Pt掺杂CaTiO3体系相平衡的理论研究-中国材料进展

文章信息/Info

Title:: A Theoretical Study of Phase Equilibria of Pt Doped Calcium Titanate

作者:: 李白海1; 2; 张秋杰1; 陈亮2; 1能源科学与工程学院，电子科技大学，四川成都 611731 2中国科学院宁波材料工程与技术研究所，浙江宁波 315201

Author(s):: ZHANG Qiujie1; LI Baihai1; 2; CHEN Liang2; 1School of Energy Science and Technology, University of Electronic Science and Technology of China, Chengdu, 611731, China 2Ningbo Institute of Materials Technology & Engineering, Chinese Academy of Sciences, Ningbo, 315201, China

摘要:: 已有实验表明贵金属Pt能够随外界氧化还原条件的改变，自发地在钙钛矿CaTiO3内部和表面之间迁移，有效抑制贵金属颗粒的烧结，使得贵金属长期保持高效的催化活性，因此该体系被称为汽车尾气“智能催化剂”。但当前对该体系中贵金属与载体之间的相互作用，以及贵金属迁移特性发生的条件以及程度的研究很少。本文采用基于第一性原理计算与集团展开法以及蒙特卡洛方法相结合构建PtOx-CaO-TiOx三元相图，对可再生汽车尾气催化剂Pt掺杂CaTiO3体系进行了理论研究。第一性原理相图分析表明Pt能够以不同浓度取代CaTiO3中的Ti原子，而热力学相图分析表明Pt掺杂到CaTiO3中将形成固溶体，更重要的是Pt能够在氧化还原条件下与CaTiO3形成固溶体或者析出，与“智能催化剂”的概念相一致。此外，相图分析还预测了其它一些氧化物以及合金结构的存在，以及得到了这些物质之间的相变规律。这些结果将为实验工作提供有益的帮助，有利于开发高效的汽车尾气催化剂。

Abstract:: Previous Experiments reported that precious-metal Pt is able to migrate between perovskite CaTiO3 surface and bulk with change of the external redox conditions. This novel process can efficiently suppress the agglomeration of precious-metal particles, and maintain the high performance of the so-called “intelligent catalysts” for a long period. However, the study of the interactions between precious-metal and CaTiO3 substrate is rather limited. The first-principles calculations combined with cluster expansion and Monte Carlo methods were employed to construct the PtOx-CaO-TiOx pseudo-ternary phase diagrams to explore the properties of Pt-doped CaTiO3 system. The first-principles phase diagrams show that Pt can be doped in CaTiO3 and occupy the Ti-site at various concentrations, and the thermodynamic phase diagrams indicate that the doped CaTi1-xPtxO3 structures evolve to solid solutions at ambient temperatures. More importantly, Pt tends to dissolve into CaTiO3 substrate under oxidizing conditions while precipitate from the perovskite matrix and exist as metallic particles under reducing conditions, which is consistent with the concept of “intelligent catalyst”. Furthermore, the investigations of the phase diagram indicate the existence of some other oxides and metal alloys in the catalyst system at various conditions. The results might inform the experiments and be helpful for preparing highly efficient catalysts for elimination of harmful exhaust gas.