Challenges and prospects in the selective photoreduction of CO 2 to C1 and C2 products with nanostructured materials: a review.

Solar fuel generation through CO 2 hydrogenation is the ultimate strategy to produce sustainable energy sources and alleviate global warming. The photocatalytic CO 2 conversion process resembles natural photosynthesis, which regulates the ecological systems of the earth. Currently, most of the work in this field has been focused on boosting efficiency rather than controlling the distribution of products. The structural architecture of the semiconductor photocatalyst, CO 2 photoreduction process, product analysis, and elucidating the CO 2 photoreduction mechanism are the key features of the photoreduction of CO 2 to generate C1 and C2 based hydrocarbon fuels. The selectivity of C1 and C2 products during the photocatalytic CO 2 reduction have been ameliorated by suitable photocatalyst design, co-catalyst, defect states, and the impacts of the surface polarisation state, etc. Monitoring product selectivity allows the establishment of an appropriate strategy to generate a more reduced state of a hydrocarbon, such as CH 4 or higher carbon (C2) products. This article concentrates on studies that demonstrate the production of C1 and C2 products during CO 2 photoreduction using H 2 O or H 2 as an electron and proton source. Finally, it highlights unresolved difficulties in achieving high selectivity and photoconversion efficiency of CO 2 in C1 and C2 products over various nanostructured materials.