Zinc citrate-based nanoporous carbon materials: Large capacitive enhancement using redox active electrolyte of p-phenylenediamine

In this work, we demonstrate a simple template carbonization method to prepare nanoporous carbon materials, in which zinc citrate serves as carbon source and the ZnO substance together with some gases in situ thermally produced as templates. The resultant carbon-800 sample has a large surface area of 740.5 m(2) g(-1), and high pore volume of 1.96 cm(3) g(-1). To further increase the porosity of the above carbon materials, ZnCl2 that can act as activation agent and template has been added into the zinc citrate precursor. As a result, the surface area of the carbon-ZnCl2-800 sample has largely increased up to 1244.2 m(2) g(-1), and pore volume up to 2.21 cm(3) g(-1). In a conventional 6 mol L-1 KOH electrolyte, the specific capacitances of the carbon-800 and carbon-ZnCl2-800 samples can reach up to 194.8 -335.6 F g(-1), respectively, at 2 A g(-1). Next, a novel redox active electrolyte of p-phenylenediamine (PPD) with quick reversible Faradaic process at the electrodeeelectrolyte interface has been introduced into the 6 mol L-1 KOH electrolyte. Remarkably, the specific capacitance of the carbon-ZnCl2-800 sample have reached up to 934.6 F g(-1) at 2 A g(-1) when designating the PPD concentration as 14 mmol L-1 in 6 mol L-1 KOH electrolyte, which is nearly 2.8 fold higher than the pristine one, clearly indicating the pseudo-capacitive effect of the PPD additive. (C) 2015 Elsevier B.V. All rights reserved.