Paracetamol degradation via electrocatalysis with B and N co-doped reduced graphene oxide: Insight into the mechanism on catalyst surface and in solution.

This paper presents the use of B and N co-doped reduced graphene oxide (BN-GN) as an electrode for paracetamol electrochemical degradation. The reaction mechanism, focused on active sites in the atom level and dominant radical species generated through the reaction, was analyzed by characterization, density functional theory (DFT) calculation, quenching experiments, and electron paramagnetic resonance analysis. The characterization results indicated that the introduction of N and B functionalities into GN improved catalytic activity due to the generation of new surface defects, active sites, and improvement of conductivity. Results of experiments and DFT showed that co-doping of B and N greatly improved the catalytic activity, and the B atoms in C-N-B groups were identified as main active sites. The main active substances of BN-GN generated in the electrocatalytic oxidation of paracetamol in the solution were O2•- and active chlorine. The influence of O2•- and active chlorine on the efficiency/path of catalytic oxidation and the proposed mechanism were also determined for paracetamol degradation. This study provides an in-depth understanding of the mechanism of BN-GN catalysis and suggests possibilities for practical applications.

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

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.