Novel Electrochemical Preparation of N-Doped TiO2/Graphene for Enhanced Stability and Photocatalysis Degradation of Humic Acid

Industrialization and urbanization have resulted in large volumes of municipal wastewater containing abundant refractory humic acid (HA), which is difficult to biodegrade with carcinogenic byproducts and has posed a great threat to human health. Photocatalysis is a promising advanced oxidation process (AOP) for the efficient degradation of HA. In this work, a novel three-step electrochemical method was employed to fabricate electrochemically converted N-doped TiO2 nanotubes/graphene (ENTG) composite film. Compared with traditional hydrothermally synthesized N-doped TiO2/graphene (NTG) nanoparticles, the ENTG photocatalyst exhibited enhanced degradation performance, recyclability and stability. It was found that ETNG can extend the range of light absorption to over 400 nm and narrow the band gap to 2.7 eV. The degradation rate for HA was up to 92.3% under the optimum condition. The preparation mechanism for ENTG is based on an electrochemical reduction-deposition hypothesis, while the degradation mechanism is dependent on adsorption and free radical oxidation. According to a free radical quenching test, both center dot OH and center dot O-2(-) radicals were produced, and center dot OH played the dominant role in HA degradation. In general, ENTG is a promising photocatalyst for further application in municipal wastewater treatment.