Effect of calcination atmosphere on TiO2 photocatalysis in hydrogen production from methanol/water solution

TiO2 photocatalysts were synthesized by a sol-gel process followed by calcination at 400degreesC in Ar, air, N-2, H-2 (3% in N-2) and vacuum (similar to5 X 10(-3) torr), respectively. Toward H-2 production from a water/methanol (vol. ratio = 1.4/1) solution, the catalysts exhibited activities in the order, according to calcination atmosphere, of At > air > N-2 > vacuum similar toH(2). The low activity resulting from either vacuum or H-2 calcination was ascribed to a reduced coverage of surface hydroxyl and high bulk defect density, based on the X-ray photoelectron and UV-Vis spectroscopic analyses, while the high activity from At calcination is to enhanced visible-light excitation. (C) 2004 Elsevier B.V. All rights reserved.