Systematic study of TiO(2)/ZnO mixed metal oxides for CO(2) photoreduction

A two component three degree simplex lattice experimental design was employed to evaluate the impact of different mixing fractions of TiO(2) and ZnO on an ordered mesoporous SBA-15 support for CO(2) photoreduction. It was anticipated that the combined advantages of TiO(2) and ZnO: low cost, non-toxicity and combined electronic properties would facilitate CO(2) photoreduction. The fraction of ZnO had a statistically dominant impact on maximum CO(2) adsorption (β(2) = 22.65, p-value = 1.39 × 10(−4)). The fraction of TiO(2) used had a statistically significant positive impact on CO (β(1) = 9.71, p-value = 2.93 × 10(−4)) and CH(4) (β(1) = 1.43, p-value = 1.35 × 10(−3)) cumulative production. A negative impact, from the interaction term between the fractions of TiO(2) and ZnO, was found for CH(4) cumulative production (β(3) = −2.64, p-value = 2.30 × 10(−2)). The systematic study provided evidence for the possible loss in CO(2) photoreduction activity from sulphate groups introduced during the synthesis of ZnO. The decrease in activity is attributed to the presence of sulphate species in the ZnO prepared, which may possibly act as charge carrier and/or radical intermediate scavengers.