Role of catalyst carriers in CO2 photoreduction over nanocrystalline nickel loaded TiO2-based photocatalysts

Nickel-based TiO2 photocatalysts were immobilized onto carriers (quartz plates and monoliths) in a unique reactor configuration to provide a high ratio of illuminated surface area of catalyst for the reduction in CO2 to fuels under UV and visible light. The incorporation of Ni2+ in the TiO2 matrix inhibits the grain growth of anatase crystallites and suppresses phase transformation. The Ni2+ atom is also found to be replacing some of the Ti atoms in the crystal lattice of TiO2 during the sol–gel method, thus causing a change in optical absorption. Using water as a reductant, vapour-phase CO2 was reduced to fuels with the monolith threaded with optical fibres and quartz plate photoreactor system following 4 h of light irradiation. More importantly, the improved conversion efficiency is ascribed to the presence of Ni2+ species which served as electrons traps that suppressed recombination, resulting in effective charge separation and CO2 reduction.