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

The influence of poisoning of MoOx–Pt catalyst by CO on the kinetics of H2 oxidation reaction (HOR) at MoOx–Pt electrode in 0.5 mol dm−3 HClO4 saturated with H2 containing 100 ppm CO, was examined on rotating disc electrode (RDE) at 25 °C. MoOx–Pt nano-catalyst prepared by the polyole method combined with MoOx post-deposition was supported on commercial carbon black, Vulcan XC-72. The MoOx–Pt/C catalyst was characterized by TEM technique. The catalyst composition is very similar to the nominal one and post-deposited MoOx species block only a small fraction of the active Pt particle surface area. MoOx 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 MoOx–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.