Different modes of attachment of graphitic carbon nitrides on glassy carbon electrode and their electrocatalytic activity

Abstract

The present investigation reveals the attachment of graphitic carbon nitride nanosheets (GCNS) on glassy carbon (GC) electrode by adsorption, drop casting and potentiodynamic methods and their electrocatalytic activity. The bulk GCN was derived from urea and then converted into GCNS via water exfoliation aided by sonication. The GCNS was then directly attached to the GC electrode (GCNS-a) by immersing it in GCNS for 12 h. The initial adsorption of GCNS on the GC electrode is similar to Michael's like nucleophilic addition, and subsequent attachment may occur via π-π stacking. In the next mode of attachment, GCNS was fabricated by drop casting (GCNS-b) a known quantity of GCNS and dried at room temperature. In the third mode of attachment (GCNS-c), GCNS was fabricated on GC electrode by fifteen potential cycles in 0.1 M H2SO4 containing 1 mg mL−1 GCNS. The GCNS modified by these three different protocols were characterized by scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS). The SEM studies reveal that the morphology of GCNS varies with respect to the mode of attachment. The GCNS modified by potential cycling shows termitarium like structure whereas sheet like structure and an aggregated transparent thin sheet were noticed for direct adsorption and drop casting methods, respectively. Among the three different modes of attachments, improved electroactive surface area (EAS) and less charge transfer resistance (RCT) value were obtained for GC/GCNS-c electrode. Further, the GCNS attached by potentiodynamic method exhibited enhanced electrocatalytic performance towards ascorbic acid (ASA), dopamine (DPA) and hydrogen peroxide (HDP) in contrast to GCNS modified by adsorption and drop casting methods. The elevated electrochemical activity was due to larger EAS and lower impedance of GCNS-c electrode. The oxidation current increased linearly increases when increasing the concentration of HDP from 100 nM to 1 mM and the limit of detection was 5.2 nM (S/N = 3). Further, GCNS-c electrode also selectively determines HDP in the presence of 500-fold higher concentration of major interferents.