Size-effect on the activity of anodic catalysts in alcohol and CO electrooxidation

The aim of this report is to investigate the particle size-effect of Pt on the catalytic activities for high surface area catalysts. Series of Pt/MWCNTs catalysts with average particle size of 1.7, 2.4, and 4.0 nm were fabricated. Size-effect on their catalytic activity towards CO as well as alcohol electrooxidation reactions was studied by CO-stripping, cyclic voltammetry, and chronoamperometry. We for the first time investigated the size-effect on the apparent activation energy for the reaction of CO electrooxidation. The results showed that the catalytic activities had a strong dependence on their Pt particle size. (1) The reaction of CO electrooxidation on the smaller Pt nanoparticles was found occurring at the higher overpotential and apparent activation energy than on the larger counterparts. The intrinsic nature of those observed phenomena were due to the stronger CO adsorption on the smaller Pt nanoparticles. (2) As the size decreased, the mass activity towards alcohol electrooxidation increased; considering the discount of this increase for the smaller particles, we concluded that the deactivation arising from their more intense CO-poisoning, which limited the beneficial effect on their higher mass activity in this case.