A facile electrochemical synthesis of covellite nanomaterials at room temperature

A novel method for the electrochemical synthesis of covellite (CuS) nanoparticles (NPs) in aqueous phase was developed. In this experiment, thioglycerol (TG) is used as the catalyst for the hydrolysis of sodium thiosulfate, the sulfur source for the synthesis of CuS. Cu foil, which acts as the sacrificing anode, is oxidized to Cu²⁺ by applying a potential of 0.5 V while OH^- was produced on the cathode surface at the same time. The production of OH^- facilitates the reaction between Cu²⁺ and thiosulfate under the catalysis of TG. The evolution of hydrogen bubbles effectively prevents the deposition of copper sulfide on the cathode. Copper sulfide sols of “golden-brown”, and “dark-green” forms can be obtained by varying the concentration of TG. The “golden-brown” copper sulfide sols are also observed to convert to the green form with time, and the rate of this conversion process is faster at higher temperatures. X-ray diffraction (XRD) and chemical analysis indicate that the “dark-green” form of product is pure hexagonal phase CuS. The obtained CuS NPs were covered by a layer of TG as suggested by Fourier transform infrared (FTIR) data. The size and morphology of the particles are studied by transmission electron microscope (TEM).