Synthesis And Catalytic Properties Of Co,Fe And Zn Based Metal Oxide Composites

Based on the research of photocatalytic degradation and electrocatalytic properties of cobalt,iron and zinc-based metal oxide composites,ZnO-ZnFe₂O₄nanomaterials were prepared by condensation reflux method.Graphene quantum dot modified ZnO-ZnFe2O4 composites were prepared by charge-induced assembly method.Using cobalt hexahydrate as the cobalt source,ZnxCo_1-x-x Fe₂O₄ composites were successfully prepared with different Zn/Co ratios.The P element was doped to the Zn_0.5Co_0.5Fe₂O₄ composite by a simple heat treatment method.The main conclusion are as follows:?1?The graphene quantum dot modified ZnO-ZnFe₂O₄ composite prepared by condensation reflow method and charge-induced assembly method has enhanced light absorption efficiency from the smaller forbidden band width and high charge transfer efficiency and active sites number from the appropriate amount of graphene quantum dots,so it has excellent photocatalytic properties.In the MB photocatalytic degradation test,the degradation properties of 1GQD/ZnO-ZnFe2O4 were respectively10 and 4 times than ZnO and ZnO-Zn Fe₂O₄.In the photocatalytic degradation of tetracycline hydrochloride,the degradation efficiency of 1GQD/ZnO-ZnFe₂O₄ was more than 90%within 30 minutes.?2?Co₃O₄ nanocrystalline materials with different sizes and morphologies were successfully synthesized by simply controlling the concentration and type of metal precursors.Compared with Cubic-18 and Triangular-9,Cubic-9 Co₃O₄ nanomaterial shows higher ultimate current density?5.5 mA/cm²?,corrected half-wave potential?0.48V vsRHE?and electron transfer process closer to 4?transfer electron number is3.68-3.79?in 0.1M KOH alkaline solution due to their larger specific surface area and high oxygen vacancy concentration..In addition,Cubic-9 type Co₃O₄ nanomaterial exhibits superior stability and resistance to methanol oxidation compared to commercial Pt/C catalysts.?3?The Zn_xCo_1-xFe₂O₄ composite was prepared by using terephthalic acid as an organic ligand and cobalt nitrate hexahydrate as a cobalt source.The OER and HER properties of ZnFe₂O₄?Zn_0.7Co_0.3Fe₂O₄?Zn_0.5Co_0.5Fe₂O₄?Zn_0.3Co_0.7Fe₂O₄ and CoFe₂O₄ were investigated in 1M KOH alkaline solution.With the decrease of Zn/Co ratio,the limiting current density tends to increase first and then decrease,and the overpotential??10?also shows a trend of decreasing first and then increasing.When the Zn/Co ratio is 1,the Zn_0.5Co_0.5Fe₂O₄ composite exhibits excellent OER and HER properties,with the highest limiting current density,the lowest overpotential?OER:305 mV,HER:331 mV?and minimum Tafel slope?OER:131 mV/Dec,177 mV/Dec?.The stability test results show that the material has good electrocatalytic OER stability and poor electrocatalytic HER stability,and the overpotential increases by about 300mV during the stability test.?4?The P-Zn_0.5Co_0.5Fe₂O₄ composite was prepared by doping the P element by heat treatment method.The electrocatalytic OER and HER properties of Zn_0.5Co_0.5Fe₂O₄and P-Zn_0.5Co_0.5Fe₂O₄ composites were compared in 1M KOH alkaline solution,it was found that P element doping can significantly improve the catalytic activity of the materials.Compared with Zn_0.5Co_0.5Fe₂O_4,the P-Zn_0.5Co_0.5Fe₂O₄ has higher oxygen vacancy concentration and electrolyzed water active sites?ECSA test results shows that the electrochemical specific surface area of P-doped materials is increased by89%.?,exhibiting greater limiting current density,smaller overpotential?OER:277mV,HER:191 mV?and smaller Tafel slope?OER:44 mV/Dec,46 mV/Dec?.The stability test result shows that the P-Zn_0.5Co_0.5Fe₂O₄ composite has excellent electrocatalytic OER and HER stability.