| AVS 64th International Symposium & Exhibition | |
| Fundamental Discoveries in Heterogeneous Catalysis Focus Topic | Thursday Sessions |
| Session HC+SA+SS-ThM |
| Session: | Mechanisms and Reaction Pathways in Heterogeneously Catalyzed Reactions |
| Presenter: | Tao Li, University of Florida, Gainesville |
| Authors: | T. Li, University of Florida, Gainesville Z. Liang, University of Florida, Gainesville M. Kim, The Ohio State University A. Asthagiri, The Ohio State University J.F. Weaver, University of Florida, Gainesville |
| Correspondent: | Click to Email |
Understanding the interactions of hydrogen with IrO2 surfaces is central to improving applications of electrocatalysis as well as exploiting the high-reactivity of IrO2 for promoting methane activation. In this talk, I will discuss our recent investigations of the dissociative chemisorption and oxidation of H2 on stoichiometric and oxygen-rich IrO2(110) surfaces. We find that H2 dissociation is highly facile on s-IrO2(110), with more than 90% of a saturated H2 layer dissociating below 225 K during temperature-programmed reaction spectroscopy (TPRS). We observe only H2O desorption in a broad TPRS peak from about 400 to 780 K after generating low H2 coverages on s-IrO2(110) at about 90 K. At high H2 coverages, we also observe small H2 desorption peaks at 200 and 530 K which we attribute to molecular and recombinative desorption processes, respectively. We present evidence that H2 dissociation on IrO2(110) occurs through a mechanism wherein H2 σ-complexes adsorbed on the coordinatively-unsaturated (cus) Ir atoms serve as precursors for H2 dissociation. We show that oxygen atoms adsorbed on the cus-Ir sites, so-called on-top O-atoms, hinder H2 dissociation on IrO2(110), while also facilitating H2O desorption and promoting H-atom transfer from bridging O-atoms to on-top O-atoms. I will also discuss the results of density functional theory calculations of H2 dissociation and initial steps of H2O formation on stoichiometric and O-rich IrO2(110).