Hydrogen Evolution Reaction Performance Research Articles

Theoretical and experimental investigations of vanadium pentoxide–based electrocatalysts for the hydrogen evolution reaction in alkaline media

AbstractA key approach towards better realization of intermittent renewable energy resources, namely, solar and wind, is green electrochemical hydrogen production from water electrolysis. In recent years, there have been increasing efforts aimed at developing noble metal-free electrocatalysts that are earth-abundant and electroactive towards hydrogen evolution reaction (HER) in alkaline electrolytes, wherein an initial water dissociation step is followed by a two-electron transfer cathodic reaction. Although relatively earth-abundant, vanadium-based electrocatalysts have been sparsely reported due to subpar electroactivity and kinetics towards water electrolysis in general and alkaline electrolysis in specific. Herein, we investigate the fine-tuning of orthorhombic V2O5-based electrocatalysts as candidates for HER through a scalable two-step sol–gel calcination procedure. Briefly, surface-induced anionic oxygen deficiencies and cationic dopants are synergistically studied experimentally and theoretically. To that end, first-principle facet-dependent density function theory (DFT) calculations were conducted and revealed that the coupling of certain dopants on V2O5 and co-induction of oxygen vacancies can enhance the catalytic HER performance by the creation of new electronic states near the Fermi level (EF), enhancing conductivity, and modulating surface binding of adsorbed protons, respectively. This was reflected experimentally through kinetically non-ideal alkaline electrochemical HER using Zn0.4V1.6O5 whereby − 194 mV of overpotential was required to attain − 10 mA/cm2 of current density, as opposed to pristine V2O5 which required 32% higher overpotential requirement at the same conditions. The disclosed work can be extended to other intrinsically sluggish transition metal (TM)–based oxides via the presented systematic tuning of surface and bulk microenvironment modulation. Graphical Abstract

Sublayer-Sulfur-Vacancy-Induced Charge Redistribution of FeCuS Nanoflower Awakening Alkaline Hydrogen Evolution.

Advancing the progress of sustainable and green energy technologies requires the improvement of valid electrocatalysts for the hydrogen evolution reaction (HER). Reconfiguring charge distribution through heteroatom doping-induced vacancy serves as an effective approach to implement high performance for HER catalysts. Here, we successfully fabricated Fe-doped CuS (FeCuS) with the sublayer sulfur vacancy to judge its HER performance and dissect the activity origins. Density functional theory calculation further elucidates that the primary factor contributing to the heightened HER activity is that the sublayer sulfur vacancies awaken the charge redistribution. In addition to effectively decreasing the energy barrier associated with the Volmer step, it modulates the adsorption/desorption capacity of H*. As a result, its intrinsic activity for the HER has significantly increased. Concretely, the obtained FeCuS displays an excellent catalytic performance, whose Tafel slope is only 59 mV dec-1 and the overpotential (at 10 mA cm-2) is as low as 71 mV in an alkaline environment, surpassing the majority of previously documented catalysts in scientific literature. This work shows that the construction of sublayer sulfur vacancies by Fe doping can achieve the charge redistribution and precise tuning of electronic structure; thereby, the inert CuS can be transformed into highly efficient electrocatalysts.

Constructing N-Containing Poly(p-Phenylene) (PPP) Films Through A Cathodic-Dehalogenation Polymerization Method.

Developing the films of N-containing unsubstituted poly(p-phenylene) (PPP) films for diverse applications is significant and highly desirable because the replacement of sp2 C atoms with sp2 N atoms will bring novel properties to the as-prepared polymers. In this research, an electrochemical-dehalogenation polymerization strategy is employed to construct two N-containing PPP films under constant potentials, where 2,5-diiodopyridine (DIPy) and 2,5-dibromopyrazine (DBPz) are used as starting agents. The corresponding polymers are named CityU-23 (for polypyridine) and CityU-24 (for polypyrazine). Moreover, it is found that both polymers can form films in situ on different conductive substrates (i.e., silicon, gold, ITO, and nickel), satisfying potential device fabrication. Furthermore, the as-obtained thin films of CityU-23 and CityU-24 exhibit good performance of alkaline hydrogen evolution reaction with the overpotential of 212.8 and 180.7mV and the Tafel slope of 157.0 and 122.4mV dec-1, respectively.

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.

Reversing the Interfacial Electric Field in Metal Phosphide Heterojunction by Fe-Doping for Large-Current Oxygen Evolution Reaction.

Developing non-precious-metal electrocatalysts that can operate with a low overpotential at a high current density for industrial application is challenging. Heterogeneous bimetallic phosphides have attracted much interest. Despite high hydrogen evolution reaction (HER) performance, the ordinary oxygen evolution reaction (OER) performance hinders their practical use. Herein, it is shown that Fe-doping reverses and enlarges the interfacial electrical field at the heterojunction, turning the H intermediate favorable binding sites for HER into O intermediate favorable sites for OER. Specifically, the self-supported heterojunction catalysts on nickel foam (CoP@Ni2P/NF and Fe-CoP@Fe-Ni2P/NF) are readily synthesized. They only require the overpotentials of 266 and 274mV to drive a large current density of 1000mA cm-2 (j1000) for HER and OER, respectively. Furthermore, a water splitting cell equipped with these electrodes only requires a voltage of 1.724V to drive j1000 with excellent durability, demonstrating the potential of industrial application. This work offers new insights on interfacial engineering for heterojunction catalysts.

Improving the Efficiency of Water Splitting and Oxygen Reduction Via Single‐Atom Anchoring on Graphyne Support

Single‐atom catalysts (SACs) have received significant interest for optimizing metal atom utilization and superior catalytic performance in hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and oxygen reduction reaction (ORR). In this study, we investigate a range of single‐transition metal (STM1 = Sc1, Ti1, V1, Cr1, Mn1, Fe1, Co1, Ni1, Cu1, Zr1, Nb1, Mo1, Ru1, Rh1, Pd1, Ag1, W1, Re1, Os1, Ir1, Pt1, and Au1) atoms supported on graphyne (GY) surface for HER/OER and ORR using first‐principle calculations. Ab initio molecular dynamics (AIMD) simulations and phonon dispersion spectra reveal the dynamic and thermal stabilities of the GY surface. The exceptional stability of all supported STM1 atoms within the H1 cavity of the GY surface exists in an isolated form, facilitating the uniform distribution and proper arrangement of single atoms on GY. In particular, Sc1, Co1, Fe1, and Au1/GY demonstrate promising catalytic efficiency in the HER due to idealistic ΔGH* values via the Volmer‐Heyrovsky pathway. Notably, Sc1 and Au1/GY exhibit superior HER catalytic activity compared to other studied catalysts. Co1/GY catalyst exhibits higher selectivity and activity for the OER, with an overpotential (0.46 V) comparable to MoC2, IrO2, and RuO2. Also, Rh1 and Co1/GY SACs exhibited promising electrocatalysts for the ORR, with an overpotential of 0.36 and 0.46 V, respectively. Therefore, Co1/GY is a versatile electrocatalyst for metal‐air batteries and water‐splitting. This study further incorporates computational analysis of the kinetic potential energy barriers of Co1 and Rh1 in the OER and ORR. A strong correlation is found between the estimated kinetic activation barriers for the thermodynamic outcomes and all proton‐coupled electron transfer steps. We establish a relation for the Gibbs free energy of intermediates to understand the mechanism of SACs supported on STM1/GY and introduce a key descriptor. This study highlights GY as a favorable single‐atom support for designing highly active and cost‐effective versatile electrocatalysts for practical applications.

Breaking Symmetry: Enhanced Hydrogen Evolution Reaction Performance of Janus Zr2COT (T = F, Cl, Br, I) MXenes by Density Functional Theory

Breaking Symmetry: Enhanced Hydrogen Evolution Reaction Performance of Janus Zr₂COT (T = F, Cl, Br, I) MXenes by Density Functional Theory

Rational Design of Dynamic Interface Water Evolution on Turing Electrocatalyst toward the Industrial Hydrogen Production.

Manipulating the structural and kinetic dissociation processes of water at the catalyst-electrolyte interface is vital for alkaline hydrogen evolution reactions (HER) at industrial current density. This is seldom actualized due to the intricacies of the electrochemical reaction interface. Herein, this work introduces a rapid, nonequilibrium cooling technique for synthesizing ternary Turing catalysts with short-range ordered structures (denoted as FeNiRu/C). These advanced structures empower the FeNiRu/C to exhibit excellent HER performance in 1 m KOH with an ultralow overpotential of 6.5 and 166.2 mV at 10 and 1000 mA cm-2, respectively, and a specific activity 7.3 times higher than that of Pt/C. Comprehensive mechanistic analyses reveal that abundant atomic species form asymmetric atomic electric fields on the catalyst surface inducing a directed evolution and the dissociation process of interfacial H2O molecules. In addition, the locally topologized structure effectively mitigates the high hydrogen coverage of the active site induced by the high current density. The establishment of the relationship between free water population and HER activity provides a new paradigm for the design of industrially relevant high performance alkaline HER catalysts.

Electrochemical deposition of nickel sulfide catalysts on commercial carbon rods as low-cost electrodes for hydrogen generation

Nowadays, the challenge of the world and the scientific community is to find and effectively use renewable energy sources. One of the renewable energy research subjects that has been hotly discussed recently is the water-splitting reaction to produce hydrogen. In this study, we focus on fabricating nickel sulfide (NiS) materials deposited on commercial carbon rod (CR) substrates and using them as electrodes for the electrochemical water-splitting reaction to produce hydrogen gas. In detail, NiS materials were decorated on commercial carbon rods (NiS/CR) by cyclic voltammetry electrochemical deposition with a potential range from 0.2 to −1.2 V (versus Ag/AgCl), a scan rate of 10 mV s−1, and 15 cycles. Benefiting a strong interfacial synergetic effect based on NiS/CR materials shows an excellent electrocatalytic activity for hydrogen evolution reaction (HER). Specifically, the NiS/CR electrode exhibits a high performance with low overpotential (70 mV for HER) and a slight Tafel slope (50 mV dec−1). Besides, annealing temperature helps increase the crystal properties, causing the appearance of NiS2 and Ni3S2 phases in NiS/CR@400 samples. Interestingly, the electrochemical surface area (ESCA) of the NiS/CR@400 sample significantly increased (17.3%) compared to the NiS/CR sample (5.8% of the total physical surface area) is due to the presence of NiS2 and Ni3S2, leading to NiS/CR@400 sample enhances the active sites by 16.0 mF cm−2. Furthermore, the long-term durability of NiS/CR@400 electrodes is good electrocatalytic over a continuous cycling 12-hour operation at 20 mA cm−2 in an alkaline environment. The NiS/CR is a promising electrode candidate for high HER performance, and here is a new design of electrocatalysts for water splitting.

Activating TiO2 through the Phase Transition-Mediated Hydrogen Spillover to Outperform Pt for Electrocatalytic pH-Universal Hydrogen Evolution.

Endowing conventional materials with specific functions that are hardly available is invariably of significant importance but greatly challenging. TiO2 is proven to be highly active for the photocatalytic hydrogen evolution while intrinsically inert for electrocatalytic hydrogen evolution reaction (HER) due to its poor electrical conductivity and unfavorable hydrogen adsorption/desorption behavior. Herein, the first activation of inert TiO2 for electrocatalytic HER is demonstrated by synergistically modulating the positions of d-band center and triggering hydrogen spillover through the dual doping-induced partial phase transition. The N, F co-doping-induced partial phase transition from anatase to rutile phase in TiO2 (AR-TiO2|(N,F)) exhibits extraordinary HER performance with overpotentials of 74, 80, and 142 mV at a current density of 10 mA cm-2 in 1.0 M KOH, 0.5 M H2SO4, and 1.0 M phosphate-buffered saline electrolytes, respectively, which are substantially better than pure TiO2, and even superior to the benchmark Pt/C catalysts. These findings may open a new avenue for the development of low-cost alternative to noble metal catalysts for electrocatalytic hydrogen production.

Loading of Single Atoms of Iron, Cobalt, or Nickel to Enhance the Electrocatalytic Hydrogen Evolution Reaction of Two-Dimensional Titanium Carbide.

The rational design of advanced electrocatalysts at the molecular or atomic level is important for improving the performance of hydrogen evolution reactions (HERs) and replacing precious metal catalysts. In this study, we describe the fabrication of electrocatalysts based on Fe, Co, or Ni single atoms supported on titanium carbide (TiC) using the molten salt method, i.e., TiC-FeSA, TiC-CoSA, or TiC-NiSA, to enhance HER performance. The introduction of uniformly distributed transition-metal single atoms successfully reduces the overpotential of HERs. Overpotentials of TiC-FeSA at 10 mA cm-2 are 123.4 mV with 61.1 mV dec-1 Tafel slope under acidic conditions and 184.2 mV with 85.1 mV dec-1 Tafel slope under alkaline conditions, which are superior to TiC-NiSA and TiC-CoSA. TiC samples loaded with transition-metal single atoms exhibit high catalytic activity and long stability under acidic and basic conditions. Density functional theory calculations indicate that the introduction of transition-metal single atoms effectively reduces the HER barrier of TiC-based electrocatalysts.

Atomically Precise Mo2Cu17 Bimetallic Nanocluster: Synergistic Mo2O4-Coupled Copper Alkynyl Cluster for the Improved Hydrogen Evolution Reaction Performance.

Electrolytic hydrogen production via water splitting holds significant promise for the future of the energy revolution. The design of efficient and abundant catalysts, coupled with a comprehensive understanding of the hydrogen evolution reaction (HER) mechanism, is of paramount importance. In this study, we propose a strategy to craft an atomically precise cluster catalyst with superior HER performance by cocoupling a Mo2O4 structural unit and a Cu(I) alkynyl cluster into a structured framework. The resulting bimetallic cluster, Mo2Cu17, encapsulates a distinctive structure [Mo2O4Cu17(TC4A)4(PhC≡C)6], comprising a binuclear Mo2O4 subunit and a {Cu17(TC4A)2(PhC≡C)6} cluster, both shielded by thiacalix[4]arene (TC4A) and phenylacetylene (PhC≡CH). Expanding our exploration, we synthesized two homoleptic CuI alkynyl clusters coprotected by the TC4A and PhC≡C- ligands: Cu13 and Cu22. Remarkably, Mo2Cu17 demonstrates superior HER efficiency compared to its counterparts, achieving a current density of 10 mA cm-2 in alkaline solution with an overpotential as low as 120 mV, significantly outperforming Cu13 (178 mV) and Cu22 (214 mV) nanoclusters. DFT calculations illuminate the catalytic mechanism and indicate that the intrinsically higher activity of Mo2Cu17 may be attributed to the synergistic Mo2O4-Cu(I) coupling.

Enabling built‐in electric fields on rhenium‐vacancy‐rich heterojunction interfaces of transition‐metal dichalcogenides for pH‐universal efficient hydrogen and electric energy generation

AbstractMost advanced hydrogen evolution reaction (HER) catalysts show high activity under alkaline conditions. However, the performance deteriorates at a natural and acidic pH, which is often problematic in practical applications. Herein, a rhenium (Re) sulfide–transition‐metal dichalcogenide heterojunction catalyst with Re‐rich vacancies (NiS2‐ReS2‐V) has been constructed. The optimized catalyst shows extraordinary electrocatalytic HER performance over a wide range of pH, with ultralow overpotentials of 42, 85, and 122 mV under alkaline, acidic, and neutral conditions, respectively. Moreover, the two‐electrode system with NiS2‐ReS2‐V1 as the cathode provides a voltage of 1.73 V at 500 mA cm−2, superior to industrial systems. Besides, the open‐circuit voltage of a single Zn–H2O cell with NiS2‐ReS2‐V1 as the cathode can reach an impressive 90.9% of the theoretical value, with a maximum power density of up to 31.6 mW cm−2. Moreover, it shows remarkable stability, with sustained discharge for approximately 120 h at 10 mA cm−2, significantly outperforming commercial Pt/C catalysts under the same conditions in all aspects. A series of systematic characterizations and theoretical calculations demonstrate that Re vacancies on the heterojunction interface would generate a stronger built‐in electric field, which profoundly affects surface charge distribution and subsequently enhances HER performance.

MOCHAs: An Emerging Class of Materials for Photocatalytic H2 Production.

Production of green hydrogen (H2) is a sustainable process able to address the current energy crisis without contributing to long-term greenhouse gas emissions. Many Ag-based catalysts have shown promise for light-driven H2 generation, however, pure Ag-in its bulk or nanostructured forms-suffers from slow electron transfer kinetics and unfavorable Ag─H bond strength. It is demonstrated that the complexation of Ag with various chalcogenides can be used as a tool to optimize these parameters and reach improved photocatalytic performance. In this work, metal-organic-chalcogenolate assemblies (MOCHAs) are introduced as effective catalysts for light-driven hydrogen evolution reaction (HER) and investigate their performance and structural stability by examining a series of AgXPh (X=S, Se, and Te) compounds. Two catalyst-support sensitization strategies are explored: by designing MOCHA/TiO2 composites and by employing a common Ru-based photosensitizer. It is demonstrated that the heterogeneous approach yields stable HER performance but involves a catalyst transformation at the initial stage of the photocatalytic process. In contrast to this, the visible-light-driven MOCHA-dye dyad shows similar HER activity while also ensuring the structural integrity of the MOCHAs. The work shows the potential of MOCHAs in constructing photosystems for catalytic H2 production and provides a direct comparison between known AgXPh compounds.

Tuning A-Site Cation Deficiency in Pr0.5La0.5BaCo2O5+ δ Perovskite to Realize Large-Scale Hydrogen Evolution at 2000mAcm-2.

Industrial-level hydrogen production from the water electrolysis requires reducing the overpotential (η) as much as possible at high current density, which is closely related to intrinsic activity of the electrocatalysts. Herein, A-site cation deficiency engineering is proposed to screen high-performance catalysts, demonstrating effective Pr0.5- xLa0.5BaCo2O5+ δ (P0.5- xLBC) perovskites toward alkaline hydrogen evolution reaction (HER). Among all perovskite compositions, Pr0.4La0.5BaCo2O5+ δ (P0.4LBC) exhibits superior HER performance along with unique operating stability at large current densities (J = 500-2000mAcm-2 geo). The overpotential of ≈636mV is achieved in P0.4LBC at 2000mAcm-2 geo, which outperforms commercial Pt/C benchmark (≈974mV). Furthermore, the Tafel slope of P0.4LBC (34.1mVdec-1) is close to that of Pt/C (35.6mVdec-1), reflecting fast HER kinetics on the P0.4LBC catalyst. Combined with experimental and theoretical results, such catalytic activity may benefit from enhanced electrical conductivity, enlarged Co-O covalency, and decreased desorption energy of H* species. This results highlight effective A-site cation-deficient strategy for promoting electrochemical properties of perovskites, highlighting potential water electrolysis at ampere-level current density.

Controllable fabrication of N-doped carbon nanotubes coated Co4N nanoparticles to boost hydrogen evolution reaction

Transition metal nitrides (TMNs) have attracted great attention as ideal active materials in the field of electrocatalysts in recent years due to their excellent electrical conductivity, wide band gap and adjustable morphology. Pure phase Co4N nanoparticles encapsulated nitrogen-doped carbon (NC) nanotubes (Co4N@NC) were in-situ synthesized by one-pot method. In this paper, the morphology of carbon nanotubes is controlled by adjusting the pyrolysis time, so that more active sites are exposed on carbon nanotubes. Thus, the cobalt nitride catalyst with excellent catalytic performance for hydrogen evolution reaction (HER) in acidic electrolyte was obtained. In summary, due to the protection of mesoporous nitrogen-doped carbon to Co4N nanoparticles, large electrochemically active surface area, good conductivity and more exposed active sites, Co4N@NC possesses excellent HER performance in acidic electrolytes. The overpotential of Co4N@NC at the current density of 10 mA cm−2 is 117 mV (η10), and it shows long-term stability in 0.5 M H2SO4 solution for 50 h. This study provides a strategy for the development of catalysts for the controllable synthesis of high-performance transition metal nitrides.

Amorphous-crystalline transition-driven synthesis of Co single-atom catalysts on MoO3 for enhanced hydrogen evolution in acidic and alkaline media

Single atom catalysts (SACs) dispersed in metal oxide supports offer not only maximized catalyst utilization but also extended modulation capabilities through interactions between the SA and its support. However, achieving facile preparation and ensuring electrochemical durability of such SACs, particularly for hydrogen evolution reaction (HER) applications, remain formidable challenges. Our study addresses these issues by employing an amorphous-to-crystalline phase transition in MoO3 to synthesize a cobalt (Co) SA catalyst. This method facilitates the production of highly selective SA catalysts at low temperatures and ensures their enhanced stability in HER applications. The Co SA MoO3 catalyst exhibits superior performance in HER, operating effectively in both acidic and alkaline environments. Significantly, it maintains stable HER activity across these diverse electrolytic conditions. Our Density Functional Theory (DFT) calculations provide insights into the exceptional HER performance of Co SA MoO3. These calculations reveal that the strong affinity for hydrogen and water, facilitated by the modulation of the p-band orbitals at specific oxygen sites adjacent to the Co SA, establishes a thermoneutral pathway for HER. This study represents a pivotal advancement, showcasing a highly practical and robust single-atom catalyst, marking a significant stride towards sustainable energy solutions.

Nanosheets-assembled hollow N-doped carbon nanospheres encapsulated with ultrasmall NiSe nanoparticles for electrocatalytic hydrogen evolution

Developing highly active and stably non-precious metal electrocatalysts for hydrogen production in alkaline conditions is of paramount importance to hydrogen economy. Herein, nanosheet-assembled hollow nitrogen-doped carbon nanospheres confined with ultrasmall NiSe nanoparticles (NiSe@NC) are synthesized by employing a SiO2 template-assisted approach. As expected, the as-prepared NiSe@NC electrocatalyst delivers an overpotential of 169 mV at the current density of 10 mA/cm2 without iR-correction, and sustains at least 80 h for continuous operation, far outperforming the NiSe-p catalyst in 1 M KOH medium toward hydrogen evolution reaction (HER). The appealing HER performance is mainly ascribed to the synergy effect between hollow nitrogen-doped carbon and highly active NiSe nanoparticles, which improves catalytically active sites, expedites electron transfer rate and optimizes the electronic structure of NiSe@NC nanomaterial. More strikingly, this study presents the feasible insights for constructing robust cost-effective electrocatalysts towards efficient HER in harsh alkaline media.

Efficient hierarchical ZIF-based electro/photocatalyst toward hydrogen generation and evolution

In this study, a well-designed hierarchical BiFeO3/ZIF-67 (BFO-ZIF) composite was successfully synthesized to improve the performance of photocatalytic hydrogen generation in comparison to bare BiFeO3 and ZIF-67. Moreover, the behavior of the resultant electrocatalysts was also investigated in the hydrogen evolution reaction (HER). The synthesized electro-photocatalysts were characterized by various physical and photo/electrochemical analyses. The remarkable outcomes of the composite with 50 wt% of ZIF-67 in hydrogen generation correspond to the high specific surface area of the photocatalyst concurrently with the formation of active sites and new charge channels, leading to a modified charge transfer pathway and lower electron-hole recombination. The maximum H2 generation rate over the optimal BFO-ZIF composite (BFO-ZIF(50)) attained 1617 μmol g−1 h−1 during visible light exposure, surpassing the rates observed for pure BFO and ZIF-67. Furthermore, the BFO-ZIF(50) electrocatalyst, with the onset potential of −0.089 V, resulted in an overpotential of −0.19 V at a current density of 10 mA cm−2, while a Tafel slope of 81.6 mV dec−1 in 1.0 M KOH showed the highest activity. The elevated photocatalytic hydrogen generation and improved HER performance of the developed catalysts signify a synergistic effect resulting from the junction and the Z-scheme charge transfer mechanism between the ZIF-67 and BFO nanomaterials. This introduces the BFO-ZIF composite as an efficient photocatalyst and electrocatalyst for hydrogen generation and evolution reaction.

VOx-doped CoP catalysts with synergistic dual-active configuration for boosting hydrogen evolution kinetics

Hydrogen evolution reaction (HER), is of great significance to harvest H2 via energy-saving alkaline water electrolysis yet still challenging. Integrating heterogeneous materials is effective in designing favorable electrocatalysts for water dissociation (WD) and H-immediate involved adsorption/desorption behavior and triggering positive interactions to break the kinetics limitation. Herein, a promising configuration of a vanadium-oxide species integrated with cobalt-phosphide plane that grown on the nickel foam (labeled as VOx-CoP/NF), is demonstrated to boost the alkaline HER kinetics comprehensively. The doped vanadium-oxide species preferentially perform the WD process to generate H-intermediates. Meanwhile, interaction between VOx and CoP induce the electronic redistribution that optimizes 3d-2p orbital hybridization state, which balances the adsorption strength of H* to facilitate the hydrogen transfer and enrichment. Eventually, VOx-CoP/NF exhibits supereminent alkaline HER performance with an overpotential of only 65/245mV at 10/400mAcm−2, superior to individual CoP and most representative cobalt-phosphide candidates. A flowing anion exchange membrane (AEM) urea-assisted water electrolyzer with VOx-CoP/NF as a bifunctional catalyst, is assembled and achieves a satisfactory performance, verifying its practical feasibility for efficient H2 production. The concept exemplified in this work is that synchronous optimization of elementary reaction step kinetics of HER through reasonable constructing well-defined configuration is instructive for the design of HER electrocatalysts.