Self-assembled porous NiCo2O4 hetero-structure array for electrochemical capacitor

Porous NiCo2O4 hetero-structure arrays on nickel foam are prepared by a facile hydrothermal method. The morphology of the arrays changes with the growth time. After hydrothermal synthesis for 8 h in combination with annealing treatment, the NiCo2O4 array presents a nanoflake-nanowire heterostructure. The porous NiCo2O4 hetero-structure array exhibits the excellent pseudocapacitive properties in 2 M KOH, with a high capacitance of 891 F g(-1) at 1 A g(-1) and 619 F g(-1) at 40 A g(-1) before activation as well as excellent cycling stability. The specific capacitance can achieve a maximum of 1089 F g(-1) at a current density of 2 A g(-1), which can still retain 1058 F g(-1) (97.2% retention) after 8000 cycles. The enhanced pseudocapacitive performances are mainly attributed to its unique hetero-structure which provides fast ion and electron transfer, large reaction surface area and good strain accommodation. (C) 2013 Elsevier B.V. All rights reserved.