Sr取代LaFeO3钙钛矿的结构性质和催化性能

摘要

Partial substitution of La3+ by Sr2+ in LaFeO3 resuhed in significant changes in its structure and catalytic activity.The perovskite structure was changed from orthorhombic in LaFeO3 to nearly cubic in La0.8Sr0.2FeO3.Replacement of La3+ by Srv induced a positive charge deficiency that was compensated for by the oxidation of some Fe3+to Fe4+ and the generation of oxygen vacancies,which greatly promoted the reducibility of the perovskite.La0.8Sr0.2FeO3 gave considerably enhanced activity in CO oxidation and methane combustion because the oxygen vacancies accelerated the dissociation of gaseous oxygen on the surface in CO oxidation and facilitated the diffusion of lauice oxygen from the bulk to the surface during CH4 combustion.%Sr2+对La3+的部分取代导致LaFeO3的结构性质和催化性能发生了显著变化钙钛矿结构由LaFeO3的正交型变成了La0.8Sr0.2FeO3的近立方型.由于电荷补偿效应,Sr2+取代La3+导致部分Fe3+氧化为Fe4+,同时产生氧空穴,因而提高了La0.8Sr0.2FeO3的还原性能.由于氧空穴的作用,La0.8Sr0.2FeO3催化剂在CO氧化和CH4燃烧反应中均表现出较LaFeO3高的催化活性.在CO氧化反应中,氧空穴有利于反应物分子的吸附并加速了气相氧分子在表面上的解离;而在CH4燃烧反应中,氧空穴则促进了晶格氧物种从体相到表面的扩散.