Nickel-based electrocatalysts are promising for industrial water electrolysis, but the dense hydroxyl oxide layer formed during the oxygen evolution reaction (OER) limits active sites accessibility and presents challenges in balancing structural stability with effective charge transfer. Based on this, an efficient in situ leaching strategy is proposed to construct grain boundary-rich catalyst structure with high charge transfer ability and a deep catalytic active layer reached >
200-nm. Under OER conditions, stable sub-nano Ni