Ta2O5 layer was prepared onto SBA-15 (Ta2O5/SBA-5) with Ta ethoxide precursor. The surface properties of Ta2O5/SBA-5 was the same as those of mesoporous Ta2O5, possessing electron accepting sites and hydrophobicity, but the structural stability upon thermal treatment was improved due to the presence of SBA-5. The drastic blue shift in UV-vis absorption band was observed when the phase of Ta2O5 became thinner. Accordingly, band gaps of Ta2O5 samples increased from 4.0 (nonporous Ta2O5) to 4.3 eV (mesoporous Ta2O5, 2.3 nm wall thickness), and further increased to 4.9 eV for thin-layered Ta2O5/SBA-5 (0.5 nm Ta2O5 layer). Thus, stable activity for photocatalytic water decomposition was not observed over thin-layered Ta2O5/SBA-5. (c) 2012 Elsevier B.V. All rights reserved.