Jain, Ruchi and Dubey , Anjani and Ghosalya , Manoj K. and Gopinath, Chinnakonda S. (2015) Gas-Solid Interaction of H2-Ce0.95Zr0.05O2:New Insights on Surface Participation in Heterogeneous Catalysis. Gas-Solid Interaction of H2-Ce0.95Zr0.05O2:New Insights on Surface Participation in Heterogeneous Catalysis, 6 (1). pp. 1746-1756. ISSN 2044-4753

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Abstract

Direct interaction between reduction medium (H2) and Ce0.95Zr0.05O2(CZ) solid surface was explored through ambient pressure photoelectron spectroscopy(APPES), with conventional x-ray and He-I photon sources, in H2 atmosphere up to 0.1 mbar pressure and 773 K.Porous CZ thin film was prepared by a combination of sol-gel and spin-coating method, and employed to understand the redox nature of ceria under reduction conditions. The maximum of 45 % Ce3+ along with corresponding oxygen vacancy was observed due to reduction.An unprecedented decrease in the valence band (VB) energy up to 1.4 eV was observed on reduction along with a narrowing of VB. Highest occupied energy band derived from Ce 4f also shift closer to EF. H2 molecular vibration observed in VB-APPES was employed as a probe to explore the surface potential changes along with dynamic change in the nature of the surface under reduction conditions. Surface potential decreases by 0.27 eV up to 673 K, and then it reverts by 0.24 eV on further reduction at 773 K for different reasons. Further, an enhancement in Ce 5d – O2p interaction occurs at the expense of Ce 4f – O2p interaction under the above reduction conditions. Vacuum annealing and H2 reduction after that shows significantly more VB shift and enhanced reduction than H2 reduction alone. Although Ce reduction occurs on high temperature vacuum annealing of CZ, rather a significantly lower amount of oxygen vacancies appear. This study shows the dynamic changes in the nature of the surface due to gas (H2) -solid (CZ) interaction and ensuing electronic structure changes that influences heterogeneous catalysis. It also underscores the necessity to study the catalytic materials under in-situ conditions or closer to that.

Item Type: Article
Subjects: Catalysis and Surface Science
Divisions: UNSPECIFIED
Depositing User: Manoj Kumar ghosalya
Date Deposited: 17 Jan 2017 08:34
Last Modified: 17 Jan 2017 10:04
URI: http://ncl.csircentral.net/id/eprint/2511

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