Recent advancements in engineering approach towards design of photo-reactors for selective photocatalytic CO₂ reduction to renewable fuels

Photocatalytic conversion of CO₂ to solar fuels, an artificial photosynthesis, is a promising solution to resolve the energy crisis and global warming issues. The overall efficiency of photo-reduction of CO₂ to fuels can be improved through the development of highly efficient catalyst and suitable photoreactor configuration. Significant efforts have been devoted to the design and developments of photo-catalysts, but very little focus has been given towards photo-reactors development. In this perspective, this review presents state of the art accomplishments in photocatalytic CO₂ reduction through engineering approach towards reactor configuration and design aspects. In the main stream, the perspectives of different types of photo-reactors employed for the photocatalytic conversion of CO₂ has been discussed. Slurry, fixed bed and membrane photo-reactors have been identified as the main categories that are critically discussed based on their operational mode, type of bed, number of phases involved, membrane used and type of light source. Comparative analysis of photo-reactors is also being employed to improve selectivity and photo-conversion rates of these photo-reactors. The influence of the factors such as light position and distribution, material of construction, temperature and pressure on the production of fuels has also been explicated. Moreover, perspective gives an overview of basic principles, thermodynamics and mass transfer involved in photocatalytic conversion of CO₂ to fuels. Finally, conclusions and future perspectives paves further improvements in the design of photo-reactors to be made to increase the efficiency of CO₂ conversion to renewable fuels.