Improvement of Air/Fuel Ratio Operating Window and Hydrothermal Stability for Pd-Only Three-Way Catalysts through a Pd-Ce2Zr2O8 Superstructure Interaction
Improvement of Air/Fuel Ratio Operating Window and Hydrothermal Stability for Pd-Only Three-Way Catalysts through a Pd-Ce2Zr2O8 Superstructure Interaction
复制标题
通过 Pd-Ce2Zr2O8 上层结构相互作用改善纯 Pd 三元催化剂的空燃比操作窗口和水热稳定性
DOI：
10.1021/acs.est.5b01361
复制
发表时间：
2015-07-07
影响因子：
11.4
通讯作者：
Zhang，Zhaoliang
中科院分区：
文献类型：
--
作者：
Zhang，Zhiliang;Fan，Yunzhao;Zhang，Zhaoliang
在包括中国在内的世界部分地区，严重且持续的雾霾问题促使了越来越严格的尾气排放法规的实施。这对三元催化剂的性能提出了越来越高的要求，特别是为了方便车载诊断系统的操作，需要扩大空气/燃料（λ）比的操作窗口。本文提出了一种通过调整TWCs的纳米结构来提高其λ活性和水热稳定性的新途径。对氧化铝改性的二氧化铈进行高温还原和温和再氧化处理，形成了立方的、完全氧化的、类似焦绿石的上层结构Ce2Zr2O8。Pd与ce2zr2o8上部结构的结合极大地提高了纯Pd三元催化剂的λ窗口。x射线粉末衍射（XRD）、H2程序升温还原（H2- tpr）和高分辨率透射电镜（HRTEM）表征证实了Pd与ce2zr2o8上层结构之间的相互作用，由于ce2zr2o8上层结构比Ce(Zr)O2具有更高的低温还原性，因此与传统的Pd - Ce(Zr)O2相互作用相比，Pd与ce2zr2o8上层结构的相互作用改变了动态储氧能力。此外，与Pd相互作用产生的ce2zr2o8上层结构在含10% H2O的空气中1000°C水热时效12 h后得到了优异的λ和发光性能。
The extremely severe and persistent haze problems in some parts of the world including China have prompted the implementation of increasingly stringent tailpipe regulations. This places increasingly higher performance requirements for three-way catalysts, and in particular a widening of the air/fuel (λ) ratio operating window to facilitate operation of the on-board diagnostic system. A new pathway is presented here by tuning the nanostructure of TWCs to improve their λ activities and hydrothermal stability. High-temperature reduction and a mild-temperature reoxidation treatment for alumina-modified ceria–zirconia brought about the formation of a cubic, fully oxidized, pyrochlore-like superstructure, Ce2Zr2O8. The combination of Pd and the Ce2Zr2O8superstructure greatly improved the λ window for Pd-only three-way catalysts. X-ray powder diffraction (XRD), temperature-programmed reduction with H2(H2-TPR) and high-resolution transmission electron microscopy (HRTEM) characterization confirmed the interaction between Pd and the Ce2Zr2O8superstructure, which modifies the dynamic oxygen storage capacity in comparison to the conventional Pd–Ce(Zr)O2interaction, due to higher low-temperature reducibility for the Ce2Zr2O8superstructure than for Ce(Zr)O2. Furthermore, the retention of the Ce2Zr2O8superstructure derived from the interaction with Pd results in superior λ and light-off performances after hydrothermal aging treatment at 1000 °C for 12 h in air containing 10% H2O.