Environmentally Friendly and Earth-Abundant Self-Healing Electrocatalyst Systems for Durable and Efficient Acidic Water Splitting

Electrochemical water splitting under acidic conditions is an efficient route for green hydrogen production from renewable electricity. Its implementation on a globally relevant scale is hindered by the lack of abundant and low-cost electrocatalysts for the oxygen evolution reaction that can operate stably and efficiently under highly acidic anodic conditions. Here, we report the design of stable and efficient acidic OER electrocatalysts consisting of a self-healing bismuth (Bi)-based matrix hosting transition metal active sites. Comprehensive structural performance investigation of Co- and Ni-BiO_x electrodes provides insights into the role of the electrolyte composition and pH in the self-healing mechanism under anodic conditions. Our best-performing [Co-Bi]O_x and [Ni-Bi]O_x anodes achieve over 200 h of continuous electrolysis at a catalytic current of 10 mA cm^-2 with an overpotential of 590 and 670 mV at a pH of 1 in a 0.1 M H₂SO₄ electrolyte. Notably, while the [Bi]O_x matrix did not contribute to the catalytic activity, it was essential to stabilize the active Co and Ni sites during the acidic OER. Our findings provide a promising strategy for the engineering of earth-abundant materials for efficient acidic water splitting, as an alternative to the use of poorly scalable and expensive noble metal catalysts.