Emerging trends of carbon nitrides and their hybrids for photo-/electro-chemical energy applications

Graphitic carbon nitrides (gCN) exhibit striking properties and features including structurally flexible, thermally stable, exposed edges/atoms with localized electron centres, and tunable visible-range band gap. However, gCN lack electrical conductivity and suffers from imminent exciton recombination, which limits their applications as photo-/electro-chemical catalysts. To overcome these limitations and to make them suitable for their candidature as suitable catalysts, they must be favourably altered. Material manipulations such as in-situ structural modifications and the generation of defects and meso-/nano-porosity in carbon nitrides can provide not only electron-rich configurations but also unique catalytically active centres which present a huge potential in electrochemical energy application. Further, the heteroatom doping and hybridisation of carbon nitrides with other conducting nanostructures can significantly improve their poor electrical conductivities and electrochemical performances. In this review, we highlight the various efforts on the synthesis of this technologically relevant catalyst system in detail and explores pathways for material modifications to equip them as efficient photo-/electro-catalysts. Finally, the main challenges and the futuristic outlook of carbon nitride materials and their hybrids for electrochemical and photocatalytic applications are also discussed.