Effect of carbonate salt addition on the photocatalytic decomposition of liquid water over Pt–TiO2 catalyst

It has been found that an addition of carbonate salts to Pt-loaded TiO 2 suspensions led to highly efficient stoichiometric photocatalytic decomposition of liquid water into H 2 and O 2 . Neither the pH nor cation directly contributes to the water splitting, and the presence of a high concentration of carbonate ions is essential for the catalytic photodecomposition of water. The carbonate ion affects both the Pt particles and the TiO 2 surface. The Pt was covered with some titanium hydroxide compounds and, therefore, the rate of the back reaction (H 2 O formation from H 2 and O 2 ) on the Pt was suppressed effectively in the presence of carbonate ions. On the other hand, the TiO 2 surface was readily covered with several types of carbonate species. It is considered that these carbonate species aid desorption of O 2 from the TiO 2 surface. A new reaction mechanism involving peroxocarbonates has been proposed.