Enhancement of quaternary nitrogen doping of graphene oxide via chemical reduction prior to thermal annealing and an investigation of its electrochemical properties

Abstract

A simple and efficient method to enhance the quaternary nitrogen doping (N-doping) of graphene has been demonstrated. Recent studies have shown that quaternary N in the graphene network provides more efficient electrocatalytic activity. Therefore, a novel strategy to enhance the quaternary N-doping is currently in high demand. The strategy employed in this work was to modify graphene oxide (GO) prior to thermal annealing so as to provide a more efficient structure for quaternary N doping. GO was first chemically reduced with hydrazine to substantially increase the formation of CC bonds and simultaneously decrease the atomic oxygen concentration. The reduced graphene oxide (RGO) was then annealed in the presence of NH₃. Although N-doping via the replacement of oxygen is preferred, the probability of carbon being substituted with N dopants in the graphitic structure of RGO could increase due to the relatively higher content of CC when compared to the atomic oxygen concentration. In addition, due to the decreased atomic oxygen concentration, the electro-conductivity was enhanced. Cyclic voltammograms (CVs) of 5 mM K₃Fe(CN)₆ and 2 mM H₂O₂ were used to examine the electrochemical response of the quaternary N-maximized RGO. An improvement in electrocatalytic reduction and a higher electro-conductivity were confirmed based on an analysis of the obtained CVs.