Investigation of the Supercapacitive Behavior of Electroless Ni-B Coatings

Abstract

Amorphous electroless Ni-B coatings were deposited on steel substrates with different surface morphologies and B contents (6.5–8.64 wt.%) that could be changed by altering the temperature and the composition of the baths. The supercapacitive behavior of the coatings was evaluated by cyclic voltammetry and galvanostatic charge–discharge measurements, and it was found that Ni-B coatings had higher capacitance than pure electroless Ni or the bulk Ni plate. A close relationship was identified between the microstructure, the B content, and the capacitive behavior of the coatings. The presence of the B alloying element had the most significant effect in determining the capacitance, while the surface area and particle size also contributed to its increase. A surface-specific capacity of 31 mF/cm2 was achieved by the coating containing the highest B content and largest AFM surface area. Furthermore, it was revealed that the particle size of the deposits was determined by the combined effect of the bath temperature and the B content under the applied experimental conditions. The obtained results indicate that Ni-B coatings are promising candidates for supercapacitive applications.