Pt-doped TiO 2 /WO 3 bi-layer catalysts on graphite substrates with enhanced photoelectrocatalytic activity for methanol oxidation under visible light

Abstract

Abstract Electrodeposition was used for preparation of WO3 on graphite substrate (Gr). After annealing at 350 °C for crystallization, electrosynthesis of TiO2 was performed on top of WO3 followed by annealing at 400 °C for calcination. Photodeposition of Cu on the bi-layer TiO2/WO3 catalyst and subsequent galvanic replacement of Cu deposit by Pt were accomplished. The Pt/TiO2/WO3/Gr electrodes were characterized by: Scanning Electron Microsco py (SEM) with Energy Dispersive Spectroscopy (EDS) and Wavelength Dispersive Spectroscopy (WDS), X-ray Diffraction (XRD), and X-ray Photoelectron Spectroscopy (XPS). The electrochemical and photoelectrochemical behavior of the Pt/TiO2/WO3 catalyst towards methanol oxidation was evaluated by cyclic voltammetry (CV), linear sweep voltammetry (LSV) and chronoamperometry (CA) in the dark and under visible (Vis) light illumination. The Pt-doped bi-layer TiO2/WO3 (1.2% w/w Pt) catalyst showed 2.6 times higher mass catalytic activity for methanol oxidation than a Pt/WO3 (1.1% w/w Pt) catalyst, further enhanced by 50% under Vis light illumination. Additionally, the oxidation current stability was observed at the Pt/TiO2/WO3/Gr electrode upon irradiation in the presence of methanol. The increased catalytic activity and stability is associated with more effective dispersion and better utilization of Pt, synergistic effect between Pt and both semiconductor oxides, as well as with enhanced electron-hole separation efficiency.