Perovskite materials are widely used as catalysts and electrocatalysts in energy conversion devices. Their bulk transport properties can be tuned flexibly for many applications. While the ion and electron transport properties in their bulk are generally well-understood, the surfaces remain much less explored and challenging. Surface instabilities give rise to compositional deviations in the near-surface region or even the precipitation of secondary phases. These deteriorate the surface catalytic properties under operating conditions, thus reducing efficiency and lifetime of devices.
In this contribution, the bulk and surface chemistry of perovskite oxides for solid oxide fuel cell applications are explored for selected compounds relevant for application. Starting with a short description of the bulk defect chemistry of perovskite oxides, the challenges for both theory and experiment in treating these materials are highlighted. Surface instabilities and a selection of mechanisms for surface stabilization are explored, such as electronic reconstruction, ionic segregation, and the formation of stable AO surface terminations. Finally, the O2 dissociation is examined at two different stable AO terminations, where it is revealed that the nature of the active sites differs for the SrO and LaO terminations on SrTiO3 and La2NiO4+δ, respectively, so that the O2 dissociation follows fundamentally different mechanisms on these surfaces.
F. Hess, A.T. Staykov, B. Yildiz, J. Kilner. (2019) In: Andreoni W., Yip S. (eds) Handbook of Materials Modeling. Springer, Cham. 10.1007/978-3-319-50257-1_132-1