g-C3N4 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-C3N4, such as photochemical stability, electrical band structure, and to decrease charge recombination rate, and towards effective light-harvesting, g-C3N4–metal oxide-based heterojunctions have been introduced. In this review, we initially discussed the preparation, modification, and physical properties of the g-C3N4 and then, we discussed the combination of g-C3N4 with various metal oxides such as TiO2, ZnO, FeO, Fe2O3, Fe3O4, WO3, SnO, SnO2, 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, CO2 reduction, and photodegradation of organic pollutants, sensors, bacterial disinfection, and supercapacitors. We show that metal oxides can improve the efficiency of the bare g-C3N4 to make the composites suitable for a wide range of applications. Finally, this review provides some perspectives, limitations, and challenges in investigation of g-C3N4–metal-oxide-based heterojunctions.

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A Comprehensive Review of Graphitic Carbon Nitride (g-C3N4)–Metal Oxide-Based Nanocomposites: Potential for Photocatalysis and Sensing

In situ fabrication of a novel S-scheme heterojunction photocatalyts Bi2O3/P-C3N4 to enhance levofloxacin removal from water

In-situ growth of β-Bi2O3 nanosheets on g-C3N4 to construct direct Z-scheme heterojunction with enhanced photocatalytic activities

Research progress on g–C3N4–based photocatalysts for organic pollutants degradation in wastewater: From exciton and carrier perspectives

Photocatalytic water purification with graphitic C3N4-based composites: Enhancement, mechanisms, and performance

Biogenic synthesis of g-C3N4/Bi2O3 heterojunction with enhanced photocatalytic activity and statistical optimization of reaction parameters

In this study, flake-like MoO3-ZnO composite was prepared using a simple and robust electrochemical setup. The composite was characterized by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, elemental analysis, X-ray photoelectron spectroscopy, thermogravimetric analysis, photoluminescence, zeta potential analysis, and electrochemical impedance study. The modified ZnO shows a remarkable catalytic activity towards the photodegradation of three potentially hazardous dyes, malachite green, crystal violet, and methylene blue. More than 95% of both malachite green and crystal violet degraded within 140 min under visible light irradiation. Scavenger studies reveal that OH· radicals produced by the photo-separated charges on MoO3-ZnO are responsible for the degradation of all three dyes. The photoactive charge carriers show less recombination rate as evidenced by the photoluminescence spectrum due to the interparticle charge migration process. This work suggests a new versatile procedure for the synthesis of MoO3-ZnO composites and establishes its photocatalytic efficacy under visible light with three common pollutant dyes found in wastewater.

Karthik Kasinathan

Papers

Biogenic synthesis of g-C3N4/Bi2O3 heterojunction with enhanced photocatalytic activity and statistical optimization of reaction parameters

Visible light photodegradation of organic dyes using electrochemically synthesized MoO3/ZnO.