We prepare a novel redox-additive organic electrolyte containing phenylenediamine for a graphenehydrogel supercapacitor. By adopting this electrolyte, significant capacity enhancement (47-596% increase) is achieved. At the concentration of 0.02 mol l(-1), the specific capacity value of the graphenehydrogel electrode reaches 171 mAh g(-1), 287mAh g(-1), and 353 mAh g(-1) at 1 A g(-1) for o-phenylenedi-amine (OPD), m-phenylenediamine (MPD), and p-phenylenediamine (PPD), respectively. The enhancement by PPD is more significant than OPD and MPD at concentrations higher than 0.02 mol l(-1). This behavior is likely caused by the para-amino groups, which exhibits less stereo-hindrance during the absorption of phenylenediamine onto the graphene surface. In the electrolyte containing 0.04 mol l(-1) of PPD, specific capacity of 516mAh g(-1) at 1 A g(-1) and energy density of 143Wh kg(-1) with power density of 1.11 kW kg(-1) are achieved. Meanwhile, 93.8% of the electrode's initial capacity (433mAh g(-1)) is retained after 5000 cycles at 2 A g(-1), demonstrating its excellent cycling stability. (c) 2018 Elsevier Ltd. All rights reserved.