Electrocatalysis and Catalyst Screening from Density Functional Theory Calculations - Fuel Cell Catalysis: A Surface Science Approach - page 76

Figure 3.15 The change in free adsorption energy as a function of the electric field. At the top
of the figure, we estimate the corresponding potential change by assuming that the potential
drops over a Helmholtz layer of thickness 3 ˚ .
DFT calculations (for details, see [Karlberg et al., 2007b]). However, as can be seen
from Fig. 3.15, the change in free energy is small, of the order of 0.1 eV, for most
species. Owing to cancellation, the effect is even smaller when the electric field-related
energy shifts are inserted into the Sabatier model. Hence, also according to this more
detailed analysis, neglecting the effect of the electric field on the free energy of adsorp-
tion appears to be a good approximation.
3.6 INTRODUCTION TO COMPUTATIONAL ELECTROCATALYST
SCREENING
Now that we have developed a fundamental, surface-science-based, first-principles
approach to modeling electrocatalytic processes, we have the fundamental tools
needed to begin to address a problem of significant importance in electrocatalyst research:
that of new electrocatalyst discovery. We have already shown how careful application of
fundamentally derived insights has led to the discovery of improved electrocatalysts for
the ORR (see above). However, although extremely important, this approach has been
limited to considering only a few (five or so) alloys with structures very similar to
pure Pt (i.e., Pt skins); in effect, the approach successfully made small perturbations to
the structure of a good catalyst (pure Pt) to obtain an improved catalyst (a Pt skin). To
have a chance of finding catalytic materials with fundamentally different structures