Direct Preparation Of Cu₂O/CuO/Cu-SiO₂ Composite Thin Films With A Single-step Electrochemical Sol-gel Method

Composite films consist of copper oxide?Cu₂O/CuO? / copper?Cu? and SiO₂ are widely applied in the fields of photonic devices, photocatalysis and sensors. The preparation of Cu₂O/CuO-SiO₂ composite materials reported in previous studies is usually have to be treated by high temperature treatment or radiation treatment by Cu-SiO₂. In this study, a single-step electrochemical sol-gel method for the preparation of Cu₂O/CuO/Cu-SiO₂ films is presented.The transparent, clear and stable Cu?II?-Cit³--SiO₂ composite sols with the [Cu?II?]:[Cit³-] mole ratio of 2:1, 1:1 and 1:2, were prepared using Cu?Ac?2 and TEOS as precursors, Na3 Cit as complexing agent. Three kinds of Cu based-SiO₂ composite films were electrodeposited directly on ITO cathode at different potentals using as-prepared Cu?II? acetate-citrate-silica sols as electrolyte at room temperature?20 oC?. The phase composition and the surface morphology of the films were determined by cyclic voltammogram?CV?, X-ray diffraction?XRD?, scanning electron microscopy/energy dispersive X-Ray spectroscopy?SEM/EDX? and X-ray photoelectron spectroscopy?XPS?, respectively. Characterization results showed that:?1?In composite sol with [Cu?II?]:[Cit³-] molar ratio of 2:1, Cu₂O-SiO₂ composite films were obtained at lower overpotentials?0^-0.42 V? and Cu₂O-CuO-SiO₂ composite films were obtained at higher overpotentials?-0.42^-1.0 V?;?2?In composite sol with [Cu?II?]:[Cit³-] molar ratio of 1:1, Cu₂O-SiO₂ composite films were prepared at lower overpotentials and Cu₂O-Cu-SiO₂ composite films were prepared at higher overpotentials through-0.8 V and-1.0 V;?3?In composite sol with [Cu?II?]:[Cit³-]molar ratio of 1:2, Cu₂O-SiO₂ composite films were obtained at lower overpotentials and Cu₂O-Cu-SiO₂ composite films were obtained at-1.0 V.Chronoamperometry?CA? experimental results exhibited that charge currents were too big to be ignored, and Langmuir Adsorption-Desorption equilibrium equation was used to extract the charge current density. And then the extracted nucleation currents were analyzed by Scharifker-Hill three-dimensional growth nucleation model under diffusion control. The results explained that:?1?In composite sol with [Cu?II?]:[Cit³-]molar ratio of 2:1, nucleation mechanism of Cu₂O/CuO follows instantaneous nucleation with three-dimensional growth among 0^-1.0 V;?2?In composite sols with [Cu?II?]:[Cit³-] molar ratio of 1:1 and 1:2, nucleation mechanism of Cu₂O/Cu turned progressive nucleation to instantaneous nucleation with the increasing overpotentials.