Synthesis and modification strategies of g-C3N4 nanosheets for photocatalytic applications

Graphitic carbon nitride nanosheets (CNNs) become the most promising member in the carbon nitride family benefitted from their two-dimensional structural features. Recently, great endeavors have been made in the synthesis and modification of CNNs to improve their photocatalytic properties, and many exciting progresses have been gained. In order to elucidate the fundamentals of CNNs based catalysts and provide the insights into rational design of photocatalysis system, we describe recent progress made in CNNs preparation strategies and their applications in this review. Firstly, the physicochemical properties of CNNs are briefly introduced. Secondly, the synthesis approaches of CNNs are reviewed, including top-down stripping strategies (thermal, gas, liquid, and composite stripping) and bottom-up precursor molecules design strategies (solvothermal, template, and supramolecular self-assembly method). Subsequently, the modification strategies based on CNNs in recent years are discussed, including crystal structure design, doping, surface functionalization, constructing 2D heterojunction, and anchoring single-atom. Then the multifunctional applications of g-C3N4 nanosheet based materials in photocatalysis including H2 evolution, O2 evolution, overall water splitting, H2O2 production, CO2 reduction, N2 fixation, pollutant removal, organic synthesis, and sensing are highlighted. Finally, the opportunities and challenges for the development of high-performance CNNs photocatalytic systems are also promising.