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Photocatalysts with atomic dimensions exhibit superior performance in photocatalytic applications owing to their large surface-to-volume ratio, enormous surface active sites, and superior light-harvesting ability. The single-unit-cell thickness reduces interlayer charge transfer resistance, facilitating the rapid transfer of electrons and holes from the interior to the surface. This review aims to provide a comprehensive discussion on the fundamentals of photocatalysis and the advancements achieved from the evolution of photocatalysts from their bulk-counterpart to atomic dimensions. State-of-the-art techniques in designing and modifying atomically thin photocatalysts, such as defect engineering, impurity doping, facet engineering, and atomic-scale heterojunction construction, for diverse photocatalytic applications will be comprehensively elucidated.

Photocatalysis, a renewable, bountiful, and viable technology, has been widely regarded as a promising method to alleviate environmental challenges and circumvent the increasingly tensed energy crisis. Specifically, substantial carbon dioxide (CO2) emission reduction can be achieved by using CO2 as the starting carbon source to generate renewable solar fuels such as methanol, methane, and formic acid. The fabrication and development of highly efficient photocatalysts are crucial determinants of this approach. The recently emerged two-dimensional (2D) materials have taken the research and energy scene by storm owing to their distinctive features of tunable bandgap, large surface-to-volume ratio, ultrathin characteristic, extraordinary electrical and optical absorption properties, copious active centers, and abundant coordinated unsaturated surface sites. These unique physicochemical properties render 2D materials as promising candidates for photocatalytic CO2 conversion into carbon-based fuels. In this article, an overview of the recent developments summarizing the CO2 photoreduction over 2D materials, namely, graphene-based photocatalysts, transition metal dichalcogenide–based photocatalysts and graphitic carbon nitride–based photocatalysts, are highlighted. In detail, the emerging strategies and recent advances for tailoring highly functional 2D material–based photocatalytic semiconductors comprising heterostructure fabrication, functionalization with advanced nanostructures, surface defect engineering, and elemental doping are discussed.