Carbon monoxide and formic acid oxidation at Rh@Pt nanoparticles

Abstract

Abstract Pt-based nanoparticle catalysts play a central role in the development of fuel cell technology. Due to their high susceptibility to poisoning by CO, the addition of a second metal is necessary to weaken its adsorption and/or increase its oxidation rate. In this work, we studied the effect of a rhodium core on CO and formic acid oxidation at core-shell nanoparticles synthesized by the sequential reduction of Rh and Pt using a polyol method. With increasing Pt coverage, the CO stripping potential was found to shift from 0.48\u202fV vs. SCE for ca. 1 monolayer of Pt to 0.61\u202fV for ca. 3 monolayers. The rapid shift with increasing Pt coverage is indicative of a strong electronic effect of the Rh core on the Pt shell. As a result of that strong electronic effect, the rate of the indirect oxidation of formic acid, via an adsorbed CO intermediate, was highest at low Pt coverages and gradually shifted towards that of Pt nanoparticles with increasing Pt coverage. In contrast, the rate of the direct oxidation increased with increasing Pt coverage up to 2.3 monolayers and then decreased, suggesting that for low Pt coverages the advantage of weak CO adsorption was offset by the effects of weaker formic acid adsorption.