Effect of the Ni(NO3)2 additive on the electrophoretic deposition of NiO nanoparticles

Abstract

In this work, we report the electrophoretic deposition of NiO nanoparticles on aluminum plates, as well as the effect of the nickel nitrate salt used as additive for coating deposition. First, the Ni(OH)2 nanoparticles were synthesized by a precipitation route with NaOH in a conventional microwave oven. This precursor was submitted to a heat treatment at 300 °C for 3 h in order to obtain the nickel oxide without any secondary phase. The NiO nanoparticles with mean crystallite size of 2.79 nm were dispersed in isopropanol and deposited by an electrophoretic procedure on aluminum substrates with 1 cm of distance and under 10 V of DC voltage for 30 min. XPS analysis of the as-prepared coatings reveals that metallic Ni is produced during the EPD process. Moreover, the presence of Ni(NO3)2 as additive on the electrophoretic procedure leads to changes in the morphological features of the coatings. In this sense, a compact and homogenous coating was formed without the presence of nickel salt, whereas a coating with porous and cavities was obtained with a 0.5 mM concentration of Ni(NO3)2. Moreover, a 1.0 mM concentration of the additive results in a poor coverage of the electrode surface. The porous structure of the coatings in combination with the formation of metallic Ni could be useful for electrochemical applications such as capacitors or electrochromic devices.