Investigation of low Ce amount doped-TiO₂ prepared by using pressurized fluids in photocatalytic N₂O decomposition and CO₂ reduction

Ce doped TiO₂ anatase/brookite composites with 0.6–5.5 wt% of Ce, as well as parent TiO₂ anatase/brookite were synthesized to be investigated in two environmentally-beneficial reactions, the photocatalytic decomposition of N₂O and the photocatalytic reduction of CO₂. Composites were prepared unconventionally, by using sol–gel method combined with the processing by pressurized hot fluids (in the sequence water/methanol/water). The physicochemical and electronic properties of all synthesized composites were characterized by organic elementary analysis, nitrogen physisorption, powder X-ray diffraction, X-ray fluorescence spectroscopy, diffuse reflectance UV-vis spectroscopy and work function measurements. It was revealed that all composites show comparable textural properties, crystallite size, as well as optical properties, except for the 5.5 wt% Ce/TiO₂ composite which showed significantly lowered band gap energy due to the significantly higher population of Ce. Concerning the composite structural properties, the addition of different amounts of Ce in the range of 0.6–5.5 wt% affected markedly the phase composition of composites, namely the anatase-to-brokite weight ratio. Concerning the photocatalytic tests the 5.5 wt% Ce/TiO₂ composite showed the highest photocatalytic performance. The highest photocatalytic performance of the 5.5 wt% Ce/TiO₂ composite can be attributed to the lowest composite work function which is affected by both the amount of Ce, as well as the phase composition.