The physicochemical properties and capacitive functionality of pyrrolic- and pyridinic-nitrogen, and boron-doped reduced graphene oxide

Much focus with regards to graphene oxide (GO) reduction has been on reducing the oxygen: carbon ratio with little focus on other associated chemical transformations. The current work presents an enlightening physical and chemical transformation study of reduced graphene oxide (RGO) samples with regards to use of ascorbic acid, hydrazine hydrate and sodium borohydride as reducing agents and their associated appropriateness in electrochemical capacitors. The physical and chemical characteristics of RGO were compared by means of elemental analysis, infra-red spectroscopy, thermal gravimetric analysis, X-ray photoelectron spectroscopy, powder X-ray diffraction, textural characteristics, scanning and transmission electron microscopies, electron impedance spectroscopy and cyclic voltammetry. Hydrazine hydrate was the most effective reducing agent with the highest nitrogen at.% (4.07), surface area of 390.55 m(2) g(-1) and was increased to 599.67 m(2) g(-1) upon thermal treatment at 750 degrees C. The nitrogen functionalities observed in pristine-GO, ascorbic acid and hydrazine hydrate reduced GO were sp(3) N-C, pyrrolic and pyridinic, respectively. Whereas sodium borohydride RGO were B-doped with at.% of 2.49 during the reduction reaction. The N-doped RGO samples were more effective in charge storage than B-doped counterparts (76-fold better) and pyrrolic-N-doped was more effective than pyridinic-N-doped-RGO (1.35 times better). (C) 2017 Elsevier Ltd. All rights reserved.