Development of high throughput evaluation for photocatalyst thin-film

A combinatorial method suitable for accelerating the development of new thin-film photocatalysts was developed. It is constituted by a high throughput evaluation of photocatalytic activity using two-dimensional pH imaging method, synthesis of thin-film libraries using laser molecular beam epitaxy (MBE) technique combined with mask system and analysis using two-dimensional fluorescence X-ray. The principle and details of the high throughput evaluation method were described. Ferric sulfate liquid film was placed on the combinatorially prepared cobalt-doped TiO2 thin-film library, and then irradiated by visible light. Photo excited electrons reduced ferric ions to ferrous ions. Positive holes oxidized water to oxygen molecules. The resulting increase of proton concentration in the liquid film was measured by two-dimensional pH imaging, indicating the strengthening of photocatalytic activity. As a demonstration of this evaluation method, a library of TiO2 films doped with cobalt was screened. Doping with cobalt at 5.4–9 atom % made TiO2 active under visible light irradiation.