Engineered surface oxidation of porous metal substrate for simultaneous enhancement of kinetics and durability in electrochemical hydrogen evolution reaction.

This study presents an effective approach to enhancing the catalytic performance, long-term stability, and surface hydrophilicity of porous nickel (Ni) substrates for the hydrogen evolution reaction (HER) via controlled surface oxidation without additional catalysts. In this study, the Ni tape-cast substrate (Ni-TCS), fabricated through a tape-casting method followed by oxidation and reduction treatments, exhibited a large surface area and fine porosity, resulting in a significantly improved catalytic activity compared to conventional Ni foam. Through partial oxidation at temperatures ranging from 300 °C to 450 °C, a catalytically favorable nickel oxide (NiO) nano layer was produced directly on the Ni-TCS surface, enhancing the HER activity and stabilizing the NiO/Ni interface for durability. Additionally, the NiO nano layer rendered the electrode surface hydrophilic as confirmed through contact angle measurements, facilitating effective electrolyte contact and improving mass transport. The Ni-TCS electrode oxidized at 400 °C (Ni-TCS400) demonstrated the highest HER activity, sustaining excellent stability at 500 mA cm^-2 over 500 h. Ni-TCS400 exhibited lower kinetic and mass-transfer overpotentials than those of the Ni-TCS in an alkaline water electrolyzer (AWE) system, while a voltage of 1.81 V was required to achieve a current density of 0.4 A cm^-2. Overall, the partial oxidation strategy circumvents the use of binders or precursors, while enabling improved stability, simplified fabrication, and high catalytic activity, making it a promising approach for the development of durable, efficient AWE electrodes.