Fe Single Atoms Reduced by NaBH4 Mediate g-C3N4 Electron Transfer and Effectively Remove 2-Mercaptobenzothiazole

Abstract

In this study, a simple and low-energy synthesis scheme of Fe single-atom anchored carbon nitride was reported to improve the photocatalytic performance of g-C3N4. Synthesized Fe single-atom doped graphite carbon nitride (Fe-SACs/g-C3N4) showed high activity and stability for the degradation of 2-mercaptobenzothiazole (MBT); under visible light irradiation, 99% of MBT could be degraded within 35 min, and the degradation ability basically did not decline after five cycles, mainly due to the synergistic effect of the Fe single atoms and carbon nitride. The results of X-ray absorption fine structure (EXAFS), X-ray photoelectron spectroscopy (XPS), and density functional theory calculations show that the single-atom Fe forms Fe-N4 coordination with pyridine nitrogen to generate a new electron transfer channel, which can significantly improve the in-plane separation and transfer of carriers, finally enhancing the generation of superoxide radicals. This is confirmed by time-resolved photoluminescence, photoelectron chemistry, and electron spin resonance measurements. The main intermediates of MBT degradation were determined using a liquid chromatograph–mass spectrometer (LC-MS), and a possible photocatalytic mechanism based on the quenching experiment and electron paramagnetic resonance (EPR) test was proposed. A deep understanding of the contribution of Fe single-atom sites with clear local coordination structures will help to design effective catalysts for photocatalytic performance.