Advances in visible light responsive titanium oxide-based photocatalysts for CO2 conversion to hydrocarbon fuels

• Enhanced visible-light responsive (VLR) TiO2 is possible by doping and sensitizing.
• Metal based sensitized TiO2 improves visible response and efficiency significantly.
• Enzymes, doped membranes and nanoclays have potential to increase TiO2 efficiency.
• High CO2 conversion by visible-light could be realized with metal-sensitized TiO2.
• Monolith photoreactor and novel sensitizer are critical to sustainable solar fuel.

Solar conversion of CO2 to hydrocarbon fuels seems promising to reduce global warming for improved sustainability. Solar energy, as direct solar irradiations, is excessively available and it is imperious to utilize it for solar fuel production. This review paper is organized to discuss recent innovations and potential applications of phototechnology to recycle CO2 via visible light responsive (VLR) TiO2-based photocatalyst. In this perspective various enhancement methods such as doping with metals and non-metals and sensitization to expand TiO2 band gap toward visible region are critically discussed. This review paper also presents applications of VLR photocatalysts, advances in photoreactors, and future prospects of VLR based technology for conversion of CO2 to hydrocarbon fuels. The findings of this study revealed both metals and non-metals could improve TiO2 photoactivity, but non-metals and especially co-metals were more efficient. The combination of co-metals with sensitizers exhibited much higher CO, CH4 and CH3OH yield rates. Among photocatalytic reactors, optical fibers and monolith photoreactors are more efficient because of their efficient light harvesting potential. Although the progress in CO2 reduction to fuels is encouraging, further considerations are required for commercialization purposes.

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