Formic Acid Tolerant Ir-Based Electrocatalysts for Oxygen Reduction Reaction

In this paper, carbon-supported Ir-Co, Ir-Ni, and Ir-Cr catalysts (Ir-Co/C, Ir-Ni/C, and Ir-Cr/C) were synthesized and characterized for the oxygen reduction reaction (ORR). Compared to both Pt/C and Pd/C catalysts, these Ir alloy catalysts demonstrated much higher formic acid tolerance capabilities during the ORR process in a 0.5 M H2SO4 solution containing both oxygen and formic acid. Rotating disk electrode measurements confirmed that if formic acid was present, these Ir alloy catalysts could still catalyze a complete 4-electron transfer ORR from O2 to H2O, while the Pt/C catalyst could only catalyze a reaction contributed by both 2- and 4-electron transfer processes, producing both H2O2 and H2O. These results strongly suggest that Ir alloy catalysts should be promising candidates for direct formic acid fuel cell applications.