Strategies for large-scale preparation of carbon dots and their roles in photocatalytic CO2 reduction: A review

As the particular zero-dimensional carbon nanomaterial, carbon dots(CDs) have attracted great attention in the field of photocatalysis due to their advantages such as efficient utilization of visible light, rapid transport of charge carriers, and adjustable energy level configuration. This paper classifies large-scale synthesis methods into solid-phase, liquid-phase and gas-phase production based on the different states of the reaction medium, and innovatively analyzes their economy. These CDs are generally without post-treatment, and their photocatalytic performance is not satisfactory. Heteroatom doping and surface modification are utilized to adjust the photocatalytic properties of CDs. The former changes the internal structure and optical properties, while the latter mainly enhances the stability. Although the two means have outstandingly improved the catalysis of CDs in recent years, the existing reviews lack a discussion of the mechanisms by which CDs play multiple roles in photocatalytic CO₂ reduction. From the perspective of the mechanism of photocatalytic CO₂ reduction, it’s found that CDs utilize their unique optical properties to broaden the absorption range of catalysts, and can also serve as photocatalysts or co-catalysts to improve the photocatalytic efficiency by broadening the available light range, reducing carrier recombination, enhancing CO₂ adsorption capacity, adjusting the morphology of catalysts and multiple synergies. Finally, the challenges and opportunities are analyzed, and the future development prospects are projected, providing new ideas for promoting the industrial preparation and photocatalytic applications of CDs.