Photocatalytic Properties of Co(3)O(4)-Coated TiO(2) Powders Prepared by Plasma-Enhanced Atomic Layer Deposition

Co(3)O(4)-coated commercial TiO(2) powders (P25) p-n junction photocatalysts were prepared by plasma-enhanced atomic layer deposition (PEALD) technique. The structure, morphology, bandgap, and photocatalytic properties under ultraviolet light were investigated systematically. Although the deposition of Co(3)O(4) does not change the anatase structure and crystallite size of P25 powders, the ultraviolet photocatalytic activity has been improved evidently. For the Co(3)O(4)-coated P25 powders, the trace Co ions exist as Co(3)O(4) nanoparticles attached to TiO(2) powder surface instead of the occupation of Ti(4+) position in TiO(2) lattice. The Co(3)O(4)-coated P25 powders exhibit enhanced photocatalytic degradation efficiency of almost 100% for methylene blue in 1.5 h under ultraviolet light, compared with P25 of 80%. The Mott-Schottky plots of photocatalyst powders confirm the p-n heterojunction formation in Co(3)O(4)–TiO(2) nanocomposite materials, which is beneficial to increase the efficiency of photogenerated electron-hole separation. In addition, the Co(3)O(4) coating also promotes the adsorption of organic dyes of methylene blue on P25 powders.