In-situ electrochemical synthesis of heteroatoms-doped reduced graphene oxide toward nonradical degradation of tetracycline

Abstract

Nonradical-based advanced oxidation processes (AOPs) catalyzed by defective carbonaceous materials have exhibited great superiorities in trace antibiotics removal from natural water matrices. However, the complicated, extensive and highly-energy consumed synthesis methods are seriously hindering its development and application. Herein an in-situ electrochemical synthesis technology was developed and N/B/F-codoped RGO was assembled on the Ti foam effectively by using ionic liquid (IL) as the heteroatoms parents. Other benefits of the IL including anti-RGO agglomeration, suppressing hydrolysis side reaction and reducing internal resistance were also demonstrated. Based on the diverse substrates exploration and comprehensive characterizations, adsorption and desolvation of the water molecules around IL-GO was found the two critical procedures for GO reduction and heteroatoms-doping. Hydrophilicity and porosity are the two essential properties for substrate selection. The solvent substitute experiments indicated electrochemical reduction of GO is a proton-mediated electron transfer reaction and the protons come from the solvent. Remarkable heteroatoms content was obtained from −1.0 V ∼ -1.2 V within 30 min under normal temperature and pressure. The degradation performance of N/B/F-codoped RGO was examined in an electrochemical system without any chemical additive. 93.0 % of trace tetracycline (5 mg L-1) was removed at −0.6 V within 60 min and the corresponding TOC removal efficiency was 40 %. Electron transfer efficiency can be even improved in the natural water matrices. The degradation mechanism investigation suggested that N/B/F-codoped RGO is able to simultaneously catalyze two nonradical pathways including electron transfer and singlet-dominated AOP. This work provides a highly effective, green and low-cost nonradical-based AOP technology for controlling antibiotics pollution in the environmental water matrices.