Electrocatalysts for Oxygen Evolution Reaction in Acidic Media.

Water electrolysis is one of the most efficient and environmentally benign methods for the hydrogen production using renewable but intermittent power sources. The well-established proton exchange membrane (PEM)-based water electrolysis, which operates under acidic conditions, possesses many advantages compared to alkaline water electrolysis, such as compact design, higher voltage efficiency and higher gas purity. However, the PEM-based water electrolysis is hampered by the low efficiency, instability and high cost of anodic electrocatalysts for the oxygen evolution reaction (OER). Many OER electrocatalysts are prone to dissolution and/or surface structure transformation under the oxidizing OER potentials in the harsh acidic environment, finally leading to a drastic decrease of catalytic performance. In this review, we comprehensively summarize, classify and discuss the recently reported acidic OER electrocatalysts. The related fundamental studies on OER mechanisms and the relationship between activity and stability are particularly highlighted in order to provide an atomistic-level understanding for the OER catalysis. A stability test protocol is suggested to evaluate the intrinsic activity degradation. We also discuss some current challenges and unresolved questions, such as the usage of carbon-based materials and the differences between the electrocatalyst performances in acidic electrolytes and PEM-based electrolyzer. Finally, the suggestions for the most promising electrocatalysts and a perspective for future research are outlined. This review presents a fresh impetus and guideline to the rational design and synthesis of high-performance acidic OER electrocatalysts for PEM-based water electrolysis. This article is protected by copyright. All rights reserved.