Electrodeposition and Growth Mechanism of Copper Sulfide Nanowires

Thiourea (TU) is widely used as a corrosion inhibitor or as an additive in metal (e.g., copper) electroplating baths. TU facilitates the formation of uniform deposits with high brightness. In this study pertaining to the electrosynthesis of copper sulfide nanowires from dilute Cu2+ containing solution, TU was used as a copper ion complexing agent and sulfur source. Nanowires with various diameters and lengths were obtained via single-step pulsed potential electrodeposition. The electrodeposition time can be used to control the diameter of the electrodeposited nanowires to within the range of 30-100 nm. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analyses showed that nanowires are formed from covellite (CuS) and djurleite (Cu1.94S). The crystal structures of these phases were observed by high-resolution transmission electron microscopy (HRTEM). Cyclic voltammetry and electrochemical impedance spectroscopy have been applied to analyze the growth process of the nanowires. The formation of complexes of copper ions and TU was found to be a key factor in the nanowire growth process. A diffusion-controlled growth mechanism is proposed to interpret the growth behavior of the nanowires and the change in the product morphology. According to the proposed mechanism, during the cathodic pulses, copper and copper sulfide deposits, and afterward, during the anodic pulses, the deposited copper electrochemically dissolves. Dissolution of copper during the anodic pulses is shown to inhibit the quasi-anomalous codeposition of copper sulfide and copper.