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-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-N-C delivers a mass activity of 0.75 A mg at 0.9 V and a peak power density of 1240 mW cm 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 dz orbital occupation state is regulated to te by spin-charge injection, suppressing the OH* site-blocking effect and effectively inhibiting HO production. This work provides valuable insights into designing high-performance and low-Pt catalysts via spintronics-level engineering.