abstract
-
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 (H2 ) production through alkaline water electrolysis (AWE). Herein, we synthesized NiCo2 O4 /NiO heterostructures with 1:1 and 1:2 Ni to Co ratios, here referred to as NiCoOx and NiCo2 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, NiCo2 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 NiCo2 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. © 2025 The Authors