Abstract:

In an effort to obtain new insights into photocatalytic phenomena, there has been a significant increase in the use of molecular-level approaches applied to model single crystal surfaces. While electron spectroscopies and desorption-oriented techniques are well suited for fundamental studies (e.g., on TiO2(110)), perhaps the most promising technique for assessment relationships between site-specific reactivity and surface structure is that of scanning tunneling microscopy (STM). This talk will highlight the use of STM technique in providing molecular- level insights into surface photochemistry on metal oxides, robust materials important in a broad range of fields, including heterogeneous photocatalysis. In particular, the rutile TiO2(110) has become an excellent model surface of reducible metal oxide, while isostructural RuO2(110) extends into metallic late transition metal oxides. Distinct photostimulated processes, representing different classes of reactions, will be considered for carefully selected probe molecules, including an oxygen and a carboxylic (trimethyl acetic) acid on TiO2 (110), as well as hydrogen on RuO2(110) surface. In all cases, corresponding adsorption properties are also briefly discussed, since these set the stage for the photochemistry. It will be illustrated that STM techniques are indispensable in finding local coordination of adsorbate/active site, observing single photoinduced events, and attaining site specific reaction rates. Among other important aspects considered are effects of charged pointdefects and/or coadsorbates (hydroxyl species). Finally, key factors that determine site-selectivity in photochemistry and a particular reaction pathway will be discussed, as well as a potential extrapolation to other photoactive materials.

Short Biography of the Speaker:

Dr. Igor Lyubinetsky is a well-known researcher of the surface chemistry on metal oxides relevant to heterogeneous catalysis and/or environmental remediation, using a fundamental, model system approach. He is best known for pioneering application of the ultra-high vacuum scanning tunneling microscopy for studies of photoreactivity on metal oxides at the atomic level. Dr. Lyubinetsky, a native of Ukraine, received his Ph.D. in condensed matter physics at the Leningrad State University, U.S.S.R. in 1986. After a stint as a senior research scientist at Kiev T. Shevchenko University, Ukraine, he came to the U.S.A. in 1996 as a visiting scientist with John Yates’ group at the University of Pittsburgh, and later worked as a research assistant scientist at the University of Maryland (group of Ellen Williams). In 2002, he has joined Pacific Northwest National Laboratory and worked there as a Scientist IV until 2016, with a following short stay at Oregon State University. Currently, Dr. Lyubinetsky is a visiting scientist with Prof. Ozensoy’s group on Marie Sklodowska-Curie/TUBITAK program. He has co-authored several reviews and more than 100 journal articles.