Nitric oxide (NO) is an air pollutant impacting the environment, human health, and other biotas. Among the technologies to treat NO pollution, photocatalytic oxidation under visible light is considered an effective means. This study describes photocatalytic oxidation to degrade NO under visible light with the support of a photocatalyst. MgO@g-C3N4 heterojunction photocatalysts were synthesized by one-step pyrolysis of MgO and urea at 550 °C for two hours. The photocatalytic NO removal efficiency of the MgO@g-C3N4 heterojunctions was significantly improved and reached a maximum value of 75.4% under visible light irradiation. Differential reflectance spectroscopy (DRS) was used to determine the optical properties and bandgap energies of the material. The bandgap of the material decreases with increasing amounts of MgO. The photoluminescence spectra indicate that the recombination of electron–hole pairs is hindered by doping MgO onto g-C3N4. Also, NO conversion, DeNOx index, apparent quantum efficiency, trapping tests, and electron spin resonance measurements were carried out to understand the photocatalytic mechanism of the materials. The high reusability of the MgO@g-C3N4 heterojunction was shown by a five-cycle recycling test. This study provides a simple way to synthesize photocatalytic heterojunction materials with high reusability and the potential of heterojunction photocatalysts in the field of environmental remediation.

Nitric Oxide (NO) is one of air pollutant that is responsible for its impacts in various environmental matrices, human health and other biota. Apart from various technology to treat NO pollution, photocatalytic oxidation process (PCO) under visible light is considered as an effective process to achieve the feat. This study uses PCO to degrade NO under visible light with the help of photocatalyst. Herein, the MgO@g-C3N4 heterojunctions are synthesized by one-step pyrolysis of MgO and Urea commercial at 550 oC for 2 h. By this way, the photocatalytic NO degradation performance is significantly increased under visible light irradiation. In detail, the photocatalytic efficiency of the MgO@g-C3N4 composites reaches 75.4% with 1.2-fold that of pure g-C3N4 and 4.5-fold that of commercial MgO. Furthermore, the characterizations of the materials are determined by X-ray diffraction (XRD), Fourier transforms infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). The morphology of the materials is determined by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). DRS determines the optical properties and bandgap of the materials. The bandgap of the materials decreases with the increasing amount of the MgO. Besides, the NO conversion, DeNOx index, apparent quantum efficiency (AQE), the trapping test, and electron spin resonance (ESR) are invested to understand the photocatalytic mechanism of the materials. The high reusability of the MgO@g-C3N4 composites is determined by 5 times recycling test.