Fig. 4 a presents cyclic voltammograms of various Pt/TiO2 catalysts in a N2-saturated 0.5 M H2SO4. All the CVs displayed two strong peaks that appear in the potential range between −0.295 Vand 0.105 V in both the forward and reverse potential scans. They originate from hydrogen desorption and adsorption on the Pt electrode surface. The doublelayer region was located between 0.105 Vand 0.305 V. Metal oxide formation and oxide reduction peaks were in the range between 0.305 V and 0.955 V.