Electrochemical analysis of Co3(PO4)2·4H2O/graphene foam composite for enhanced capacity and long cycle life hybrid asymmetric capacitors

In this paper, we explore the successful hydrothermal approach to make Co3(PO4)2·4H2O/GF micro-flakes composite material. The unique sheet-like structure of the graphene foam (GF) significantly improved the conductivity of the pristine Co-based material, which is a key limitation in supercapacitors application. The composite electrode material exhibited superior capacitive conduct in 6 M KOH aqueous electrolyte in a 3-electrode set-up as compared to the pristine cobalt phosphate material. The material was subsequently adopted as a cathode in an asymmetric cell configuration with carbonization of Fe cations adsorbed onto polyaniline (PANI) (C-Fe/PANI), as the anode. The Co3(PO4)2·4H2O/GF//C-FP hybrid device showed outstanding long life cycling stability of approximately 99% without degradation up to 10000 cycles. A specific energy density as high as 24 W h kg−1, with a corresponding power density of 468 W kg−1 was achieved for the device. The results demonstrated the efficient utilization of the faradic-type Co3(PO4)2·4H2O/GF composite along with a functionalized carbonaceous electric double layer (EDL)-type material to produce a hybrid device with promising features suitable for energy storage applications.The South African Research Chairs Initiative (SARChI) of the Department of Science and Technology and the National Research Foundation (NRF) of South Africa (Grant No. 61056). Abdulmajid A. Mirghni acknowledges the financial support from University of Pretoria, the NRF through the SARChI in Carbon Technology and Materials, and also Al Fashir University, Sudan.http://www.elsevier.com/locate/electacta2019-09-01hj2018Physic

High electrochemical performance of hierarchical porous activated carbon derived from lightweight cork (Quercus suber)

Activated carbon (AC) derived from biomass lightweight cork (Quercus suber) material was synthesized by KOH activation with different mass ratios of Q. suber: KOH in order to investigate the electrochemical properties of the AC in relation to KOH concentration. A well-defined porous activated carbon was obtained with a high surface area of 1081 m2 g−1 and a high pore volume of 0.66 cm3 g−1 when the Q. suber: KOH mass ratio was fixed at 1:2. A specific capacitance of 166 F g−1 was obtained for the symmetric device at 0.5 A g−1 in 1 M Na2SO4 with energy and power densities of 18.6 and 449.4 W Kg−1, respectively. The device displays good cycling stability after floating test for 200 h at 1.8 V and also displays 99.8% capacitance retention after cycling for 5000 cycles. The excellent electrochemical performance of the device makes it a potential material for supercapacitor application.National Research Foundation (NRF) of South Africahttp://link.springer.com/journal/10853Lightweight cork (Quercus suber)2018-09-30hj2017Physic