Jeffrey I. Zink Inorganic Chemistry Seminar Series – Prof. James Mayer

“Proton-Coupled Electron Transfer at Solid/Solution Interfaces Analogies and Differences vs. Molecular PCE”

Abstract: Chemical oxidation and reduction (redox) reactions are often described as the transfer of electrons, but protons frequently play an equally important role. Such proton-coupled electron transfer (PCET) reactions are central to many interfacial chemical processes, from catalysis to corrosion. Understanding interfacial PCET will require studies of individual reaction steps rather than the overall processes, and the Mayer lab has focused on colloidal nanoparticles as model systems. Colloids of small nanoparticles, typically 2-5 nm in diameter, have very high surface areas and are amenable to analysis by molecular techniques. For instance, changes in surface stoichiometries in chemical reactions have been probed by ‘simple’ titration experiments. A variety of systems have been examined, including aqueous gold, titanium dioxide, and iridium dioxide nanoparticles, cerium oxide and iron carbide nanoparticles suspended in aprotic solvents, nickel oxide films on electrodes, and high surface area cobalt phosphide. Some common features are emerging from these diverse studies. First, the principles developed for molecular PCET carry over to interfacial processes, with additional features. The surface–H bond strength is not a single value, as for a molecule, but can vary by up to 0.7 eV as a function of surface coverage. Such broad and non-ideal binding isotherms have major effects on the kinetics of the surface reactivity. These studies are showing that diversity of surface sites and the effects of surface coverage play a central role in interfacial reactivity that needs to be developed.