Electrocatalysis and Catalyst Screening from Density Functional Theory Calculations - Fuel Cell Catalysis: A Surface Science Approach - page 62

Figure 3.2 Cyclic voltammograms for H adsorption on Pt(111) and Pt(100). Two different
methods have been applied. In (a) and (b), the H particles were assumed not to interact in the
expression for the configurational entropy. In (c) and (d), the more elaborate model involving
Metropolis Monte Carlo was applied. As can be seen, for these homogenous surfaces, the
simple method suffices. The figure is adopted from [Karlberg et al., 2007a], where the full
details of the calculations can also be found.

3.3.2 Electrochemical Phase Diagram

Having established the theoretical reference electrode, we are now able to estimate
electrochemical phase diagrams. The starting point of the electrochemical phase dia-
gram is the relative stability of the different species on the surface. If we consider a
metal electrode in an acid electrolyte, we obtain

H þ þ e ! H
DG H (U) ¼ DG H

(3 : 11)

0 þ eU

H 2 O ! H þ þ e þ OH
DG OH (U) ¼ DG OH
0

(3 : 12)

eU

H 2 O ! 2H þ þ 2e þ O
DG O (U) ¼ DG O

(3 : 13)

0 2eU