Separate-type Pt-free photofuel cell based on a visible light-responsive TiO2 photoanode: Effect of hydrofluoric acid treatment of the photoanode Original Research Article

The present study deals with the effect of a hydrofluoric acid (HF) treatment of visible light-responsive TiO2 (Vis-TiO2) thin film photocatalysts on their photoelectrochemical performances. The Vis-TiO2 thin film photocatalysts have been prepared on Ti metal substrates by a magnetron sputtering deposition method and then treated by an HF solution. The HF treatment of Vis-TiO2 thin film photocatalysts leads to the dramatic enhancement of their photoelectrochemical performances under UV light and visible light irradiation. Moreover, separate-type Pt-free photofuel cells (SPFCs) constructed using the Vis-TiO2 thin films as photoanodes can generate electricity under light irradiation and simultaneously decompose methanol. The SPFC based on the Vis-TiO2 thin film photoanode etched by HF solution shows the enhanced cell performances with two times higher short-circuit current density and higher energy conversion efficiency than that based on the untreated Vis-TiO2 thin film photoanode. In addition to the increase of surface area and surface roughness, the enhanced conductivity by HF treatment, which is confirmed by Mott–Schottky analyses, is found to be responsible for improvement of cell performances of the SPFC.