Iron adsorption engineering facilitated by Cu doping on cobalt hydroxide host with enhanced oxygen evolution reaction

Iron plays a crucial role in improving the oxygen evolution reaction (OER) activity of hydroxide materials. Increasing the number of iron active sites at the solid–liquid interface is beneficial to enhancing the OER performance of catalysts but still challenging. Here, by systematic exploring the activity trends of M(OH)_x and Cu-M(OH)_x (M = Mn, Cu, Ni, Fe, and Co), we discover that the Cu doping can promote the deposition of Fe active sites on metal hydroxide and Cu-Co(OH)₂ shows the most favorable iron adsorption capacity. When loaded on a conductive substrate (cobalt foam (CF), the M-Cu-Co(OH)₂/CF (Co(OH)₂ prepared by molten salt method) exhibits an attractive low overpotential of 337 mV at 1,000 mA·cm⁻². Using in anion exchange membrane (AEM) water electrolyzer, the single cell with M-Cu-Co (OH)₂/CF as anode catalyst performs a stable cell voltage of 2.02 V to reach 1,000 mA·cm⁻² over 24 h, indicating a great application potential for actual electrolytic water. Therefore, the promoted adsorption of copper on iron provides a new perspective for further enhancing the OER activity of other metal hydroxides.