Insights into the synergistic catalytic mechanism on the customized dual sites of an efficient ORR catalyst†

PtCo alloys as compelling catalysts for the oxygen reduction reaction (ORR) have been loaded on heteroatom-modified carbon carriers in recent years to modulate their electronic structure and influence their interaction with intermediates. However, the actual active sites remain unclear and their interaction with intermediates is still controversial. Herein, PtCo/PC catalysts were synthesized by loading PtCo alloys on P-modified carbon carriers, and their catalytic mechanism was investigated using in situ Raman spectroscopy. In the results, the distorted and disordered PtCo alloy sites and the P-C defect sites are pinpointed and clarified as the double active sites for such catalysts. Among which, PtCo/PC-2 has the most abundant active sites, an optimal hierarchical porous structure, and the strongest Co–P binding, thereby showing ORR activity and stability. Combined with in situ Raman analysis, it exposits that the doped P atom in PtCo/PC-2 possesses strong electron-donating ability, which indirectly helps Pt function as an electron reservoir to donate electrons for OOH* on PtCo alloy sites, and directly weakens the adsorption energy of OOH* on P–C defect sites. Furthermore, the dynamic evolution of OOH* discloses that the double active sites on PtCo/PC-2 synergistically promote the ORR process via an associative pathway.