High-concentration CoNi-C interface for efficient alkaline hydrogen evolution

The rational design of metal-carbon interfaces is pivotal for advancing alkaline hydrogen evolution reactions (HER) in sustainable energy technologies. However, conventional approaches often suffer from low interface concentrations, restricting catalytic activity and hydrogen production rates. Herein, we report a self-supporting electrode featuring a highly concentrated CoNi alloy-carbon interface on nickel foam (Co_xNi-C/NF), achieved via precursor size engineering. By electrodepositing ZIF-67 with Ni(NO₃)₂ and trimesic acid, we synthesized Co, Ni-containing trimesic acid (Co_xNi-BTC) precursors with tunable sizes, enabling precise control over metal dispersion and interface density. Following pyrolysis, the resulting Co_xNi-C/NF electrode exhibits an interface concentration of up to 4 %. Notably, Co₅₀Ni-C/NF delivers outstanding HER performance in 1 M KOH, with a low overpotential (η₁₀) of 30 mV cm^-2, a Tafel slope of 45.1 mV dec^-1, and remarkable stability over 72 h. In a practical anion exchange membrane water electrolyzer (AEMWE) at 60 °C, the Co₅₀Ni-C/NF||RuO₂/NF system achieves 0.5 A cm^-2 at 1.93 V and maintains stable operation for 100 h at 0.2 A cm^-2, demonstrating exceptional durability. Density functional theory (DFT) calculations reveal that the dense CoNi-C interface enhances conductivity, strengthens *H₂O adsorption, promotes H-OH bond cleavage, and accelerates H₂ evolution. This work provides key insights into constructing high-concentration transition metal-carbon interfaces, offering a promising strategy for next-generation HER electrodes.