Practical Classification of Catalysts for Oxygen Reduction Reactions: Optimization Strategies and Mechanistic Analysis

Abstract Oxygen reduction reaction (ORR) is the core reaction of fuel cell/metal–air battery at the cathode, and it is of great significance to develop high‐performance ORR catalyst. Generally speaking, ORR catalysts are classified according to the class of materials they use, which often makes it difficult for different types of catalysts to have a clear connection with some unified optimization mechanism and creates difficulties in designing improvement strategies. Here, this review proposes three major strategies that can affect the activity of ORR catalysts: designing morphology, defect control, and heteroatom doping. The core content of this review is to analyze the principles of various optimization strategies that affect the performance of catalysts individually or synergistically at the micro level. In addition, the problems and challenges still faced in the design of ORR catalysts are sorted out, and possible solutions are proposed. This review makes the research direction of ORR catalysts clearer, and provides theoretical support and new ideas for the design of high‐efficiency electrocatalysts.