Facile synthesis of double-layered CoNiO2/CoO nanowire arrays as multifunction electrodes for hydrogen electrocatalysis and supercapacitors

The development of bifunctional electrochemical active heterostructures for both hydrogen evolution reaction (HER) and supercapacitors provides the possibility to integrate energy conversion and storage into one single system. In this article, we have designed and investigated three-dimensional (3D) hybrid CoNiO2/CoO composites through simple hydrothermal and annealing processes, in which CoNiO2 nanowires layered on CoO nanowires arrays with distinctive hierarchically nanowires structure were supported on nickel foam. Specifically, the CoNiO2/CoO-140-400 composite (optimum experimental conditions: hydrothermal temperature 140 degrees C, annealing temperature 400 degrees C) can efficiently catalyse the HER in an alkaline electrolyte with a small overpotential of 70 mV at 10 mA cm(-2) current density, and exhibit a beneficial kinetics and excellent long-term stability of 15 h without obvious fluctuations. Moreover, the material shows an areal capacitance of 5.37 F cm(-2) at a current density of 1 mA cm(-2), remarkable rate capability (83.9% capacity retention at 20 mA cm(-2)) and cycle stability (82.9% retention after 5000 cycles) for supercapacitor. This work reveals that the synergistic effects between CoNiO2 and CoO in CoNiO2/CoO-140-400 heterostructures are powerful for electrochemical property and provide a strategy to explore low cost and highly efficient electrocatalysts for the energy conversion and storage applications. (C) 2020 Elsevier Ltd. All rights reserved.