Ga2O3 was used as a photocatalyst for the photoreduction of CO2 in the presence of H-2 as a reductant; in this process CO gas was selectively produced at room temperature and ambient pressure. The optimum conversion of CO2 was approximately 3% using beta-Ga2O3 calcined at 1073 K for 6 h. The formation of CO depended on the amounts of H-2 and CO2 introduced into the system. The photoreduction of CO2 on Ga2O3 involves two chemisorbed species-H-2 and CO2. This implies that the photocatalytic reaction would proceed on the basis of the typical Langmuir-Hinshelwood mechanism. (C) 2008 Elsevier B.V. All rights reserved.