Synthesis Of Porous Metal Oxides Nanomaterials With Application In Catalysis And Gas Sensing

In today's world,the production and living standards of human beings are constantly improving,but the environmental pollution that comes with it is becoming more and more serious,and air pollution is among the first.The burning of fossil fuels,the emission of automobile exhaust and volatilization of organic reagents used in building decoration will all produce toxic and harmful polluting gases,which will be threatened to human health when discharged into the atmosphere.Therefore,it is urgent to find materials that can efficiently and environmentally detect and process these gases.In recent years,the rapid development of nanomaterials has significantly improved the problem of air pollution.Nanomaterials have the advantages of large specific surface area,regular pore structure and many active sites due to their special physical and chemical characteristics and special structure on nanometer scale.They are widely used as catalytic materials,sensing materials,biomedical materials,etc.Among them,spinel nanomaterials,as gas-sensitive materials,have the advantages of low detection limit,high sensitivity,and good selectivity in the detection of volatile organic compounds,and have become current research hotspots.Microporous nanomaterials have been widely concerned in the treatment of nitrogen oxides in exhaust gas,not only overcome the shortcomings of toxic vanadium-based catalysts,narrow temperature windows,etc.,but also have the advantages of high activity and good hydrothermal stability.However,how to synthesize nanomaterials with new structures using simpler,environmentally friendly,green,efficient and inexpensive methods has become a current research hotspot.Aiming at the problem that the current nano material synthesis process is cumbersome and cannot be applied to actual production and life.In this paper,spinel-type NiCo₂O₄ nanomaterials and CHA-type microporous Cu-SSZ-13 nanomaterials are prepared by a simple,mild,and environmentally friendly one-step hydrothermal synthesis method.Their preparation methods,topography,composition,and the properties of detection and catalysis of toxic and harmful gases were systematically investigated.This paper mainly studied the following aspects:In the first part,this paper explored the optimal synthesis conditions,reaction temperature and time for one-step hydrothermal synthesis.Through experimental exploration,it was found that using polyethylene glycol 6000 as a surfactant and reacting at 160°C for 20 hours,nano-sheet-like NiCo-LDH precursors were synthesized,and then NiCo₂O₄ nano-mesoporous materials with different crystallinity,specific surface area and pore size were prepared by calcination at different temperatures.Their gas-sensitivity properties were investigated as gas-sensitive materials for the detection of volatile organic compound triethylamine.Among them,NiCo₂O₄ calcined at 500°C not only had a significant response to 10 ppm of triethylamine at 220°C,but also had the highest selectivity to triethylamine.In the second part,using green and environmentally-friendly synthesis method was used to form a Cu-TEPA structure directing agent by using the inexpensive and readily available template agent tetraethylenepentamine.The optimal reaction temperature was 140°C and the reaction was carried out for 4 days.The original Cu-SSZ-13 with high Cu content was prepared.In order to reduce the Cu content of the original sample,Cu-SSZ-13 with different morphologies,different specific surface areas and different pore sizes was prepared by ion exchange using 1 M NH₄NO₃ and 0.1 M HNO₃ solutions.The catalytic performance of the catalysts prepared under different exchange conditions in the selective catalytic reduction of NH₃ was investigated.Comparison of catalytic performance,Cu-SSZ-13 synthesized by us can achieve 100%conversion of nitrogen oxides at 125?after two nitric acid exchanged for 5 h.It can maintain95%conversion at a high temperature of 500?.