Noble-metal-free oxygen evolution reaction electrocatalysts working at high current densities over 1000 mA cm−2 : from fundamental understanding to design principles

Alkaline water electrolysis provides a promising route for "green hydrogen" generation, where anodic oxygen evolution reaction (OER) plays a crucial role in coupling with cathodic hydrogen evolution reaction. To date, the development of highly active and durable OER catalysts based on earth-abundant elements has drawn wide attention; nevertheless, their performance under high current densities (HCDs ≥1000 mA cm−2) has been less emphasized. This situation has seriously impeded large-scale electrolysis industrialization. In this review, in order to provide a guideline for designing high-performance OER electrocatalysts, the effects of HCD on catalytic performance involving electron transfer, mass transfer, and physical/chemical stability are summarized. Furthermore, the design principles were pointed out for obtaining efficient and robust OER electrocatalysts in light of recent progress of OER electrocatalysts working above 1000 mA cm−2. These include the aspects of developing self-supported catalytic electrodes, enhancing intrinsic activity, enhancing the catalyst-support interaction, engineering surface wettability, and introducing protective layer. Finally, summaries and outlooks in achieving OER at industrially relevant HCDs are proposed.