Electrochemical anchoring of dual doping polypyrrole on graphene sheets partially exfoliated from graphite foil for high-performance supercapacitor electrode

Abstract

Partial exfoliation of graphene from graphite foil (GF) is achieved by a convenient one-step electrochemical exfoliation method to afford partially exfoliated graphene electrode (Ex-GF) with graphene sheets standing on GF matrix stably. Electropolymerization of pyrrole is carried out on Ex-GF with 1,5-naphthalene disulfonate (NDS) and 2-naphthalene sulfonate (NMS) as the ‘permanent’ doping anions to prepare Ex-GF/PPy-NDS and Ex-GF/PPy-NMS, respectively, in which the polymer is anchoring on the surfaces of graphene sheets. The PPy displays an opened structure due to the facilitated homogeneous nucleation on Ex-GF and so exhibits enhanced specific capacitance compared to the polymers deposited on pristine GF (to afford GF/PPy-NDS and GF/PPy-NMS). Specifically, Ex-GF/PPy-NDS film maintains 79% of its specific capacitance when the discharge current density increases from 1 to 20 A g−1. Moreover, discharge potential window of the polymer is enlarged to 1.3 V (from −0.8 to 0.5 V vs. SCE) due to the dual doping mode. Ex-GF/PPy-NDS film displays a high energy density of 82.4 Wh kg−1 at the power density of 650 W kg−1 and 65.1 Wh kg−1 at the power density of 13 kW kg−1. The cyclic charge/discharge stability of the polymer is also improved due to synergistic effect with partially exfoliated graphene.