Methane is photocatalytically converted to mainly ethane and hydrogen over gallium oxide at room temperature and also at higher temperatures. On the other hand, in the presence of carbon dioxide, although only hydrocarbons and hydrogen were formed on gallium oxide photocatalyst at room temperature, CO was additionally produced photocatalytically at mild temperatures such as 473 K. The additional thermal energy was suggested to enhance the reaction between methane and carbon dioxide by promoting the thermally activation steps in reaction mechanism, such as desorption of the products or electron migration from the bulk to the surface of Ga2O3. (c) 2007 Elsevier B.V. All rights reserved.