| As an inexhaustible renewable clean energy source,hydrogen has attracted great attention in recent years.In addition,hydrogen also has important applications in other fields,for example,metallurgical plants need to use H2 as a reducing agent to smelt metal,and the power plant's engine needs to use hydrogen as a coolant.However,hydrogen gas is a colorless,odorless,flammable and explosive gas.The molecule is very small and leaks easily.At present,hydrogen gas detection is mainly a semi-conductor type sensor.It is based on a hydrogen-sensitive material that causes resistance or voltage signals after it encounters hydrogen.Changes in the detection of hydrogen concentration usually require an external electrical signal processor,and in the presence of electromagnetic interference,the output signal will be distorted,and it may also cause electrical sparks that can lead to potential safety incidents.Therefore,it is of great practical significance to develop sensitive materials that respond quickly to hydrogen and have high sensitivity and non-electrical response.In this paper,MoO3 nanowire paper was prepared by hydrothermal method and self-assembly processes,and precious metal(Pd and Pt)nanoparticles were deposited on the surface of MoO3 nanowires by ultraviolet light reduction method to study the effect of noble metal modified MoO3 nanowire paper on room temperature.Discoloration properties,color change kinetics and discoloration mechanisms.Get the following conclusions:1.MoO3 nanowires with a length of?1 mm and a diameter of?100 ?m were synthesized by a hydrothermal method.A4 sized MoO3 nanowire paper was prepared by self-processing and then reduced by ultraviolet light(wavelength:254 nm,illumination).5h)Modification of noble metal Pd and Pt nanoparticles on the surface of nanowire paper.The results show that the noble metal modification has almost no effect on the phase and morphology of the MoO3 nanowires.The Pd and Pt nanoparticles uniformly adhere to the surface of the Mo03 nanowires,and the size of the Pd nanoparticles is 5 im to 10 nm.The Pt nanoparticles size from 50 nm to 100 nm.2.The Pd-modified MoO3 nanowire paper is discolored significantly in a concentration of 0.1%to 100%hydrogen atmosphere.At a concentration of 0.1%H2,the Pd-modified Mo03 nanowires exhibit a dark blue color,and the color change only takes 65 s,while the Pt-modified MoO3 nanowires require 120 s;as the hydrogen concentration increases,the nanowires paper discoloration time showed a decreasing trend.-When the hydrogen concentration was 100%,the Pd-modified MoO3 nanowire paper had a color rendering time of 3 s,while the Pt-modified MoO3 nanowire paper required 30 s;and at the same hydrogen concentration and the same Under the reaction time,Pd-modified MoO3 nanowire paper has a deeper color than Pt.In addition,the color change and color fading of the two nanowire papers were almost unchanged after 12 times,indicating that the nanowire paper has good repeatability.3.Reflectance spectroscopy studies show that the Pd-modified MoO3 nanowire papers reflect the relationship between the intensity of reflection and the time to meet the exponential decay kinetics;Fourier transform infrared spectroscopy,Raman spectroscopy and X-ray diffraction spectra to study the color of the Pd The phase and structure of the modified nanowire paper were changed.The discoloration had almost no effect on the overall structure and properties of the MoO3 nanowires.The valence changes of the Mo and O elements were analyzed by XPS spectra.The results show that the Mo6+ is in the process of discoloration.It is reduced to Mo5+,and the oxygen absorption increases.This shows that the lattice oxygen in MoO3 combines with hydrogen to form water in the event of hydrogen,and it spreads out to generate oxygen vacancies to form the color center,which leads to the change of color. |
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