Pengtao Yan

A novel approach of binary doping sulfur and nitrogen into graphene layers for enhancing electrochemical performances of supercapacitors

In this paper, we present a novel route to prepare sulfur and nitrogen co-doped reduced graphene oxide, in which, two main procedures – the preparation of a sulfur doped graphite intercalation compound (S-GIC) and the construction of the sulfur and nitrogen co-doped reduced graphene oxide (SN-RGO) – are included. The loading of sulfur and nitrogen in SN-RGO, which is tracked by X-ray photoelectron spectroscopy, is 1.47 and 3.90 at%, respectively. SN-RGO possesses an almost two times higher specific surface area (SSA) than RGO and a narrow pore size distribution. Electrochemical investigations demonstrate that SN-RGO exhibits an outstanding capacitive performance, its specific capacitance at the scan rate of 5 mV s−1 in a 6 M KOH aqueous electrolyte being up to 402.4 F g−1, which is, to the best of our knowledge, among the highest values so far reported for S/N co-doped carbon materials. Furthermore, SN-RGO also exhibits an excellent cycling stability (almost 95% specific capacitance being retained even after 10 000 cycles). This work suggests that constructing doped graphene-based materials by using the intercalated substances among the graphite layers as the dopant sources can be considered as a promising strategy for the development of high performance electrodes for supercapacitors.

High-Performance Supercapacitor Based on the NaOH Activated D-Glucose Derived Carbon

In this work, a mechanism of catalytic graphitization of D-glucose derived carbon during NaOH activation process is disclosed. The catalytic graphitization is caused by sodium atom, which is produced in the reaction between NaOH and carbon. Due to the combined action of activation and catalytic graphitization resulting from the NaOH, the activated D-glucose derived carbon behaves as a hierarchical micro- and meso-porous structure and has high electrical conductivity. Electrochemical investigations demonstrate that the activated sample exhibits an outstanding rate capability (70% of capacity retention even at a scan rate of 2V s−1) and high specific capacitance (106F g−1) in 6M KOH aqueous electrolyte, which makes it a promising electrode material for high-power supercapacitors.

Ultrahigh-power supercapacitors based on highly conductive graphene nanosheet/nanometer-sized carbide-derived carbon frameworks

In order to develop energy storage devices with high power performance, electrodes should hold well-defined pathways for efficient ionic and electronic transport. Herein, we demonstrate a highly conductive graphene nanosheet/nanometer-sized carbide-derived carbon framework (hcGNS/nCDC). In this architecture, nCDC possesses short transport paths for electrolyte ions, thus ensuring the rapid ions transportation. The excellent electrical conductivity of hcGNS can reduce the electrode internal resistance for the supercapacitor and thus endows the hcGNS/nCDC composite electrodes with excellent electronic transportation performance. Electrochemical measurements show that the cyclic voltammogram of hcGNS/nCDC can maintain a rectangular-like shape with the increase of the scan rate from 5 mV s-1 to 20 V s-1, and the specific capacitance retention is up to 51% even at a high scan rate of 20 V s-1, suggesting ultrahigh power performance, which, to the best of our knowledge, is among the best power performances reported so far for the carbon materials. Furthermore, the hcGNS/nCDC composite also shows an excellent cycling stability (no drop in its capacitance occurs even after 10000 cycles). This work demonstrates the advantage in the ultrahigh power performance for the framework having both short transport pathways for electrolyte ions and high electrical conductivity.