A Comprehensive Review of Graphitic Carbon Nitride (g-C 3 N 4 )-Metal Oxide-Based Nanocomposites: Potential for Photocatalysis and Sensing.

g-C 3 N 4 has drawn lots of attention due to its photocatalytic activity, low-cost and facile synthesis, and interesting layered structure. However, to improve some of the properties of g-C 3 N 4 , such as photochemical stability, electrical band structure, and to decrease charge recombination rate, and towards effective light-harvesting, g-C 3 N 4 -metal oxide-based heterojunctions have been introduced. In this review, we initially discussed the preparation, modification, and physical properties of the g-C 3 N 4 and then, we discussed the combination of g-C 3 N 4 with various metal oxides such as TiO 2 , ZnO, FeO, Fe 2 O 3 , Fe 3 O 4 , WO 3 , SnO, SnO 2 , etc. We summarized some of their characteristic properties of these heterojunctions, their optical features, photocatalytic performance, and electrical band edge positions. This review covers recent advances, including applications in water splitting, CO 2 reduction, and photodegradation of organic pollutants, sensors, bacterial disinfection, and supercapacitors. We show that metal oxides can improve the efficiency of the bare g-C 3 N 4 to make the composites suitable for a wide range of applications. Finally, this review provides some perspectives, limitations, and challenges in investigation of g-C 3 N 4 -metal-oxide-based heterojunctions.