A gas-solid heterogeneous system for solar-chemical energy conversion of CO2-SCR (Selective Catalytic Reduction) with H2O on different nanostructure photocatalysts and the photocatalysis pathway were discussed. Different crystal phases and sizes of low-dimensional nano-TiO2 and Pt-metal supported photocatalysts are synthesized and characterized with X-ray diffraction, high-resolution transmission electron microscopy, photoluminescence, CO pulse chemisorptions, N-2 adsorption-desorption analysis at 77 K and X-ray fluorescence spectrometry. The catalytic activity was tested in a fixed-bed photocatalsis reactor and the CH4 yield on the Pt/TiO2 nanotube photocatalysts is more remarkable. It increased with the increase of the UV irradiation time and accumulated to about 4.8 mu mol h(-1) g(Ti)(-1), enhanced as the increase of the reaction temperature and H2O/CO2 molar ratio as well. (C) 2009 Elsevier B.V. All rights reserved.