Intrinsic ORR Activity Enhancement of Pt Atomic Sites by Engineering the d-Band Center via Local Coordination Tuning

Abstract

A considerable amount of platinum (Pt) is required to ensure an adequate rate for the oxygen reduction reaction (ORR) in fuel cells and metal-air batteries. Thus, the implementation of atomic Pt catalysts holds promise for minimizing the Pt content. In this contribution, atomic Pt sites with nitrogen (N) and phosphorus (P) co-coordination on a carbon matrix (PtNPC) are conceptually predicted and experimentally developed to alter the d-band center of Pt, thereby promoting the intrinsic ORR activity. PtNPC with a record-low Pt content (≈0.026 wt %) consequently shows a benchmark-comparable activity for ORR with an onset of 1.0 VRHE and half-wave potential of 0.85 VRHE. It also features a high stability in 15 000-cycle tests and a superior turnover frequency of 6.80 s−1 at 0.9 VRHE. Damjanovic kinetics analysis reveals a tuned ORR kinetics of PtNPC from a mixed 2/4-electron to a predominately 4-electron route. It is discovered that coordinated P species significantly shifts d-band center of Pt atoms, accounting for the exceptional performance of PtNPC.