Nanoarchitectonics of eco-friendly nickel oxide nanoplatelets for energy storage

[EN] Nanostructured nickel hydroxide coatings were prepared directly by aqueous electrophoretic deposition (EPD) method without binder or organic solvent. β-Ni(OH) nanoplatelets were first synthetized by chemical precipitation from nickel nitrate in ammonia under ultrasound. These particles, stabilized at pH ≈ 8, present an equivalent diameter of 250 nm and an electrophoretic mobility of ≈ + 2.5 × 10 m V s. Cathodic EPD was performed at room temperature for different values of particles concentration, deposition time and applied electric field. An optimal coating was achieved using a 1 g L of β-Ni(OH) particles suspension during 30 min deposition time at an electric field of 75 V m. In this work, the suspension conductivity was studied showing that a very narrow range of conductivity can leads to efficient deposition in aqueous EPD. The β-Ni(OH) coatings were heated at 325 °C in air for 1, 2 and 3 h to form NiO films. The electrochemical properties of the NiO films were evaluated by cyclic voltammetry (CV) and galvanostatic charge/discharge (GCD). Significant differences were observed in term of specific capacitance values as a function of annealing time and film thickness. Finally, the film microstructure was determined by the calculation of the electrochemically active surface area (ECSA) using Randles–Ševčík equation.