Performance of graphitic carbon nitride nanosheets derived from liquid and thermal exfoliations towards the electrochemical reduction of nitrobenzene

Abstract

The present investigation reports the preparation of graphitic carbon nitride nanosheets (GNNS) from bulk GN (B-GN) by liquid and thermal exfoliation methods and compares their electrocatalytic activity towards the reduction of nitrobenzene (Nb). The SEM images of GNNS powder prepared by water exfoliation (GNNS-S) show the presence of thin sheets along with a few multilayers, whereas highly crumpled thin sheets containing small pores were noticed for GNNS prepared by thermal exfoliation (GNNS-T). The charge transfer resistance (R_CT) values obtained from Nyquist plots were found to be 19.2, 21.9, 5.49 and 2.11 kΩ, respectively, for bare GC, B-GN, GNNS-T and GNNS-S modified GC electrodes indicating the lowest impedance of GNNS-S. Furthermore, the electroactive surface area (EAS) of the respective electrodes was estimated to be 0.062, 0.039, 0.108 and 0.123 cm², revealing that the EAS of the GC/GNNS-S electrode was higher than that of GC/GNNS-T. The performance of the GNNS-S and GNNS-T modified electrodes was compared by studying the electrochemical reduction of Nb. In contrast to the GC/GNNS-T electrode, GC/GNNS-S enhanced the reduction current by 1.2-fold. The higher electrocatalytic activity of GC/GNNS-S was ascribed to its higher electronic conductivity and EAS than that of the GC/GNNS-T electrode. The Nb reduction current was increased linearly upon increasing its concentration from 0.5 to 2000 μM and the LOD was found to be 7.3 nM (S/N = 3). Finally, the practical application of the present sensor was established by determining Nb in tap water samples.