Advanced nanomaterials for highly efficient CO 2 photoreduction and photocatalytic hydrogen evolution.

At present, CO 2 photoreduction to value-added chemicals/fuels and photocatalytic hydrogen generation by water splitting are the most promising reactions to fix two main issues simultaneously, rising CO 2 levels and never-lasting energy demand. CO 2 , a major contributor to greenhouse gases (GHGs) with about 65% of the total emission, is known to cause adverse effects like global temperature change, ocean acidification, greenhouse effects, etc. The idea of CO 2 capture and its conversion to hydrocarbons can control the further rise of CO 2 levels and help in producing alternative fuels that have several further applications. On the other hand, hydrogen being a zero-emission fuel is considered as a clean and sustainable form of energy that holds great promise for various industrial applications. The current review focuses on the discussion of the recent progress made in designing efficient photocatalytic materials for CO 2 photoreduction and hydrogen evolution reaction (HER). The scope of the current study is limited to the TiO 2 and non-TiO 2 based advanced nanomaterials (i.e. metal chalcogenides, MOFs, carbon nitrides, single-atom catalysts, and low-dimensional nanomaterials). In detail, the influence of important factors that affect the performance of these photocatalysts towards CO 2 photoreduction and HER is reviewed. Special attention is also given in this review to provide a brief account of CO 2 adsorption modes on the catalyst surface and its subsequent reduction pathways/product selectivity. Finally, the review is concluded with additional outlooks regarding upcoming research on promising nanomaterials and reactor design strategies for increasing the efficiency of the photoreactions.