Fabrication And Hydrogen Sensing Characteristics Of Closely-spaced Palladium-nickel Alloy Nanoparticle Arrays

In a certain extent, metal alloy nanoparticles can improve some physical and chemical properties of pure metal nanoparticles. Pd nanoparticle arrays have hydrogen absorption response characteristics, but when Pd nanoparticle are mixed with other metal nanoparticles, its hydrogen absorption response characteristics will be improved. In this thesis, we prepared Pd/Ni alloy nanoparticle arrays to study its hydrogen absorption response characteristics.Pd/Ni alloy nanoparticle arrays are prepared by using magnetron plasma gas aggregation cluster beam system. The Pd/Ni alloy nanoparticles have uniform size and high crystallinity. With the increase of Ni content in the samples, the average grain size of alloy nanoparticles increases gradually.We studied the form of the binary alloy in the Pd/Ni alloy nanoparticles. We found that the structure in the prepared samples existed in the form of mixed pattern. What’s more, with the increase of Ni content in the samples, the surface spacing of (111) increases gradually.The incorporation of Ni into the Pd nanoparticles largely change the α-β phase transition behavior. For different components of the Pd/Ni alloy nanoparticles, the rule of its hydrogen absorption response characteristics is the same. Three typical response region were observed, which is associated with three phase regions of PdHx:α phase region, α to β phase transition region and P phase region. The sensor shows the highest growth in α to β phase transition region, due to the expansion of the Pd lattice induced by the α to β phase transition of PdHx, which is much larger than that induced by the hydrogen absorption in the a phase or the β phase. When the content of Ni is over 60%,the sample shows no hydrogen absorption response characteristics.With the increase of Ni content, the value of ΔG/GO presents a trend of increasing first and then decreasing for the same pressure in α-PdHx and shows a trend of decreasing first and then increasing for the same pressure in β-PdHx phase. Taking into consideration various factors, Pd75Ni25 shows the best performance in the all samples.We compared the hydrogen absorption response characteristics of Pd/Ni alloy nanoparticle arrays and Pd nanoparticle arrays. Research shows that the linear response region can even be extended to as high as 2kPa, which will be beneficial to measure the low-pressure hydrogen. Pd/Ni alloy nanoparticles have a higher resolution when the concentration of hydrogen exceeds 4% in air than Pd nanoparticles. They can both give a fast response to hydrogen. The response is slowed down in the α to β phase transition area. From the overall trend, the response time of Pd75Ni25 nanoparticles is the shortest between all Pd/Ni alloy nanoparticles and faster than Pd nanoparticles.We also tested the stability of the sensor. With the increase of hydrogen absorption/desorption cycle, the conductance value can return to the initial value after the desorption of hydrogen. The sensor shows good stability.