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Interaction of Hydrogen with Ceria: Hydroxylation,Reduction, and Hydride Formation on the Surface and in the Bulk |
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| Authors: | Zhaorui Li Dr Kristin Werner Lu Chen Aiping Jia Dr Kun Qian Dr Jian-Qiang Zhong Dr Rui You Dr Lihui Wu Liyuan Zhang Dr Haibin Pan Prof?Dr Xin-Ping Wu Prof?Dr Xue-Qing Gong Dr Shamil Shaikhutdinov Prof Weixin Huang Prof?Dr Hans-Joachim Freund |
| Institution: | 1. Hefei National Laboratory for Physical Sciences at Microscale, Key Laboratory of Surface and Interface Chemistry and Energy Catalysis, of Anhui Higher Education Institutes, CAS Key Laboratory of Materials, for Energy Conversion and Department of Chemical Physics, University of Science and Technology of China, Hefei, 230026 P. R. China
These authors contributed equally to this work.;2. Fritz-Haber-Institut der Max-Planck Gesellschaft, Faradayweg 4–6, Berlin, 14195 Germany;3. Key Laboratory for Advanced Materials and Joint International Research, Laboratory for Precision Chemistry and Molecular Engineering, Feringa, Nobel Prize Scientist Joint Research Center, Centre for Computational, Chemistry and Research Institute of Industrial Catalysis, School of, Chemistry and Molecular Engineering, East China University of Science, and Technology, 130 Meilong Road, Shanghai, 200237 P. R. China These authors contributed equally to this work.;4. Hefei National Laboratory for Physical Sciences at Microscale, Key Laboratory of Surface and Interface Chemistry and Energy Catalysis, of Anhui Higher Education Institutes, CAS Key Laboratory of Materials, for Energy Conversion and Department of Chemical Physics, University of Science and Technology of China, Hefei, 230026 P. R. China Key Laboratory of the Ministry of Education for Advanced Catalysis, Materials, Institute of Physical Chemistry, Zhejiang Normal University, Jinhua, 321004 P. R. China;5. Hefei National Laboratory for Physical Sciences at Microscale, Key Laboratory of Surface and Interface Chemistry and Energy Catalysis, of Anhui Higher Education Institutes, CAS Key Laboratory of Materials, for Energy Conversion and Department of Chemical Physics, University of Science and Technology of China, Hefei, 230026 P. R. China;6. National Synchrotron Radiation Laboratory, University of, Science and Technology of China, Hefei, 230029 P. R. China;7. Key Laboratory for Advanced Materials and Joint International Research, Laboratory for Precision Chemistry and Molecular Engineering, Feringa, Nobel Prize Scientist Joint Research Center, Centre for Computational, Chemistry and Research Institute of Industrial Catalysis, School of, Chemistry and Molecular Engineering, East China University of Science, and Technology, 130 Meilong Road, Shanghai, 200237 P. R. China |
| Abstract: | The study reports the first attempt to address the interplay between surface and bulk in hydride formation in ceria (CeO2) by combining experiment, using surface sensitive and bulk sensitive spectroscopic techniques on the two sample systems, i.e., CeO2(111) thin films and CeO2 powders, and theoretical calculations of CeO2(111) surfaces with oxygen vacancies (Ov) at the surface and in the bulk. We show that, on a stoichiometric CeO2(111) surface, H2 dissociates and forms surface hydroxyls (OH). On the pre-reduced CeO2?x samples, both films and powders, hydroxyls and hydrides (Ce?H) are formed on the surface as well as in the bulk, accompanied by the Ce3+ ? Ce4+ redox reaction. As the Ov concentration increases, hydroxyl is destabilized and hydride becomes more stable. Surface hydroxyl is more stable than bulk hydroxyl, whereas bulk hydride is more stable than surface hydride. The surface hydride formation is the kinetically favorable process at relatively low temperatures, and the resulting surface hydride may diffuse into the bulk region and be stabilized therein. At higher temperatures, surface hydroxyls can react to produce water and create additional oxygen vacancies, increasing its concentration, which controls the H2/CeO2 interaction. The results demonstrate a large diversity of reaction pathways, which have to be taken into account for better understanding of reactivity of ceria-based catalysts in a hydrogen-rich atmosphere. |
| Keywords: | ceria density functional calculations hydride hydrogenation surface structure |