Highly efficient Ag2O/Na-g-C3N4 heterojunction for photocatalytic desulfurization of thiophene in fuel under ambient air conditions

A composite photocatalyst of Ag2O and Na doped g-C3N4 (Ag2O/Na-CN) with high efficiency was investigated for photocatalytic oxidative desulfurization (PODS). The concentration and lifetime of carriers are increased with Na-CN. Under light conditions, it produces more charge carriers for the generation of radical species, such as superoxide radicals and holes. In addition, Na-CN and Ag2O form a p-n heterojunction, facilitating the transfer and separation of photogenerated electrons and holes, and increasing the concentration of holes on the valence band of Ag2O. The significantly improved charge separation alone with the higher carrier concentration of Ag2O/Na-CN makes the activation and oxidation of thiophene easier. Free radical capture experiments, electron paramagnetic resonance, and gas chromatography-mass spectrometry tests showed that holes, electrons, and superoxide radicals are the most critical active species in the PODS process, supporting the proposed PODS mechanism.