403c Different Wetting Behaviors of Pd and Rh on the CeO2(111) Surface. A DFT and Hrtem Study

Liang Chen1, Xiaoqing Pan2, and George Graham2. (1) Institute of Materials Technology and Engineering, Chinese Academy of Sciences, 519 Zhuangshi Blvd. C210, Ningbo, China, (2) Department of Materials Science and Engineering, Unversity of Michigan, Ann Arbor, MI 48109

The catalysts comprising noble metals supported on ceria surfaces are widely utilized in water-gas shift reactions and automotive exhaust-gas converters. In this work we present a systematic study on the interaction of noble metals Pd and Rh with the CeO2(111) surface using density functional theory (DFT) and high-resolution transmission electron microscopy (HRTEM). HRTEM studies revealed that Pd and Rh show different wetting behaviors on the CeO2(111) surface. Rh tends to form 2-dimensional layers, while Pd can form 2-dimensional islands followed by transformation into 3-dimensional particles upon heating. Our DFT calculations indicated that for both Rh and Pd 3-dimensional clusters are energetically more favorable than 2-dimensional layers, which is a result of a delicate balance between metal-metal and metal-support interactions. However, the transformation of Rh from the monolayer to clusters is prohibitively difficult due to a significant reaction barrier.