Progress in carbon-free oxygen evolution electrocatalysts for high-current-density water electrolysis in acidic media

Hydrogen production through water electrolysis technology has received great attention toward the global mission of carbon neutrality. Industrial proton exchange membrane (PEM) electrolyzers stand out from other water electrolysis techniques due to their advantages such as high-current-density (HCD) operation capability, high efficiency, and more compact devices. The PEM water electrolysis efficiency largely depends on the activity and stability of the involved anodic electrocatalysts where the oxygen evolution reaction (OER) occurs. Especially for HCD water electrolysis toward large-scale hydrogen production, the operating environment of anodes is usually harsh, which accelerates the corrosion of OER catalysts particularly under such high-potential and oxygen-rich conditions. Hence, developing robust electrocatalysts for efficient OER is a longstanding challenge. Although carbon-based materials have been extensively investigated in electrocatalytic fields, the insufficient antioxidant capacity of carbonous substrates limits their practical application in the OER. Therefore, the development of carbon-free OER electrocatalysts for HCD water splitting in acidic media is highly meaningful. This contribution systematically reviews the existing problems and solutions of acidic OER, the key factors for rational design of carbon-free catalysts, and the designing strategies of supported/unsupported catalysts for industry under acidic conditions. Finally, the challenges and future research orientations in carbon-free electrocatalysts for HCD acidic OER are rationally proposed.