Direct Adsorption of Graphene Oxide on a Glassy Carbon Electrode: An Investigation of Its Adsorption and Electrochemical Activity.

Abstract

Different modes of attachment of graphene oxide (GO) on an electrode surface resulted in unusual catalytic behavior respective of attachment because of film thickness. The present work investigates the direct adsorption of GO to the surface of a glassy carbon (GC) electrode. Scanning electron microscopy images revealed that multilayers of GO get adsorbed on the GC substrate and the adsorption was limited by folding up of the GO sheets at their edges. π-π and hydrogen bonding interactions between the GO and GC substrate flagged the adsorption of GO. pH studies revealed that higher adsorption of GO was achieved at pH = 3 rather than at pH = 7 and 10. Even though the electroactive surface area of adsorbed GO (GOads) was not remarkable (0.069 cm2), upon electrochemical reduction of GOads (Er-GOads), the electroactive surface area was escalated to be 0.174 cm2. Similarly, the RCT of Er-GOads was boosted to 2.9 kΩ compared to GOads which is 19 kΩ. Open circuit voltage was recorded to study the adsorption of GO on the GC electrode. Multilayered GO best fitted with the Freundlich adsorption isotherm, and the Freundlich constants like n and KF were found to be 4 and 0.992, respectively. The Freundlich constant "n" revealed the adsorption of GO on the GC substrate to be a physisorption process. Furthermore, the electrocatalytic performance of Er-GOads was demonstrated by taking uric acid as a probe. The modified electrode showed excellent stability toward the determination of uric acid.