Facile synthesis method of C self-doped g-C3N4 and its performance in photodegradation of sulfamethoxazole

Abstract

A simple method for preparing C self-doped g-C3N4 (CCN) was proposed by calcining urea and barbituric acid to effectively degrade sulfamethoxazole (SMX). X-ray photoelectron spectroscopy and element content analysis implied C atom replaced the original position of the bridging N atom to form CCN. Compared to g-C3N4, the absorption edge of CCN was red-shifted. As a result, the band gap of CCN was reduced, which improved the light absorption capacity of CCN and the separation efficiency of photogenerated electron-hole. Ultimately, the photocatalytic activity of CCN was finally boosted. CCN can effectively degrade SMX under visible light. Among CCN with various C dosage, when 0.05 g of barbituric acid was added in the preparation process, the obtained sample (CCN-0.05) exhibited uppermost degradation efficiency on SMX, which can reach 99.0 % after irradiation for 60 min. Additionally, the first-order kinetic reaction rate constant (0.086 min−1) was 8.9 times higher than that of g-C3N4 (0.0097 min−1). Electron paramagnetic resonance and trapping experiments showed that the dominant reactive species on SMX degradation were surface ·O2− and photogenerated holes by CCN-0.05 under visible light. Moreover, CCN-0.05 can still achieve effective removal of SMX under actual water backgrounds and showed selective degradation on sulfonamides.