Proton-Conducting Polymer Wrapped Cathode Catalyst for Enhancing Triple-Phase Boundaries in Proton Exchange Membrane Fuel Cells

The performance of proton exchange membrane fuel cells (PEMFCs) depends on the oxygen reduction reaction (ORR) kinetics and durability of the cathode catalyst. This can be achieved by tailoring cathode structure to increase the number of triple-phase boundaries. Herein, different weight percentages of proton-conducting poly(vinylphosphonic acid) (PVPA) wrapped nitrogen and sulfur dual atoms doped longitudinally exfoliated carbon nanotubes (PX_NSPNT, X-1, 3, 6, and 9 wt %) is synthesized as the catalyst support for Pt/Pt-alloy nanoparticles (Pt/PX_NSPNT) to improve the triple-phase boundary density and durability of cathode catalyst. Raman spectroscopy and transmission electron microscopy analysis infer that polymer coating and N–S dopant sites provide the anchoring sites for Pt nanoparticles, which can enhance the durability of the catalyst. Besides, half-cell studies shows that with increasing PVPA wt % (until 6 wt %), the activity of the electrocatalyst also increases, suggesting PVPA has contributed to enhancing the diffusion of ions and mass-transfer kinetics. The accelerated durability test signifies the robustness of Pt/P6_NSPNT catalyst, which can retain 80% of its electrochemical active surface area after 15000 potential cycles. In single-cell studies, Pt/P6_NSPNT and Pt–Co/P6_NSPNT cathode electrocatalyst deliver power densities of 923 and 1090 mW cm–2, respectively, at 60 °C, which is the highest among all other PVPA weight percentages, Pt/NSPNT, and commercial Pt/C catalyst. The methodical variation of PVPA wt % helps to find the optimum proton-conducting polymer content on the electrocatalyst for achieving high-performance and durability of PEMFC.