Preparation Of Spinel Structure AB₂X₄ Material And Their Application In Magnetic Property And Photovoltaic Effect

Spinel cobaltates have excellent magnetic,thermal stability,electrochemical properties and catalytic activity etc.,which are widely applied in many areas,such as information,energy and medical science.All of these are attributed to the functional diversity caused by various composition and structure of the spinel compounds.Spinel compounds,such as NiCo2O4,ZnCo2O4,NiCo2S4 and ZnCo2S4,were successfully synthesized by hydrothermal method in this work,which were systematically studied by X-ray diffraction(XRD),Raman,scanning electron microscope(SEM),transmission electron microscope(TEM).We explored the magnetism performance of the spinel NiCo2O4 and ZnCo2O4 at room temperature,and the electrochemical property of NiCo2S4 and ZnC02S4 as the counter electrode in DSSCs.Various electrochemical tests proved the spinel NiCo2S4 and ZnC02S4 replacing Pt as the counter electrode in DSSCs has great potential in the future.The main content of this paper are as follows:1.We successfully prepared the spinel NiCo2O4 samples with different morphologies by controlling the hydrothermal temperature.The structure and morphology of the samples were characterized by many means,such as XRD,Raman,SEM,TEM,and the magnetic properties of samples were tested by the VSM at room temperature.With the increase of hydrothermal temperature(120 °C to 160 °C and then to 200 ?),the morphology of obtained samples transformed from spongy nanosphere to ellipse-like,then to peanut-like structure and an effective blue shifting of Raman spectroscopy occurred.The blue shifting of Raman spectroscopy is attributed to small size effect,which can be verified by SEM and TEM image,namely the spongy nanosphere obtained at 120 °C is composed of numerous small particles.The magnetic measurements indicated that the materials transform from paramagnetic to ferromagnetic with the increase of hydrothermal temperature.Similarly,we also successfully prepared the spinel NiCo2S4 samples with the different morphologies by ion exchange method.In the same test conditions,the NiCo2S4 spongy nanospheres were equipped with the CE of DSSCs and obtained highest PCE than others.They also show similar electrochemical performance with Pt due to the large surface area and more reaction sites of the spongy nanospheres,which proves that the different morphologies of samples have a great influence on their photoelectric conversion efficiency.2.We successfully prepared the spinel ZnCo2O4 nanospheres by a hydrothermal-calcination method.The influence about the heat treatment condition(heating rate)to morphology and magnetic property of ZnCo2O4 sample was investigated.The structure and morphology of the samples were characterized by XRD,Raman,SEM,TEM,and the magnetic properties of samples were tested by the VSM at room temperature(magnetic field range from 1 to 10000 Oe).It is found that the magnetic properties of the sample change with the increase of heating rate(1 °C/min,4 °C/min and 10 °C/min).The samples obtained at 1 °C/min in heating rate show weakly ferromagnetic and the obtained materials transform from weak ferromagnetic to paramagnetic with the increase of heating rate.Then,the spinel ZnCo2S4 samples were successfully prepared by ion exchange method,and the morphology(nanosheet,nanoflower)of spinel ZnC02S4 samples can be controlled by changing reaction time,which was used as the counter electrode in DSSCs.In the same test conditions,the DSSCs equipped with ZnC02S4 nanoflower as counter electrode obtained a higher PCE(6.41%)than Pt(6.26%).This is due to the special 3D spatial structure of ZnCo2S4 nanoflowers,which has the large surface area and more reaction sites.Therefore,the morphology of ZnC02S4 samples has a great influence on their photoelectric conversion efficiency.