Synthesis And Electrochemical Performance Of Lanthanum-strontium-manganese Perovskite Catalysts

Metal-air batteries are characterized by their high energy density,low cost,safety and environmental friendliness,which are expected to be applied to emerging electrification and energy storage.Metal-air batteries generally use Pt as the electrocatalysts for oxygen reduction,but Pt is expensive and has poor stability.These disadvantages show serious implications for practical application of metal-air batteries.In recent years,it has been found that perovskite has many advantages,such as high catalytic activity,variety and low cost.It is expected to replace Pt as electrocatalysts for metal-air batteries.Previous studies have shown that La_0.8Sr_0.2MnO_3-δhas excellent catalytic activity for ORR（Oxygen reaction reduction）.However,the perovskite catalyst prepared by traditional method shows limited surface area and thus its poor oxygen reduction activity which needs futher improved,Therefore advanced preparation methods have been adopted to alleviate these critical issues.In this thesis,layered porous(La_0.8Sr_0.2)_0.95MnO_3-δwas prepared by sol-gel method using PVP（Polyvinyl pyrrolidone）as complexing agent,and one-dimensional porous La_0.8Sr_0.2MnO_3-δnanorods were prepared by electrospinning.The main results are listed as follows:（1）Layered porous(La_0.8Sr_0.2)_0.95Mn O_3-δelecrocatalyst was successfully prepared by sol-gel method using PVP as complexing agent.The optimal calcination temperature is determined to be 600℃.The obatined layered porous(La_0.8Sr_0.2)_0.95MnO_3-δhas large specific surface area of 15.99 m² g^-1,high ORR activity with an onset potential of⁰.90 V and a limiting current density of⁵.61 mA cm^-22 at 1600 rpm,as well as high charge-storage performance of 101.19 F g^-1 at 10mV s^-1.The prepared perovskite can not only be used as electrocatalysts for metal-air batteries,but also can be applied to supercapacitors.（2）One-dimensional porous La_0.8Sr_0.2MnO_3-δnanorods were successfully prepared by electrospinning and sintering at 650℃.The specific surface area of one-dimensional porous La_0.8Sr_0.2MnO_3-δnanorods is 30.27 m² g^-1,which is 9 times higher than that prepared by tradition sol-gel method.The ORR activity of the one-dimensional porous La_0.8Sr_0.2MnO_3-δnanorods is attractive with an initial potential of⁰.91 V and a current limit of⁵.62 mA cm^-2.The current density can still reach⁵.07 m A cm^-2 without the addition of carbon as conductive support.The ORR activity stays stable after 1000 cycles of cyclic voltammetry.Therefore specific surface area and ORR activity is greatly improved by electrospinning.The obtained one-dimensional porous La_0.8Sr_0.2Mn O_3-δnanorods are also expected to replace Pt as electrocatalysts for metal-air batteries.In summary,we have successfully prepared two kinds of electrocatalysts with excellent electrochemical performance by optimizing the preparation method.The applied methods are promising for developing efficient and stable perovskite electrocatalysts for pratical application.