| Using the photoelectric chemical properties of semiconductor materials to achieve the decomposition of water into hydrogen is a promising technology to realize the conversion and storage of solar energy, which can also completely get rid of the current reliance on fossil fuels and to achieve thermal equilibrium of our planet. However, the efficiency of the anode material limits the technology breakthrough in this area. WO3, a typical n-type semiconductor with photoelectric catalysis effect, could produce high photocurrent under exposure of visible light. WO3 could make use of sunlight more efficient than TiO2 due to its band gap of 2.6 eV, which makes it one of the most promising materials to realize the decomposition of water into hydrogen by its photoelectric chemical properties. In addition, W has multiple changeable valence states, and oxygen vacancy shows different contents in WO3. They both contribute to chromism effect in this material. The principle is based on the intercalation and release of positive ions and electrons when there is an excitation. It has been reported that photocatalysis material has been coupled into WO3, and the storage for photo-generated electrons has been achieved with intercalation effect. In the Study of photoelectric chemical properties of WO3, the photocurrent is often decreased as time changes, which requires further research to clarify the mechanism of the process and to distinguish the water oxidation reaction WO3 surface currents.In this experiment, WO3 thin film with nanostructures is fabricated on the surface of W by electrochemical anodizing. Detailed analysis about features with different technological parameters in fabrication process is discussed. Crystal structures of WO3 was studied through XRD, feature and composition analysis was carried out with SEM and XPS, spectral absorption properties were investigated by UV-Vis, and photoelectrochemistry properties and in situ energy storage properties were tested by electrochemical workstation.The main results are as fowllows:1?During the anodic oxidation process, the composition of the electrolyte and applied voltage have a great influence on generating of nanoporous WO3 film. As the concentration of F ion and the applied voltage increase, the nanostructure will appear first and eventually being corroded. In this work, ordered nanoporous arrays of tungsten oxide on the tungsten foil was prepared by regulating the parameters of anodic oxidation. Moreover, the absorption of WO3 for visible light has been improved significantly after annealing because of the generation of W4+and W5+ions.2?In this work, the linear sweep voltammetry curves of WO3 indicates there are two oxidation peaks under 0.4 V and 0.8 V, and the photocurrent density increases when time increases. This occurs as a result of the high specific surface area of WO3 flim, improvement of the absorption of visible light caused by the generation of W4+ and W5+ ions, and a large number of carriers produced. Some of the electronics were used in photoelectric chemical reaction. At the same time, the rest of the electrons were used in intercalation reaction with the diffusion of Na ions in the solution, and tungsten bronze was formed as a lower resistivity material, and caused the increase of the current density. The current density of tested WO3 film is not suddenly dropped to the initial value but rather a gradual decrease when turn off the light. This is due to the discharge of the electron which is stored under PEC measurement.The discharged electrons also can used for photoelectrocatalysis as the photogenerated electrons.3?TiO2 coating on WO3 surface as composite-electrolyte is useful to improve the photoelectric conversion efficiency. However, the existence of TiO2 is hindered the diffusion of Na ion inside the WO3 film and caused the difficulty to form NaxWO3. Therefore, the property of the energy store is reduced. |
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