Dependence of Activity of Rutile Titanium(IV) Oxide Powder for Photocatalytic Overall Water Splitting on Structural Properties

Rutile TiO2 powder having a band gap of 3.0 eV was studied as a photocatalyst for overall water splitting with respect to structural properties. The structures of rutile TiO2 samples were characterized by means of X-ray diffraction, scanning electron microscopy, photoacoustic spectroscopy, and a photoelectrochemical technique. It was found that rutile TiO2 particles that are photocatalytically active for the reaction exhibit a lower density of surface trapping states that slow water oxidation kinetics, as well as spatially separated reduction/oxidation sites at exposed crystal faces. This study also demonstrated that the photocatalytic activity of rutile TiO2 for overall water splitting, even when the material was well crystallized, was sensitive to defects that exist in (or near) the surface rather than in the bulk crystal.