Ultrafine MoOx clusters anchored on g-C3N4 with nitrogen/oxygen dual defects for synergistic efficient O2 activation and tetracycline photodegradation

Photocatalytic O-2 activation to generate reactive oxygen species is crucially important for purifying organic pollutants, yet remains a challenge due to poor adsorption of O-2 and low efficiency of electron transfer. Herein, we demonstrate that ultrafine MoOx clusters anchored on graphitic carbon nitride (g-C3N4) with dual nitrogen/oxygen defects promote the photocatalytic activation of O-2 to generate center dot O-2(-) for the degradation of tetracycline hydrochloride (TCH). A range of characterization techniques and density functional theory (DFT) calculations reveal that the introduction of the nitrogen/oxygen dual defects and MoOx clusters enhances the O-2 adsorption energy from -2.77 to -2.94 eV. We find that MoOx clusters with oxygen vacancies (Ov) and surface Ovmediated Mod+ (3 = d = 2) possess unpaired localized electrons, which act as electron capture centers to transfer electrons to the MoOx clusters. These electrons can then transfer to the surface adsorbed O-2, thus promoting the photocatalytic conversion of O-2 to center dot O-2(-) and, simultaneously, realizing the efficient separation of photogenerated electron-hole pairs. Our fully-optimized MoOx/gC(3)N(4) catalyst with dual nitrogen/oxygen defects manifests outstanding photoactivities, achieving 79% degradation efficiency toward TCH within 120 min under visible light irradiation, representing nearly 7 times higher activity than pristine g-C3N4. Finally, based on the results of liquid chromatograph mass spectrometry and DFT calculations, the possible photocatalytic degradation pathways of TCH were proposed.