Metal powder addition effect on the photocatalytic reactions and the photo-generated electric charge collected at an inert electrode in aqueous TiO2 suspensions

The photocatalytic reaction in an aqueous TiO₂ suspension has been found to be enhanced by the additiona of some metal powders such as copper, silver, nickel and cobalt into the suspension. Just mixing a metal powder into the suspension gave nearly the same efficiency as metal-loading on the semiconductor particles. The effect is attributed to the rapid transfer of the photogenerated electrons from the TiO₂ to the metal particles, resulting in the effective separation of the electrons and holes.

The photo-current measurements were performed using inert collecting electrodes in the suspensions of TiO₂, where formate was added as a hole scavenger, with and without a metal powder. Higher anodic photocurrent was obtained in the presence of a metal than in its absence, indicating that the metal-mediated electron transfer reaction occurs more effectively from the electron-rich TiO₂ particles to the collecting electrode than the direct discharge of the electron-rich TiO₂ on the collecting electrode.