Acidic oxygen evolution reaction: Mechanism, catalyst classification, and enhancement strategies

As the most desirable hydrogen production device, the highly efficient acidic proton exchange membrane water electrolyzers (PEMWE) are severely limited by the sluggish kinetics of oxygen evolution reaction (OER) at the anode. Rutile IrO2 is a commercial acid-stable OER catalyst with poor activity and high cost, which has motivated the development of alternatives. However, hitherto most of the designed acidic OER catalysts have disadvantages of low activity or stability, which cannot meet the requirement of industrial applications. Thus, exploring suitable strategies to enhance the activity and stability of cost-effective acidic OER catalysts is crucial for developing the PEMWE technique. In this review, the main OER mechanisms, different types of catalysts, and their activity and stability characteristics are summarized and discussed, and then possible strategies to improve activity and stability are proposed. Finally, the problems and prospects of such catalysts are generalized to shed some light on the future research of advanced catalysts for acidic OER.