Comparative Study on Morphological and Electrochemical Properties of Nickel–Cobalt Double Hydroxide, Cobalt Hydroxide, and Nickel Hydroxide

The morphological and electrochemical properties of nickel–cobalt double hydroxide (Ni-Co DH), cobalt hydroxide [Co(OH)2], and nickel hydroxide [Ni(OH)2] prepared directly on a transparent conductive oxide substrate via a simple one-pot wet-chemical method have been investigated and compared. All samples were composed of nanosheets vertically aligned on the substrate. Comparison of the results showed that Ni-Co DH with submicrometer-scale pores had more compact structure than Ni(OH)2 or Co(OH)2. Moreover, the highly symmetric cyclic voltammetry (CV) curves of Ni-Co DH indicated its good electrochemical reversibility. The specific capacitance value of Ni-Co DH was ∼ 286 F/g and ∼ 210 F/g at scan rate of 2 mV/s and 100 mV/s, respectively, indicating its better rate capability, particularly at high scan rate, than Ni(OH)2 or Co(OH)2. In addition, after CV cycling test, the Ni-Co DH nanosheets showed no noticeable morphological change. Furthermore, the electrochromic performance of Ni-Co DH was sustained over 10000 s. Thus, Ni-Co DH prepared via a facile one-step process exhibited promising characteristics as a cost-effective functional material for use in electrochemical devices.