Single Pd atoms anchored graphitic carbon nitride for highly selective and stable photocatalysis of nitric oxide

Abstract

Efficient, stable, and selective photocatalytic conversion of nitric oxide (NO) into nitrogen dioxide (NO 2 ) is highly desirable but remains a big challenge. We prepare single atom catalyst (SAC) by anchoring single Pd atoms onto graphitic carbon nitride (CNPd) via chemical impregnation followed by calcination. The prepared CNPd SAC is confirmed by aberration-correction high-angle-annular-dark field scanning transmission electron microscopy and X-ray absorption fine structure spectroscopy. The synthesized SAC outperforms its competitors reported earlier for photocatalytic removal of NO under visible light and simulated sunlight irradiation in terms of selectivity and stability. The SAC maintains a NO removal efficiency of 83% and an instantaneous selectivity for NO 2 of 92.8% over 117.6 h under simulated sunlight with the inlet NO concentration of 12 ppm. This duration is about 23.5 times the longest duration tested for other catalysts in the literature. The experimental results and density functional theory (DFT) calculations reveal that single Pd atom promotes the photocatalytic degradation of NO. Moreover, the DFT calculations prove that the nitrate ions that accumulate on the surface of the SAC can react with NO to produce NO 2 . This reaction enhances the selectivity for NO 2 and stability of the SAC. The CNPd catalyst exhibits high photocatalytic activity, selectivity and stability for the removal of NO under visible light. • The CNPd SACs exhibit stable and high photocatalytic removal of NO. • The CNPd SACs show ultra-high selectivity for the conversion of NO into NO 2 which can be easily addressed by wet scrubbing. • NO removal efficiency of CNPd SACs remain 83% after solar irradiation over 117.6 h. • DFT calculations reveal the mechanism of photocatalytic over CNPd SACs. • DFT calculations explain the reason for selective conversion of NO to NO 2 .