Influence of the irradiation wavelength on the photocatalytic activity of Au-Pt nanoalloys supported on TiO2 for hydrogen generation from water

Seven samples of P25 titania containing Au-Pt nanoalloys at constant total metal loading (0.25% wt), very similar particle size (1.5 nm) and different proportions of Pt (0.0, 22.8, 27.8, 35.0, 50.0, 69.0 and 100.0% wt) have been prepared and characterized. Formation of real nanoalloys was supported by the shifts in the binding energy values of Au and Pt 4f(7/2) peaks in XPS. Using 532 nm laser excitation it was observed that the six samples exhibit similar photocatalytic activity for hydrogen generation in the presence of methanol as a sacrificial electron donor. In contrast, in pure water remarkable differences in efficiency for hydrogen generation between the sample containing exclusively Au that was the most active and the others containing Pt were observed. In addition, oxygen evolution was also observed in the absence of methanol under visible light irradiation. Our results illustrate the potential that nanoalloys offer to optimize the photocatalytic activity of TiO2.