We are investigating the atomic structure of surfaces in dynamic equilibrium with gases and liquids. The 'dynamic atomic structure' of surfaces can be quite different from the 'static surface structure' measured at ultra-high vacuum (UHV) and/or cryogenic temperatures (T<100 K). This can be best justified in terms of the chemical potential, Δμ. At cryogenic temperatures and UHV: Δμ→0, but under ambient conditions (assuming p=1 Torr, and RT=295 K) the ‘pressure driving force’ is roughly 0.6 eV, lifting the kinetic limitations encountered in classical surface science.
We used high pressure scanning tunnelling microscopy (HPSTM) to show that the low Miller-index Cu surfaces break up into nanoclusters in the presence of reactant gases such as CO or CO2 in the Torr pressure range at RT. Such an atomistic phenomenon has a great significance in heterogeneous catalysis as it directly affects the electronic structure and thereby the chemical properties of the surface. The reason behind clustering of such compact surfaces is the high difference in adsorption energy at the low-coordinated Cu atoms (steps, kinks) and high-coordinated Cu atoms (terraces). Unlike CO and CO2, gas-phase CH3OH does not cause the break-up of Cu into clusters.
In our new group, we are planning to work on more complex surfaces like bimetallic surfaces and metal/oxide interfaces.
B. Eren, H. Kersell, R. S. Weatherup, C. Heine, E. J. Crumlin, C. M. Friend, M. Salmeron. Structure of the Clean and Oxygen-Covered Cu(100) Surface in the Presence of Methanol Gas in the 10 to 200 mTorr Pressure Range, J. Phys. Chem. B, 122, (2018), 548-54.
B. Eren, R. S. Weatherup, N. Liakakos, G. A. Somorjai, M. Salmeron. Dissociative carbon dioxide adsorption and morphological changes on Cu(100) at ambient pressures J. Am. Chem. Soc., 138, (2016), 8207-11.
B. Eren, Z. Liu, D. Stacchiola, G. A. Somorjai, M. Salmeron. Structural changes of Cu(110) and Cu(110)-(2×1)-O surfaces under carbon monoxide in the Torr pressure range studied with scanning tunneling microscopy and infrared reflection absorption spectroscopy J. Phys. Chem. C, 120, (2016), 8227-31.
B. Eren, D. Zherebetskyy, Y. Hao, L. L. Patera, L.-W. Wang, G. A. Somorjai, M. Salmeron. One-dimensional nanoclustering of the Cu(100) surface under CO gas in the mbar pressure range Surf. Sci., 651, (2016), 210-4.
B. Eren, D. Zherebetskyy, L. L. Patera, C. H. Wu, H. Bluhm, C. Africh, L.-W. Wang, G. A. Somorjai, M. Salmeron. Activation of Cu(111) surface by decomposition into nanoclusters driven by CO adsorption Science, 351, (2016), 475-8.