Enhancement of Photocatalytic Water Oxidation by the Morphological Control of LaTiO2N and Cobalt Oxide Catalysts

Controlled morphological and structural variations of LaTiO2N and CoOx nanoparticles loaded as a cocatalyst increased the photocatalytic O-2 evolution. Four different LaTiO2N samples were prepared from two varied La2Ti2O7 precursors by thermal ammonolysis with and without flux. The most effective transformation from La2Ti2O7 into LaTiO2N in terms of crystallinity and nitrogen contents was obtained in the following two cases: flux-assisted ammonolysis of La2Ti2O7 characterized by a comparatively small particle size and a large surface area and ammonolysis without flux of highly crystalline La2Ti2O7. In both cases, high activity for O-2 evolution under visible-light illumination (lambda >= 420 nm) (similar to 50 mu mol h(-1)) was obtained. Loading LaTiO2N with CoOx enhanced the photocatalytic activity for O-2 evolution, although the effect of CoOx depended on the morphologies of LaTiO2N as a support. The promotional effect was most pronounced for LaTiO2N with a skeletal morphology, because such LaTiO2N contain most unsaturated bonds that act as nucleation centers that in turn generate small and highly dispersed CoOx nanoparticles.