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 addition 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. (C) 1997 Elsevier Science S.A.