Partially dissociated water dimers at the water-hematite interface

Z. Jakub, F. Kraushofer, M. Bichler, J. Balajka, J. Hulva, J. Pavelec, I. Sokolović, M. Müllner, M. Setvin, M. Schmid, U. Diebold, P. Blaha, G. S. Parkinson

Institut für Angewandte Physik, TU Wien, 1040 Wien, Austria
Institute of Materials Chemistry, TU Wien, 1060 Wien, Austria

ACS Energy Lett. 4 (2019) 390-396

The oxygen evolution reaction (OER) is thought to occur via a four-step mechanism with *O, *OH, and *OOH as adsorbed intermediates. Linear scaling of the *OH and **OOH adsorption energies is proposed to limit the oxides' efficiency as OER catalysts, but the use of simple descriptors to screen candidate materials neglects potentially important water-water interactions. Here, we use a combination of temperature-programmed desorption (TPD), X-ray photoemission spectroscopy (XPS), noncontact atomic force microscopy (nc-AFM), and density functional theory (DFT)-based computations to show that highly stable HO-H2O dimer species form at the (1 -1 0 2) facet of hematite; a promising anode material for photoelectrochemical water splitting. The UHV-based results are complemented by measurements following exposure to liquid water and are consistent with prior X-ray scattering results. The presence of strongly bound water agglomerates is generally not taken into account in OER reaction schemes but may play a role in determining the required OER overpotential on metal oxides.

Corresponding author: Gareth S. Parkinson (parkinson at iap_tuwien_ac_at).

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