Spin occupancy regulation of the Pt d-orbital for a robust low-Pt catalyst towards oxygen reduction

Disentangling the limitations of O-O bond activation and OH* site-blocking effects on Pt sites is key to improving the intrinsic activity and stability of low-Pt catalysts for the oxygen reduction reaction (ORR). Herein, we integrate of PtFe alloy nanocrystals on a single-atom Fe-N-C substrate (PtFe@Fe_SAs-N-C) and further construct a ferromagnetic platform to investigate the regulation behavior of the spin occupancy state of the Pt d-orbital in the ORR. PtFe@Fe_SAs-N-C delivers a mass activity of 0.75 A mg_Pt^-1 at 0.9 V and a peak power density of 1240 mW cm^-2 in the fuel-cell, outperforming the commercial Pt/C catalyst, and a mass activity retention of 97%, with no noticeable current drop at 0.6 V for more than 220 h, is attained. Operando spectroelectrochemistry decodes the orbital interaction mechanism between the active center and reaction intermediates. The Pt dz² orbital occupation state is regulated to t_2g⁶e_g³ by spin-charge injection, suppressing the OH* site-blocking effect and effectively inhibiting H₂O₂ production. This work provides valuable insights into designing high-performance and low-Pt catalysts via spintronics-level engineering.