钙钛矿型复合氧化物用于汽车尾气催化净化的研究进展(一)

Advances on research of perovskite catalyst for purification of motor-vehicle's exhaust (part 1)

综述了钙钛矿型汽车催化剂的研究进展。和过渡金属简单氧化物相比 ,钙钛矿型复合氧化物 ( ABO3)在热稳定性、化学稳定性和结构稳定性方面具有一定的优越性 ,因而表现出更高的催化活性。在满足容限因子的条件下 ,有多种元素可以形成钙钛矿结构的化合物。通常 ,B位离子决定了钙钛矿型化合物的催化活性 ,A位离子是影响化合物结构和 B位离子价态的重要因素。当 A位离子或 B位离子被不同价态的离子取代时 ,通过形成氧离子空穴或者形成混合价态来保持化合物的电中性。氧空穴的形成或 B位离子价态的变化使得化合物具有更高的活性。贵金属和钙钛矿型化合物结合 ,不仅可以有效防止贵金属的烧结 。

The present article aims to present a detailed review on the up-to-date advances in the research of motor-vehicle's exhaust catalyst with perovskite being the main structure. As is known, compared with the simple transition metal oxides, pertovskite-type mixed oxides (ABO_3) enjoys the advantage of higher thermal, chemical and structural stability so as to be able to ameliorate the catalytic activity in many cases. As to the tolerance factor, there are a great variety of elements that can help to build perovskite-type compounds. In general practice, B-site ions are responsible for the catalytic activity of the compounds while A-site ions serve as the essential factor that may influence the compound structure and the B-site element valence. In the case of substitution of A-site or B site ions by other ions of different oxidation states, the charge compensation can be achieved either by the formation of oxygen ion vacancies or by the formation of mixed oxidation states. The high catalytic activity of such substituted compounds originates from their structural defects and the effect of the valence alternation. In order to improve the performance of the catalysts, the present authors have made great efforts in combining noble metals and the type of mixed oxides. Such a combination can not only prevent the noble metals from sintering, but also lead to a pronounced enhancement of catalytic activity of the perovskite-type oxides.