UV-driven overall water splitting using unsupported gold nanoparticles as photocatalysts.

We confirmed that Au nanoparticles (>10 nm) exhibit photocatalytic overall water splitting into H2 and O2 simultaneously with a ratio close to 2 : 1 without the assistance of sacrificial electron donors and cocatalysts under UV illumination for the first time. The hydrogen production rate of 5.7 μmol g-1 h-1 in pure water was achieved, which is higher than that of TiO2 nanoparticles (P25, 1.2 μmol g-1 h-1). The interband transitions from 5d (valence band) to 6sp (conduction band) are responsible for this photocatalytic activity over Au nanoparticles.