Two-dimensional nanomaterials for photocatalytic CO2 reduction to solar fuels

As a "kill two birds with one stone" approach, photocatalytic CO2 reduction to solar fuels can save supplying energy and simultaneously protect our environment. Specifically, the use of CO2 as the starting carbon source can help with the required emission cuts. Meanwhile, it directly generates short-chain hydrocarbon products such as CH4, CH3OH, C2H6 and so on, which can serve as a renewable energy source (solar fuels) to alleviate the increasingly tense energy crisis. Two-dimensional (2D) nanomaterials possess several extraordinary advantages, including large surface-to-volume ratio, abundant active sites, atomic thickness, and a high fraction of coordinated unsaturated surface sites, making them promising candidates with high photocatalytic activity for CO2 reduction. This review summarizes a series of typical 2D nanomaterials for photocatalytic CO2 conversion, such as graphene-based photocatalysts, graphitic carbon nitride-based photocatalysts, 2D metal oxide-based photocatalysts, 2D metal chalcogenidebased photocatalysts, 2D metal oxyhalide-based photocatalysts, and layered double hydroxide-based photocatalysts. Furthermore, based on the characteristics of 2D materials and the current status of research on photocatalytic CO2 reduction, the challenges and opportunities of 2D materials as prospective photocatalysts for CO2 reduction will also be discussed.