Visible‐Light Photoresponse of Gold Nanoparticles Supported on TiO2: A Combined Photocatalytic,Photoelectrochemical, and Transient Spectroscopy Study

In the context of gaining understanding on the origin of the visible‐light photoresponse of TiO₂ containing gold nanoparticles, the photocurrent spectra and photocatalytic H₂ evolution of titania (P25) and Au–P25 were compared. Whereas no photocurrent was detected upon visible‐light irradiation for either of the two photocatalysts, Au–P25 exhibited photocatalytic H₂ evolution for wavelengths between 400 and 575 nm. This contradictory behavior under visible‐light irradiation of Au–P25 was rationalized by transient absorption spectroscopy. It was suggested that photocatalytic H₂ generation results from methanol quenching of the charge‐separation state in each semiconductor nanoparticle, but the lack of photocurrent is due to the short lifetime of the charge separation, which makes interparticle charge migration for micrometric distances unlikely.