钙钛矿型LaMnO_(3-δ)及La_(1-x)Sr_xMnO_(3-δ)纳米粒子的XPS表征

XPS Characterization of Nanometer LaMnO_(3-δ) and La_(1-x)Sr_xMnO_( 3-δ)

采用 XPS手段对钙钛矿型 La Mn O3-δ及 L a1- x Srx Mn O3-δ纳米粒子进行了表征 ,结果显示 ,随L a Mn O3-δ纳米粒子粒径减小 ,其表面氧空位浓度增加 ,表面化学吸附氧性质发生变化 ,同时单位质量试样上化学吸附氧含量增加 ,这些导致化学吸附氧反应活性提高 ,使 CO氧化的起始反应温度降低和一定温度下单位质量催化剂上 CO氧化速率提高。 La Mn O3-δ中的镧被锶部分取代后表面氧空位浓度显著提高 ,表面有 Mn3+ 和 Mn4 + 共同存在 ,CO氧化的催化活性也明显提高。

Nanometer LaMnO 3-δ and La 1-x Sr xMnO 3-δ with perovskite structure were characterized by XPS technique.It was shown that with the decrease of the particle size of LaMnO 3-δ ,on one hand,the property of chemical adsorbed oxygen changed and the concentration of the oxygen vacancy increased,on the other hand,the quantity of the chemical adsorbed oxygen increased.The former resulted in elavation of the activity of the chemical adsorbed oxygen and decrease of the light-off temperature of CO oxidation,the latter leaded to the reaction rate of CO to CO 2 increase.When the substitution of Sr for La in LaMnO 3-δ nanoparticle was made,Mn 4+ was detected on the surface and the oxygen vacancy concentration increased significantly,meanwhile the catalytic activity for CO oxidation increased.