Synergistic NiO-NiCo Heterostructure Electrode for Highly Active and Durable Hydrogen Evolution in Industrial...

Although its economic and environmental advantages make alkaline water electrolysis (AWE) a promising route to sustainable hydrogen production, the sluggish alkaline hydrogen evolution reaction (HER) necessitates efficient electrocatalysts to enhance AWE performance. Ni-based materials are well-suited for this purpose but exhibit poor alkaline HER activity because the Volmer step acts as a critical kinetic barrier restricting the overall reaction rate. To address this limitation, NiO and NiCo alloy (NiCo) are herein integrated to leverage their synergistic effects, with NiO promoting the Volmer step and NiCo providing additional catalytic sites, as confirmed by electrochemical analysis. A Ni foam-supported NiO-NiCo electrode achieves an overpotential of 22.7 mV at 10 mA cm^-2 under alkaline conditions, demonstrating a performance comparable with NiO and NiCo-based electrocatalysts containing noble metals. In a single-cell configuration, this electrode operates at 2.01 V and 1 A cm^-2, i.e., 262 mV lower than a bare Ni-foam electrode. Furthermore, after the on-off durability testing, in which the current density was alternately switched between 0 and 400 mA cm^-2 at 30 min intervals, the electrode overpotential increased by only 13 mV, indicating high stability. These results highlight the potential of NiO-NiCo electrodes for industrial AWE.