Preparation Of Copper Oxides Films By Anodic Oxidation Of Brass In Alkaline Solutions

The adequate and clean energy, including solar energy and hydrogen energy,is the ideal energy to support future development. The metal oxides semiconductor material was one of the important materials for solar energy conversion. Cuprous oxide （Cu₂O） and copper oxide （CuO） were typical p-type semiconductors. The band gap of them were 1.9～2.2 eV and 1.2 eV, respectively. So they can absorb visible light, and thus can be used as visible light photocatalysts.In this thesis, brass was used as the substrate. The metal oxide film was prepared by chronopotentiometry with two electrode system. We prepared nano granular Cu₂O and nano plate CuO. By using X-ray powder diffraction （XRD）, scanning electron microscopy （SEM）, transmission electron microscopy （TEM） and laser Raman spectroscopy （Raman） techniques, the oxides were characterized. And the photoelectrochemical properties of the films were analysis under visible light. The main research contents and results were following:1. The formation of a small amount of oxide surface of brass was observed, after only 150℃ high temperature oxidation treatment of 2 h. Its photoelectrochemical properties was weak. Dense and porous oxides nano plates on the surface of the brass can only be obtained after anodic oxidation of 300 s with a current density of 10 mA·cm-2. XRD analysis showed that the samples containing both CuO and Cu₂O. When the samples were anodized followed by high temperature oxidation, the crystallinity and the photocurrent both increased.2. In 1 mol·L-1 NaOH solution, the Cu₂O/CuO particles （NPS） double-layer structure was obtained; In 3.0 mol·L-1 and 5 mol·L-1 NaOH solution, the Cu₂O/CuO nano flake double-layer structure can be obtained; And in 8 mol·L-1 and 10.0 mol·L-NaOH solution, granular polyhedral Cu₂O can be obtained. In 3.0 mol·L-1 NaOH solution, samples obtained have the maximum photocurrent. This film on the surface of the sample contained Cu₂O/CuO double-layer structure withnano scale CuO on the outside which was conducive to the separation of light absorption and photo carrier. The formation of nano scale CuO may be result of Cu （OH）₂ hydrolysis. The necessary factors in the formation of nano CuO with constant current anodic oxidation process was the formation of Cu₂O dense cover.3. In 5.0 mol·L-1 NaOH solution with the temperature of 30 and 40℃, CuO nano granular aggregates was obtained; At the temperature between 50 and 70℃, nano scale CuO was obtained; At the temperature of 80℃, granular polyhedron Cu₂O was obtained. At a temperature of 55℃, the sample obtained has the maximum photocurrent. CuO nano thin film was conducive to the light absorption and the separation of photogenerated carrier. The formation of nano scale CuO may be results of Cu （OH） 2 hydrolysis. The temperature was above or below 50℃, there were different reactions. With the increase of temperature,the formation of Cu₂O passivation film was more difficult.The transition time increases, so it was unable to form a complete and compact passivation film.4. Electrochemical cathodic reduction and glucose reduction can prepare Cu₂O/CUO composite oxide on the basis of CuO nano sheets. The films glucose reduced shown better photoelectrochemical properties.