Sodium ethoxide treatment induced enrichen nitrogen vacancies on g-C3N4 for efficient photocatalytic CO2 reduction and Cr(VI) removal

Abstract

Introducing vacancies on g-C₃N₄ is considered an effective strategy to enhance photocatalytic performance. However, introducing vacancies by a mild and efficient approach still remains a significant challenge in the field of photocatalysis. In this study, g-C₃N₄ photocatalysts with enriched nitrogen vacancies were successfully prepared by sodium ethoxide treatment at room temperature. X-ray photoelectron spectroscopy (XPS) and low temperature electron paramagnetic resonance (EPR) demonstrate that the treatment with sodium ethoxide successfully introduces nitrogen vacancies. The photoelectrochemical experiments confirm that introduction of nitrogen vacancies modulates the band structure of g-C₃N₄ and accelerates the separation of photogenerated charges. Additionally, nitrogen vacancies serve as effective active sites and adsorption centers for target molecules, facilitating the reaction of electrons with the target molecules and significantly boosting photocatalytic efficiency. Under irradiation of a 300 W xenon lamp, the 9GCN sample treated by 9 g of sodium ethoxide exhibits the best photocatalytic performance. The conversion rate of CO₂ into CO and CH₄ is 3.07 and 8.58 times higher than that on the single sample, respectively. In situ diffuse reflectance Fourier-transform infrared spectroscopy (DRIFTS) confirms the dynamic process of CO₂ conversion to CO and CH₄. Additionally, result of photocatalytic reduction of Cr(VI) further confirms the versatility of the photocatalyst. This work provides a practical pathway for the development of defective g-C₃N₄ photocatalysts for applications in carbon cycling and environmental purification.