The effect of deposition cycles on intrinsic and electrochemical properties of metallic cobalt sulfide by Simple chemical route

Abstract

In this paper, cobalt sulfide thin film was synthesized on glass and steel substrates via chemical route. The structure, surface morphology, and optical characterization of the deposited thin films indicated a strong relationship between the number of deposition cycles and intrinsic properties. The scanning electron microscope (SEM) showed a uniform morphology with randomly oriented nano-grains of cobalt sulfide film at varying deposition cycles. The XRD spectra revealed that the films became amorphous as the number of deposition cycles increased. The crystalline films had a hexagonal structure of average crystallite size of 27.55 nm. The optical transmission spectra of the films gave a direct band gap energy which varied between 1.90 eV and 2.20 eV with an average value of the optical conductivity was 1.77 1017 S̶ 1. The electrochemical energy storage behavior of the electrodes was evaluated using cyclic voltammetery (CV), galvanostatic charge-discharge (GCD) technique and electrochemical impedance spectroscopy (EIS) in a neutral electrolyte of 0.1 M solution of Na2SO4 performed on films deposited on a steel substrate. A specific capacity of 298.4 mAh/g at a scan rate of 20 mV/s was obtained at 30 deposition cycles. The SILAR deposited CoS thin film electrodes is a promising material for both energy storage and optoelectronics application based on the electrochemical properties obtained. The material showed about 80% charge capacity retention after 1000 cycles.