Activating High-Valent Cu III Species via Co-Doping in Covellite CuS for Water Oxidation

Developing Cu-based catalysts for the oxygen evolution reaction (OER) holds great promise as an alternative to noble-metal catalysts yet is hampered by the large energy cost required for generating active CuIII species. Here, we uncover a surface reconstruction of the graphene-supported CuS enabled by Co-doping (Co-CuS/G) that can effectively activate and stabilize high-valent CuIII species for OER. Unlike undoped CuS that partially converts into CuO, Co-CuS/G undergoes deep reconstruction into Cu(OH)2 and subsequently to the active phase CuOOH at ∼1.35 V vs RHE, much lower than the most reported Cu-based catalysts (≥1.62 V vs RHE). Theoretical calculations further confirm that CuIII species and Co dopants synergistically strengthen the adsorption of key oxygenated intermediates, lowering the energy barrier of the rate-determining step. Therefore, Co-CuS/G achieves good catalytic ability and durability, outperforming both undoped CuS and even commercial IrO2. This work offers a strategy to lower the energetic threshold for CuIII generation in Cu-based OER catalysts.