PNNL

Abstract

In catalysis, MgO is often used to modify the acid-base properties of support oxides and to stabilize supported metal atoms and particles on oxides. In this study, we show how the sublimation of MgO powder can be used to deposit MgO monomers, hither on anatase TiO2(101). A combination of X-ray electron spectroscopy, high-resolution scanning tunneling microscopy, and density functional theory is employed to gain insight into the MgO monomer binding, electronic and vibrational properties, and thermal stability. In the most stable configuration, the Mg and O of the MgO monomer bind to two surface oxygens and one undercoordinated surface titanium, respectively. The additional binding weakens the Mg-O monomer bond and makes the Mg more ionic. The monomers are thermally stable up to 650 K, where the onset of diffusion into the TiO2 bulk is observed. The monomeric MgO species on TiO2(101) represent an ideal, atomically precise system with modified acid-base properties and will be employed in our future catalytic studies. This work was supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Chemical Sciences, Geosciences, and Biosciences Division. Experiments were performed in EMSL, a national scientific user facility sponsored by the Department of Energy’s Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory (PNNL). PNNL is a multiprogram national laboratory operated for DOE by Battelle. under Contract DE-AC05-76RL01830. Computational Resources were provided by a user proposal at the National Energy Research Scientific Computing Center (NERSC) located at Lawrence Berkley National Laboratory (LBNL). Author contributions: Z.D. designed and guided the study; N.D., G.C., R. R. P., P.K.G., and M.-S.L. performed research; N.D., G.C., and R. R. P. analyzed data; N.D., G.C., V.-A.G., D.D, R.R., and Z.D. wrote the paper.