Catalytic activities of PtBi nanoparticles toward methanol electrooxidation in acid and alkaline media

Abstract

Spherical PtBi nanoparticles are electrodeposited from aqueous solution according to the preset composition. Their catalytic activities toward methanol electrooxidation are examined by cyclic voltammetry and chronoamperometry in acid media and first in alkaline media. Experimental results show that, methanol electrooxidation has lower onset potentials on PtBi than on Pt in either acid or alkaline media. The improved catalytic activities are due to the electronic effects of bismuth in PtBi. At higher overpotentials, the electrolyte acidity has produced different influences on the kinetics of methanol electrooxidation on PtBi and Pt. In acid media, PtBi is inferior to Pt for methanol oxidation at above 0.460 V, because that fewer continuous Pt sites on PtBi are not enough for the adsorption and dehydrogenation of methanol molecules. In alkaline media, the oxidation current on PtBi becomes much higher than that on Pt at above 0.768 V. The raised current can be credited to the bifunctional mechanism. Bi2O5 sites on PtBi surface serve for OHad adsorption and Pt sites for methanol dehydrogenation. The better catalytic activity of PtBi nanoparticles in alkaline media suggests their promising application in alkaline direct alcohol fuel cells.