Synthesis of anisotropic Cu_2−xS-based nanostructures by thermal oxidation

Flower-like copper sulfides nanostructures were synthesized via the solvothermal route. The structural, optical and electrochemical properties of the synthesized materials were characterized by means of X-ray diffraction (XRD), scanning electron microscopy, ultraviolet–visible spectrometry and Fourier transform infrared spectroscopy (FTIR). Thermal behavior of the obtained flower-like materials was analyzed by TG, XRD and FTIR in situ measurements, over the temperature range of 25–800 °C. It was found that both shape and phase composition remain stable until the temperature reaches 200 °C. Phase transformation mechanism was discussed. During annealing, mixture of CuS and Cu_1.8S is converted to copper sulfide hydroxides (200–500 °C) and further to CuO (700 °C and higher). Nevertheless, hierarchically porous structure is stable only to 200 °C. Applying higher temperatures affects the solubility of the material and inflicts structural damage, resulting in the formation of dense oval particles with size of 20 to 200 nm.