Pt–N Interactions and Nitrogen-Doped Graphene-Shell Encapsulation in Platinum Electrocatalysts Supported by SWCNTs for Enhanced ORR Activity and Durability

Abstract

Polymer electrolyte membrane fuel cells (PEFCs) have garnered significant attention as energy conversion devices due to high efficiency and environmental benefits. However, the high cost and susceptibility to corrosion of platinum-based catalysts, widely used in PEFCs, remain major barriers to their development. In this study, we report nitrogen-doped few-layer graphene-shell-encapsulated platinum electrocatalysts supported by single-walled carbon nanotubes (Pt@N-FLG/SWCNT). Experimental analysis indicated that the strong interaction between Pt and nitrogen-doped graphene effectively reduced the 5d hole population and oxidation state of Pt, thereby modulating the d-band center. Consequently, Pt@N-FLG/SWCNT exhibited high oxygen reduction reaction activity in a rotating disk electrode test, with electrochemical surface area (ECSA) of 96.3 m2 g–1 and mass activity of 369 mA mg–1 at 0.9 V vs reversible hydrogen electrode, exceeding commercial Pt/C. More importantly, Pt@N-FLG/SWCNT demonstrated high durability as a cathode catalyst layer in membrane electrode assembly, achieving an ECSA retention of 96.9% after 30,000 accelerated durability test cycles (0.6–0.95 V) and voltage loss of 22.8 mV at 0.8 A cm–2. The high chemical durability of SWCNTs further enhanced the stability of the catalyst. After 5000 cycles of rigorous high-voltage triangular-wave cycling (accelerated stress test, 1–1.5 V), the ECSA loss was 27.2%, and no voltage loss was observed at 1.5 A cm–2. Pt@N-FLG/SWCNT exceeded the dual durability targets set by the U.S. Department of Energy 2025 targets for both carbon supports and electrocatalysts.