Preparation,Structure And Photocatalytic Performance Of Porous Molybdenum Oxide

Porous photocatalyst is a new functional material with good adsorption properties and photocatalytic properties.Compared with the traditional photocatalyst,catalyst with high specific surface area of porous structure,is beneficial to the catalyst to absorb pollutants and concentration,and high specific surface area has a high density of the active center,accelerate the photocatalytic reaction rate.The porous structure makes the incident light to reflect and scatter in the hole to improve the light adsorption rate.At present,most of the preparation of porous photocatalyst are confined to hydrothermal method,which are costly,long period and contaminate the environment.Based on the principle of freeze drying and solution combustion synthesis,the porous MoO3 photocatalyst was prepared by using freeze-drying method and spray freeze-drying method,respectively.The effect of calcination temperature on the crystal phase,pore structure and photocatalytic properties of MoO3 was studied.A variety of pore morphology MoO3 microspheres and their composite materials were prepared by adding surfactants,cryogenic support agents and Ti O2.In addition,amorphous porous MoO2 microspheres were synthesized by ultrasonic spray solution combustion with citric acid as fuel,and the reaction process,pore formation mechanism and photocatalytic properties of the products were studied.The results showed that the porous MoO3 photocatalyst was obtained by freezedrying and subsequent thermal treatment.It was found that the calcined ammonium molybdate was completely decomposed into MoO3 at temperatures above 300°C,but the product had hexagonal and orthorhombic phase at 300°C,and completely transformed to orthorhombic phase at temperatures above 400 °C.With the increase of calcination temperature,the photocatalytic activity of MoO3 was gradually reduced.Among them,the overall performance of MoO3 prepared at 400°C was the best: the adsorption rate was 53.1% in the dark treatment for 30 min,and the photocatalytic rate was 99.2%.After four cycles,the photocatalytic efficiency can still reach 98.1%.The solution is sprayed directly into liquid nitrogen,and after freeze-drying a photocatalyst microsphere with porous structure is successful synthesized.Adding surfactant and freezing support agent to the solution can produce microsphere particles with different pore shapes;The microspheres with hierarchical pore structure can be prepared by adding dichloromethane oil solvent;Change the spray distance could prepared porous microspheres with different sizes;Nano Ti O2 was added to prepare MoO3-Ti O2 heterojunction.The results show that the prepared porous catalyst has good photocatalytic performance for methylene blue and rhodamine B,and photocatalytic efficiency up to 90%.So,spray-freeze-drying is a controllable preparation method.According to the principle of combustion synthesis solution,to improve the traditional process,the ultrasonic spray solution combustion synthesis method was invented.As the preparation temperature increased,MoO2 gradually changed into a crystal and was oxidized to MoO3,and the adsorption and photocatalytic performance gradually decreased.