TY - JOUR
T1 - Surface Reactivity of Ag-Modified Ceria to Hydrogen
T2 - A Combined Experimental and Theoretical Investigation
AU - Benedetti, Stefania
AU - Righi, Giulia
AU - Luches, Paola
AU - D'Addato, Sergio
AU - Magri, Rita
AU - Selloni, Annabella
N1 - Funding Information:
The authors thank Sergio Valeri for his support and for fruitful discussions. The work is performed with the financial support of Università degli Studi di Modena e Reggio Emilia through the FAR2016 project titled “Innovative (oxide-based) materials and methods for fuel cell electrodes implementation”. Financial support from MIUR through PRIN project no. 2015CL3APH is also acknowledged. A.S. acknowledges support from DoE-BES, Division of Chemical Sciences, Geosciences and Biosciences under Award DESC0007347. We also acknowledge use of computational resources at the TIGRESS high performance computer center at Princeton University.
Funding Information:
The authors thank Sergio Valeri for his support and for fruitful discussions. The work is performed with the financial support of Universita? degli Studi di Modena e Reggio Emilia through the FAR2016 project titled "Innovative (oxide-based) materials and methods for fuel cell electrodes implementation". Financial support from MIUR through PRIN project no. 2015CL3APH is also acknowledged. A.S. acknowledges support from DoE-BES, Division of Chemical Sciences, Geosciences and Biosciences under Award DESC0007347. We also acknowledge use of computational resources at the TIGRESS high performance computer center at Princeton University.
Publisher Copyright:
Copyright © 2020 American Chemical Society.
PY - 2020/6/17
Y1 - 2020/6/17
N2 - We investigate the mechanism of H2 activation on Ag-modified cerium oxide surfaces, of interest for different catalytic applications. The study is performed on thin epitaxial cerium oxide films, investigated by X-ray photoemission spectroscopy to assess the changes of both the Ag oxidation state and the concentration of Ce3+ ions, O vacancies, and hydroxyl groups on the surface during thermal reduction cycles in vacuum and under hydrogen exposure. The results are interpreted using density functional theory calculations to model pristine and Ag-modified ceria surfaces. Although the reactivity of ceria toward H2 oxidation improves when a fraction of Ce cations is substituted with Ag, the concentration of reduced Ce3+ ions in Ag-modified ceria is found to be lower than in pure ceria under the same conditions. This behavior is observed even though the number of surface oxygen vacancies caused by the thermal treatment under hydrogen exposure is larger for the Ag-modified surface. These results are explained in terms of a change of the oxidation state of the surface Ag, which is able to acquire some of the extra surface electrons created by the oxygen vacancies and the adsorbed hydrogen atoms. Our findings provide new insights into the reactivity of Ag-modified ceria, which has been proposed as a promising alternative to platinum electrodes in electrochemical devices.
AB - We investigate the mechanism of H2 activation on Ag-modified cerium oxide surfaces, of interest for different catalytic applications. The study is performed on thin epitaxial cerium oxide films, investigated by X-ray photoemission spectroscopy to assess the changes of both the Ag oxidation state and the concentration of Ce3+ ions, O vacancies, and hydroxyl groups on the surface during thermal reduction cycles in vacuum and under hydrogen exposure. The results are interpreted using density functional theory calculations to model pristine and Ag-modified ceria surfaces. Although the reactivity of ceria toward H2 oxidation improves when a fraction of Ce cations is substituted with Ag, the concentration of reduced Ce3+ ions in Ag-modified ceria is found to be lower than in pure ceria under the same conditions. This behavior is observed even though the number of surface oxygen vacancies caused by the thermal treatment under hydrogen exposure is larger for the Ag-modified surface. These results are explained in terms of a change of the oxidation state of the surface Ag, which is able to acquire some of the extra surface electrons created by the oxygen vacancies and the adsorbed hydrogen atoms. Our findings provide new insights into the reactivity of Ag-modified ceria, which has been proposed as a promising alternative to platinum electrodes in electrochemical devices.
KW - X-ray photoemission spectroscopy
KW - ceria
KW - density functional theory
KW - hydrogen dissociation
KW - metal dopants
KW - reaction kinetics
KW - silver
KW - surface reduction
UR - http://www.scopus.com/inward/record.url?scp=85086682636&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85086682636&partnerID=8YFLogxK
U2 - 10.1021/acsami.0c03968
DO - 10.1021/acsami.0c03968
M3 - Article
C2 - 32508088
AN - SCOPUS:85086682636
SN - 1944-8244
VL - 12
SP - 27682
EP - 27690
JO - ACS applied materials & interfaces
JF - ACS applied materials & interfaces
IS - 24
ER -