Effect of chemisorbed CO on MoO x–Pt/C electrode on the kinetics of hydrogen oxidation reaction

Abstract

The influence of poisoning of MoO x –Pt catalyst by CO on the kinetics of H 2 oxidation reaction (HOR) at MoO x –Pt electrode in 0.5 mol dm −3 HClO 4 saturated with H 2 containing 100 ppm CO, was examined on rotating disc electrode (RDE) at 25 °C. MoO x –Pt nano-catalyst prepared by the polyole method combined with MoO x post-deposition was supported on commercial carbon black, Vulcan XC-72. The MoO x –Pt/C catalyst was characterized by TEM technique. The catalyst composition is very similar to the nominal one and post-deposited MoO x species block only a small fraction of the active Pt particle surface area. MoO x deposition on the carbon support can be ruled out from the EDAX results and from the low mobility of these oxides under used conditions. Based on Tafel–Heyrovsky–Volmer mechanism the corresponding kinetic equations from a dual-pathway model were derived to describe oxidation current–potential behavior on RDE over entire potential range, at various CO coverages. The polarization RDE curves were fitted with derived polarization equations according to the proposed model. The fitting showed that the HOR proceeded most likely via the Tafel–Volmer (TV) pathway. A very high electrocatalytic activity observed at MoO x –Pt catalyst for the hydrogen oxidation reaction in the presence of 100 ppm CO is achieved through chemical surface reaction of adsorbed CO with Mo surface oxides.