Synthesis and modification of ultrathin g-C3N4 for photocatalytic energy and environmental applications

Nanostructured heterogeneous photocatalysts process represent attractive strategies to convert directly solar energy to chemical energy, which is important to address the increasing challenges of clean energy and environmental issues. Graphitic carbon nitride, as a metal-free photocatalyst with a suitable bandgap, has played an irreplaceable role in energy and environmental fields. Ultrathin g-C3N4 (UCN) with few layers owns a larger specific area for more reactive sites and intimate interface contact possibility, which provides more function modifications for overcoming inherent drawbacks to realize target-specific applications. In the last few years, developments have been witnessed in the studies of UCN with different synthesis methods or further modifications in photocatalytic energy and environmental application. This review first comprehensively summarized two synthetic approaches of UCN, namely, top-down exfoliation approaches and bottom-up molecular assembly approaches. Then, various modification strategies of UCN including element doping, introduction of vacancies and formation of heterostructure were elaborated for multifarious photocatalytic applications. The roles of UCN in diversiform applications and specific mechanisms are detailly discussed. Finally, on account of clear cognition and a general overview of the state of UCN, the promising direction of designing and application of UCN was emphasized based on the existing opportunities and challenges.