Facilely synthesized α phase nickel–cobalt bimetallic hydroxides: Tuning the composition for high pseudocapacitance

Abstract

A facile and novel precursor conversion method is successfully developed to grow Ni–Co hydroxides with α phase structure. The method is robust and versatile enough to be employed to prepare α phase Ni–Co hydroxides with similar interconnected flower-like nanostructures even at different Ni and Co contents. When used as the electroactive materials for supercapacitors, the bimetallic Ni–Co hydroxides deliver much higher specific capacitance with improved rate capability and cycling stability than monometallic Ni hydroxide. Especially, the Ni0.5Co0.5 hydroxide exhibits the highest specific capacitance of 1600Fg−1 at a current density of 1Ag−1. Meanwhile, the mechanism for better cycling stability of the bimetallic Ni–Co hydroxides is studied by FT-IR measurement. It is found that the introduction of Co ions contributes to the stable existence of ethylene glycol molecules in the interlayer space of the α phase Ni–Co hydroxides, resulting in superior cycling stability of the bimetallic Ni–Co hydroxides.