(240d) Oxide Heterostructure Systems for Oxygen Evolution Reaction - Activation of SrTiO3 with Subsurface SrRuO3

Designing energy conversion materials with simultaneous satisfying activity and stability properties is a challenge especially for electrochemical reaction such as the water splitting reaction. Often, high electrocatalytic activity of an oxide catalyst material is accompanied by structural instability. A core-shell oxide design, where an active core catalyst is covered with a stable shell, is an attractive solution to the problem of catalyst instability. However, the influence of the core during electrocatalytic reactions on the surface of the shell of oxide systems is not well understood. In this contribution, we demonstrate how ultrathin heterostructures composed of unstable active and stable inactive layers can be used for studies of model core–shell oxide architectures. In particular, we show that as little as a one unit cell subsurface layer of an active perovskite SrRuO₃‘‘core’’ can activate a SrTiO₃‘‘shell’’ surface layer towards oxygen evolution reaction (OER). While, as little as a two unit cell shell layer is enough to completely protect the inherently unstable catalyst against corrosion during OER. Using density functional theory calculations and a simplified electronic structure model, we unravel the mechanism for the subsurface activation for a class of oxide heterostructures and rationalize the choice of the SrTiO₃-SrRuO₃ system, which is realized experimentally.¹

1. A. Akbashev, L. Zhang, J.T. Mefford, J. Park, B. Butz, H. Luftman, W. Chueh, and A. Vojvodic, "Activation of SrTiO₃with Subsurface SrRuO₃for Oxygen Evolution Reaction", Energy & Environmental Science, Accepted (2018). DOI:10.1039/C8EE00210J