| Hydrogen is renewable and clean new energy. However, one of the major bottlenecks in the applications of hydrogen energy is a lack of reliable and inexpensive hydrogen sensors that can detect possible hydrogen leakage. One of the key issues in developing hydrogen sensors is the synthesis of hydrogen sensitive materials and the preparation of sensitive components. V2O5 thin film is an important gas sensitive material. But hydrogen sensing properties of V2O5/Pd thin films were rarely studied. In this thesis, V2O5/Pd films with different thickness were prepared on glass substrates and the end faces of multimode optic fibers with magnetron sputtering method. V2O5/Pd films were characterized with XRD, AFM, SEM and so on. Hydrogen sensing properties of V2O5/Pd films were tested using a UV-Vis spectrophotometer, the sensitivity of V2O5/Pd films to hydrogen gas was also studied through an optical fiber sensing system, and the sensitive mechanisms were discussed on basis of in situ Raman spectra. The main contents of this thesis and experimental results are as follows:(1) XRD data show that V2O5 and V2O5/Pd films prepared with magnetron sputtering method are amorphous, and the AFM images show that V2O5/Pd thin films possess low surface roughness.(2) V2O5/Pd films with different thickness were deposited on glass substrates, the sensitivity of V2O5 and V2O5/Pd films to hydrogen gas were studied by a UV-Vis spectrophotometer. The results indicate that V2O5 thin film has low sensitivity to hydrogen gas at room temperature and that the V2O5/Pd films are more sensitive to hydrogen gas. After exposed to hydrogen gas, obviously changes in the relative transmittance of the V2O5/Pd films can be observed. When the thickness of Pd thin film is constant, as the thickness of V2O5 thin film increases, the relative transmittance gradually increase; when the thickness of V2O5 thin film is constant, the relative transmittance also increase gradually. By testing the V2O5/Pd films with different thickness, the highest change in relative transmittance can be achieved with the V2O5 (280 nm)/Pd (30 nm) thin film. At the wavelength of 560 nm and 4% hydrogen/nitrogen, the change of the relative transmittance of the film is about 25%, and respondence of this film to 0.01% H2 can be observed. The results also show that there is a good linear relationship between the relative transmittance and hydrogen concentration in a certain hydrogen concentration range.(3) V2O5/Pd films with different thickness were coated on the end faces of multimode optic fibers, the sensitivity of V2O5/Pd films to hydrogen gas was also studied through an optical fiber sensing system. For the V2O5/Pd films, when the thickness of palladium film is 20 nm, different thicknesses of V2O5 thin films have an important effect on the reflected light intensity. When the V2O5 thickness of V2O5/Pd film increase, the response times of the sensor become longer, but the relative reflected light intensity gradually increase. When the V2O5 (280 nm)/Pd (20 nm) exposed to 4% H2, a change of 20% in relative reflected light intensity can be observed. However, for the V2O5 (40 nm)/Pd (20 nm) film, the relative reflected light intensity change only 3%. The results also show that the sensitivity of V2O5 thin film to hydrogen gas is significantly influenced by different catalysts coated onto the V2O5 thin films. The experimental results show that the catalyst effect of the Pd-Pt films is better than that of the Pd films.(4) The sensing mechanism of the V2O5/Pd thin films are discussed on basis of the in situ Raman spectra. The results suggest that Pd thin film mainly palys a role of catalyzer. The insertion of hydrogen atoms into the interlayers of V2O5 causes the transformation of V5+to V4+, and as a result, causes the changes in the transmitance of the films.
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