| 초록 |
The Hydrogen evolution via water splitting in the photo-electrochemical cells is an environmentally familiar technology. Recently a few groups have been studied dual photoelectrode system which is consisted of the n-type semiconductor photoanode for water oxidation reaction and the p-type semiconductor photocathode for water reduction reaction. This system is having several advantages such as a without external bias for effective operation, a reducing on-set potential, a selectivity of reaction, a replacing counter electrode instead of Pt metal can reduce a cost compared with formal system which is semiconductor/metal which is specifically Pt. Up to now, mainly n-type semiconductor photoanodes are studying such as TiO2, ZnO, WO3 Hematite and so on. Because of the oxygen vacancies which are easily made during synthesis processes of metal oxide photocatlysts suppressed becoming a p-type semiconductor. Therefore, development of PEC cell that does not require external bias is critical for efficiently converting the solar energy. The CuO can be utilized as a p-type semiconductor due to its narrow bandgap and suitable band configuration. However, it shows highly self-oxidation reaction by photo-excited electrons due to its reducing standard potential is located within its band gap. Thus self-oxidation of CuO reduce a faradaic efficiency, not to mention. In this work, we demonstrate fabrication and analysis of TiO2 and ZnO as a passivation layer coated CuO nanosheets on FTO glass substrate as a p-type photoelectrode. Morphology and microstructural properties of the CuO and TiO2 electrodes were examined by FE-SEM, XRD and HRTEM analysis. Photocatalytic properties of both electrodes were confirmed by measuring photocurrents responses under both white and visible light illumination. The effects of passivation layer were also examined by measuring pulsed photocurrent versus elapsed time curve. By increasing thickness of TiO2, ZnO and TiO2/ZnO films, stability of CuO electrode were increased. Furthermore, hydrogen evolution tests will be confirmed by using PEC cell with passivation layer coated CuO and TiO2 electrodes that can generate hydrogen and oxygen gases without external bias. |
