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

Green hydrogen (H 2 ) is an important sustainable energy carrier due to its eco-friendly nature and high energy density. However, the large overpotentials associated with the oxygen evolution reaction (OER) present a challenge for industrial-scale (H 2 ) production through alkaline water electrolysis (AWE). Herein, we synthesized NiCo 2 O 4 /NiO heterostructures with 1:1 and 1:2 Ni to Co ratios, here referred to as NiCoOx and NiCo 2 Ox, respectively, via a hydrothermal method. The catalysts were thoroughly characterized and their OER activity was evaluated at room temperature in 1 M and 7 M KOH solutions using a rotating disk electrode setup. A comparison of these two sets revealed a strong activation process over time that correlates to the presence of metal impurities in the electrolyte. Moreover, NiCo 2 Ox outperformed NiCoOx, likely due to their differences in phase and elemental composition. To assess their applicability in industry-like conditions, the performance of Ni plate-supported NiCo 2 Ox was investigated by chronopotentiometry at 40 °C in 1 M and 7 M KOH at 200 mA cm −2 using 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 under industry-like conditions. • NiCo oxides were prepared by hydrothermal method and comprehensively characterized. • The materials consist of NiO/NiCo 2 O 4 heterostructures and different metal ratios. • Sample composition and electrolyte impurities influence the catalytic performance. • NiCo 2 O x outperformed NiCoO x in purified and unpurified 1 M and 7 M KOH electrolytes. • NiCo 2 O x /Ni plate is stable during 24 h electrolysis under industry-like conditions.