Site specific nitrogen incorporation in reduced graphene oxide using imidazole as a novel reducing agent for efficient oxygen reduction reaction and improved supercapacitive performance

Abstract

Nitrogen-functionalized reduced graphene oxide (NrGO) has emerged as an inexpensive and metal-free electrocatalyst for the oxygen reduction reaction (ORR) due to the presence of pyridinic, amine, and/or graphitic nitrogen on the reduced graphene oxide sheet. Herein we report a facile synthetic route to prepare NrGO at 90 °C (NrGO-90) using imidazole as a novel reducing agent as well as a targeted nitrogen precursor while circumventing the high-temperature annealing step. The substantial atomic percentage of pyridinic and amine nitrogen has been incorporated in NrGO-90, which facilitates the ORR via the four-electron pathway. NrGO-90 exhibits higher limiting-diffusion current density (−3.7 mA/cm2), onset potential (0.82 vs. RHE), and lower Tafel slope (67 mV/Decade), as compared to hydrazine hydrate reduced graphene oxide (rGO). In addition, our samples show higher performance in tolerance of methanol corrosion and longer cycling stability (90%) after 3.5 h compared to standard Pt/C. Furthermore, the NrGO-90 exhibits a specific capacitance of 287.5 F g-1 at 0.5 A g−1 with 90% retention after 10000 cycles suggesting facile interaction between electrolyte ions and active sites of rGO sheets. Such dual proficiency in a single rGO material has rarely been achieved so far employing simple solution chemistry.