Preparation And Electrochemical Property Of Cu₂O/Cu Electrode With Electrochemical Deposition Method

Cuprous oxide is generally considered as a direct bandgap semiconductor with a bandgap of2.17eV. It has been widely used in gas sensors, photocatalytic degradation, solar energy conversion, biological sensors and magnetic storage device due to its low price, non-toxicity, unique optical properties and catalytic properties.Nanomaterials’property is closely related to their structure. The particle size, morphology, pore structure, crystal facet exposure will affect their physical and chemical properties. This thesis adopts the method of electrochemical deposition. Through adjusting the experimental parameters in the process, we synthesized a variety of different morphology of cuprous oxide thin films on copper substrate. Then the related growth mechanism was studied and finally, the performance of the electrochemical reduction of carbon dioxide by using the prepared thin film electrodes was explored. The details are as follow.1. By changing the electrochemical deposition conditions, Cu2O films with different morphology are deposited onto Cu substrate. In alkaline electrolyte, low pH value and the small deposition current density can make Cu2O crystal favor<100> direction growth, so as to result in a tetrahedron morphology of Cu2O film. Large current density or high pH conditions, the growth direction of Cu2O tend to<111>. As a result, the morphology gradually transforms from the tetrahedron to triangle cone.2. With the presence of CuCl2in electrolyte, Cu2O rods were deposited on the Cu substrate. In the growth process, Cl-will restrain the growth of the<100> direction so that the rods are obtained. Because of the Cl-doping, the conductivity of the Cu2O film is greatly improved compared to pure Cu2O. It is also found that the bandgap narrows after doping from2.02eV to1.73eV.3. By changing the pH of the electrolyte, we prepared the p-rype and n-type Cu2O film in alkaline and acidic conditions respectively. For the electrochemical reduction of CO2, it is found that no methane is generated when the prepared Cu2O/Cu samples are used as working electrode. The corresponding ethylene yield of p-type and n-type Cu2O/Cu electrode is19346.5ppm and13240.4ppm respectively, which is much higher than pure Cu electrode. Additionally, p-type Cu2O has better electrochemical catalytic activity than n-type Cu2O on Cu substrate.4. By controlling the reaction time, different facet exposed Cu2O films have been prepared under constant voltage. It is found that the activity for the facet exposed samples is not as good as that of the samples prepared under constant current density for catalytic reduction of CO2. The evolved amount of ethylene on{100} and {111} facet exposed the Cu2O/Cu electrode is1048.9ppm and5020.1ppm respectively.