V-347 FY 2013 Annual Progress Report DOE Hydrogen and Fuel Cells Program Co-PI: Progress Report Water-Mediated Proton Hopping on an Iron Oxide Surface 1

Objectives The main objective of this combined theoretical and experimental project is to: (i) design from first-principles, (ii) synthesize using advanced nanosynthesis techniques, and (iii) experimentally evaluate new metal and alloy nanoparticles, with unique catalytic properties for a number of important chemical reactions. We also want to address the fundamentals of reactivity at metal/metal oxide interfaces. Technical Barriers 1. Low-temperature polymer electrolyte membrane (PEM) fuel cells present an attractive method of generating electricity for portable devices. However, the commercial feasibility of these systems is limited by the high cost of Pt-based catalysts. Experimental screening of catalytic materials is costly and time-consuming. From a fundamental understanding of reaction mechanisms, developed through first-principles calculations, we are able to identify promising materials using reactivity appropriate reactivity descriptors. 2. Water plays a significant role in surface reactions, even if only a spectator species, including at impurity levels. In addition, spillover of atoms from metal to metal oxide supports and the reverse has been shown to play a key role in heterogeneous catalysis. We address the role of water on hydrogen atom diffusion, and thereby spillover, at FeO/Pt interfaces. Abstract The catalysts designed in this project can impact a number of applications, including low temperature fuel cells, hydrogen production and purification, and liquid fuels production. The importance of the atomic-scale architecture of these new theoretically-designed catalysts to their unique properties is driving the development of new inorganic materials synthesis approaches, which are capable of synthesizing the theoretically determined optimal, and in some cases, metastable, nanoscale catalytic architectures. Over the past year, we have made progress toward our objectives through a combination of theoretical and experimental studies. We have used DFT calculations to show that water is able to assist hydrogen diffusion on a FeO/Pt moire structure. This finding has substantial implications for reactions where water participates as a reactant, product, solvent, or impurity in the reaction mixture. We have also designed "onion"-structured alloy catalysts from first principles that demonstrate a high activity for the oxygen reduction reaction (ORR). These alloys, composed of a Pt monolayer deposited on a substrate metal (or alloy) with a number of 1-atom-thick Pd layers in between, have been synthesized experimentally and verified to have higher catalytic activity than pure Pt ORR catalysts. The diffusion of hydrogen is an important process in a number of applications, including catalytic hydrogen evolution and reforming, hydrogenation/dehydrogenation of hydrocarbons, and hydrogen storage. Hydrogen diffusion is practically important in cases where the "spillover" effect operates, where active sites for H 2 dissociation and association are spatially separated from the active sites for other reactions. Mechanisms involving hydrogen spillover V.N.29 Atomic-Scale Design of Metal and Alloy Catalysts: a Combined Theoretical and Experimental Approach Progress Repor