Preparation And(Photo) Electrochemical Properties Of Metal Oxide Semiconductor Materials

Metal oxide semiconductor materials have been widely used in fields of electrochemical sensors and photocatalysis for their unique optical,electrochemical and magnetic properties.During the electrochemical processes,the activities of chemicals absorbed on the electrode and transportation of charges would be the constraints that limit the performances of the materials.Thus,the investigation of highly active surface and efficient charge separation and transport are important for improving the electrochemical sensors and photocatalytic performance.In the case,this study aimed at designing the surface and bulk structure ?-Fe2O3 single crystal and preparing the orientated ?-Fe2O3 films and the CaFe2O4/ZnFe2O4 composite photocatalyst with p-n junction.The alignment of single crystal ?-Fe2O3 along the direction of good conductivity will reduce the resistance for electron transport.The specific exposed facets will improve the adsorption of chemicals,and then enhance the electrochemical sensing performance.While,the photogenerated charges can be separated efficiently by p-n junction structure,which will increase the photocatalytic activity.The main results are as follows:(1)The synthesized ?-Fe2O3 single crystals were used to prepared films by its magnetic anisotropy.The ?-Fe2O3 films with[110]orientation,[001]orientation and random-orientation were prepared by drop-casting method in an external magnetic field.The results showed that the conductivity of the ?-Fe2O3 film was related to the orientations,the[110]orientation was the best and[001]orientation was the worst.The influence of exposing different crystal facets of ?-Fe2O3 were also studied on electrochemical sensor performance by detecting the nitrite.The order of electrocatalytic activity of the exposing facts was(110)>(001)>(012),which was due to the facet-dependent adsorption ability to nitrite ions.This study proved that the electrochemical properties of the sensor response can be improved not only by enlarging the specific surface area of electrode material,but also by taking the advantage specific exposed crystal facets,which will be a new method for the preparation of efficient electrochemical sensors.(2)CaFe2O4/ZnFe2O4 composite photocatalyst with porous structure was successfully prepared by cation exchange reaction.The separation and transportation of photogenerated charges can be promoted by the internal field,which was formed by the p-n junction of CaFe2O4 and ZnFe2O4.The proportion of CaFe2O4 and ZnFe2O4 can be adjusted by cation exchange reaction temperature,reaction time and other parameters.In the photocatalytic degradation of methylene blue,CaFe2O4/ZnFe2O4 composite photocatalyst showed higher catalytic activity than any single photocatalyst for the promoted the separation of electrons and holes due to the p-n junction structure.The porous structure formed by cation exchange reaction increased the specific surface area of the photocatalyst,which also contribute to the improved photocatalytic activity.