EFFECT OF NA2CO3 ADDITION ON PHOTOCATALYTIC DECOMPOSITION OF LIQUID WATER OVER VARIOUS SEMICONDUCTOR CATALYSTS

Photocatalytic decomposition of liquid water into H-2 and O2 over various semiconductor catalysts, such as TiO2, Ta2O5 and ZrO2, suspended in pure water, was studied with a special interest on the effect of Na2CO3 addition. It was found, for the first time, that both RuO2-Ta2O5 and NiOx-Ta2O5 photocatalysts were able to decompose liquid water into H-2 and O2 in pure water as well, as with the addition of Na2CO3. It was speculated that a negative flat-band potential and wide band gap of the photocatalysts are very important for the stoichiometric decomposition of liquid water. Furthermore, the addition of Na2CO3 is very effective for the photocatalytic decomposition of water for Pt-Na2Ti6O13, Pt-K2Ti6O13 and Pt-K4Nb6O17 catalysts which did not show photocatalytic activity in pure water. The significant effect of Na2CO3 addition was observed commonly for both the TiO2 catalyst system and the Pt-loaded catalyst system.