posted on 2023-08-24, 18:37authored byAbhinav
S. Raman, Annabella Selloni
Iridium oxide (IrO2) is one of the most efficient
catalytic
materials for the oxygen evolution reaction (OER), yet the atomic
scale structure of its aqueous interface is largely unknown. Herein,
the hydration structure, proton transfer mechanisms, and acid–base
properties of the rutile IrO2(110)–water interface
are investigated using ab initio based deep neural-network
potentials and enhanced sampling simulations. The proton affinities
of the different surface sites are characterized by calculating their
acid dissociation constants, which yield a point of zero charge in
agreement with experiments. A large fraction (≈80%) of adsorbed
water dissociation is observed, together with a short lifetime (≈0.5
ns) of the resulting terminal hydroxy groups, due to rapid proton
exchanges between adsorbed H2O and adjacent OH species.
This rapid surface proton transfer supports the suggestion that the
rate-determining step in the OER may not involve proton transfer across
the double layer into solution, as indicated by recent experiments.