Photocatalytic conversion of CO2 and H2O to fuels by nanostructured Ce–TiO2/SBA-15 composites

Abstract

Cerium-doped titanium oxide (Ce–TiO₂) nanoparticles were prepared by a simple sol–gel method. Ce-doping decreased the crystal size of TiO₂, increased the catalyst surface area, and inhibited the growth of rutile TiO₂ crystals. Ce–TiO₂ nanoparticles were also dispersed on SBA-15, mesoporous silica with one-dimensional pores, forming a Ce–TiO₂/SBA-15 nanocomposite. The nanocomposite materials were well characterized and tested as photocatalysts to convert CO₂ and H₂O to value-added fuels, mainly CO and CH₄, under UV-vis illumination. Compared with pristine TiO₂, TiO₂ doped by 1 or 3% Ce improved the production of CO by four times. The reason may be due to the facilitated charge transfer induced by the doped Ce ions, the higher surface area of the catalyst, as well as the stabilization of anatase phase. However, too high a Ce concentration reduced the catalytic activity, likely due to the formation of recombination centers. Compared with unsupported Ce–TiO₂, Ce–TiO₂ supported on SBA-15 remarkably enhanced the CO₂ reduction rate. Ce–TiO₂/SBA-15 with a Ti : Si ratio of 1 : 4 demonstrated 8-fold enhancement in CO production and 115-fold enhancement in CH₄ production. By contrast, amorphous silica as the substrate was much inferior to SBA-15. The findings in this work reveal a promising nanostructured catalyst material for solar fuel production using CO₂ and H₂O as the feedstock.