Invited Paper AS+CA+LS-WeA1
Probing the Electronic Structure of Electrocatalysts and the Formation of Reaction Intermediates

Wednesday, October 23, 2019, 2:20 pm, Room A211

Electrocatalysts are important constituents in numerous energy conversion and storage processes. Reactants adsorb onto the electrocatalyst surface, where the interplay of electronic states results in a lower activation barrier for the transfer of electronic and ionic species in the reaction pathway to product formation. Rational design of electrocatalysts with greater activity for higher efficiency devices requires an understanding of the material’s electronic structure in situ, as well as the reaction intermediates involved.

Many surface science techniques, such as X-ray photoelectron spectroscopy (XPS), collect information from inherently surface-sensitive low-energy processes, requiring operation in ultrahigh vacuum. This constraint is lifted for ambient pressure XPS, which can probe the surface in equilibrium with the gas phase at pressures up to ~a few Torr, or with thin liquid layers using a higher incident photon energy. This presentation will discuss the insights obtained with this technique regarding the electronic structure of oxide electrocatalysts in an oxidizing or humid environment, as well as the reaction intermediates of relevance to electrocatalysis.¹ I will then extend the technique to probe electrocatalysts in operando,² driving current through a thin layer of liquid electrolyte and employing a tender X-ray source.

References:

[1] Stoerzinger,K.A.Wang, L. Ye, Y. Bowden, M. Crumlin, E.J. Du, Y. Chambers, S.A. “Linking surface chemistry to photovoltage in Sr-substituted LaFeO₃ for water oxidation”. Journal of Materials Chemistry A 6 (2018) 22170-22178.

[2] Stoerzinger, K.A. Wang, X.R. Hwang, J. Rao, R.R Hong, W.T Rouleau, C.M. Lee, D. Yu, Y. Crumlin, E.J. Shao-Horn, Y. “Speciation and electronic structure of La_1-xSr_xCoO_3-δ during oxygen electrolysis”. Topics in Catalysis 61 (2018) 2161–2174.