Evaluation of the electrochemical energy storage performance of symmetric supercapacitor devices based on eco-friendly synthesized nitrogen-doped graphene-like derivative electrodes from the perspective of their nanostructural characteristics†

The potential use of several ecofriendly nitrogen-doped 2D graphene-like derivatives (N-2D GDs) with various graphitic structural features as electrode materials for symmetric 2-electrode supercapacitor devices was explored. The N-2D GDs were synthesized via a novel, facile, ecofriendly, economic and scalable technique. The synthesis technique is simply a single-step hydrothermal treatment of glucose using traces of cetyltrimethylammonium bromide (CTAB) and ammonia as structure-directing agents. Graphitic structural characteristics were controlled by manipulating hydrothermal process temperature and CTAB dose. Electrochemical energy storage performance was found to be strongly dependent on the oxidation level, doped-N content and configuration, density of graphitic surface-capping by CTAB, morphological architecture and graphitic structural order of N-2D GD-based electrodes. Interestingly, such graphitic structural parameters influenced overall charge-storage capacitance through EDLC and pseudocapacitance mechanisms in a competitive manner. An N-2D GD sample synthesized at a hydrothermal temperature of 270 °C and CTAB/glucose molar ratio of 1/6 (NG-HCD270) exhibited the best energy storage capacitive performance in a symmetric 2-electrode supercapacitor system owing to the almost pure well-ordered N-doped graphene. It showed excellent electrochemical energy storage performance as compared to other 2D graphene derivatives reported in the literature synthesized via toxic conventional methods, with a specific capacitance of 553 F g⁻¹, energy density of 84.5 W h kg⁻¹, power density of 550.2 W kg⁻¹ and 88.5% capacitance retention after 5000 cycles. Thus, the NG-HCD270 graphitic sample can be considered a promising ecofriendly and cost-effective electrode material for high-performance supercapacitors, which can benefit the substantial development of electrical energy storage industry and, hence, electrical power production from renewable energy sources at competitive costs.