in various foods. We conducted the investigation into concentration changes of α-DCs including 3-deoxyglucosone (3-DG), glyoxal (GO), and methylglyoxal (MGO) in fresh fruits and decapped commercial juices during storage at room temperature and 4 °C, as well as in homemade juices during storage at 4 °C. The studies indicate the presence of α-DCs in all samples. The initial contents of 3-DG in the commercial juices (6.74 to 65.61 µg/mL) are higher than those in the homemade ones (1.97 to 4.65 µg/mL) as well as fruits (1.58 to 3.33 µg/g). The initial concentrations of GO and MGO are normally less than 1 µg/mL in all samples. During storage, the α-DC levels in the fruits exhibit an initial increase followed by a subsequent decrease, whereas, in all juices, they tend to accumulate continuously over time. As expected, 4 °C storage reduces the increase rates of the α-DC concentrations in most samples. From the viewpoint of the α-DC contents, fruits and homemade juices should always be the first choice for daily intake of nutrients and commercial juices ought to be mostly avoided.

Artificial Heterointerfaces with Regulated Charge Distribution of Ni Active Sites for Urea Oxidation Reaction.

In contrast to the thermodynamically unfavorable anodic oxygen evolution reaction, the electrocatalytic urea oxidation reaction (UOR) presents a more favorable thermodynamic potential. However, the practical application of UOR has been hindered by sluggish kinetics. In this study, hierarchical porous nanosheet arrays featuring abundant Ni-WO3 heterointerfaces on nickel foam (Ni-WO3/NF) is introduced as a monolith electrode, demonstrating exceptional activity and stability toward UOR. The Ni-WO3/NF catalyst exhibits unprecedentedly rapid UOR kinetics (200 mA cm-2 at 1.384 V vs. RHE) and a high turnover frequency (0.456 s-1), surpassing most previously reported Ni-based catalysts, with negligible activity decay observed during a durability test lasting 150 h. Ex situ X-ray photoelectron spectroscopy and density functional theory calculations elucidate that the WO3 interface significantly modulates the local charge distribution of Ni species, facilitating the generation of Ni3+ with optimal affinity for interacting with urea molecules and CO2 intermediates at heterointerfaces during UOR. This mechanism accelerates the interfacial electrocatalytic kinetics. Additionally, in situ Fourier transform infrared spectroscopy provides deep insights into the substantial contribution of interfacial Ni-WO3 sites to UOR electrocatalysis, unraveling the underlying molecular-level mechanisms. Finally, the study explores the application of a direct urea fuel cell to inspire future practical implementations.

Self-Powered Hydrogen Production with Improved Energy Efficiency via Polysulfides Redox.

In the pursuit of efficient solar-driven electrocatalytic water splitting for hydrogen production, the intrinsic challenges posed by the sluggish kinetics of anodic oxygen evolution and intermittent sunlight have prompted the need for innovative energy systems. Here, we introduce an approach by coupling the polysulfides oxidation reaction with the hydrogen evolution reaction for energy-saving H2 production, which could be powered by an aqueous zinc-polysulfides battery to construct a self-powered energy system. This unusual hybrid water electrolyzer achieves 300 mA cm-2 at a low cell voltage of 1.14 V, saving electricity consumption by 100.4% from 5.47 to 2.73 kWh per m3 H2 compared to traditional overall water splitting. Benefiting from the favorable reaction kinetics of polysulfides oxidation/reduction, the aqueous zinc-polysulfides battery exhibits an energy efficiency of approximately 89% at 1.0 mA cm-2. Specially, the zinc-polysulfide battery effectively stores intermittent solar energy as chemical energy during light reaction by solar cells. Under an unassisted light reaction, the batteries could release energy to drive H2 production through a hybrid water electrolyzer for uninterrupted hydrogen production. Therefore, the aim of simultaneously generating H2 and eliminating the restrictions of intermittent sunlight is realized by combining the merits of polysulfides redox, an aqueous metal-polysulfide battery, and solar cells. We believe that this concept and utilization of polysulfides redox will inspire further fascinating attempts for the development of sustainable energy via electrocatalytic reactions.

Enabling Internal Electric Field in Heterogeneous Nanosheets to Significantly Accelerate Alkaline Hydrogen Electrocatalysis.

Efficient bifunctional hydrogen electrocatalysis, encompassing both hydrogen evolution reaction (HER) and hydrogen oxidation reaction (HOR), is of paramount significance in advancing hydrogen-based societies. While non-precious-metal-based catalysts, particularly those based on nickel (Ni), are essential for alkaline HER/HOR, their intrinsic catalytic activity often falls short of expectations. Herein, an internal electric field (IEF) strategy is introduced for the engineering of heterogeneous nickel-vanadium oxide nanosheet arrays grown on porous nickel foam (Ni-V2 O3 /PNF) as bifunctional electrocatalysts for hydrogen electrocatalysis. Strikingly, the Ni-V2 O3 /PNF delivers 10 mA cm-2 at an overpotential of 54 mV for HER and a mass-specific kinetic current of 19.3 A g-1 at an overpotential of 50 mV for HOR, placing it on par with the benchmark 20% Pt/C, while exhibiting enhanced stability in alkaline electrolytes. Density functional theory calculations, in conjunction with experimental characterizations, unveil that the interface IEF effect fosters asymmetrical charge distributions, which results in more thermoneutral hydrogen adsorption Gibbs free energy on the electron-deficient Ni side, thus elevating the overall efficiency of both HER and HOR. The discoveries reported herein guidance are provided for further understanding and designing efficient non-precious-metal-based electrocatalysts through the IEF strategy.

High-entropy alloys in electrocatalysis: from fundamentals to applications.

High-entropy alloys (HEAs) comprising five or more elements in near-equiatomic proportions have attracted ever increasing attention for their distinctive properties, such as exceptional strength, corrosion resistance, high hardness, and excellent ductility. The presence of multiple adjacent elements in HEAs provides unique opportunities for novel and adaptable active sites. By carefully selecting the element configuration and composition, these active sites can be optimized for specific purposes. Recently, HEAs have been shown to exhibit remarkable performance in electrocatalytic reactions. Further activity improvement of HEAs is necessary to determine their active sites, investigate the interactions between constituent elements, and understand the reaction mechanisms. Accordingly, a comprehensive review is imperative to capture the advancements in this burgeoning field. In this review, we provide a detailed account of the recent advances in synthetic methods, design principles, and characterization technologies for HEA-based electrocatalysts. Moreover, we discuss the diverse applications of HEAs in electrocatalytic energy conversion reactions, including the hydrogen evolution reaction, hydrogen oxidation reaction, oxygen reduction reaction, oxygen evolution reaction, carbon dioxide reduction reaction, nitrogen reduction reaction, and alcohol oxidation reaction. By comprehensively covering these topics, we aim to elucidate the intricacies of active sites, constituent element interactions, and reaction mechanisms associated with HEAs. Finally, we underscore the imminent challenges and emphasize the significance of both experimental and theoretical perspectives, as well as the potential applications of HEAs in catalysis. We anticipate that this review will encourage further exploration and development of HEAs in electrochemistry-related applications.

Heteroatom-Induced Accelerated Kinetics on Nickel Selenide for Highly Efficient Hydrazine-Assisted Water Splitting and Zn-Hydrazine Battery.

Hydrazine-assisted water electrolysis is a promising energy conversion technology for highly efficient hydrogen production. Rational design of bifunctional electrocatalysts, which can simultaneously accelerate hydrogen evolution reaction (HER)/hydrazine oxidation reaction (HzOR) kinetics, is the key step. Herein, we demonstrate the development of ultrathin P/Fe co-doped NiSe2 nanosheets supported on modified Ni foam (P/Fe-NiSe2) synthesized through a facile electrodeposition process and subsequent heat treatment. Based on electrochemical measurements, characterizations, and density functional theory calculations, a favorable "2 + 2" reaction mechanism with a two-step HER process and a two-step HzOR step was fully proved and the specific effect of P doping on HzOR kinetics was investigated. P/Fe-NiSe2 thus yields an impressive electrocatalytic performance, delivering a high current density of 100 mA cm-2 with potentials of - 168 and 200 mV for HER and HzOR, respectively. Additionally, P/Fe-NiSe2 can work efficiently for hydrazine-assisted water electrolysis and Zn-Hydrazine (Zn-Hz) battery, making it promising for practical application.

Taking Advantage of Potential Coincidence Region: Advanced Self-Activated/Propelled Hydrazine-Assisted Alkaline Seawater Electrolysis and Zn-Hydrazine Battery.

Hydrazine-assisted water electrolysis presents a promising energy conversion technology for highly efficient hydrogen production. Owing to the potential coincidence region between hydrogen evolution reaction (HER) and hydrazine electro-oxidation, hydrazine oxidation reaction (HzOR) exhibits specific advantages on strategy combination, device construction, and application expansion. Herein, we report a bifunctional electrocatalyst of porous Ni foam-supported interfacial heterogeneous Ni2P/Co2P microspheres (denoted NiCoP/NF), which takes full advantage of this potential coincidence region. Thanks to the 3D microsphere structure and strong interfacial coupling effects between Ni2P and Co2P, NiCoP/NF demonstrates excellent bifunctional electrocatalytic performance, requiring ultralow overpotentials of 70 and 230 mV at 10 mA cm-2 for HER and HzOR, respectively. When using NiCoP/NF as both electrodes, HzOR-assisted water electrolysis exhibits considerably decreased potentials compared with the electro-oxidation of other chemical substrates. Furthermore, the potential coincidence region of 0.1 V makes the application of self-activated/propelled hydrazine-assisted alkaline seawater electrolysis, hydrazine-containing wastewater treatment, and Zn-hydrazine (Zn-Hz) battery realistic. The concept of potential coincidence region provided in this work has significant implications for water electrolysis and other related applications.

Rational Synthesis of Core-Shell-Structured Nickel Sulfide-Based Nanostructures for Efficient Seawater Electrolysis.

Versatile electrocatalysis at higher current densities for natural seawater splitting to produce hydrogen demands active and robust catalysts to overcome the severe chloride corrosion, competing chlorine evolution, and catalyst poisoning. Hereto, the core-shell-structured heterostructures composed of amorphous NiFe hydroxide layer capped Ni3 S2 nanopyramids which are directly grown on nickel foam skeleton (NiS@LDH/NF) are rationally prepared to regulate cooperatively electronic structure and mass transport for boosting oxygen evolution reaction (OER) performance at larger current densities. The prepared NiS@LDH/NF delivers the anodic current density of 1000 mA cm-2 at the overpotential of 341 mV in 1.0 m KOH seawater. The feasible surface reconstruction of Ni3 S2 -FeNi LDH interfaces improves the chemical stability and corrosion resistance, ensuring the robust electrocatalytic activity in seawater electrolytes for continuous and stable oxygen evolution without any hypochlorite production. Meanwhile, the designed Ni3 S2 nanopyramids coated with FeNi2 P layer (NiS@FeNiP/NF) still exhibit the improved hydrogen evolution reaction (HER) activity in 1.0 m KOH seawater. Furthermore, the NiS@FeNiP/NF||NiS@LDH/NF pair requires cell voltage of 1.636 V to attain 100 mA cm-2 with a 100% Faradaic efficiency, exhibiting tremendous potential for hydrogen production from seawater.

Interface Metal Oxides Regulating Electronic State around Nickel Species for Efficient Alkaline Hydrogen Electrocatalysis.

Heterogeneous electrocatalysis typically depends on the surface electronic states of active sites. Modulating the surface charge state of an electrocatalysts can be employed to improve performance. Among all the investigated materials, nickel (Ni)-based catalysts are the only non-noble-metal-based alternatives for both hydrogen oxidation and evolution reactions (HOR and HER) in alkaline electrolyte, while their activities should be further improved because of the unfavorable hydrogen adsorption behavior. Hereto, Ni with exceptional HOR electrocatalytic performance by changing the d-band center by metal oxides interface coupling formed in situ is endowed. The resultant MoO2 coupled Ni heterostructures exhibit an apparent HOR activity, even approaching to that of commercial 20% Pt/C benchmark, but with better long-term stability in alkaline electrolyte. An exceptional HER performance is also achieved by the Ni-MoO2 heterostructures. The experiment results are rationalized by the theoretical calculations, which indicate that coupling MoO2 with Ni results in the downshift of d-band center of Ni, and thus weakens hydrogen adsorption and benefits for hydroxyl adsorption. This concept is further proved by other metal oxides (e.g., CeO2 , V2 O3 , WO3 , Cr2 O3 )-formed Ni-based heterostructures to engineer efficient hydrogen electrocatalysts.

Defect-rich cobalt pyrophosphate hybrids decorated Cd0.5Zn0.5S for efficient photocatalytic hydrogen evolution: Defect and interface engineering.

Photocatalysts with highly efficient charge separation are of critical significance for improving photocatalytic hydrogen production performance. Herein, a cost-effective and high-performance composite photocatalyst, cobalt-phosphonate-derived defect-rich cobalt pyrophosphate hybrids (CoPPi-M) modified Cd0.5Zn0.5S is rationally devised via defect and interface engineering, in which the co-catalyst CoPPi-M delivers a strong interaction with host photocatalyst Cd0.5Zn0.5S, rendering Cd0.5Zn0.5S/CoPPi-M with a remarkably improved efficiency of charge separation and migration. Besides, Cd0.5Zn0.5S/CoPPi-M exhibits a hydrophilic surface with ample access to electrons and a strong reduction ability of electrons. Benefiting from these advantages, the integration of defect-rich cobalt pyrophosphate and Cd0.5Zn0.5S enables Cd0.5Zn0.5S/CoPPi-M-5% with high photocatalytic H2 production rate of 6.87 mmol g-1h-1, which is 2.46 times higher than that of pristine Cd0.5Zn0.5S, and the notable apparent quantum efficiency (AQE) is 20.7% at 420 nm. This work provides a promising route for promoting the photocatalytic performance of non-precious hybrid photocatalyst via defect and interface engineering, and advances energy-generation and environment-restoration devices.

Aqueous Rechargeable Zn-N2 Battery Assembled by Bifunctional Cobalt Phosphate Nanocrystals-Loaded Carbon Nanosheets for Simultaneous NH3 Production and Power Generation.

Developing cost-effective and controllable technologies beyond traditional overall N2 electrocatalysis is critical for the large-scale production of NH3 through electrochemical N2 reduction reaction (NRR) under ambient conditions. Herein, the aqueous rechargeable Zn-N2 battery, assembled by coupling the bifunctional cobalt phosphate nanocrystals-loaded heteroatoms-doped carbon nanosheets (CoPi/NPCS) as cathode electrocatalyst and the commercial Zn plate as anode with KOH electrolyte, was fabricated for the sustainable reduction of N2 to NH3 and power generation during discharge process. Benefiting from the desirable active components of cobalt phosphate nanocrystals and the synergistic effect between nanocrystals and carbon substrates, the CoPi/NPCS catalyst exhibits the enhanced NRR and oxygen evolution reaction (OER) performance in alkaline electrolyte. And the cobalt phosphates are confirmed as active components through the associative pathway toward NRR. When measured in the flow battery configuration with gas diffusion electrode by flowing N2 during discharge, this CoPi/NPCS-catalyzed Zn-N2 battery enables the high N2-to-NH3 yield rate of 14.7 µg h-1 mgcat.-1 and Faradaic efficiency of 16.35% at 0.6 V vs Zn2+/Zn, which can be able to maintain stable in discharge processes during cycling tests. Moreover, the impressive power output of the peak power density of 0.49 mW cm-2 and the energy density of 147.6 mWh gzn-1 are still achieved by this Zn-N2 battery, which are both higher than those of previously reported Zn-N2 batteries. This work not only provides the guideline for the rational design of robust and active bifunctional NRR-OER catalysts but also develops a reasonable and promising technology for efficient electrochemical N2-to-NH3 and power generation.

Spatially isolated cobalt oxide sites derived from MOFs for direct propane dehydrogenation.

The "active site isolation" strategy has been proved to be efficient for enhancing the catalytic performance in propane dehydrogenation (PDH). Herein, spatially isolated cobalt oxide sites within nitrogen-doped carbon (NC) layers supported on silicalite-1 zeolite (CoOx@NC/S-1) were synthesized by a two-step process consisting of the pyrolysis of bimetallic Zn/Co zeolitic imidazole frameworks loaded on silicalite-1 (ZnCo-ZIF/S-1) under N2 and the subsequent calcination in air atmosphere. This catalyst possesses exceptional catalytic performance for PDH with the propane conversion of 40% and the propene selectivity of >97%, and no apparent deactivation is observed after 10 h PDH reaction at 600 °C. With intensive characterizations and experiments, it is indicated that the real active sites of CoOx@NC/S-1 are isolated CoO sites during the PDH process. In situ FT-IR spectroscopy shows the same intermediate product (Co-C3H7) during both propane dehydrogenation and propene hydrogenation, indicating that they have a reverse reaction process, and a reaction mechanism for PDH is proposed accordingly.

Mesoporous CdxZn1-xS with abundant surface defects for efficient photocatalytic hydrogen production.

The practical application of photocatalytic water splitting for hydrogen evolution hinges on the development of high-efficient and low-cost photocatalysts. Defects engineering has emerged as a promising strategy to enhance photocatalytic activity effectively. Herein, a facile and versatile co-precipitation method is proposed to fabricate mesoporous Cd-Zn-S solid solutions (E-CdxZn1-xS) with abundant surface defects by the inorganic salts formed in the reaction system as self-template. Compared with Cd-Zn-S solid solutions (W-Cd0.65Zn0.35S) prepared by the traditional co-precipitation method, the enhanced specific surface area and abundant surface defects endow E-Cd0.65Zn0.35S with more accessible active sites and effective separation of electron-hole pairs for the photocatalytic water splitting reaction. The E-Cd0.65Zn0.35S solid solution exhibits hydrogen evolution rate of 5.2 mmol h-1 g-1 without loading noble metal as cocatalyst under visible light, which is 1.13 times higher than that of W-Cd0.65Zn0.35S sample. The present work provides a simple, low-cost and prospective strategy for the synthesis of defective Cd-Zn-S solid solutions, and it also delivers guidance to design and develop the advanced visible-light photocatalyst in the future.

Transition Metal Phosphide-Based Materials for Efficient Electrochemical Hydrogen Evolution: A Critical Review.

As hydrogen has been increasingly considered as promising sustainable energy supply, electrochemical overall water splitting driven by highly efficient non-noble metal electrocatalysts has aroused extensive attention. Transition metal phosphides (TMPs) have demonstrated remarkable electrocatalytic performance, including high activity and robust durability towards hydrogen evolution reaction (HER) in acidic and alkaline as well as neutral electrolytes. In this Review, up-to-date progress of TMP-based HER electrocatalysts is summarized. Various synthesis strategies of TMPs based on selected phosphorus sources are presented, and the reaction mechanisms of HER as well as the contribution of phosphorus in the TMPs to HER activity are briefly discussed. The multiscale approaches for promoting the activity and stability of TMP-based catalysts are discussed with respect to intrinsic electronic structure, hybrids, microstructure, and working electrode interface. Some crucial issues and future perspectives of TMPs are pointed out. These modulated approaches and challenges are also instructive for constructing other high-activity energy-related electrocatalysts.

Iron-Salt Thermally Emitted Strategy to Prepare Graphene-like Carbon Nanosheets with Trapped Fe Species for an Efficient Electrocatalytic Oxygen Reduction Reaction in the All-pH Range.

Earth-abundant, highly active, and durable electrocatalysts toward oxygen reduction reaction (ORR) in the all-pH range are highly required for practical application of electrochemical energy conversion technologies. Here, non-noble-metal graphene-like carbon nanosheets with trapped Fe species (Fe-N/GPC) are developed by an iron-salt thermally emitted strategy, which integrates the modulation of the electronic structure for boosted intrinsic activity with the engineering of hierarchical porosity for enriched active sites. The ORR electrocatalytic performance of Fe-N/GPC-800 achieves the half-wave potentials of 0.86 and 0.77 V with limiting current densities of 6.1 and 4.7 mA cm-2 in 0.1 M KOH and 0.1 M PBS solutions, respectively, as well as respectable stability. Furthermore, Fe-N/GPC-800 also shows considerable ORR catalytic activity in acid media accompanied by stability superior to those of Pt/C catalysts. The as-prepared Fe-N/GPC-800, as a cathodic catalyst, is assessed in a Zn-air battery test and delivers an open-circuit voltage of 1.44 V with a power density of 134 mW cm-2 as well as the outstanding durability after 350 cycles at 10 mA cm-2, demonstrating appreciable promise in application of metal-air batteries. This work provides an enabling and versatile strategy for facile and scale-up preparation of high-performance non-noble-metal electrocatalysts.

Engineering the Core-Shell-Structured NCNTs-Ni2Si@Porous Si Composite with Robust Ni-Si Interfacial Bonding for High-Performance Li-Ion Batteries.

A new strategy has been innovatively proposed for wrapping the Ni-incorporated and N-doped carbon nanotube arrays (Ni-NCNTs) on porous Si with robust Ni-Si interfacial bonding to form the core-shell-structured NCNTs-Ni2Si@Si. The hierarchical porous silicon core was first fabricated via a novel self-templating synthesis route based on two crucial strategies: in situ thermal evaporation of crystal water from the perlite for producing porous SiO2 and subsequent magnesiothermic reduction of porous SiO2 into porous Si. Ni-NCNTs were subsequently constructed based on the Ni-catalyzed tip-growth mechanism and were further engineered to fully wrap the porous Si microparticles by forming the Ni2Si alloy at the heterojunction interface. When the prepared NCNTs-Ni2Si@Si was evaluated as the anode material for Li-ion batteries, the hierarchical porous system in the Si core and the rich void spaces in carbon nanotube arrays contributed to the remarkable accommodation of volume expansion of Si as well as the significant increase of Li+ diffusion and Si utilization. Moreover, the Ni2Si alloy, which chemically linked the Ni-NCNTs and porous Si, not only provided good electronic contact between the Si core and carbon shell but also effectively prevented the CNTs' detachment from the Si core during cycling. The multifunctional structural design rendered the whole electrode highly stable and active in Li storage, and the electrochemically active NCNTs-Ni2Si@Si electrode delivered a high reversible capacity of 1547 mAh g-1 and excellent cycling stability (85% capacity retention after 600 discharge-charge cycles) at a current density of 358 mA g-1 (0.1 C) as well as good rate performance (778 mAh g-1 at 2 C), showing great potential as an efficient and stable anode for high energy density Li-ion batteries.

Well-Defined Mo2C Nanoparticles Embedded in Porous N-Doped Carbon Matrix for Highly Efficient Electrocatalytic Hydrogen Evolution.

On the design of efficient and affordable electrocatalysts for water reduction half reaction, this paper fabricates molybdenum carbide nanoparticles uniformly loaded in highly porous N-doped carbon matrix derived from polyaniline-molybdate monolith with the use of graphitic carbon nitride (g-C3N4) as template. The obtained molybdenum carbide-carbon hybrid catalysts (MoC@NCS) exhibit extraordinarily electrochemical hydrogen evolution activity with a small overpotential of 89 and 81 mV to deliver a current density of 10 mA cm-2 in alkaline (1.0 M KOH) and acidic (0.5 M H2SO4) medium, respectively, even comparable to noble-metal Pt/C benchmark. Specially, MoC@NCS also shows excellent long-term durability in alkaline or acidic electrolyte. Furthermore, the obtained carbon matrix (NCS) featuring high content of N dopants and hierarchically porous architecture exhibits high catalytic efficiency for oxygen evolution reaction in alkaline electrolyte. For a further step, the obtained NCS coupled with the MoC@NCS, working as anodic and cathodic electrodes, in a two-electrode alkaline electrolyzer for overall water splitting, which can obtain a current density of 10 mA cm-2 at 1.69 V, along with robust operation durability. The synergistic effect of the porous carbon matrix of high nitrogen content and the molybdenum carbide nanoparticles of uniform distribution, together with hierarchically porous structure, should be responsible for the outstanding electrocatalytic HER performance. This work presents an easy and cost-effective strategy to prepare molybdenum-based materials with controlled size for electrocatalytic hydrogen evolution.

Uniquely integrated Fe-doped Ni(OH)2 nanosheets for highly efficient oxygen and hydrogen evolution reactions.

Developing high-efficiency electrocatalysts for both oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) is vital for the production of hydrogen on a large scale by electrocatalytic splitting of water. Herein, Fe-doped Ni(OH)2 nanosheets directly grown on commercial Ni foam (FeNiOH/NF) were fabricated through a facile hydrothermal method in (NH4)2S2O8 aqueous solution containing iron salts. The integrated architecture with hierarchical pores is beneficial for exposing sufficient catalytically active sites and providing evaluated structural and electrical properties. In particular, the Fe-induced partial-charge-transfer greatly modifies the electronic structure of Ni(OH)2, which evidently promotes the electrocatalytic activity of the as-fabricated FeNiOH/NF for OER and HER. Thus, as an electrocatalyst for OER, FeNiOH/NF exhibits excellent activity with overpotentials of 271 and 318 mV to deliver current densities of 20 and 100 mA cm-2, respectively, with a small Tafel slope of 72 mV dec-1 in 1.0 M KOH, demonstrating the very high level of novelty and sufficient improvement over the current state-of-the-art IrO2 electrocatalyst. Most importantly, there is an increase in overpotential by only 23 mV during continuous reaction for over 20 h at an applied potential of 1.62 V to deliver current density of 500 mA cm-2. The as-fabricated electrocatalyst also enables high HER activity with robust stability. Finally, an overall water splitting current density of 10 mA cm-2 can be obtained at a cell voltage of 1.67 V in a two-electrode alkaline electrolyzer using FeNiOH/NF as both anode and cathode, along with impressive operation stability. This development with significant over the state-of-the-art IrO2 electrocatalyst can be widely extended to large-scale fabrication of versatile electrocatalysts for efficient water splitting technology.