Direct photoelectrochemical characterization of photocatalytic H, N doped TiO2 powder suspensions

Abstract

The photoelectrochemical (PEC) properties of photocatalysts as powder suspensions were measured directly by an electrochemical technique that allows the action spectrum and relative activities to be measured. This technique was applied to various photocatalyst powders, such as TiO2 synthesized in various ways to produce materials claimed to be active in the visible region (e.g. so-called "black TiO2"), in the presence of a sacrificial electron donor reactants. Hydrogen treated TiO2 photocatalytic powders do not show visible light photocurrents, and ammonia treated TiO2 photocatalyst powders can utilized visible lights photoelectrochemically although their incident photon to current efficiency, at 450, is two hundredths of that at 320 nm. Structural and elemental analysis of these types of modified TiO2 revealed that an amorphous layer and slight nitrogen doping on the crystalline surface provides the capability of visible light utilization for rutile TiO2. The generality of the technique with other particles (BiVO4, WO3) and its advantages over simple photodecomposition experiments is also discussed.