Plasma-treatment of polymeric carbon nitride for efficient NO abatement under visible light

Photocatalysis is considered to be efficient in combatting emission nitrogen oxide (NOx), which is one of the atmospheric pollutants affecting human health. Polymeric carbon nitride (PCN) is a low-cost polymeric photocatalyst with a two-dimensional structure that is sensitive to the visible sunlight in the solar spectrum, but its photocatalytic efficiency needs to be enhanced for the purpose of pollutant abatement. In this study, PCN was treated using a facile ambient pressure dielectric barrier discharge (DBD) plasma in air, Ar and Ar-5% H2 flow. According to the spectroscopic characterization and NO removal tests, the DBD plasma did not destroy the crystal structure of PCN, but improved the separation efficiency of photogenerated charges and enhanced the capacity of NO abatement. The plasma treatment in Ar-5% H2 showed an optimal removal efficiency of 69.19% and a selectivity for nitrate of 90.51% under visible light irradiation. The hydrogen plasma etched the PCN surface, resulting in more defects (carbon vacancies) and carbonyl group on the surface, while the air plasma was found to increase the suspending –NOx bonding on the surface for the increased NOx emission under illumination. The generation of high-energy electron and reactive radicals in the electrical discharges could cause the surface modification of PCN for efficient photocatalysis.