Volcano-type relationship between interfacial Pt–S bonds and oxygen reduction activity in sulfur-doped carbon-supported Pt3Co catalysts

Pt-based nanoalloys, as the state-of-the-art oxygen reduction reaction (ORR) catalysts, still face significant challenges in terms of activity and long-term stability in proton-exchange membrane fuel cells (PEMFCs). Here, we report a dual-sulfur regulation strategy to achieve gradient regulation of the interfacial platinum–sulfur (Pt–S) bonds in sulfur-doped carbon-supported Pt₃Co catalysts, revealing a volcano-type relationship between the ORR activity and the amount of interfacial Pt–S covalent bonds. The optimized Pt₃Co-SH/S-C catalyst exhibits superior ORR performance with a half-wave potential (E_1/2) of 0.923 V, which is 23 mV higher than that of the commercial Pt/C, and remarkable stability, with only a 3 mV decrease in E_1/2 after 80,000 cycles of accelerated durability testing (ADT). Furthermore, the Pt₃Co-SH/S-C cathode-based membrane electrode assembly (MEA) could deliver a peak power density of 1.15 W cm⁻² in H₂-O₂ mode at 90 °C with exceptional durability. Theoretical calculations reveal that interfacial Pt–S covalent bonds cause a downward shift of the Pt d-band center, as compared to that in Pt₃Co, alleviating the excessive adsorption of *OH and thus enhancing ORR kinetics. This work establishes a new paradigm for tailoring metal-support interactions via interfacial bonding engineering, providing a rational strategy for designing durable high-performance ORR catalysts for PEMFCs.