Catalytic performance and mechanism of graphene electrode doped with S and N heteroatoms for N-(4-hydroxyphenyl)ethanamide electrochemical degradation.

Abstract

As operation performance of electro-oxidation is strongly influenced by feature of anode materials, apparently oriented preparation of electrode materials to maximize stable degradation efficiency would be top-priority consideration for system optimization. Recently, heteroatoms hybrid graphene is well known as one of major matrices popularly constructed onto anode modification due to its excellent electronic properties and long-term operation stability. The novelty focused on the first proposed competitive interactions between N and S species on graphene edges for improving operation efficiency. Due to the complicated characteristics of heteroatoms hybrid graphene, the mechanism of synergistic or antagonistic interactions of different heteroatoms was still open to be explored. To clarify the functions of S and N heteroatoms on graphene electrode, N and S co-doped graphene were prepared by hydrothermal method. Analyses upon characterization of materials, dominant radical species reacted through reaction, density functional theory (DFT) calculation, N-(4-hydroxyphenyl)ethanamide degradation pathway and the influence of heteroatom species on the efficiency/path of electrocatalytic oxidation and proposed mechanism were determined. The findings indicated that S doped graphene had more promising electrocatalytic activity than N, and that the co-existence of S and N converted the N species from pyrrolic N (the N species with the highest activity) into graphitic N (the N species with the least activity). Apparently, the activity of S was also repressed. With S and N co-doping, active sites for direct electrocatalytic oxidation was possibly properly placed at carbon atoms with S or hydroxyl group. Moreover, the S species and hydroxyl groups are more favorable for indirect electrocatalytic oxidation via HO• and active chlorine species generation. The analysis in-depth with the proposed mechanism was suggested as guideline for optimal design of functional electrodes.