Hybrid core–shell nanostructured electrodes made of polypyrrole nanotubes coated with Ni(OH)2 nanoflakes for high energy-density supercapacitors

This work describes the design of Ni(OH)@PPy-NTs core-shell nanostructures with potential application as an electrode material for supercapacitors. Initially, one dimensional (1D) polypyrrole nanotubes (PPy-NTs) were synthesized through a chemical oxidation mediated soft template-directed route using as the anion the azo dye methyl orange (MO). Subsequently, three dimensional (3D) Ni(OH) nanoflakes were grown onto PPy-NTs by a simple hydrothermal route. This exclusive Ni(OH)@PPy-NTs nano-architecture helps to improve the overall electrochemical performance of the electrode, due to the high surface area provided by 3D nanoflakes and excellent electronic/ionic conductivity of 1D nanotubes. The maximum specific capacitance obtained for Ni(OH)@PPy-NTs was 536 F g with good capacity retention after 1000 charge/discharge cycles. Last but not least, EIS technique showed a low electrochemical series resistance for Ni(OH)@PPy-NTs confirming their promise as a high-performance energy storage material.The authors acknowledge the financial support of the CAPES Foundation, Ministry of Education of Brazil: Process BEX 3196/14-3. Authors appreciate the award to DPD with the support of the Secretary for Universities and Research of the Ministry of Economy and Knowledge of the Government of Catalonia and the Co-fund programme of the Marie Curie Actions of the 7th R&D Framework Programme of the European Union. Partial funding from Spanish Grant MAT2012-39199-C02-01 is acknowledged. ICN2 acknowledges support of the Spanish MINECO through the Severo Ochoa Centers of Excellence Program under Grant SEV-2013-0295.Peer Reviewe