Controlled synthesis of hierarchical nanoflake structure of NiO thin film for supercapacitor application

The nickel-based oxides or hydroxides are considered a promising electroactive material for supercapacitor application owing to its low cost, well-defined redox activity, and prospect of controllable nanostructures. However, control of nanomorphology and uniform deposition onto a conductive substrate for Ni-based materials remains a critical challenge. Herein, we demonstrate the controlled synthesis of hierarchical nanoflake structure of NiO thin film by a simple and inexpensive successive ionic layer adsorption and reaction (SILAR) method and its consequent effect on supercapacitive performances. The as-prepared NiO thin films confirmed kinetically controlled growth model for the anisotropic nanostructure through a systematic investigation of controlling reaction temperatures and times. The as-optimized binder-free NiO thin film electrodes exhibited a reversible electrochemical feature, providing a high specific capacitance of 674 F g(-1) and cycling stability of 72.5% after 2000 cycles. These performances of NiO thin films were attributed to its open mesoporous and large accessible area of hierarchical nanoflakes structure, as well as the fast ion diffusion into the active sites. This work opens new avenues for the design of high capacity metal oxide thin films with hierarchical architecture for electrochemical energy storage applications. (c) 2018 Elsevier B.V. All rights reserved.