Surface/Near-Surface Structure of Highly Active and Durable Pt-Based Catalysts for Oxygen Reduction Reaction: A Review

Proton exchange membrane fuel cells (PEMFCs) are highly promising energy-conversion devices because of their zero-emission and high efficiency. A great deal of Pt is of significant necessity on the cathode to accelerate the rate of kinetically sluggish oxygen reduction reaction (ORR) and maintain the long-term operation, leading to the prohibitive cost of PEMFCs and limiting their widespread deployment. In the past decades, numerous efforts including manipulation of composition, morphology, and structure have been devoted to improving their higher activity and stability, but still lag behind the actual requirement. ORR is a typical surface-sensitive electrochemical reaction and its process is mainly determined by surface/near-surface structure. Herein, the recent advances in the manipulation of surface structure are summarized. The ORR mechanism and evaluation method for activity and stability are introduced. Then, solutions toward the engineering of surface structure and its effect on activity and stability are presented. Finally, comments on the future direction of nanocatalysts for ORR are presented in terms of engineered surface structure.