Nature of Synergistic Effect of N and S Co-Doped Graphene for Enhanced Simultaneous Determination of Toxic Pollutants

Weiqing Zhu ^†, Juanjuan Gao ^†, Haiou Song ^‡, Xuezhen Lin ^†, and Shupeng Zhang ^†,*

^† School of Chemical Engineering, Nanjing University of Science and Technology, Nanjing, 210094, PR China

^‡ School of Environment, Nanjing Normal University, Nanjing, 210097, PR China

ABSTRACT

N-doped graphene (NG), S-doped graphene (SG) and N and S co-doped graphene nanocatalysts with different doping sequences (N-SG and S-NG) are successfully synthesized by a facile low-temperature hydrothermal method. By changing the synthetic sequence, S-NG significantly increases the electron transport rate of the sensor and the electrocatalytic ability compared to NG, SG and N-SG due to the optimal proportion of doping element content and suitable N- and S-bonding configurations. The origin of the synergistic effect of N and S co-doped graphene is confirmed. Traces of S doping greatly enhance the electrochemical performance. The large volume of S-O_x groups may prevent the analytes approaching the catalytic sites of the sensing materials due to a steric hindrance effect. S-NG, which possesses less S-O_x groups, exhibits better performance than that of N-SG. Pyridinic N plays an important role in enhancing the electrochemical activity and conductivity. The simultaneous determination of aniline (AN), p-phenylenediamine (PPD) and nitrobenzene (NB) as typical toxic pollutants is performed by employing the S-NG nanoarchitecture. The detection limits (S/N = 3) for AN, PPD and NB are 0.023, 0.051, 0.216 μM, respectively. In addition, the S-NG sensors also have excellent anti-interference, stability and reproducibility. The precise control and synthesis of multi-heteroatoms into graphene represent a promising strategy to enhance the electrocatalytic performance in energy and environmental fields.