First-Principles Simulation of the Active Sites and Reaction Environment in Electrocatalysis - Fuel Cell Catalysis: A Surface Science Approach - page 92

& CHAPTER 4
First-Principles Simulation of the Active
Sites and Reaction Environment
in Electrocatalysis
MICHAEL J. JANIK
Department of Chemical Engineering, Pennsylvania State University, University Park, PA 16802, USA
SALLY A. WASILESKI
Department of Chemistry, University of North Carolina at Asheville, Asheville, NC 28804, USA
CHRISTOPHER D. TAYLOR
Materials Science and Technology Division, Los Alamos National Laboratory, Los Alamos,
NM 87545, USA
MATTHEW NEUROCK
Departments of Chemical Engineering and Chemistry, University of Virginia, Charlottesville,
VA 19904, USA
4.1 INTRODUCTION
Electrocatalysis is controlled by the complex interplay between the active catalytic
sites and the influence of their complex environment at the electrified aqueous/
metal interface. The most active electrocatalytic materials exquisitely integrate the
atomic assembly of the active metal sites responsible for the elementary bond
making and breaking steps, together with the carbon support to carry out efficient elec-
tron transfer, and polymer electrolyte and water to facilitate proton transfer, thus estab-
lishing an optimal three-phase interface. Understanding the elementary catalytic
processes along with the atomic scale features that control them, however, is obscured
by the complexity of this three-phase interface and the dynamic changes that occur to it
under operating conditions. A simple schematic of the interface is shown in Fig. 4.1 in
order to highlight some of the complexity. Many of the same issues that plague our
ability to understand traditional vapor phase heterogeneous catalysts are also present