Electrochemical activity of self-supporting nitrogen-doped graphene for the degradation and in-situ determination of methylene blue

Environmentally friendly wastewater treatment and online pollution monitoring systems, important for water quality control, are yet to be developed. Electrochemical strategies combining the electrocatalytic degradation and electroanalysis of organic pollutants are expected to achieve this key technology. This study employed a chemical vapor deposition method using N2 gas as the nitrogen source and applying an alternating electric field to prepare self-supporting nitrogen-doped graphene (NG) tubes with a wall thickness of up to 480 mu m comprising few-layer NG nanosheets. The correlation between the properties of these materials and the electrocatalytic activity for methylene blue (MB) was investigated. The feasibility of the electrochemical strategy for online wastewater treatment and detection was validated using a combination of UV-visible spectroscopy and differential pulse voltammetry. The NG tube with the N-C bond distribution regulated by adjusting the methane flow rate and growth time exhibited high electrocatalytic activity, rapidly degrading 50 mg L-1 of MB within 36 min and tracking changes in MB concentration. The NG tubes were assembled in an electrocatalytic meter pen for water treatment, achieving a degradation efficiency of 99.4 % and a detection limit of 0.3 mg L-1 for the MB solution, quite satisfactory for emerging simultaneous degradation and monitoring processes. The developed selfsupporting NG tubes are promising materials for electrocatalytic degradation anodes and sensing electrodes in water treatment. Dual-functional electrocatalytic systems have potential applications in water quality monitoring and improvement.