Study On The Hydrothermal Growth Of Nb₂O₅ Nanorod Arrays And Their Characterizations

Hydrogen(H2)gas has been intensively investigated recently as a renewable,efficient,and clean energy source that can replace petroleum for different applications.However,hydrogen is flammable and explosive when its concentration exceeds 4%in air.Accurate and fast detection of H2 is therefore necessary for the extensive adoption of hydrogen use in energy production.Semiconductor metal oxide-based hydrogen sensors have attracted great attention over several decades due to their high sensitivity,low cost,fabrication ease and good compatibility to silicon microfabrication.Nb2O5 has a very excellent ability of decomposition and absorption of hydrogen.In this paper,the growth of Nb2O5 nanorod arrays is studied by the hydrothermal method;we also studied the change of phase morphology of Nb2O5 nanorod arrays by the conditions of the hydrothermal growth,and got the hydrothermal growth mechanism of Nb2O5 nanorod arrays.Finally we studied the optical properties of Nb2O5 nanorod arrays and sensitivity to hydrogen at room temperature.1?The Nb2O5 nanorod arrays of hexagonal phase were prepared by the hydrothermal method with H2O2 as oxidizer and NH4F as mineralizer respectively.We studied the change in the phase and morphology of product with hydrothermal temperature,concentrations of NH4F and H2O2 and reaction time,found that the relative peak intensity of Nb2O5 to Nb would increase gradually by the rise of temperature of hydrothermal,concentrations of NH4F and hydrothermal time.In addition,the rise of temperature could make nanorods thinner and longer,also could make the distribution of nanorods sparse.the increase of concentrations of NH4F could promote the epitaxial growth of Nb2O5 nanorods.The best proportion of H2O2 to H20 is 1:1.2?The growth of Nb2O5 nanorod arrays could be divided into the following processes.In the initial stage,metal Nb was oxidized to form Nb2O5 nanoparticles as the buffer layer during the subsequent growth.Then the oriented growth of Nb2O5 nanorods started to dominate that leaded to the increase of the aspect ratio of Nb2O5 nanorods.Finally,the nanorods became dense by the lateral growth of it,at the same time the new nucleation occurred and the aggregation growth started to dominate.3?The Nb2O5 nanorod arrays had an excitation peak in 379 nm at the low temperature,we could infer that the band-gap of Nb2O5 nanorod arrays was 3.3eV.The emission peaks in 456 nm exciated by the light of 379 nm were from the excitation between the conduction band and the acceptor while the emission peaks in 490 nm exciated by the same light were from the excitation between the donor and the acceptor.4.The Nb2O5 nanorod arrays had good sensitivity to hydrogen at room temperature.The sensitivity was up to 86.2%and the response time was about 10s.The sensitivity of Nb2O5 nanorod arrays was influenced by the concentrations of NH4F.The highest concentrations of NH4F could lead to the best sensitivity.Because the specific surface area of the Nb2O5 nanorod arrays would be larger while the concentration of NH4F was higher,and it could accelerate the speed of decomposition and absorption of hydrogen.