Shuo Li^a, Jing Liu^a,*, Shengchang Li^a, Teng Fu^a, Yi Zong^a, Han Ding^d, Yecheng Zou^d, Yongming Zhang^d, Xuejing Cui^a, Xin Zhou^b,c,*, and Luhua Jiang^a,*

^{a College of Materials Science and Engineering, Qingdao University of Science and Technology, Qingdao 266042, P. R. China}

^b Interdisciplinary Research Center for Biology and Chemistry, Liaoning Normal University, Dalian 116029, P. R. China

^c College of Environment and Chemical Engineering, Dalian University, Dalian 116622, P. R. China

^d Shandong Dongyue Future Hydrogen Energy Materials Co. Ltd., Zibo 256401, P. R. China

* Corresponding authors. E-mail: liuj955@qust.edu.cn (J. Liu); zhouxin@dlu.edu.cn; luhuajiang@qust.edu.cn (L. Jiang)

Abstract:

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, 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.

Keywords: Oxygen reduction reaction; Metal-support interaction; Sulfur-doped carbon; Pt-S bond; Proton exchange membrane fuel cell.