The influence of platinum surface morphology on the electrooxidation of methanol in alkaline solutions

In this work we compare methanol oxidation characteristics in pH 0 and pH 14 electrolytes, and examine the effect of methanol concentration and platinum surface condition (e.g. H-UPD, OH adsorption, Pt oxidation/reduction, planar, nanoporous) on the oxidation current. We observe that in rotating disc electrode (RDE) experiments the oxidation currents on smooth platinum decrease with increasing rotation rate. We show that this decrease is associated with increasing the rate at which oxidation intermediates are swept into the bulk electrolyte before being fully oxidized. To increase the dwell time of intermediates a platinum electrode with 3 nm length scale surface porosity was synthesized by dealloying a Pt-Cu alloy. We then perform the same RDE experiments and show that in this case the methanol oxidation current increases with increasing convection. We attribute this behavior to the trapping of reaction intermediates that otherwise were swept away on the polished sample.