Study On Hydrogen Sensing Performance Based On Pd And Pt Nanowires At Room Temperature

Palladium（Pd）and platinum（Pt）are widely used in the field of catalysis and sensing,and have been practically used in H₂sensors.However,when Pd film and Pt film are used as sensitive materials,their hydrogen sensing performance are poor and cannot meet the actual needs.Nanowires possess a relatively high specific surface area,which can be effective improve the hydrogen sensing performance and material utilization of H₂ sensors.Hence,hydrogen sensors based on single Pd and Pt nanowires are prepared using photolithography and electron beam exposure lithography,and room temperature hydrogen sensing performance and its mechanism are studied as follows:1.The hydrogen sensors based on a single Pd nanowire are constructed on Si substrates by photolithography and electron beam lithography.The results show that Pd nanowires significantly improve the response sensitivity at room temperature.When the Pd nanowires are thick（>20 nm）,the resistance of the Pd nanowires increases in the H₂ environment,and the response sensitivity is about 1%when the concentration of H₂ is 0.1%.The surface of Pd adsorbs and cleaves H₂ after the reaction with H₂,and then proton hydrogen gradually diffuses into the body of Pd,generating Pd Hx exhibits a block-like performance,so its resistance becomes larger.And when the thickness of Pd nanowires is thin（<20 nm）,the resistance in H₂environment becomes smaller,the response sensitivity is significantly improved,the maximum can reach 5.3%at 0.1%H₂ concentration.Due to the significant surface effect,H replaces the original O adsorbed on the Pd surface,resulting in weaker surface electron scattering,thereby the overall resistance decreases.2.Single Pt nanowires are prepared by photolithography and electron beam lithography,and the hydrogen sensitivity of the nanowires at room temperature is studied.The results show that the sensitivity of the single Pt nanowire is 8.5%at 0.1%H₂ concentration,and the response time is 10 s.The resistance of Pt nanowires decreases,which is mainly due to the reduction of surface electron scattering caused by H instead of O on the surface of Pt.3.Increasing the grain boundary defects on the nanowires by bombing Pt nanowires with gallium（Ga）ion irradiation technology.The study finds that with the increase of Ga ion irradiation,the hydrogen sensitive reaction of the nanowires gradually weaken until it becomes 0,and the response is getting slower.When Pt with a large number of grain boundary defects reacts with H₂,there are not only surface reaction,but also a large amount of H is adsorbed on the grain boundary,internal electron scattering is enhanced,and its resistance increases.4.The Pt nanowire arrays are deposited using Ga ion induced deposition technology,and the H₂ sensor is constructed and tested.The results show that their resistance increase in the H₂ environment,the response sensitivity is about 14.1%when the concentration of H₂ is 0.1%,.In addition,the microstructure analysis shows that the grain diameters are about 3 nm,and there are a large number of grain boundary defects inside.It is proved that when the defects（grain boundaries）of Pt nanowires increase,the grain boundary defects adsorb a large amount of H（increased resistance）to dominate the hydrogen sensitive reaction of Pt nanowires.