Preparation And Electrochemical Properties Of Transition Metal(Mn,Co,Mo,Fe) Oxide Matrix Composites

With the growing demand for clean and sustainable energy,the development of low-cost and high-efficiency energy technologies has received extensive research attention in recent years.The development of novel electrode materials with excellent electrochemical performance is a key issue to be solved in the field of electrochemical energy storage devices.Metal oxides and their composite materials,including transition metal oxides such as Mn,Co,Mo,and Fe due to their inherent activity,sufficient stability in an oxidizing electrochemical environment and much higher theoretical capacity than conventional graphite materials,have attracted much attention in clean energy such as metal-air batteries and lithium-ion batteries?LIBs?.The specific research content of this paper is as follows:?1?The precursor of the product was synthesized by a hydrothermal method,then the double metal oxide/graphene composite MnCo₂O₄-rGO was obtained through thermal decomposition technology,and its oxygen reduction reaction?ORR?and oxygen evolution reaction?OER?properties were studied.The results showed that the MnCo₂O₄-rGO nanocomposites exhibited superior ORR activity,showing a more positive onset potentials?0.89 V vs.RHE?,peak potential?0.72 V vs RHE?,and a much higher peak current density(2.58 mA cm^-2)than MnCo₂O₄(0.83 V,0.60 V and 1.32 mA cm^-2,respectively);The OER dynamics were evaluated with the corresponding Tafel plots.The slope of MnCo₂O₄-rGO was 106.9 mV dec^-1,better than pure MnCo₂O₄(130.0 mV dec^-1)and Pt/C(134.0 mV dec^-1).These results all indicate that the composites with graphene added have higher electrocatalytic activity and are closer to commercial Pt/C.?2?Precipitation method was used to synthesize the bimetallic precursor MnCo-MOF,and the double metal oxide MnCo₂O₄ was obtained by thermal decomposition technique.The electrochemical performance of the lithium-ion battery was studied by using it as the anode material.The results showed that the specific capacity of MnCo₂O₄ hollow microspheres was stable at 200 mAh g^-1 after 200 cycles at a current density of 100 mA g^-1.The excellent cycle stability is exhibited due to the high conductivity of the hollow microsphere structure and metal oxides?cobalt oxide,manganese oxide?,which facilitates rapid electron transfer.?3?The precursor of the product was synthesized by hydrothermal method,and the double metal oxide FeMo₃O₈ was obtained by thermal decomposition technique,and its ORR performance was studied.The results show that although compared with Pt/C(onset potential is 0.96 V,current density is-3.73 mA cm^-2 at voltage of 0.36 V),Fe₂Mo₃O₈exhibits slightly lower electrocatalytic activity?onset potential 0.89 V,current density is-1.76 mA cm^-22 at a voltage of 0.36 V?.However,the slope of the Tafel curve of Fe₂Mo₃O₈ is-164.0 mV dec^-1,which is better than the slope of Pt/C(-100.0 mV dec^-1).These results indicate that Fe₂Mo₃O₈ is a relatively good ORR electrocatalyst.?4?The precursor of the product was synthesized by hydrothermal method,and the polyanion compound Fe₂?MoO₄?₃ was obtained through thermal decomposition technology.The electrochemical performance of the lithium-ion battery was studied by using it as the anode material.The results show that under the current density of 100 mA g^-1,the specific capacity of the sample after calcination at 500 ^oC is about 579.2 mAh g^-1 after 200 cycles,and the specific capacity of the sample after calcining at 550 ^oC is 759.0 mAh g^-1.These results show that the cycle performance of the sample after calcination at 550 ^oC is better than that after calcination at 500 ^oC,further indicating that the calcining temperature has a great influence on the lithium-electric properties.