title: Fast vacancy-mediated oxygen ion incorporation across the ceria-gas electrochemical interface.
abstract: Electrochemical incorporation reactions are ubiquitous in energy storage and conversion devices based on mixed ionic and electronic conductors, such as lithium-ion batteries, solid-oxide fuel cells and water-splitting membranes. The two-way traffic of ions and electrons across the electrochemical interface, coupled with the bulk transport of mass and charge, has been challenging to understand. Here we report an investigation of the oxygen-ion incorporation pathway in CeO2-δ (ceria), one of the most recognized oxygen-deficient compounds, during hydrogen oxidation and water splitting. We probe the response of surface oxygen vacancies, electrons and adsorbates to the electrochemical polarization at the ceria-gas interface. We show that surface oxygen-ion transfer, mediated by oxygen vacancies, is fast. Furthermore, we infer that the electron transfer between cerium cations and hydroxyl ions is the rate-determining step. Our in operando observations reveal the precise roles of surface oxygen vacancy and electron defects in determining the rate of surface incorporation reactions.
authors.affiliation: 1] Department of Applied Physics, Stanford University, Stanford, California 94305, USA [2] Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA.
authors.forename: Zhuoluo A
authors.initials: ZA
authors.lastname: Feng
authors.affiliation: Materials Physics Department, Sandia National Laboratories, Livermore, California 94550, USA.
authors.forename: Farid
authors.initials: F
authors.lastname: El Gabaly
authors.affiliation: Department of Materials Science and Engineering, Stanford University, Stanford, California 94305, USA.
authors.forename: Xiaofei
authors.initials: X
authors.lastname: Ye
authors.affiliation: 1] Department of Applied Physics, Stanford University, Stanford, California 94305, USA [2] Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA.
authors.forename: Zhi-Xun
authors.initials: ZX
authors.lastname: Shen
authors.affiliation: 1] Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA [2] Materials Physics Department, Sandia National Laboratories, Livermore, California 94550, USA [3] Department of Materials Science and Engineering, Stanford University, Stanford, California 94305, USA.
authors.forename: William C
authors.initials: WC
authors.lastname: Chueh