Electrochemistry at Well-Characterized Bimetallic Surfaces - Fuel Cell Catalysis: A Surface Science Approach - page 263

Figure 8.17 Activities of Pt(111)-nML Pd electrodes from rotating disk electrode measure-
ments, with corresponding ball models: (a) electro-oxidation of formic acid in 0.1 M HClO 4 ;
(b) oxygen reduction reaction in 0.1 M KOH.
exploration of all of these factors has allowed us to understand how to tune the catalytic
activity of bi/multimetallic systems by systematic changes in the electronic/structural
properties of the catalysts and ultimately to minimize the amount of precious metals
needed by maximizing the catalytic properties of Pt-based multimetallic catalysts.
8.4 CONCLUSION
In spite of the important insights obtained from well-defined bimetallic surfaces, many
fundamental aspects of the structure - reactivity relationship are not understood even in
these idealized systems. Hence, much more needs to be learned to permit the develop-
ment of a truly rational, science-based approach to tailoring and making multimetallic
surfaces with targeted reactivity properties. With few exceptions (such as the work
from our team), the field of electrocatalysis on multimetallic surfaces is still in its
early years, and there is little knowledge available concerning the structure and com-
position of electrochemical interfaces under in situ conditions or of trends in the reac-
tivity of simple molecules with multimetallic surfaces. In the particular case of the
crucially important ORR—the cathodic half-cell reaction in fuel cells—bimetallic
PtNi alloys with nanosegregated surfaces, for example, were demonstrated to be 90
times more active than the existing state-of-the-art Pt/C catalysts. The use of well-
defined systems has enabled us to determine that this remarkable activity is due, in
part, to the presence of a Pt-skin on the alloy surfaces, and to the effect on the surface
electronic structure of the near-surface composition.
Overall, this chapter aimed to emphasize and demonstrate the great potential of uti-
lizing a multidisciplinary approach to bimetallic systems that combines computational
methods with a number of highly sophisticated in situ and ex situ surface-sensitive
techniques at electrified solid - liquid interfaces. Advances in the understanding of
fundamental properties that govern catalytic processes at well-defined multimetallic