Construction Of Tungsten Oxide Based Composite Gas Sensors With Porous Structure

Tungsten oxide(W03)is a very promising gas sensing material,how to achieve its high performance and specificity in detecting a gas has been the difficulties and hot spots of the scientific research.The composition and structure of the materials are both key factors in determining their gas sensing properties.The noble metal elements(Pd,Au)are good chemical and electron sensitizers.The larger surface area of the three dimensional ordered macroporous structure(3DOM)can provide more active sites for the surface reaction;the interconnected macropores structure can provide a more favorable channel for the diffusion and transport of gas molecules.Although there are many studies on precious metal loading in the field of gas sensing applications,W03 composites with 3DOM structure have not been reported.In this paper,3DOM W03 nanomaterials were prepared by using a colloidal crystal templating method,and the Pd-loaded 3DOM W03 nanomaterials and Au-loaded 3DOM WO3 nanomaterials were prepared by in situ reduction method.The relationship between structural properties and gas sensing performance of the materials were established.The contents are as follows:1.The Pd-loaded 3DOM W03 nanomaterials were prepared and their gas response to 50 ppm hydrogen was tested.The results show that the Pd loading can significantly improve the response and selectivity of the 3DOM W03 materials to hydrogen.The response of the 3DOM Pd/W03(1-1)sample to 50 ppm hydrogen at the optimum operating temperature of 130 ? is as high as 382,which is 225 times of the pure 3DOM W03 sample.The sensor exhibits a rapid response(29 s)and recovery(15 s)as well as excellent hydrogen selectivity.Pd-loaded 3DOM W03 nanomaterials have an absolute advantage in detecing low concentrations of hydrogen.The results show that the synthesized sample has a highly ordered macroporous structure.The results show that the 3DOM Pd/W03(1-1)sample has the highest electron carrier concentration and the most structural defects.Pd-loaded 3DOM W03 nanomaterials significantly enhance the hydrogen-sensitive properties mainly due to the synergistic effect between the Pd sensitization and the structural defects.Pd nanoparticles are chemical and electron sensitizers for hydrogen detection,so all Pd-loaded 3DOM W03 samples exhibit more excellent hydrogen-sensitive properties than the pure 3DOM W03 sample;3DOM Pd/W03(1-1)sample has the most structural defects among all Pd-loaded 3DOM W03 samples,thus exhibiting the highest hydrogen response.2.The Au-loaded 3DOM W03 nanomaterials were prepared by in situ reduction method and their gas response to 100 ppm acetone was tested.The results show that the Au loading can improve the response and selectivity of the 3DOM W03 materials to acetone.The response of the 3DOM 1%Au/WO3 sample to 100 ppm acetone at the optimum operating temperature of 210 ? is as high as 201,which is close to 15 times of the response of the pure 3DOM WO3 sample.The sensor exhibits excellent acetone selectivity,repeatability and stability.Therefore,the Au-loaded 3DOM WO3 nanomaterials are ideal materials for achieving high performance detection of acetone.