Kavli Affiliate: Darrell G. Schlom
| First 5 Authors: Lei Zhang, Jan Kloppenburg, Chia-Yi Lin, Luka Mitrovic, Simon Gelin
| Summary:
Understanding the dehydrogenation of transition metal oxide surfaces under
electrochemical potential is critical to the control of important chemical
processes such as the oxygen evolution reaction (OER). Using first principles
computations, we model the thermodynamic dehydrogenation process on
RuO$_2$(110) and compare the results to experimental cyclic voltammetry (CV) on
single crystal. We use a cluster expansion model trained on *ab initio* energy
data coupled with Monte Carlo (MC) sampling to derive the macroscopic
electrochemical observables, i.e., experimental CV, from the energetics of
different hydrogen coverage microstates on well-defined RuO$_2$(110). Our model
reproduces the unique "two-peaks" cyclic voltammogram observed experimentally
with current density peak positions and shapes in good qualitative agreement.
We show that RuO$_2$(110) starts as a water-covered surface with hydrogen on
bridge (BRG) and coordination-unsaturated sites (CUS) at low potential (less
than 0.4 V vs. reversible hydrogen electrode, RHE). As the potential increases,
the hydrogens on BRG desorb, becoming the main contributor to the first CV peak
with smaller contributions from CUS. When all BRG hydrogens are desorbed
(before 1.2 V vs. RHE), the remaining CUS hydrogens desorb abruptly in a very
small potential window leading to the sharp second peak observed during CV. Our
work shows that above 1.23 V, the OER proceeds on a fully dehydrogenated
RuO$_2$(110) surface.
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