We report the facile synthesis of freestanding MnO2 nanoflakes/porous carbon nanofibers (MnO2/PCNFs) for high performance flexible supercapacitor electrodes. PCNFs are firstly synthesized via a electrospinning method using phenol-formaldehyde resin as the carbon precursor with tetraethyl orthosilicate and triblock copolymer Pluronic P123 as porous and soft templates, respectively. MnO2 nanoflakes are then in-situ deposited on PCNFs based on the self-limiting reaction between KMnO4 and carbon. The obtained MnO2/PCNF hybrid shows a porous structure with ultra-high specific surface area of 1814m(2) g (1), providing numerous electroactive sites to accommodate more charges. As a result, the MnO2/PCNF hybrid electrode exhibits extremely high specific capacitance (520 F g (1) at 0.5 A g (1)) and superior cycling stability (92.3% retention after 4000 cycles) in a 6M KOH aqueous solution. Such excellent electrochemical behavior may render this hybrid a promising candidate for flexible, freestanding and high-performance supercapacitor electrodes. (C) 2015 Elsevier Ltd. All rights reserved.