Tuning of Trifunctional NiCu Bimetallic Nanoparticles Confined in a Porous Carbon Network with Surface Composition and Local Structural Distortions for the Electrocatalytic Oxygen Reduction, Oxygen and Hydrogen Evolution Reactions

CuNi alloy anchored on dual-substrate TiOx/N-doped carbon nanofibers as a bifunctional electrocatalyst for rechargeable zinc-air batteries

Development of non-noble metal-based electrocatalysts to enhance the performance of zinc-air batteries (ZABs) is of great significance, but it remains a formidable challenge due to their poor stability and activity. Herein, a bifunctional CuNi-TiOx/NCNFS electrocatalyst, featuring with electron-rich copper-nickel (CuNi) alloy nanoparticles anchored on titanium oxide/N-doped carbon nanofibers (TiOx/NCNFS), is constructed by a dual-substrate loading strategy. The introduction of TiOx has led to a significant increase in the stability of the dual-substrate. The strong electronic interaction between CuNi and TiOx strengthens the anchoring of active metal sites, thus accelerating the electron transfer. Theoretical calculations unclose that NCNFS can regulate the charge distribution of TiOx, inducing the charge transfer from NCNFS → TiOx → CuNi, thereby reducing the d-band center of Cu and Ni, which is beneficial to the desorption of intermediate oxide species of the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR). Therefore, CuNi-TiOx/NCNFS delivers a remarkable bifunctional performance with a low OER overpotential of 258 mV at 10 mA cm-2 and an ORR half-wave potential of 0.85  V. When assembled into ZABs, CuNi-TiOx/NCNFS shows a low potential gap of 0.64 V, a higher power density of 149.6 mW cm-2 at 330 mA cm-2, and an outstanding stability for 250 h at 5mA cm-2. This study provides a novel approach by constructing dual-substrate to tune the electronic structure of active metal sites for efficient rechargeable ZABs.

Synergistic Effect of P and Co Dual Doping Endows CuNi with High-Performance Hydrogen Evolution Reaction

The rational design of highly active and durable non-noble electrocatalysts for hydrogen evolution reaction (HER) is significantly important but technically challenging. Herein, a phosphor and cobalt dual doped copper-nickel alloy (P, Co-CuNi) electrocatalyst with high-efficient HER performance is prepared by one-step electrodeposition method and reported for the first time. As a result, P, Co-CuNi only requires an ultralow overpotential of 56 mV to drive the current density of 10 mA cm-2, with remarkable stability for over 360 h, surpassing most previously reported transition metal-based materials. It is discovered that the P doping can simultaneously increase the electrical conductivity and enhance the corrosion resistance, while the introduction of Co can precisely modulate the sub-nanosheets morphology to expose more accessible active sites. Moreover, XPS, UPS, and DFT calculations reveal that the synergistic effect of different dopants can achieve the most optimal electronic structure around Cu and Ni, causing a down-shifted d-band center, which reduces the hydrogen desorption free energy of the rate-determining step (H2O + e- + H* → H2 + OH-) and consequently enhances the intrinsic activity. This work provides a new cognition toward the development of excellent activity and stability HER electrocatalysts and spurs future study for other NiCu-based alloy materials.

A(CoFe)(S2)2/CoFe heterostructure constructed in S, N co-doped carbon nanotubes as an efficient oxygen electrocatalyst for zinc-air battery

Transition metal alloys can exhibit synergistic intermetallic effects to obtain high activities for oxygen reduction/evolution reactions (ORR/OER). However, due to the insufficient stability of active sites in alkaline electrolytes, conventional alloy catalysts still do not meet practical needs. Herein, by using polypyrrole tubes and cobalt-iron (CoFe) Prussian blue analogs as precursors, CoFe sulfides is in-situ formed on CoFe alloys to construct (CoFe)(S2)2/CoFe heterostructure in sulfur (S) and nitrogen (N) co-doped carbon nanotubes (CoFe@NCNTs-nS) via a low-temperature sulfidation strategy. The as-marked CoFe@NCNTs-12.5S exhibits a comparable ORR activity (half-wave potential of 0.901 V) to Pt/C (0.903 V) and a superior OER activity (overpotential of 272 mV at 10 mA cm-2) to RuO2 (299 mV). CoFe@NCNTs-12.5S also exhibits ultralow charge transfer resistances (ORR-6.36 Ω and OER-0.21 Ω) and an excellent potential difference of 0.617 V. The sulfidation-induced (CoFe)(S2)2/CoFe heterojunctions can accelerate interfacial charge transfer process. Tubular structure not only disperses the (CoFe)(S2)2/CoFe heterostructure, but also reduces the corrosion of active-sites to enhance catalysis stability. Zinc-air battery with CoFe@NCNTs-12.5S achieves a high specific capacity (718.1 mAh g-1), maintaining a voltage gap of 0.957 V after 400 h. This work reveals the potential of interface engineering for boosting ORR/OER activities of alloys via in-situ heterogenization.

Performance of Nitrogen-Doped Carbon Nanoparticles Carrying FeNiCu as Bifunctional Electrocatalyst for Rechargeable Zinc-Air Battery

Catalysts for zinc-air batteries (ZABs) must be stable over long-term charging-discharging cycles and exhibit bifunctional catalytic activity. In this study, by doping nitrogen-doped carbon (NC) materials with three metal atoms (Fe, Ni, and Cu), a single-atom-distributed FeNiCu-NC bifunctional catalyst is prepared. The catalyst includes Fe(Ni-doped)-N4 for the oxygen evolution reaction (OER), Fe(Cu-doped)-N4 for the oxygen reduction reaction (ORR), and the NiCu-NC catalytic structure for the oxygen reduction reaction (ORR) in the nitrogen-doped carbon nanoparticles. This single-atom distribution catalyst structure enhances the bifunctional catalytic activity. If a trimetallic single-atom catalyst is designed, it will surpass the typical bimetallic single-atom catcalyst. FeNiCu-NC exhibits outstanding performance as an electrocatalyst, with a half-wave potential (E1/2) of 0.876 V versus RHE, overpotential (Ej = 10) of 253 mV versus RHE at 10 mA cm-2, and a small potential gap (ΔE = 0.61 V). As the anode in a ZAB, FeNiCu-NC can undergo continuous charge-discharged cycles for 575 h without significant attenuation. This study presents a new method for achieving high-performance, low-cost ZABs via trimetallic single-atom doping.

Effect of design parameters in nanocatalyst synthesis on pyrolysis for producing diesel-like fuel from waste lubricating oil

Converting waste lubricating oil into diesel-like liquid fuels using pyrolysis presents a dual solution, addressing environmental pollution while offering a viable response to the fossil energy crisis. However, achieving high-quality fuel with a substantial yield necessitates the utilization of highly active and cost-effective catalysts. We report the development of Fe-Ni nanocatalysts, synthesized using a green approach and supported on TiO2, as a promising strategy for converting waste lubricating oil into premium-grade diesel-like fuel. To ensure efficient and effective pyrolysis processes, tailoring the synthesis parameters of these nanocatalysts is indispensable. In this study, we investigate the effect of design parameters on nanocatalyst synthesis, such as the concentrations of pre-catalysts and reducing agents, reducing time, and the amount of support material, and evaluate their impact on the quality and quantity of pyrolysis products. Through optimization of the synthesis process, a high quality diesel-like fuel with a product yield of about 54% at a mild reaction temperature of 400 °C was obtained. This study highlights the critical role of nanocatalysis in addressing persistent environmental and energy challenges while showcasing the potential of green nanocatalysts in sustainable waste-to-energy conversion processes.

KOH Activated Carbon Coated 3D Wood Solar Evaporator with Highest Water Transport Height and Evaporation Rate for Clean Water Production

The water evaporation rate of 3D solar evaporator heavily relies on the water transport height of the evaporator. In this work, a 3D solar evaporator featuring a soil capillary-like structure is designed by surface coating native balsa wood using potassium hydroxide activated carbon (KAC). This KAC-coated wood evaporator can transport water up to 32 cm, surpassing that of native wood by ≈8 times. Moreover, under 1 kW m-2 solar radiation without wind, the KAC-coated wood evaporator exhibits a remarkable water evaporation rate of 25.3 kg m-2 h-1, ranking among the highest compared with other reported evaporators. The exceptional water transport capabilities of the KAC-coated wood should be attributed to the black and hydrophilic KAC film, which creates a porous network resembling a soil capillary structure to facilitate efficient water transport. In the porous network of coated KAC film, the small internal pores play a pivotal role in achieving rapid capillary condensation, while the larger interstitial channels store condensed water, further promoting water transport up more and micropore capillary condensation. Moreover, this innovative design demonstrates efficacy in retarding phenol from wastewater through absorption onto the coated KAC film, thus presenting a new avenue for high-efficiency clean water production.

Oxygen-bridging Fe, Co dual-metal dimers boost reversible oxygen electrocatalysis for rechargeable Zn-air batteries

Rechargeable zinc-air batteries (ZABs) are regarded as a remarkably promising alternative to current lithium-ion batteries, addressing the requirements for large-scale high-energy storage. Nevertheless, the sluggish kinetics involving oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) hamper the widespread application of ZABs, necessitating the development of high-efficiency and durable bifunctional electrocatalysts. Here, we report oxygen atom-bridged Fe, Co dual-metal dimers (FeOCo-SAD), in which the active site Fe-O-Co-N6 moiety boosts exceptional reversible activity toward ORR and OER in alkaline electrolytes. Specifically, FeOCo-SAD achieves a half-wave potential (E1/2) of 0.87 V for ORR and an overpotential of 310 mV at a current density of 10 mA cm-2 for OER, with a potential gap (ΔE) of only 0.67 V. Meanwhile, FeOCo-SAD manifests high performance with a peak power density of 241.24 mW cm-2 in realistic rechargeable ZABs. Theoretical calculations demonstrate that the introduction of an oxygen bridge in the Fe, Co dimer induced charge spatial redistribution around Fe and Co atoms. This enhances the activation of oxygen and optimizes the adsorption/desorption dynamics of reaction intermediates. Consequently, energy barriers are effectively reduced, leading to a strong promotion of intrinsic activity toward ORR and OER. This work suggests that oxygen-bridging dual-metal dimers offer promising prospects for significantly enhancing the performance of reversible oxygen electrocatalysis and for creating innovative catalysts that exhibit synergistic effects and electronic states.

Fabrication of N and S co-doped lignin-based porous carbon aerogels loaded with FeCo alloys and their application to oxygen evolution and reduction reactions in Zn-air batteries

Zn-air batteries are a highly promising clean energy sustainable conversion technology, and the design of dual-function electrocatalysts with excellent activity and stability is crucial for their development. In this work, FeCo alloy loaded biomass-based N and S co-doped carbon aerogels (FeCo@NS-LCA) were fabricated from chitosan and lignosulfonate-metal chelates via liquid nitrogen pre-frozen synergistic high-temperature carbonization with application in electrocatalytic reactions. The abundant oxygen-containing functional groups on lignosulfonates have a chelating effect on metal ions, which can avoid the aggregation of metal nanoparticles during carbonation and catalysis, facilitating the construction of a nanoconfinement catalytic system with biomass carbon as the domain-limiting body and FeCo nanoparticles as the active sites. FeCo@NS-LCA exhibited catalytic activity (E1/2 = 0.87 V, JL = 5.7 mA cm-2) comparable to the commercial Pt/C in the oxygen reduction reaction (ORR), excellent resistance to methanol toxicity and stability. Meanwhile, the overpotential of oxygen evolution reaction (OER) was 324 mV, close to that of commercial RuO2 catalysts (351 mV). This study utilizes the coordination action of lignosulfonate to provide a novel and environmentally friendly method for the preparation of confined nano-catalysts and provides a new perspective for the high-value utilization of biomass resources.

Oxygen Doping Cooperated with Co-N-Fe Dual-Catalytic Sites: Synergistic Mechanism for Catalytic Water Purification within Nanoconfined Membrane

Atom-site catalysts, especially for graphitic carbon nitride-based catalysts, represents one of the most promising candidates in catalysis membrane for water decontamination. However, unravelling the intricate relationships between synthesis-structure-properties remains a great challenge. This study addresses the impacts of coordination environment and structure units of metal central sites based on Mantel test, correlation analysis, and evolution of metal central sites. An optimized unconventional oxygen doping cooperated with Co-N-Fe dual-sites (OCN Co/Fe) exhibits synergistic mechanism for efficient peroxymonosulfate activation, which benefits from a significant increase in charge density at the active sites and the regulation in the natural population of orbitals, leading to selective generation of SO4 •-. Building upon these findings, the OCN-Co/Fe/PVDF composite membrane demonstrates a 33 min-1 ciprofloxacin (CIP) rejection efficiency and maintains over 96% CIP removal efficiency (over 24 h) with an average permeance of 130.95 L m-2 h-1. This work offers a fundamental guide for elucidating the definitive origin of catalytic performance in advance oxidation process to facilitate the rational design of separation catalysis membrane with improved performance and enhanced stability.

Realizing the Tailored Catalytic Performances on Atomic Pt-Promoted Transition Metal Moieties Implanted Layered Double Hydroxides for Water Electrolysis

High-performance production of green hydrogen gas is necessary to develop renewable energy generation technology and to safeguard the living environment. This study reports a controllable engineering approach to tailor the structure of nickel-layered double hydroxides via doped and absorbed platinum single atoms (PtSA) promoted by low electronegative transition metal (Mn, Fe) moieties (PtSA-Mn,Fe-Ni LDHs). We explore that the electron donation from neighboring transition metal moieties results in the well-adjusted d-band center with the low valence states of PtSA(doped) and PtSA(ads.), thus optimizing adsorption energy to effectively accelerate the H2 release. Meanwhile, a tailored local chemical environment on transition metal centers with unique charge redistribution and high valence states functions as the main center for H2O catalytic dissociation into oxygen. Therefore, the PtSA-Mn,Fe-Ni LDH material possesses a small overpotential of 42 and 288 mV to reach 10 mA·cm-2 for hydrogen and oxygen evolution, respectively, superior to most reported LDH-based catalysts. Additionally, the mass activity of PtSA-Mn,Fe-Ni LDHs proves to be 15.45 times higher than that of commercial Pt-C. The anion exchange membrane electrolyzer stack of PtSA-Mn,Fe-Ni LDHs(+,-) delivers a cell voltage of 1.79 V at 0.5 A·cm-2 and excellent durability over 600 h. This study presents a promising electrocatalyst for a practical water splitting process.

Highly Reversible Zn-Air Batteries Enabled by Tuned Valence Electron and Steric Hindrance on Atomic Fe-N4-C Sites

The bifunctional oxygen electrocatalyst is the Achilles' heel of achieving robust reversible Zn-air batteries (ZABs). Herein, durable bifunctional oxygen electrocatalysis in alkaline media is realized on atomic Fe-N4-C sites reinforced by NixCo3-xO4 (NixCo3-xO4@Fe1/NC). Compared with that of pristine Fe1/NC, the stability of the oxygen evolution reaction (OER) is increased 10 times and the oxygen reduction reaction (ORR) performance is also improved. The steric hindrance alters the valence electron at the Fe-N4-C sites, resulting in a shorter Fe-N bond and enhanced stability of the Fe-N4-C sites. The corresponding solid-state ZABs exhibit an ultralong lifespan (>460 h at 5 mA cm-2) and high rate performance (from 2 to 50 mA cm-2). Furthermore, the structural evolution of NixCo3-xO4@Fe1/NC before and after the OER and ORR as well as charge-discharge cycling is explored. This work develops an efficient strategy for improving bifunctional oxygen electrocatalysis and possibly other processes.

Scalable One-Pot Fabrication of Carbon-Nanofiber-Supported Noble-Metal-Free Nanocrystals for Synergetic-Dependent Green Hydrogen Production: Unraveling Electrolyte and Support Effects

Electrocatalytic hydrogen evolution reactions (HER) are envisaged as the most promising sustainable approach for green hydrogen production. However, the considerably high cost often associated with such reactions, particularly upon scale-up, poses a daunting challenge. Herein, a facile, effective, and environmentally benign one-pot scalable approach is developed to fabricate MnM (M═Co, Cu, Ni, and Fe) nanocrystals supported over in situ formed carbon nanofibers (MnM/C) as efficient noble-metal-free electrocatalysts for HER. The formation of carbon nanofibers entails impregnating cellulose in an aqueous solution of metal precursors, followed by annealing the mixture at 550 °C. During the impregnation process, cellulose acts as a reactor for inducing the in situ reductions of MnM salts with the assistance of ether and hydroxyl groups to drive the mass production (several grams) of ultralong (5 ± 1 μM) carbon nanofibers ornamented with MnM nanoparticles (10-14 nm in size) at an average loading of 2.87 wt %. For better electrocatalytic HER benchmarking, the fabricated catalysts were tested over different working electrodes, i.e., carbon paper, carbon foam, and glassy carbon, in the presence of different electrolytes. All the fabricated MnM/C catalysts have demonstrated an appealing synergetic-effect-dependent HER activity, with MnCo/C exhibiting the best performance over carbon foam, close to that of the state-of-the-art commercial Pt/C (10 wt % Pt), with an overpotential of 11 mV at 10 mA cm-2, a hydrogen production rate of 2448 mol g-1 h-1, and a prolonged stability of 2 weeks. The HER performance attained by MnCo/C nanofibers is among the highest reported for Pt-free electrocatalysts, thanks to the mutual alloying effect, higher synergism, large surface area, and active interfacial interactions over the nanofibers. The presented findings underline the potential of our approach for the large-scale production of cost-effective electrocatalysts for practical HER.

Graphene Chainmail Shelled Dilute Ni─Cu Alloy for Selective and Robust Aqueous Phase Catalytic Hydrogenation

Cost-effective non-noble metal-based catalysts for selective hydrogenation with excellent activity, selectivity, and durability are still the holy grail. Herein, an oxygen-doped carbon (OC) chainmail encapsulated dilute Cu-Ni alloy is developed by simple pyrolysis of Cu/Ni-metal-organic framework. The CuNi0.05@OC catalyst displays superior performance for atmospheric pressure transfer hydrogenation of p-chloronitrobenzene and p-nitrophenol, and for hydrogenation of furfural, all in water and with exceptional durability. Comprehensive characterizations confirm the close interactions between the diluted Ni sites, the base Cu, and optimized three-layered graphene chainmail. Theoretical calculations demonstrate that the properly tuned lattice strain and Schottky junction can adjust electron density to facilitate specific adsorption on the active centers, thus enhancing the catalytic activity and selectivity, while the OC shell also offers robust protection. This work provides a simple and environmentally friendly strategy for developing practical heterogeneous catalysts that bring the synergistic effect into play between dilute alloy and functional carbon wrapping.

Remodeling the Electronic Structure of Metallic Nickel and Ruthenium via Alloying in a Molecular Template for Sustainable Hydrogen Evolution

The reasonably constructed high-performance electrocatalyst is crucial to achieve sustainable electrocatalytic water splitting. Alloying is a prospective approach to effectively boost the activity of metal electrocatalysts. However, it is a difficult subject for the controllable synthesis of small alloying nanostructures with high dispersion and robustness, preventing further application of alloy catalysts. Herein, we propose a well-defined molecular template to fabricate a highly dispersed NiRu alloy with ultrasmall size. The catalyst presents superior alkaline hydrogen evolution reaction (HER) performance featuring an overpotential as low as 20.6 ± 0.9 mV at 10 mA·cm-2. Particularly, it can work steadily for long periods of time at industrial-grade current densities of 0.5 and 1.0 A·cm-2 merely demanding low overpotentials of 65.7 ± 2.1 and 127.3 ± 4.3 mV, respectively. Spectral experiments and theoretical calculations revealed that alloying can change the d-band center of both Ni and Ru by remodeling the electron distribution and then optimizing the adsorption of intermediates to decrease the water dissociation energy barrier. Our research not only demonstrates the tremendous potential of molecular templates in architecting highly active ultrafine nanoalloy but also deepens the understanding of water electrolysis mechanism on alloy catalysts.

Temporally Decoupled Ammonia Splitting by a Zn-NH3 Battery with an Ammonia Oxidation/Hydrogen Evolution Bifunctional Electrocatalyst as a Cathode

Ammonia splitting to hydrogen is a decisive route for hydrogen economy but is seriously limited by the complex device and low efficiency. Here, we design and propose a new rechargeable Zn-NH3 battery based on temporally decoupled ammonia splitting to achieve efficient NH3-to-H2 conversion. In this system, ammonia is oxidized into nitrogen during cathodic charging (2NH3 + 6OH- → N2 + 6H2O + 6e-) with external electrical energy conversion and storage, while during cathodic discharging, water is reduced to hydrogen (2H2O + 2e- → H2 + 2OH-) with electrical energy generation. In this loop, continuous and efficient H2 production without separation and purification is achieved. With the help of the ammonia oxidation reaction (AOR) and hydrogen evolution reaction (HER) bifunctional catalyst of Mo2C/NiCu@C, a rechargeable Zn-NH3 battery is realized that exhibits a high NH3-to-H2 FE of 91.6% with outstanding durability for 900 cycles (300 h) at 20 mA/cm2, enabling efficient and continuous NH3-to-H2 conversion.

Thermally Enhanced Relay Electrocatalysis of Nitrate-to-Ammonia Reduction over Single-Atom-Alloy Oxides

The electrochemical nitrate reduction reaction (NO3RR) holds promise for converting nitrogenous pollutants to valuable ammonia products. However, conventional electrocatalysis faces challenges in effectively driving the complex eight-electron and nine-proton transfer process of the NO3RR while also competing with the hydrogen evolution reaction. In this study, we present the thermally enhanced electrocatalysis of nitrate-to-ammonia conversion over nickel-modified copper oxide single-atom alloy oxide nanowires. The catalyst demonstrates improved ammonia production performance with a Faradaic efficiency of approximately 80% and a yield rate of 9.7 mg h-1 cm-2 at +0.1 V versus a reversible hydrogen electrode at elevated cell temperatures. In addition, this thermally enhanced electrocatalysis system displays impressive stability, interference resistance, and favorable energy consumption and greenhouse gas emissions for the simulated industrial wastewater treatment. Complementary in situ analyses confirm that the significantly superior relay of active hydrogen species formed at Ni sites facilitates the thermal-field-coupled electrocatalysis of Cu surface-adsorbed *NOx hydrogenation. Theoretical calculations further support the thermodynamic and kinetic feasibility of the relay catalysis mechanism for the NO3RR over the Ni1Cu model catalyst. This study introduces a conceptual thermal-electrochemistry approach for the synergistic regulation of complex catalytic processes, highlighting the potential of multifield-coupled catalysis to advance sustainable-energy-powered chemical synthesis technologies.

Synergistic Co-N/V-N dual sites in N-doped Co3V2O8 nanosheets: pioneering high-efficiency bifunctional electrolysis for high-current water splitting

Developing affluent dual-metal active sites bifunctional electrocatalysts for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is essential to achieve large-scale water electrolysis, whereas still remains challenging. Herein, a novel nitrogen-doped cobalt-vanadium oxide with abundant Co-N and V-N dual active sites supported on nickel foam (N-Co3V2O8@NF) is constructed by a controllable impregnation-thermal nitridation strategy. The staggered nanosheet structure ensures optimal exposure of active sites. More importantly, N doping effectively regulates the electronic structure of the metal centers and induces the formation of Co-N and V-N dual active sites, which is conducive to improving the conductivity and hydrophilicity, thus synergistically enhancing the electrocatalytic efficiency. Consequently, the optimized N-Co3V2O8@NF exhibits prominent HER (63 mV@10 mA cm-2) and OER (256 mV@10 mA cm-2) activities, surpassing most contemporary bifunctional electrocatalysts. In practical application, the assembled N-Co3V2O8@NF(+/-) electrolyzer consistently achieved ultra-low cell voltages of 1.97 and 2.03 V at 500 and 1000 mA cm-2, respectively, superior to the benchmark RuO2@NF(+) || Pt/C@NF(-) and showcasing robust durability. This paves the way for its prospective adoption in industrial water electrolysis applications.

Movable-type printing method to fabricate ternary FeCoNi alloys confined in porous carbon towards oxygen electrocatalysts for rechargeable Zn-air batteries

Transition metal-based carbon catalysts are a promising class of electrocatalysts to enhance the efficiency of energy conversion and storage devices. However, it remains a challenging task to develop multi-metal alloy catalysts. Herein, ternary FeCoNi alloy nanoparticles (NPs) confined in nitrogen-doped carbon (NC) catalysts were fabricated via a facile movable-type printing method, where a range of transition metals confined in NC catalysts was prepared using the same technique except for the adjustment of the metal precursors. Due to the unique electronic structure and significant active sites of the medium-entropy alloy, the FeCoNi-NC catalysts demonstrated highly efficient bifunctional electrocatalytic activities for the oxygen reduction (E1/2 = 0.838 V) and evolution (Eoverpotential = 330 mV, 10 mA cm-2) reactions, which were comparable to those of Pt/C and RuO2. Moreover, the FeCoNi-NC-based liquid rechargeable ZABs displayed a substantial power density of 231.2 mW cm-2, and the homemade flexible ZABs also exhibited outstanding activity and cycling durability. Thus, this movable-type printing method is suitable for constructing a variety of multi-metal-based catalysts for metal air batteries.

Rare earth oxide based electrocatalysts: synthesis, properties and applications

As an important strategic resource, rare earths (REs) constitute 17 elements in the periodic table, namely 15 lanthanides (Ln) (La-Lu, atomic numbers from 57 to 71), scandium (Sc, atomic number 21) and yttrium (Y, atomic number 39). In the field of catalysis, the localization and incomplete filling of 4f electrons endow REs with unique physical and chemical properties, including rich electronic energy level structures, variable coordination numbers, etc., making them have great potential in electrocatalysis. Among various RE catalytic materials, rare earth oxide (REO)-based electrocatalysts exhibit excellent performances in electrocatalytic reactions due to their simple preparation process and strong structural variability. At the same time, the electronic orbital structure of REs exhibits excellent electron transfer ability, which can reduce the band gap and energy barrier values of rate-determining steps, further accelerating the electron transfer in the electrocatalytic reaction process; however, there is a lack of systematic review of recent advances in REO-based electrocatalysis. This review systematically summarizes the synthesis, properties and applications of REO-based nanocatalysts and discusses their applications in electrocatalysis in detail. It includes the hydrogen evolution reaction (HER), oxygen evolution reaction (OER), hydrogen oxidation reaction (HOR), oxygen reduction reaction (ORR), carbon dioxide reduction reaction (CO2RR), methanol oxidation reaction (MOR), nitrogen reduction reaction (NRR) and other electrocatalytic reactions and further discusses the catalytic mechanism of REs in the above reactions. This review provides a timely and comprehensive summary of the current progress in the application of RE-based nanomaterials in electrocatalytic reactions and provides reasonable prospects for future electrocatalytic applications of REO-based materials.

Direct methanol fuel cell with enhanced oxygen reduction performance enabled by CoFe alloys embedded into N-doped carbon nanofiber and bamboo-like carbon nanotube

The exploration of cost-effective electrocatalysts with high catalytic activity and methanol tolerance to replace precious metal catalysts in the oxygen reduction reaction (ORR) is highly desirable for direct methanol fuel cells (DMFCs). Herein, we report a novel complex composed of a CoFe alloy with a modulated electronic structure confined to nitrogen-doped carbon nanofiber (NCNF) and bamboo-like carbon nanotube (BCNT) by tuning the molar ratio of Co and Fe (CoFe@NCNF/BCNT). The synthetized catalysts possess one-dimensional (1D) mesoporous structure, high specific surface area, and rich pyridinic-N content. Notably, the Co1Fe1@NCNF/BCNT and Co1Fe3@NCNF/BCNT (Co:Fe ≈ 1:1 and 1:3) exhibited enhanced oxygen reduction activity and methanol tolerance, compared to unmodified samples. In addition, alkaline DMFCs containing Co1Fe1@NCNF/BCNT and Co1Fe3@NCNF/BCNT presented high power density (29.10 and 31.11 mW cm-2), exceeding that of Pt/C-modified DMFC (27.23 mW cm-2). Furthermore, the Co1Fe1@NCNF/BCNT-catalyzed DMFC exhibited high stability. This improved catalytic activity can be attributed to the rich surface area, controllable alloy composition, optimized N configuration, and favorable electronic interaction. The as-developed CoFe@NCNF/BCNT with multifunctional components may open a new avenue for designing highly active cathode catalysts for various fuel cells.

Photothermal therapy of copper incorporated nanomaterials for biomedicine

Studies have reported on the significance of copper incorporated nanomaterials (CINMs) in cancer theranostics and tissue regeneration. Given their unique physicochemical properties and tunable nanostructures, CINMs are used in photothermal therapy (PTT) and photothermal-derived combination therapies. They have the potential to overcome the challenges of unsatisfactory efficacy of conventional therapies in an efficient and non-invasive manner. This review summarizes the recent advances in CINMs-based PTT in biomedicine. First, the classification and structure of CINMs are introduced. CINMs-based PTT combination therapy in tumors and PTT guided by multiple imaging modalities are then reviewed. Various representative designs of CINMs-based PTT in bone, skin and other organs are presented. Furthermore, the biosafety of CINMs is discussed. Finally, this analysis delves into the current challenges that researchers face and offers an optimistic outlook on the prospects of clinical translational research in this field. This review aims at elucidating on the applications of CINMs-based PTT and derived combination therapies in biomedicine to encourage future design and clinical translation.

Spark plasma sintered catalytic nickel-copper alloy and carbon nanotube electrodes for the hydrogen evolution reaction

We report the proof-of-concept of spark plasma sintered (SPS) consolidated mesoporous composite catalytic electrodes based on nickel-copper alloys and carbon nanotubes for the electrocatalytic hydrogen evolution reaction (HER) in alkaline media. The optimized electrode (203 m2 g-1, 5 wt% Ni75Cu25) operated at -0.1 A cm-2 (current of -0.15 A) for 24 h with a stable overpotential of about 0.3 V. This newly described freestanding SPS approach allows the rational control of specific surface area, metal loading, and electrocatalytic performance, thus opening a new route to catalytic electrodes with controllable physical and catalytic properties.

Iron doping and interface engineering on amorphous/crystalline Fe-NixSy heterostructures toward high-stability and kinetically accelerated water splitting

It is very important to develop transition metal-based electrocatalysts with excellent activity, high stability and low-cost for overall water splitting. In this work, the Fe-doped NixSy/NF amorphous/crystalline heterostructure nanoarrays (Fe-NixSy/NF) was synthesized by a simple one-step method. The resulting hierarchically structured nanoarrays offer the advantages of large surface area, high structural void fraction and accessible internal surfaces. These advantages not only furnish additional catalytically active sites, but also enhance the stability of the structure and effectively accelerate mass diffusion and charge transport. Experimental and characterization results indicate that Fe doping increases the electrical conductivity of amorphous/crystalline NixSy/NF, and the NiS-Ni3S2 heterojunctions evoke interfacial charge rearrangement and optimize the adsorption free energy of the intermediates, which allows the catalyst to exhibit low overpotential and superior electrocatalytic activity. Especially, the overpotentials of hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) of Fe-NixSy/NF at 10 mA cm-2 in an alkaline environment are 102.4 and 230.5 mV, respectively. When applied as a bifunctional catalyst for overall water splitting, it requires only 1.45 V cell voltage to deliver a current density of 10 mA cm-2, which is preferable to the all-noble metal Pt/C || IrO2 electrocatalyst (1.62 mV @ 10 mA cm-2). In addition, Fe-NixSy/NF has excellent stability, and there is no obvious degradation after 96 h continuous operation at a current density of 100 mA cm-2. This work affords insights into the application of doping strategies and crystalline/amorphous synergistic modulation of the electrocatalytic activity of transition metal-based catalysts in energy conversion systems.

A 3d-4d-5d High Entropy Alloy as a Bifunctional Oxygen Catalyst for Robust Aqueous Zinc-Air Batteries

High entropy alloys (HEAs) are highly suitable candidate catalysts for oxygen evolution and reduction reactions (OER/ORR) as they offer numerous parameters for optimizing the electronic structure and catalytic sites. Herein, FeCoNiMoW HEA nanoparticles are synthesized using a solution-based low-temperature approach. Such FeCoNiMoW nanoparticles show high entropy properties, subtle lattice distortions, and modulated electronic structure, leading to superior OER performance with an overpotential of 233 mV at 10 mA cm-2 and 276 mV at 100 mA cm-2 . Density functional theory calculations reveal the electronic structures of the FeCoNiMoW active sites with an optimized d-band center position that enables suitable adsorption of OOH* intermediates and reduces the Gibbs free energy barrier in the OER process. Aqueous zinc-air batteries (ZABs) based on this HEA demonstrate a high open circuit potential of 1.59 V, a peak power density of 116.9 mW cm-2 , a specific capacity of 857 mAh gZn -1 , and excellent stability for over 660 h of continuous charge-discharge cycles. Flexible and solid ZABs are also assembled and tested, displaying excellent charge-discharge performance at different bending angles. This work shows the significance of 4d/5d metal-modulated electronic structure and optimized adsorption ability to improve the performance of OER/ORR, ZABs, and beyond.

Influence of boron doping level and calcination temperature on hydrogen evolution reaction in acid medium of metal-free graphene aerogels

In this work, metal-free boron-doped graphene-based aerogels were successfully synthesized via a one-step autoclave assembly followed by freeze-drying and used as electrocatalysts for the hydrogen evolution reaction (HER) in acidic media. The synthesized reduced graphene oxide aerogels (rGOA) showed improved electrocatalytic activity by introducing boron and structural defects. The amount of boric acid used both as a dopant and reducing agent in the synthesis was optimized (boric acid/GO mass ratio = 17.5) to practically reach the crystallization limit of boric acid (boric acid/GO mass ratio = 20). It was observed that the higher the amount of boric acid added, the more boron was incorporated into the carbonaceous structure, improving the electrocatalytic activity of the final aerogel. Furthermore, calcination of the boron-doped electrocatalyst at 600 °C resulted in final aerogels with low oxygen content, moderate surface area, bimodal pore size distribution, and a high electrochemical active surface area. The final 3D graphene aerogel developed in this work, showed such outstanding electrocatalytic activity in HER as to replace noble metal-based electrocatalysts in the future.

Breaking the Activity and Stability Bottlenecks of Electrocatalysts for Oxygen Evolution Reactions in Acids

Oxygen evolution reaction (OER) is a cornerstone reaction for a variety of electrochemical energy conversion and storage systems such as water splitting, CO2 /N2 reduction, reversible fuel cells, and metal-air batteries. However, OER catalysis in acids suffers from extra sluggish kinetics due to the additional step of water dissociation along with its multiple electron transfer processes. Furthermore, OER catalysts often suffer from poor stability in harsh acidic electrolytes due to the severe dissolution/corrosion processes. The development of active and stable OER catalysts in acids is highly demanded. Here,  the recent advances in OER electrocatalysis in acids are reviewed and the key strategies are summarized to overcome the bottlenecks of activity and stability for both noble-metal-based and noble metal-free catalysts, including i) morphology engineering, ii) composition engineering, and iii) defect engineering. Recent achievements in operando characterization and theoretical calculations are summarized which provide an unprecedented understanding of the OER mechanisms regarding active site identification, surface reconstruction, and degradation/dissolution pathways. Finally, views are offered on the current challenges and opportunities to break the activity-stability relationships for acidic OER in mechanism understanding, catalyst design, as well as standardized stability and activity evaluation for industrial applications such as proton exchange membrane water electrolyzers and beyond.

Progress in electrocatalytic hydrogen evolution of transition metal alloys: synthesis, structure, and mechanism analysis

At present, the problems of high energy consumption and low efficiency in electrocatalytic hydrogen production have limited the large-scale industrial application of this technology. Constructing effective catalysts has become the way to solve these problems. Transition metal alloys have been proved to be very promising materials in hydrogen evaluation reaction (HER). In this study, the related theories and characterization methods of electrocatalysis are summarized, and the latest progress in the application of binary, ternary, and high entropy alloys to HER in recent years is analyzed and studied. The synthesis methods and optimization strategies of transition metal alloys, including composition regulation, hybrid engineering, phase engineering, and morphological engineering were emphatically discussed, and the principles and performance mechanism analysis of these strategies were discussed in detail. Although great progress has been made in alloy catalysts, there is still considerable room for applications. Finally, the challenges, prospects, and research directions of transition metal alloys in the future were predicted.

Designed NiMoC@C and NiFeMo2C@C core-shell nanoparticles for oxygen evolution in alkaline media

Electrochemical water splitting is one of the most promising and clean ways to produce hydrogen as a fuel. Herein, we present a facile and versatile strategy for synthesizing non-precious transition binary and ternary metal-based catalysts encapsulated in a graphitic carbon shell. NiMoC@C and NiFeMo2C@C were prepared via a simple sol-gel based method for application in the Oxygen Evolution Reaction (OER). The conductive carbon layer surrounding the metals was introduced to improve electron transport throughout the catalyst structure. This multifunctional structure showed synergistic effects, possess a larger number of active sites and enhanced electrochemical durability. Structural analysis indicated that the metallic phases were encapsulated in the graphitic shell. Experimental results demonstrated that the optimal core-shell material NiFeMo2C@C exhibited the best catalytic performance for the OER in 0.5 M KOH, reaching a current density of 10 mA cm-2 at low overpotential of 292 mV for the OER, superior to the benchmark IrO2 nanoparticles. The good performances and stability of these OER electrocatalysts, alongside an easily scalable procedure makes these systems ideal for industrial purposes.

Engineering Cu/NiCu LDH Heterostructure Nanosheet Arrays for Highly-Efficient Water Oxidation

The development of stable and efficient electrocatalysts for oxygen evolution reaction is of great significance for electro-catalytic water splitting. Bimetallic layered double hydroxides (LDHs) are promising OER catalysts, in which NiCu LDH has excellent stability compared with the most robust NiFe LDH, but the OER activity is not satisfactory. Here, we designed a NiCu LDH heterostructure electrocatalyst (Cu/NiCu LDH) modified by Cu nanoparticles which has excellent activity and stability. The Cu/NiCu LDH electrocatalyst only needs a low over-potential of 206 mV and a low Tafel slope of 86.9 mV dec^-1 at a current density of 10 mA cm^-2 and maintains for 70 h at a high current density of 100 mA cm^-2 in 1M KOH. X-ray photoelectron spectroscopy (XPS) showed that there was a strong electronic interaction between Cu nanoparticles and NiCu LDH. Density functional theory (DFT) calculations show that the electronic coupling between Cu nanoparticles and NiCu LDH can effectively improve the intrinsic OER activity by optimizing the conductivity and the adsorption energy of oxygen-containing intermediates.

Graphitized Cu-β-cyclodextrin polymer driving an efficient dual-reaction-center Fenton-like process by utilizing electrons of pollutants for water purification

Excessive consumption of energy and resources is a major challenge in wastewater treatment. Here, a novel heterogeneous Fenton-like catalyst consisting of Cu-doped graphene-like catalysts (Cu-GCD NSs) was first synthesized by an enhanced carbothermal reduction of β-cyclodextrin (β-CD). The catalyst exhibits excellent Fenton-like catalytic activity for the degradation of various pollutants under neutral conditions, accompanied by low H₂O₂ consumption. The results of structural characterization and theoretical calculations confirmed that the dual reaction centers (DRCs) were constructed on Cu-GCD NSs surface through C-O-Cu bonds supported on zero-valent copper species, which play a significant role in the high-performance Fenton-like reaction. The pollutants that served as electron donors were decomposed in the electron-poor carbon centers, whereas H₂O₂ and dissolved oxygen obtained these electrons in the electron-rich Cu centers through C-O-Cu bonds, thereby producing more active species. This study demonstrates that the electrons of pollutants can be efficiently utilized in Fenton-like reactions by DRCs on the catalyst surface, which provides an effective strategy to improve Fenton-like reactivity and reduce H₂O₂ consumption.

Phosphorus-Doped directly interconnected networks of amorphous Metal-Organic framework nanowires for efficient methanol oxidation

Developing high-performance and low-cost electrocatalysts toward methanol oxidation reaction (MOR) is essential for fuel cell applications. Herein, we report a defect engineering strategy integrating amorphization and phosphorization to construct directly interconnected networks of amorphous NiCo-based metal-organic framework nanowires (a-NiCo-MOFNWs) with phosphorus (P) doping. The resulting P-doped a-NiCo-MOFNWs (a-NiCo-MOFNWs-P) network displays superior MOR efficiency and long-term durability over 1000 cyclic voltammetry (CV) measurements. The special structure of directly interconnected networks and the synergistic effect between the amorphous MOFs and dispersed phosphorus species give rise to abundant exposed active sites, accelerated electron transport, and increased porosity for mass transfer, thus boosting the reaction kinetics of MOR. This work provides additional insights into the network assembly and structural evolution of one-dimensional (1D) MOFs, and also opens up new avenues for the design of highly reactive and robust non-precious metal-based electrocatalysts.

Tailored Bimetallic Ni-Sn Catalyst for Electrochemical Ammonia Oxidation to Dinitrogen with High Selectivity

Direct electrochemical ammonia oxidation reaction (eAOR) is an efficient and sustainable strategy to process wastewater containing ammonia, and it endures overoxidation and severely competitive oxygen evolution reaction (OER). Herein, we synthesized a Ni(OH)₂/SnO₂ composite catalyst by a multistep strategy and applied it to the eAOR process. Ni(OH)₂/SnO₂ exhibited a N₂-N Faradaic efficiency (FE_N2-N) of 84.2%, with a N₂ partial current density (j_N2-N) of 2.7 mA cm^-2 at 1.55 V vs reversible hydrogen electrode (RHE) in 0.5 M K₂SO₄ with 10 mM NH₃-N (pH 11). The oxophilic Sn promoted NH₃ absorption on Ni sites while suppressing the OER. As the active species, NiOOH accelerated the dimerization of intermediates (*NH₂ or *NH) to form N₂.

In-situ exsolution of Fe-Ni alloy catalysts for H2 and carbon nanotube production from microwave plasma-initiated decomposition of plastic wastes

The management of plastic wastes has become an urgent issue due to the overconsumption of single-use plastic products. As a promising avenue for plastic waste valorization, chemical recycling by converting plastics into value-added products has attracted tremendous attention. In this paper, the Fe-Ni alloy catalysts via in-situ exsolution were employed for the straightforward microwave plasma-initiated decomposition of plastic wastes for high yield H₂ and carbon nanotubes. The partial substitution of Fe by Ni promoted in-situ exsolution of alloy nanoparticles homogeneously. Specifically, characterization results showed that the introduction of Ni modulated metal-support interaction, which further affected the crystalline phase, nanoparticle size and oxygen vacancies. The exsolved Fe-Ni alloy catalyst exhibited the highest catalytic activity, over which 96 % hydrogen of plastic wastes rapidly evolved out in the form of gas products accompanied with high-purity carbon nanotubes. The H₂ yield was 415 mmol·g^-1H_plastic, which exhibited an over 2 times improvement versus the supported catalyst. Moreover, the successive cycle test displayed the potential for converting plastic wastes into H₂-rich fuels and high-quality CNTs continuously. Generally, the in-situ exsolution strategy of Fe-Ni alloy catalysts contributed to the sustainable and high-efficient recycling of plastic wastes into H₂-rich gas products and carbon nanotubes under microwave plasma.

Coaxial electrospinning synthesis of size-tunable CuO/NiO hollow heterostructured nanofibers: Towards detection of glucose level in human serum

Nanofibers (NFs) have found wide applications by virtue of their particular morphology and high specific surface area. In this study, size-tunable hollow CuO/NiO NFs were synthesized by coaxial electrospinning and subsequent calcination. The synthesized hollow CuO/NiO NFs owned large specific surface area for catalytic active sites. In addition, the formation of heterostructure interface between CuO and NiO was beneficial to improve the electrocatalytic performance. As non-enzymatic electrode material, the synthesized CuO/NiO NFs exhibited superior electrocatalytic capability for glucose oxidation. When the molar ratio of CuO to NiO is 0.4, the composite NFs achieved the optimal electrocatalytic ability for glucose oxidation, performing high sensitivity of 1324.17 μA mM^-1 cm^-2 and wide liner range from 1 to 10,000 μM. The constructed electrode has been utilized to detect glucose concentration in real serum with excellent recovery, indicating that CuO/NiO hollow heterostructured NFs are promising materials for biomedical applications.

In Situ Confinement of Ultrasmall Metal Nanoparticles in Short Mesochannels for Durable Electrocatalytic Nitrate Reduction with High Efficiency and Selectivity

Electrocatalytic reduction is a sustainable approach for NO₃ ^- removal and high-value N-containing compounds manufacturing, which, however, is strongly obstructed by sluggish kinetics, low selectivity, and poor stability. Herein, the in situ confinement of ultrasmall CuPd alloy nanoparticles in mesochannels of conductive core-shell structured carbon nanotubes@mesoporous carbon substrates (CNTs@mesoC@CuPd) via a simple molecule-mediated interfacial assembly method is reported. As a catalyst for electrocatalytic NO₃ ^- reduction, the CNTs@mesoC@CuPd shows a splendid conversion efficiency (100%), N₂  selectivity (98%), cycling stability (>30 days), and removal capacity as high as 30 000 mg N g^-1 CuPd, which are much superior to most of the prior reports. Notably, experimental (in situ testing and isotopic labeling) and theoretical results unveil that bimetallic and monometallic catalysts for electrocatalytic NO₃ ^- reduction exhibit exclusive selectivity for N₂  and NH₃ , respectively. This in situ confinement strategy is universal for the synthesis of stable and highly accessible metallic catalysts, which opens an appealing way to synthesize advanced catalysts with high activity, selectivity, and stability.

A critical review of research progress for metal alloy materials in hydrogen evolution and oxygen evolution reaction

Hydrogen produced by electrolyzing water has attracted extensive attention as an effective way to generate and store new energy by using renewable energy. Electrocatalytic hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) were the core reactions in the process of hydrogen production by water electrolysis, however, due to the low efficiency of the electrolytic device caused by its slow kinetic reaction and the dependence on noble metal catalysts (platinum and iridium/ruthenium (oxide)), which limited its wide application. The preparation of high-efficiency catalysts with high catalytic activity, stability, low cost and scalability played a vital role in promoting the development of hydrogen production technology from electrolytic water and has become a current research hotspot. Metal alloy catalysts have been widely studied as high-efficiency electrocatalysts. This study introduced and analyzed the mechanism and application of metal alloy catalyst in hydrogen and oxygen evolution reaction, summarized and discussed the progress in the design, preparation and application of metal alloy electrocatalysts. Finally, the strategy and prospect of new high-efficiency electrocatalysts were proposed.

Recent advances in understanding and design of efficient hydrogen evolution electrocatalysts for water splitting: A comprehensive review

An unsustainable reliance on fossil fuels is the primary cause of the vast majority of greenhouse gas emissions, which in turn lead to climate change. Green hydrogen (H₂), which may be generated by electrolyzing water with renewable power sources, is a possible substitute for fossil fuels. On the other hand, the increasing intricacy of hydrogen evolution electrocatalysts that are presently being explored makes it more challenging to integrate catalytic theories, catalytic fabrication procedures, and characterization techniques. This review will initially present the thermodynamics, kinetics, and associated electrical and structural characteristics for HER electrocatalysts before highlighting design approaches for the electrocatalysts. Secondly, an in-depth discussion regarding the rational design, synthesis, mechanistic insight, and performance improvement of electrocatalysts is centered on both the intrinsic and extrinsic influences. Thirdly, the most recent technological advances in electrocatalytic water-splitting approaches are described. Finally, the difficulties and possibilities associated with generating extremely effective HER electrocatalysts for water-splitting applications are discussed.

"Electron Complementation"-Induced Molybdenum Nitride/Co-Anchored Graphitic Carbon Nitride Porous Nanoparticles for Efficient Overall Water Splitting

Maximizing the usable space of electrocatalysts and fine-tuning the interface geometry as well as the electronic structure to facilitate hydrogen and oxygen evolution reactions (HER and OER) have always been the focus of research. Herein, a homogeneous porous nanoparticle construction strategy was proposed, in which molybdenum nitride (Mo₂N) particles were prepared by controlled heat treatment of the precursor nanoparticle induced by polyethylene glycol, and the Mo₂N/Co-C₃N₄ heterostructure with a pore size of about 1.13 nm was obtained by compounding Co-anchored graphitic carbon nitride. In particular, exploring the change of charge distribution at the interface based on the principle of "electron complementation" shows that under the regulation of nitrogen with high electronegativity, the affinity of active site Co to oxygenated species in the OER process and the adsorption as well as cleavage ability of HER reactants in the active site were effectively optimized. Thus, Mo₂N/Co-C₃N₄ not only inherits the functions of each component, but also provides an ideal heterogeneous interface for exhibiting impressive bifunctional activity, which only needs 100 and 210 mV to deliver 10 mA cm^-2 for the HER and OER, respectively. In addition, the Mo₂N/Co-C₃N₄ catalyst also demonstrates high overall water splitting stability with a slight current decrease after 95 h. Manipulating the electronic structure of multiple sites by constructing electronically complementary interfaces may provide another avenue to develop highly active catalysts for overall water splitting and other applications.

Bismuth-nickel bimetal nanosheets with a porous structure for efficient hydrogen production in neutral and alkaline media

Active and durable electrocatalysts are very important for efficient and economically sustainable hydrogen generation via electrocatalytic water splitting. A bismuth-nickel (Bi-Ni) bimetal nanosheet with a mesoporous structure was prepared via a self-template electrochemical in situ process. The Bi-Ni catalyst required overpotentials of 56 mV and 183 mV at 10 mA cm^-2 for the hydrogen evolution reaction (HER), which were close to that of commercial Pt/C in 1.0 M KOH and 1.0 M PBS (pH 7.0), respectively. The electrocatalyst maintained a steady current density during 20 h electrolysis in 1.0 M KOH and 1.0 M PBS (pH 7.0). Density functional theory (DFT) indicated that the alloying effect could induce charge transfer from the Bi atom to Ni atom and thus modulate the d-band centre of Bi-Ni nanosheets, which could efficiently accelerate H* conversion and H₂ desorption at the Ni active site. This promotes the HER kinetics. By adopting the Bi_84.8Ni_15.2 alloy as the cathode to establish a full-cell (IrO₂∥Bi_84.8Ni_15.2) for water splitting in 1.0 M KOH, the required cell voltage was 1.53 V to drive 10 mA cm^-2, which was lower than that of the IrO₂∥Pt/C electrolyzer (1.64 V@10 mA cm^-2).

Oxygen Spillover Effect at Cu/Fe2O3 Heterointerfaces to Enhance Oxygen Electrocatalytic Reactions for Rechargeable Zn-Air Batteries

Rational design and synthesis of high-performance electrocatalysts for the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) are critical for practical application of Zn-air batteries (ZABs). In this work, the bifunctional composite Cu-Fe₂O₃/PNC was prepared by a simple and effective wet-hydrothermal coupled dry-annealing synthesis strategy. The Cu-Fe₂O₃/PNC displayed excellent catalytic activity in ORR and OER with a potential difference of 0.63 V. More importantly, the ZAB assembled with Cu-Fe₂O₃/PNC exhibited a high-power density of 138.00 mW cm^-2 and an excellent long-term cyclability. X-ray photoelectron spectroscopy (XPS) demonstrated that the excellent performance is due to the strong electronic interaction between Cu and Fe₂O₃ that arises as a result of the fast electron transfer through the Cu-O-Fe bond and the higher concentration of surface oxygen vacancies. Meanwhile, the spillover factor Bsp/2zF of Cu/PNC and Cu-Fe₂O₃/PNC obtained by the rotating disk experiment was 1.00 × 10^-7 and 1.10 × 10^-7 cm²·s^-1, respectively, indicating that the oxygen spillover effect between Cu and Fe₂O₃ lowers the energy barrier, increases the number of active sites, and alters the rate-determining reaction step. This work demonstrated the significant potential of Cu-Fe₂O₃/PNC in energy conversion and storage applications, providing a new perspective for the rational design of bifunctional electrocatalysts.

Solar-driven methanogenesis with ultrahigh selectivity by turning down H2 production at biotic-abiotic interface

Integration of methanogens with semiconductors is an effective approach to sustainable solar-driven methanogenesis. However, the H₂ production rate by semiconductors largely exceeds that of methanogen metabolism, resulting in abundant H₂ as side product. Here, we report that binary metallic active sites (namely, NiCu alloys) are incorporated into the interface between CdS semiconductors and Methanosarcina barkeri. The self-assembled Methanosarcina barkeri-NiCu@CdS exhibits nearly 100% CH₄ selectivity with a quantum yield of 12.41 ± 0.16% under light illumination, which not only exceeds the reported biotic-abiotic hybrid systems but also is superior to most photocatalytic systems. Further investigation reveal that the Ni-Cu-Cu hollow sites in NiCu alloys can directly supply hydrogen atoms and electrons through photocatalysis to the Methanosarcina barkeri for methanogenesis via both extracellular and intracellular hydrogen cycles, effectively turning down the H₂ production. This work provides important insights into the biotic-abiotic hybrid interface, and offers an avenue for engineering the methanogenesis process.

Highly efficient and stable catalysts-covalent organic framework-supported palladium particles for 4-nitrophenol catalytic hydrogenation

A covalent organic framework (COF) was used as the support of the catalyst in this work in order to obtain an environmentally friendly catalyst with high catalytic performance, selectivity and stability for 4-nitrophenol hydrogenation. Pd tiny particles are fixed in the cavity of COF to obtain Pd/COF catalysts, which has a quite narrow particle size distribution (5.09 ± 1.30 nm). As-prepared Pd/COF catalysts (Pd loading-2.11 wt%) shows excellent catalytic performance (conversion - 99.3%, selectivity >99.0% and turnover frequency (TOF)-989.4 h^-1) for 4-nitrophenol hydrogenation under relatively mild reaction conditions of reaction temperature-40 °C and reaction pressure-3.0 MPa H₂, and Pd/COF catalysts have high stability. Pd/COF catalysts were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscope energy-dispersive X-ray spectroscopy (SEM-EDS), transmission electron microscope (TEM), high resolution TEM (HRTEM), Brunauer-Emmett-Teller (BET), scanning TEM energy-dispersive X-ray spectroscopy (STEM-EDS) elemental analysis techniques to prove that the Pd nanoparticles are highly dispersed on the COF. Pd/COF catalysts have good stability and reusability hence with certain industrial application value.

Rational Design of a Low-Dimensional and Metal-free Heterostructure for Efficient Water Oxidation: DFT and Experimental Studies

A nitrogen-doped fullerene dimer is synthesized and compounded with multi-walled carbon nanotubes (MWCNTs) to construct a low-dimensional and metal-free 0D-1D heterostructure for electrocatalytic water oxidation. The (C₅₉N)₂/MWCNTs heterostructure exhibits a highly efficient performance, as verified by both first-principles density functional theory and experimental studies. The *O → *OOH process is confirmed as the rate-determining step of water oxidation. The negatively charged N-doping leads to electronic redistribution and intermolecular charge transfer and thus reduces the uphill free energies of intermediates on the (C₅₉N)₂/MWCNTs interface. Therefore, the (C₅₉N)₂/MWCNTs heterostructure has great potential to emit light and heat in metal-free-based electrocatalytic water oxidation.

Synergistic doping and structural engineering over dendritic NiMoCu electrocatalyst enabling highly efficient hydrogen production

The development of non-precious metal electrocatalysts with remarkable activity is a major objective for achieving high-efficiency hydrogen generation. Here, a trimetallic electrocatalyst with a dendritic nanostructure, which is denoted as NiMoCu-NF, was fabricated on nickel foam via a gas-template electrodeposition strategy. By virtue of the metallic doping and structural optimization, NiMoCu-NF exhibits superior HER electrocatalytic activity with an overpotential of 52 mV at 10 mA cm^-2. Additionally, the NiMoCu-NF-derived nickel-based (oxy)hydroxide species in the oxidation operating state deliver considerable electrocatalytic urea oxidation reaction (UOR) performance to match the efficient H₂ generation, with a low voltage of 1.54 V to realize overall electrolysis at 50 mA cm^-2. Impressively, combined experimental and simulation analysis demonstrate that the NiMoCu-NF with a favorable 3D nanostructure feature effectively regulates the heterogeneous interface states, inducing a "Gas Microfluidic Pumping" (GMP) effect that improved electron-mass transfer properties to accelerate the electrocatalytic reaction kinetics of either the HER or UOR.