  Density Functional Theory (DFT) calculations have been widely used to predict
the activity of catalysts based on the free energies of reaction intermediates.
The incorporation of the state of the catalyst surface under the
electrochemical operating conditions while constructing the free energy diagram
is crucial, without which even trends in activity predictions could be
imprecisely captured. Surface Pourbaix diagrams indicate the surface state as a
function of the pH and the potential. In this work, we utilize error-estimation
capabilities within the BEEF-vdW exchange correlation functional as an ensemble
approach to propagate the uncertainty associated with the adsorption energetics
in the construction of Pourbaix diagrams. Within this approach,
surface-transition phase boundaries are no longer sharp and are therefore
associated with a finite width. We determine the surface phase diagram for
several transition metals under reaction conditions and electrode potentials
relevant for the Oxygen Reduction Reaction (ORR). We observe that our surface
phase predictions for most predominant species are in good agreement with
cyclic voltammetry experiments and prior DFT studies. We use the OH$^*$
intermediate for comparing adsorption characteristics on Pt(111), Pt(100),
Pd(111), Ir(111), Rh(111), and Ru(0001) since it has been shown to have a
higher prediction efficiency relative to O$^*$, and find the trend
Ru>Rh>Ir>Pt>Pd for (111) metal facets, where Ru binds OH$^*$ the strongest. We
robustly predict the likely surface phase as a function of reaction conditions
by associating c-values to quantifying the confidence in predictions within the
Pourbaix diagram. We define a confidence quantifying metric using which certain
experimentally observed surface phases and peak assignments can be better
rationalized.
