Ni-Bi co-doped TiO2 as highly visible light response nano-photocatalyst for CO2 photo-reduction in a batch photo-reactor

Photocatalytic reduction of CO2 is considered as a promising strategy for production of a wide range of renewable hydrocarbon fuels by solar energy. In this investigation, a series of Ni and Bi doped TiO2 catalysts with different Ni and Bi contents were synthesized by the conventional sol-gel method and tested for CO2 photo reduction under visible light irradiation. Synthesized nano-photo-catalysts were characterized by XRD, FESEM, TEM, DRS, PL, FTIR and BET analyses. BET results indicated that the doping of Ni or/and Bi in the TiO2 framework resulted in BET specific surface area increment with respect to pure TiO2. DRS analysis showed that Ni doped TiO2, Bi doped TiO2, and co-doped samples had narrower band gap energy and consequently considerably higher light absorption in the visible region compared with pure TiO2. Doping Ni and Bi in TiO2 suppressed the rate of electron-hole recombination as indicated by PL spectra. CO2 adsorption capacity were increased in presence of Bi ions in comparison with pure TiO2 and Ni doped sample as a result of reactant adsorption increase on the surface of catalyst. The yield of methane considerably increased in the presence of Ni and Bi doped samples. The highest methane production (21.13 mu mol/g(cat)) was obtained for 1 wt% Ni-3 wt% Bi co-doped TiO2, which was almost 6.5 times greater than that for pure TiO2.