Heteroatom-doped g-C₃N₄/C-supported Pt catalysts toward Low-Pt cathode applications in proton exchange membrane fuel cells

This study investigates Pt catalysts supported on H-, F-, O-, and P-doped g-C₃N₄ as cathode electrocatalysts for proton exchange membrane fuel cells (PEMFCs) under identical synthesis and testing conditions. Unlike conventional studies that rely primarily on half-cell measurements, this work establishes a direct correlation between half-cell metrics and single-cell PEMFC performance, enabling a realistic evaluation of catalyst behavior. The results demonstrate that catalytic performance is not solely governed by electrochemically active surface area (ECSA), but is strongly influenced by dopant-dependent electronic interactions and metal–support coupling. Although H-doped g- C₃N₄-supported Pt exhibited the highest ECSA (128 m²gPt^-1), it delivered the lowest membrane–electrode assembly (MEA) performance. In contrast, P-doped Pt–g-C₃N₄/C achieved the highest PEMFC performance, reaching a maximum power density of 123.2 mWcm^-2 and a mass activity of 2800 mAmgPt^-1 at 0.6 V outperforming.This clear discrepancy between half-cell activity and practical fuel cell performance highlights the limitations of conventional electrochemical descriptors in predicting real operating behavior. The findings demonstrate that heteroatom-induced electronic modulation plays a decisive role in determining catalytic efficiency under realistic conditions. Among the investigated systems, P-doped Pt–g-C₃N₄/C exhibits the most favorable balance between electronic properties, structural stability, and practical performance, making it a promising low-Pt cathode catalyst for next-generation PEMFC applications.