Carbon quantum dots (CQDs) have been developed as a new member of nanocarbons, characterized by the relatively easy preparation from a wide spectrum of carbonaceous precursors through either bottom-up or top-down routes. Attractive optoelectronic properties have been observed with CQDs, including efficient light absorption, variable photoluminescence (PL), unique up-conversion PL and prominent electron transport ability, which make CQDs an important component with great potential in the design of efficient visible light-driven photocatalysts. In this chapter, detailed contribution of CQDs to the enhanced visible light-driven photocatalysis will be included, in the classification of the role as electron mediator, photosensitizer, spectral converter and sole photocatalyst
