Reconciling the Experimental and Computational Hydrogen
Evolution Activities of Pt(111) through DFT-Based Constrained MD Simulations
Posted on 2021-06-17 - 20:15
The computational
hydrogen evolution activity of Pt(111) remains
controversial due to apparent discrepancies with experiments concerning
rate-determining activation free energies and equilibrium hydrogen
coverages. A fundamental source of error may lie within the static
representations of the metal–water interface commonly employed
in density functional theory (DFT)-based kinetic models neglecting
important entropic effects on reaction dynamics. In this work, we
present a dynamic reassessment of the Volmer–Tafel hydrogen
evolution pathway on Pt(111) through DFT-based constrained molecular
dynamics simulations and thermodynamic integration. Hydrogen coverage
effects are gauged at two distinct surface saturations, while the
critical potential dependence and constant potential conditions are
accounted for using a capacitive model of the electrified interface.
The uncertainty in the highly nontrivial treatment of the electrode
potential is carefully examined, and we provide a quantitative estimation
of the error associated with dynamically simulated electrochemical
barriers. The dynamic description of the electrochemical interface
promotes a substantial decrease of the Tafel free energy barrier as
the coverage is increased to a full monolayer. This follows from a
decreased entropic barrier due to suppressed adlayer dynamics compared
to the unsaturated surface, a detail easily missed by static calculations
predicting notably higher barriers at the same coverage. Due to observed
endergonic adsorption of active hydrogen intermediates, the Tafel
step remains rate-determining irrespective of the coverage as illustrated
by composed Volmer–Tafel free energy landscapes. Importantly,
our explicitly dynamic approach avoids the ambiguous choice of frozen
solvent configuration, decreasing the reliance on error cancellation
and paving the way for less biased electrochemical simulations.
CITE THIS COLLECTION
Kronberg, Rasmus; Laasonen, Kari (2021). Reconciling the Experimental and Computational Hydrogen
Evolution Activities of Pt(111) through DFT-Based Constrained MD Simulations. ACS Publications. Collection. https://doi.org/10.1021/acscatal.1c00538
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AUTHORS (2)
RK
Rasmus Kronberg
KL
Kari Laasonen
KEYWORDS
energy landscapesComputational Hydrogen Evolution Ac...hydrogen intermediatesadlayer dynamicserror cancellationelectrochemical barriersPtTafel steprate-determining activationequilibrium hydrogen coverageselectrochemical interfacesurface saturationsenergy barrierendergonic adsorptionnontrivial treatmentHydrogen coverage effectsentropic effectsreaction dynamicscapacitive modelhydrogen evolution activityentropic barrierelectrochemical simulationsVolmerDFT-Based Constrained MD Simulationsdynamics simulations