Investigation of the Supercapacitive Behavior of Electroless Ni-B Coatings

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/cm(2) 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.