Nickel cobalt oxide-based heterostructures as electrocatalysts for the oxygen evolution reaction at industry-relevant conditions

Green hydrogen (H2) is an important sustainable energy carrier due to its eco-friendly nature and high energydensity. However, the large overpotentials associated with the oxygen evolution reaction (OER) present achallenge for industrial-scale (H2) production through alkaline water electrolysis (AWE). Herein, we synthesizedNiCo2O4/NiO heterostructures with 1:1 and 1:2 Ni to Co ratios, here referred to as NiCoOx and NiCo2Ox,respectively, via a hydrothermal method. The catalysts were thoroughly characterized and their OER activity wasevaluated at room temperature in 1 M and 7 M KOH solutions using a rotating disk electrode setup. A comparisonof these two sets revealed a strong activation process over time that correlates to the presence of metal impuritiesin the electrolyte. Moreover, NiCo2Ox outperformed NiCoOx, likely due to their differences in phase andelemental composition. To assess their applicability in industry-like conditions, the performance of Ni platesupported NiCo2Ox was investigated by chronopotentiometry at 40 ◦C in 1 M and 7 M KOH at 200 mA cm− 2using an H-type cell. This electrocatalyst exhibited a fast activation followed by a stable performance for 24 h,showing promise for application in AWE. This study highlights the importance of evaluating performance underindustry-like conditions.