Electrospun carbon nanofibers (CNFs) present an attractive application for energy storage devices. However, current CNFs suffer from poor graphitic structure. In this work, the graphitic structure was improved by adding a small amount of graphene oxide (GO) into water-soluble phenolic resin to prepare flexible carbon nanofibers prior to processing. The obtained CNFs exhibit improved electrochemical performance compared with pristine carbon nanofibers. The flexible hybrid membranes with NiMoO4 uniformly anchored give rise to a high specific capacitance (593 Fg(-1) at 1 Ag-1 based on the mass of hybrid membranes), good rate performance (465 Fg(-1) at 10 Ag (-1)) and intriguing cycling stability (95.4% after 2000 cycles), simultaneously. The symmetric solid-state supercapacitor fabricated by using the as-prepared hybrid membrane had a maximum energy density of 9.3 Wh kg(-1) and a power density of 3430.6 W kg(-1). It also possessed high rate capability of 92.4% with the current density ranging from 0.2 to 10 Ag-1, as well as excellent cyclic lifetime over which 80.8% of the capacitance were maintained after 5000 cycles at 5 Ag-1. (C) 2017 Elsevier Ltd. All rights reserved.