NiCoP/g-C3N4 Schottky heterojunctions towards efficient photocatalytic NO oxidation

Abstract

NiCoP/g-C3N4 Schottky heterojunctions were created by a two-step synthesis for enhanced NO oxidation. NiCo-layered double hydroxides (LDH) were grown on superior thin graphic carbon nitride (g-C3N4) nanosheets by a controlling chemical co-precipitation method. A phosphating process at 300 °C resulted in the transformation in situ of NiCo-LDH into NiCoP composite nanoparticles to create Schottky heterojunctions. Using optimized conditions, heterojunction sample 15-NiCoP/CN revealed excellent photocatalytic NO oxidation with a removal rate of 78%. Photogenerated electrons were efficiently separated and transferred because of Schottky barrier, interfacial charge transport channel, and enhanced light absorption efficiency. Photogenerated electrons reacted with adsorbed O2 to generate superoxide radicals (·O2¯) as crucial active species of NO oxidation. The test indicated that the concentration of·O2¯ for sample 15-NiCoP/CN reached 7.1 × 10−5 M which was 6.5 times higher than that of g-C3N4 after light irradiation. In addition, low NO2 generation and mineralization rate (92%) suggested that NO was converted into NO3- or NO2- rather than NO2 to mitigate secondary pollution. This result supplied a novel approach to explore the application of transition metal phosphides and g-C3N4 in photocatalytic NO oxidation.