Effect of molar concentration on the physical properties of NiS thin film prepared by spray pyrolysis method for supercapacitors.

The present study reports on the deposition of Nickel sulfide (NiS) thin films on glass substrates by spray-pyrolysis at 300 ± 5 °C with different concentrations of nickel precursor (0.03, 0.05, and 0.07 M). The precursor aqueous solutions were synthesized using hexahydrated nickel nitrates and thiourea with a stabilization ratio nickel/sulfur of 1/3. The X-ray diffraction (XRD) study revealed a polycrystalline character with a hexagonal crystal structure. The crystallites size varied from 23.9 to 42.7 nm with an increase in the precursor's concentration. Furthermore, the optical band gap decreases from 1.07 to 0.96 eV. The elementary composition analysis confirmed the presence of Ni and S elements in the samples. Both scanning electron microscopy (SEM) and atomic force microscopy (AFM), revealed a homogenous crack-free and compact appearance in all scanned areas with spherical grains. In addition, the roughness of the films significantly increases with the increase of the precursor's concentration. On the other hand, the film prepared with 0.05 M exhibits a high electrical conductivity and capacitance ca. 1.97 × 10³ S/cm and 115 µF/cm², respectively, at room temperature. The above results showed that the films prepared in this study are very attractive as an electrode material for application in supercapacitors. [ABSTRACT FROM AUTHOR]