Manipulating Oxygen Reduction Mechanisms of Platinum with Nonmetallic Phosphorus and Metallic Copper Synergistic Alloying

Alloying of platinum (Pt) nanostructures with heteroelements, commonly including transition-metals and nonmetals, is an effective strategy to improve the electrocatalytic performance for oxygen reduction reaction (ORR). However, the distinct mechanisms by which metal/nonmetal alloying improves ORR activity remain unclear. Herein, based on the successful alloying of porous network Pt nanospheres (NSs) with metallic copper (Cu) and non-metallic phosphorus (P) and systematically integrating the electrochemical tests, density functional theory calculations, and in situ electrochemical Raman spectroscopy, this study reveals that the internal Cu-alloying is responsible for modulating the binding strength of oxygenated intermediates to lower the free energy barrier of the potential-determining step (PDS) along the ORR associative mechanism, while the further surface P-alloying can transform the ORR pathway to dissociative mechanism, in which the PDS has a quite low barrier. As a result, the carbon-supported P/Cu co-alloyed porous network Pt nanospheres (P-PtCu_NSs/C) catalyst synthesized by confinement growth and post-phosphorization demonstrates excellent electrocatalytic ORR activity and stability compared to the commercial Pt/C catalyst both in half-cells and proton exchange membrane fuel cells. In particular, the hydrogen (H₂)-oxygen (O₂) single cell with P-PtCu_NSs/C as the cathode catalyst achieves a high mass activity of 0.52 A mg_Pt ^-1 at the voltage of 0.90 V, surpassing the U.S. Department of Energy's current activity target.