Electrochemical supercapacitive studies of chemically deposited Co_1-xNi_xS thin films

In the present work, we demonstrate the synthesis of Co_1-xNi_xS (0 ≤ x ≤ 0.2) metal chalcogenide thin films via a simple, inexpensive solution growth process and its subsequent studies aiming towards supercapacitive application. The as-prepared Co_1-xNi_xS thin films revealed microstructure similar to spirulina algae-like nanowires with uniform substrate coverage. The highest average, total roughness and particle height values were observed from atomic force microscopy measurement for x = 0.05 composition. The electrochemical measurements on thin-film electrodes have been done via cyclic voltammetry, galvanostatic charge-discharge studies, and electrochemical impedance spectroscopy. The as-grown Co_1-xNi_xS (x = 0.05) thin-film electrodes demonstrated a reversible electrochemical feature, offers a high specific capacitance of 880 F g⁻¹ at 6 mA cm⁻² current density and cycling stability of 79% after 5000 cycles. This performance of Co_1-xNi_xS electrodes at x = 0.05 was credited to its porous and large accessible area of entangled nanowire structure and effective intercalation of electrolyte ions through the electrode. This report opens new opportunities for the development of the metal chalcogenide thin films for high capacity electrochemical devices.