Methanol oxidation and photo-oxidation at Pt/WO3 electrocatalysts on graphite substrates

Pt/WO3 catalyst layers were prepared by electrosynthesis of WO3 on a graphite (Gr) support and electrodeposition of Cu on WO3, followed by a galvanic replacement process, involving treatment of the Cu/WO3/Gr composite electrode with a chloroplatinate solution. Both the platinized and the precursor WO3/Gr electrodes were characterized by SEM microscopy/EDS spectroscopy and X-ray diffraction. Their electrochemical and photoelectrochemical behavior was assessed by voltammetry and chronoamperometry in the dark and under visible (Vis) light irradiation. The Pt/WO3/Gr electrode showed more pronounced intrinsic catalytic activity for methanol oxidation than a commercial Pt/C catalyst, which can be further enhanced under Vis light illumination for optimized Pt content. The increased catalytic activity is associated both with a synergistic effect between Pt and WO3 for methanol oxidation at Pt sites (enhancement of methanol and adsorbed CO oxidation) as well as with the simultaneous occurrence of methanol photooxidation at WO3 sites.