A Novel Bimetallic Nickel-Molybdenum Carbide Nanowire Array for Efficient Hydrogen Evolution

In-situ revealed inhibition of W2C to excessive oxidation of CoOOH for high-efficiency alkaline overall water splitting

The design of low-cost, efficient, and stable multifunctional basic catalysts to replace the high-cost noble metal catalysts remains a challenge. In this work, we report a dual-component Co-W2C catalytic system which achieves excellent properties of hydrogen evolution reaction (HER, η10 = 63 mV), oxygen evolution reaction (OER, η10 = 259 mV) and overall water splitting (η10 = 1.53 V) by adjusting the interfacial electronic structure of the material. Further density functional theory (DFT) calculations indicate that the efficient electronic modulation at the W2C/Co interface leads to the generation of favorable hydroxyl and hydrogen species energetics on the hybrid surface. The results of the in-situ Raman spectra show that W2C can suppress the excessive oxidation of the active site during the OER process, and the existence of core-shell structure also protects the W2C substrate. The stable and efficient catalytic performance of Co-W2C is attributed to the common advantages of structural and interface manipulation.

Transition metal-based electrocatalysts for alkaline overall water splitting: advancements, challenges, and perspectives

Water electrolysis is a promising method for efficiently producing hydrogen and oxygen, crucial for renewable energy conversion and fuel cell technologies. The hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) are two key electrocatalytic reactions occurring during water splitting, necessitating the development of active, stable, and low-cost electrocatalysts. Transition metal (TM)-based electrocatalysts, spanning noble metals and TM oxides, phosphides, nitrides, carbides, borides, chalcogenides, and dichalcogenides, have garnered significant attention due to their outstanding characteristics, including high electronic conductivity, tunable valence electron configuration, high stability, and cost-effectiveness. This timely review discusses developments in TM-based electrocatalysts for the HER and OER in alkaline media in the last 10 years, revealing that the exposure of more accessible surface-active sites, specific electronic effects, and string effects are essential for the development of efficient electrocatalysts towards electrochemical water splitting application. This comprehensive review serves as a guide for designing and constructing state-of-the-art, high-performance bifunctional electrocatalysts based on TMs, particularly for applications in water splitting.

N, P co-doped Ni/Mo-based multicomponent electrocatalysts in situ decorated on Ni foam for overall water splitting

Developing the robust non-precious metal bifunctional electrocatalyst is highly imperative for the hydrogen evolution from overall water splitting. Herein, a Ni foam (NF)-supported ternary Ni/Mo bimetallic complex (Ni/Mo-TEC@NF), hierarchically constructed by coupling the in-situ formed MoNi₄ alloys and Ni₂Mo₃O₈ with Ni₃Mo₃C on NF, has been developed through a facile method involving the in-situ hydrothermal growth of the Ni-Mo oxides/polydopamine (NiMoO_x/PDA) complex on NF and a subsequent annealing in a reduction atmosphere. Synchronously, N and P atoms are co-doped into Ni/Mo-TEC during the annealing procedure using phosphomolybdic acid and PDA raw materials as P and N sources, respectively. The resultant N, P-Ni/Mo-TEC@NF shows outstanding electrocatalytic activities and tremendous stability for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), due to the multiple heterojunction effect-promoted electron transfer, the large number of exposed active sites, and the modulated electronic structure by the N and P co-doping. It only needs a low overpotential of 22 mV to afford the current density of 10 mA·cm^-2 for HER in alkaline electrolyte. More importantly, as the anode and cathode, it requires only 1.59 and 1.65 V to achieve 50 and 100 mA·cm^-2 for overall water splitting, respectively, comparable to the benchmark Pt/C@NF//RuO₂@NF couple. This work could spur the search for economical and efficient electrodes by in situ constructing multiple bimetallic components on 3D conductive substrates for practical hydrogen generation.

meta-Position synergistic effect induced by Ni-Mo co-doped WSe2 to enhance the hydrogen evolution reaction

Transition metal dichalcogenides have been the most attractive two-dimensional layered materials for electrocatalytic hydrogen evolution due to their unique structure and multi-phase electronic states. However, the enhancement of the WSe₂ electrocatalytic hydrogen evolution reaction (HER) performance by bimetal co-doping has been rarely reported. Herein, the NiMo-WSe₂ catalyst has been synthesized by a one-step hydrothermal reaction, with lower overpotentials of 177 and 188 mV at a current density of 10 mA cm^-2 in 0.5 M H₂SO₄ and 1 M KOH, respectively. The large specific surface area and thinner edge morphology provide more active sites for hydrogen production, thereby significantly improving the charge transfer kinetics. Density functional theory calculation results show that under acidic conditions the ΔG_H* values of NiMo-WSe₂ with different structures and hydrogen adsorption sites are also different, when the hydrogen adsorption site was located at the top of the Se-Ni bond, the meta NiMo-WSe₂ has a ΔG_H* value (-0.04 eV) that is closest to 0. Meanwhile, NiMo-WSe₂ (meta) also has a minimum of ΔG_H* under alkaline conditions. DOS confirmed that Ni doping has a large impact on the electronic states at the WSe₂ Fermi level, while NiMo co-doping greatly reduces the potential energy barrier of the HER reaction, jointly increasing the current density, and thus improving the HER performance.

Metal–Organic Frameworks for Electrocatalytic Sensing of Hydrogen Peroxide

The electrochemical detection of hydrogen peroxide (H₂O₂) has become more and more important in industrial production, daily life, biological process, green energy chemistry, and other fields (especially for the detection of low concentration of H₂O_2). Metal organic frameworks (MOFs) are promising candidates to replace the established H₂O₂ sensors based on precious metals or enzymes. This review summarizes recent advances in MOF-based H₂O₂ electrochemical sensors, including conductive MOFs, MOFs with chemical modifications, MOFs-composites, and MOF derivatives. Finally, the challenges and prospects for the optimization and design of H₂O₂ electrochemical sensors with ultra-low detection limit and long-life are presented.

Dual-anions engineering of bimetallic oxides as highly active electrocatalyst for boosted overall water splitting

Bimetallic oxides have unique advantages in driving both oxygen and hydrogen evolution reactions (OER/HER). Surface engineering of bimetallic oxides is a promising way to boost the catalytic activity by the regulation of electronic structure and surface property. Herein, a dual P, S-anions modification strategy is developed to optimize the catalytic performance of CoMoO₄ nanowire arrays. The formations of CoP and Co₃S₄ species on the CoMoO₄ surface bring heterojunction interfaces for more catalytic active sites and strong electronic interaction for faster interfacial charge transfer. Benefiting from these advantages, the P, S-CoMoO₄ catalyst on nickel foam (NF) delivers excellent catalytic activity and stability. The overpotentials at 10 mA cm^-2 of P, S-CoMoO₄/NF for HER are just 31 mV in acid media and 58 mV in alkaline media, respectively. In addition, by assembling the P, S-CoMoO₄/NF as bifunctional electrodes for overall water splitting, the electrolyzer exhibits a voltage of as low as 1.66 V at a current density of 50 mA cm^-2. This work put forward a new avenue for the development of advanced bifunctional electrocatalysts for water splitting.

Self-Supported Vanadium Carbide by an Electropolymerization-Assisted Method for Efficient Hydrogen Production

Exploring efficient electrodes toward the hydrogen evolution reaction (HER) remains a great challenge for large-scale hydrogen production. Owing to its high earth abundance, low electrical resistivity, and small density, vanadium carbide (VC) is a promising HER electrode candidate but has been rarely explored. In this work, VC nanoparticles encased in nitrogen-doped carbon matrix on carbon cloth (VC@NC/CC) were prepared as a binder-free HER cathode through electropolymerization followed by carbothermal reduction under argon. In the first step of pyrrole electropolymerization, the VO₄ ^3- anions, serving as both vanadium source and supporting electrolyte, were homogeneously incorporated in the positively charged polypyrrole (PPy) framework through coulombic interaction. The electropolymerization was effective for preparation of binder-free metal carbide materials with various polymer monomers as carbon source, which was favorable for the high performance of metal carbide electrodes. During the pyrolysis process, the polymeric hybrids were converted to VC nanoparticles and entrapped in the PPy-derived N-doped carbon matrix. The optimized VC@NC/CC electrode exhibited high catalytic activity and durability in both acidic and alkaline media. The use of VC for efficient HER is remarkable, and such a convenient and versatile electropolymerization-assisted method is appealing for the fabrication of industrially scalable large-area VC electrodes for efficient hydrogen production.

Surface reconstruction and the effect of Ni-modification on the selective hydrogenation of 1,3-butadiene over Mo2C-based catalysts

In the current study, Mo₂C, NiMo₂C, H–Mo₂C and H–NiMo₂C were synthesized to understand the effects of Ni modification and surface reconstruction.

Ni–Mo modified metal–organic frameworks for high-performance supercapacitance and enzymeless H2O2 detection

The growth process for A(B)-Ni_xMo_y-MOFs@AAC hybrids.

CZTS Decorated on Graphene Oxide as an Efficient Electrocatalyst for High-Performance Hydrogen Evolution Reaction

Cu2ZnSnS4 (CZTS) was synthesized by the sonochemical method using 2-methoxyethanol as the solvent and subsequently decorated onto graphene oxide (GO synthesized by the modified Hummers' method) using two different approaches such as in situ growth and ex situ synthesis followed by deposition. Preliminary characterizations indicated that the synthesized CZTS belongs to the kesterite structure with a sphere-like morphology. The in situ-synthesized CZTS/GO (I-CZTS/GO) composite is used as an efficient electrocatalyst for hydrogen evolution reaction (HER) which revealed superior electrocatalytic activity with a reduced overpotential (39.3 mV at 2 mA cm-2), Tafel slope (70 mV dec-1), a larger exchange current density of 908 mA cm-2, and charge transfer resistance (5 Ω), significantly different from pure CZTS. Besides, the I-CZTS/GO composite exhibits highest HER performance with high current stability of which shows no noticeable degradation after i-t amperometry. The catalytic activity demonstrates that the I-CZTS/GO composite could be a promising electrocatalyst in hydrogen production from their cooperative interactions.

A hierarchically-assembled Fe–MoS2/Ni3S2/nickel foam electrocatalyst for efficient water splitting

Hierarchically-assembled Fe–MoS₂/Ni₃S₂/NF demonstrates excellent HER, OER and full water splitting catalytic performances in an alkaline electrolyte.

Lamellar NiMoCo@CuS enabling electrocatalytic activity and stability for hydrogen evolution

We demonstrate a NiMoCo@CuS/NF catalyst for the high-efficiency hydrogen evolution reaction, simultaneously with a significantly enhanced stability.

Walnut-like Transition Metal Carbides with Three-Dimensional Networks by a Versatile Electropolymerization-Assisted Method for Efficient Hydrogen Evolution

Mo₂C@NPC (N,P-doped carbon) electrocatalysts are developed on carbon cloth (CC) as binder-free cathodes for efficient hydrogen evolution through a facile route of electropolymerization followed by pyrolysis. Electropolymerization of pyrrole to form polypyrrole occurs with the homogeneous incorporation of PMo₁₂, driven by Coulombic force between the positively charged polymer backbone and PMo₁₂ anions. This electrochemical synthesis is easily scaled up, requiring neither complex instrumentation nor an intentionally added electrolyte (PMo₁₂ also acts as an electrolyte). After pyrolysis, the resultant Mo₂C@NPC/CC electrode exhibits a unique interconnected walnut-like porous structure, which ensures strong adhesion between the active material and the substrate and favors electrolyte penetration into the electrocatalyst. This method is effective with other monomers such as aniline and is readily extended to fabricate other metal carbide electrodes such as WC@NPC/CC. These carbide electrodes exhibit high catalytic performance for hydrogen production, for example, WC@NPC/CC can deliver an unprecedented current density of 600 mA cm^-2 at an overpotential of only 200 mV either in an acidic or an alkaline solution. Considering the simplicity, scalability, and versatility of the synthetic method, the unique electrode structure, and the excellent catalysis performance, this study opens up new avenues for the design of various novel binder-free metal carbide cathodes based on electropolymerization.