Ag含量对钙钛矿型La-Ca-Co-O氧还原催化剂电催化特性的影响

摘要

为了提高钙钛矿型La-Ca-Co-O的氧还原催化性能,采用柠檬酸辅助的溶胶-凝胶法制备添加AgNO3的Lao0.4Ca0.6CoO3粉体.采用 XRD、SEM和EDAX分析手段研究凝胶在700℃焙烧后的产物,通过电位阶跃技术测定定不同Ag含量粉体的电化学有效表面积.通过线性扫描伏安法测定催化剂粉体催化氧还原反应的极化特性;通 过Tafel技术测定其催化氧还原反应的交换电流密度.采用粉末压片和直流电路测定催化剂的表观电导率.结果表明:Ag+固溶入La0.4Ca0.6CoO3晶格导致晶格膨胀;添加AgNO3的粉体中还有单质Ag颗粒析出.在La0.4Ca0.6CoO3中引入Ag+可显著提高其对氧还原的电催化活性,在Ag含量为2%时,催化氧还原的交换电流密度达到最大值0.2988 A/m2;而La0.4Ca0.6CoO3的表观电导率随着Ag含量增加而增大.%In order to improve electrocatalytic property to oxygen reducing, the La0.4Ca0.6CoO3 powders with AgNO3 addition were prepared through citric acid sol-gel method.After being annealed at 700 ℃, the products were studied by XRD, SEM and EDAX.The electrochemical effective area of powders was determined through CA technology.The electrochemical polarization of powder for catalyzing oxygen reduction was investigated by LSV technology.The exchange current density was measured through Tafel technology.The apparent conductance of powder pellet was measured by DC method.The result shows that the silver ion dissolves into La0.4Ca0.6CoO3 lattice and brings on the latter expanding, the metal silver particles are affirmed in the microstructure.The electrocatalysis activity to oxygen reducing can be improved remarkably by introducing silver ion into La0.4Ca0.6CoO3 lattice.The maximum exchange current density,0.298 8 A/m2, can be obtained when the silver content (mass fraction) is 2％.In addition, the apparent conductance increases with increasing the silver content.