Self-supporting NiCo₂O₄ nanoneedle arrays on atomic-layer-deposited CoO nanofilms on nickel foam for efficient and stable hydrogen evolution reaction

Owing to easy recycling and the pollution-free nature of hydrogen fuel, electrochemical hydrogen production is attracting increasing attention. In this work, 3D NiCo₂O₄ nanoneedle arrays are prepared on porous nickel foam (NF) coated with a cobalt oxide nanofilm (CNF) produced by atomic layer deposition (ALD) to form a stable and robust catalyst for the hydrogen evolution reaction (HER). As a result, the optimized NiCo₂O₄@C12NF electrode exhibits excellent catalytic activity with a low overpotential of 96 mV versus RHE at a current density of 10 mA cm⁻², small Tafel slope of 50.6 mV dec⁻¹, and outstanding stability for over 25 h in 1 M KOH. The excellent characteristics stem from synergistic effects of the unique nanoneedle arrays, abundant active sites, and short channels at the electrode–electrolyte interface. ALD is demonstrated to be a desirable technique to produce highly efficient HER electrocatalysts for commercial water electrolysis.