CeO₂/CuO/TiO₂heterojunction photocatalysts for conversion of CO₂to ethanol

An attempt to reduce CO₂emissions has led to the development of CeO₂/CuO/TiO₂heterojunction photocatalysts for photoconversion of CO₂to useful products, e.g. ethanol. Composite photocatalysts were simply prepared by mixing TiO₂(P25) with different mass ratios of CeO₂(1 wt%) and CuO (2 or 3 wt%) by ball milling. The prepared photocatalysts had uniformly distributed CeO₂and CuO phases, throughout the TiO₂phase. The integration of CeO₂and CuO into TiO₂at 1 wt% CeO₂and 3 wt% CuO produced a composite, with a reduced band gap of 2.88 eV, allowing absorption of lower energy light and a lower electron-hole recombination rate. The 1%CeO₂/3%CuO/TiO₂photocatalysts yielded ethanol at 30.5μmol g_cat^-1h^-1, almost three times higher than the yield from pure TiO₂. This improved CO₂conversion efficiency was due to contributions from properties of both additives: CeO₂increased light absorption, while CuO acted as an electron trap and enhanced CO₂adsorption. In addition, the heterojunction at the interfaces facilitated the photogenerated charge separation, which, in turn, increased the charge participation in the catalyzed conversion reactions.