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Title: Giant onsite electronic entropy enhances the performance of ceria for water splitting

Previous studies have shown that a large solid-state entropy of reduction increases the thermodynamic efficiency of metal oxides, such as ceria, for two-step thermochemical water splitting cycles. In this context, the configurational entropy arising from oxygen off-stoichiometry in the oxide, has been the focus of most previous work. Here we report a different source of entropy, the onsite electronic configurational entropy, arising from coupling between orbital and spin angular momenta in lanthanide f orbitals. We find that onsite electronic configurational entropy is sizable in all lanthanides, and reaches a maximum value of ≈4.7 k B per oxygen vacancy for Ce 4+/Ce 3+ reduction. This unique and large positive entropy source in ceria explains its excellent performance for high-temperature catalytic redox reactions such as water splitting. Our calculations also show that terbium dioxide has a high electronic entropy and thus could also be a potential candidate for solar thermochemical reactions.
Authors:
 [1] ; ORCiD logo [1] ; ORCiD logo [2] ; ORCiD logo [3] ;  [4] ;  [1]
  1. Northwestern Univ., Evanston, IL (United States). Department of Materials Science and Engineering
  2. Technical University of Denmark (Denmark). Department of Energy Conversion and Storage
  3. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
  4. Yale Univ., New Haven, CT (United States). Department of Applied Physics; Yale Energy Sciences Institute, West Haven, CT (United States)
Publication Date:
Grant/Contract Number:
AC52-07NA27344; FG02-07ER46433
Type:
Accepted Manuscript
Journal Name:
Nature Communications
Additional Journal Information:
Journal Volume: 8; Journal Issue: 1; Journal ID: ISSN 2041-1723
Publisher:
Nature Publishing Group
Research Org:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; Computational methods; Electronic structure; Energy modelling
OSTI Identifier:
1395468