Mechanistic Study of NOx Storage and Reduction Behavior over Pt/Alkali Metal Nitrate Nanocomposite Catalysts

最近，我们发现K-钛酸盐纳米带(KTN)作为载体具有最高的容量和对NOx存储还原过程的良好响应。为了研究这一过程的机理，我们采用了各种物理化学表面技术，如XPS、XRD、EXAFS和FT-IR。我们还采用了不同的晶体结构、不同的负载量的铂和硝酸钾的二氧化钛载体来研究NSR过程的活性和选择性控制因素。我们可以得出以下三个因素作为PtK/TiO2NSR催化剂的重要因素：(1)用于快速NO氧化和KNO3还原的较小的铂金属颗粒；(2)在NOx存储和还原过程中K离子容易地从富K层迁移到富K层；(3)存在一定的表面结构以保持K离子的高分散性。

Recently we have found that K-titanate nanobelts (KTN) possess highest capacity and excellent response for NOx storage reduction processes as supports. To investigate the mechanism of this process, we have employed various physico-chemical surface techniques such as XPS, XRD, EXAFS and FT-IR. We have also employed different crystalline structure TiO2 supports with various loading amounts of Pt and KNO3 to study the activity and selectivity controlling factors for NSR processes. We could conclude the following three factors were important as the NSR catalyst in the Pt-K/TiO2 system; (1) smaller Pt metal particles for rapid NO oxidation and KNO3 reduction, (2) facile migration of K cations from and back to the K-rich layers during NOx storage and reduction processes, (3) existence of a certain surface structure to maintain high dispersion of K cations.