Light weight and flexible fiber-shaped supercapacitors (FSSCs) that are considered to be ideal energy storage devices for powering wearable electronics. A flexible, high energy density all-solid-state Pt/n-CNT@PANI FSSCs was fabricated by using a simple method. The electrode was formed by twisting a number of CNT yarns (n) with one platinum filament as current collector, upon which PANI nanowires were deposited in-situ to form the final Pt/n-CNT@ PANI FSSCs. The electrode structure with n = 5 fabricated at a twist level of 1000 T/m showed the best electrochemical performance. The optimum flexible Pt/5-CNT@PANI FSSC exhibited a specific capacitance of 217.7 F/g at the current density of 0.2 A/g, indicating a 7-fold increase in specific capacitance than the initial Pt/1-CNT@PANI with one CNT yarn (n = 1) of about 29.9 F/g. The Pt/5-CNT@PANI FSSC showed an energy density of 30.22 Wh/kg accompanied by a power density of 91.88 W/kg. The Pt/5-CNT@PANI exhibits remarkable electrocatalytic activity for hydrogen evolution reaction (HER) with a low onset overpotential of - 188 mV and low Tafel slope of 84.99 mV/dec. The Pt/5-CNT@PANI yarns can be used as not only FSSC with excellent cycle stability and flexibility and but also an active and stable electrocatalyst for HER in alkaline electrolytes. (C) 2017 Elsevier Ltd. All rights reserved.