Highly active small palladium clusters supported on ferric hydroxide for carbon monoxide-tolerant hydrogen oxidation

Proton-exchange membrane fuel cells have been regarded as one of the most promising candidates for efficient energy conversion. However, the CO poisoning of the anode and the scarcity of the Pt metal are two major barriers to their commercialization. Development of CO-tolerant Pd electrocatalysts is considered to be a plausible approach to overcome these problems. Herein we report that for the CO-tolerant H₂ oxidation, sub-2-nm size Pd clusters as well as single atoms, supported on FeO_x nanocrystallites, are highly active and durable at a wide temperature range of 20-120 °C. Experimental data demonstrated that CO preferentially adsorbs on these small Pd clusters or single atoms linearly, resulting in weakened CO binding and enhanced H₂ competitive adsorption. Therefore, FeO_x-supported small Pd clusters or single atoms provide a higher CO-tolerant performance. This finding may offer a new strategy to develop CO-tolerant Pd-based electrodes. Small and fine wins every time: FeO_x-supported Pd clusters of sub-2-nm size are extremely active and durable for CO-tolerant H₂ oxidation over a wide temperature range (20-120 °C). The high activity originates from the very small clusters and even single-atom dispersion of Pd, which results in weakened adsorption of CO.