Electrochemical trends of a hybrid platinum and metal–nitrogen–carbon catalyst library for the oxygen reduction reaction†

Abstract

Enhancing the activity and durability of Pt nanoparticles for the oxygen reduction reaction (ORR) is of critical importance in achieving an optimal, cost-efficient proton exchange membrane fuel cell (PEMFC) catalyst. Aimed at improving the intrinsic catalytic activity and durability of the Pt nanoparticles, this work utilizes a library of fourteen 3d, 4d, 5d, and f metal atomically dispersed metal–nitrogen–carbon (M–N–C) catalysts as active supports, synthesizing a corresponding library of Pt/M–N–C catalysts. XPS and XANES measurements indicate a reduced oxidation state of the Pt nanoparticles due to interactions with the M–N–C support. Further alteration of the electronic structure of the Pt nanoparticles arising from interactions with the M–N_x sites is evidenced through the CO oxidation peak, which experiences broadening, shoulder formation and peak shifting over varying M–N–C supports. ORR performance reveals the significantly enhanced intrinsic catalytic activity of the Pt nanoparticles on M–N–Cs over a Pt/C standard, through specific activity calculations. This work demonstrates the application of highly active hybrid Pt/M–N–C catalysts, showcasing the variation in activity as one traverses the periodic table, while highlighting important design criteria to achieve highly active and durable ORR catalysts.