Photocatalytic reduction of gaseous carbon dioxide over NiO/TiO2 under UV light illumination

Several NiO/TiO2 composites fabricated by the impregnation method were employed as photocatalysts for the photoreduction of gaseous CO2 in this study. The characterizations of fabricated photocatalysts were observed by XRD, FE-SEM, EDS, N2 adsorption-desorption, and UV–vis spectroscopy. The distribution of Ni, Ti, and O atoms on the surface of these photocatalysts was demonstrated to be uniform, and the BET surface areas were varied slightly with the increase of NiO loading. Meanwhile, the absorption edge of fabricated photocatalysts was found to shift towards the visible region and the bandgap energy was decreased. The photocatalytic reaction was conducted in a continuous-flow reactor under UV irradiation. Methane was identified to be the main product and produced in the order: 10 wt% NiO/TiO2 > TiO2 > 20 wt% NiO/TiO2. The maximum methane yield reached at 4.69 mmol/gcatalyst over 10 wt% NiO/TiO2 and was twice higher than that of P-25. The formation of p-n junction significantly improved the photocatalytic activity of P-25. Furthermore, the proposed schematic diagram for photocatalytic CO2 reduction in the gaseous phase under NiO-TiO2 / UV process was introduced.