Surface SnO2 Decoration: An economical and efficient alternative to Pt shells in Pt-Co catalysts for enhanced oxygen reduction reaction

Pt-metal alloy catalysts have been regarded as improvements over traditional Pt catalysts for the oxygen reduction reaction (ORR), but suffering from instability due to the increased oxophilicity and susceptibility to oxidation. To address this issue, two strategies, Pt shell and metal-oxide decoration, have been proposed for further enhancement of ORR performance. However, comparative studies investigating how these two strategies affect the electronic structure of active sites, including their structure evolution and redox capabilities during the ORR process, are relatively limited. In this study, we decorated commercial Pt3Co catalysts with Pt shell (Pt3Co@Pt) and SnO2 species (Pt3Co-SnO2) to investigate their similarities and differences in electronic structures, dynamic evolutions, and underlying mechanisms of ORR active sites. Operando X-ray absorption spectroscopy (XAS) revealed that both strategies mitigated issues related to Pt oxidation, reaction hysteresis, and oxygen affinity in commercial Pt3Co, with SnO2 demonstrating even greater efficacy. The Pt3Co-SnO2 catalyst exhibited kinetic mass activities as high as 824 mA/mgPt with superior stability, markedly outperforming those of commercial Pt, commercial Pt3Co, and Pt3Co@Pt. Computational simulations further confirm that SnO2 surface decoration effectively masks inactive sites with high oxophilicity on Pt3Co for the excellent ORR activity, while accumulating negative charges from surface oxygen and mitigating phase segregation for enhanced ORR stability.