D. Wayne Goodman

High-resolution photoemission illustrates that the band structure of graphene on Ru(0001) exhibits a well-defined splitting. This splitting is largest with the graphene directly on the Ru(0001) substrate, whereas with a chemisorbed oxygen spacer layer between the graphene and the metal substrate, this splitting is considerably reduced. This splitting is attributed to a combination of chemical interactions between graphene and Ru(0001) and to screening of the former by the latter, not spin-orbit coupling.

Au deposited on Ru(0001)-supported extended, continuous graphene moiré forms large 2-D islands at room temperature that are several nanometers in diameter but only 0.55 nm in height, in the apparent absence of typical binding sites such as defects and adsorbates. These Au islands conform to the corrugation of the underlying graphene and display commensurate moiré patterns. Several extended Au structure models on graphene/Ru(0001) are examined using density functional theory calculations. Close-packed Au overlayers are energetically more stable, but all interact weakly with the support. Preliminary tests found the Au islands/graphene/Ru(0001) surface to be active for CO oxidation at cryogenic temperature, which suggests that the Au itself is the locus of catalytic activity.

Fischer–Tropsch (FT) synthesis has received considerable recent attention from academic and industrial researchers. Cobalt catalysts exhibit excellent activity/selectivity for FT; however its relative cost is high. Therefore the design of enhanced Co catalysts is economically attractive. To achieve this goal, the fundamental processes occurring on the surface of cobalt catalysts need to be better understood. Surface science studies, with the aid of model catalysts, can provide such crucial information. Numerous review articles concerning the details of technical FT catalysts are available, however very few of these specifically address cobalt model catalysts. In this review, we briefly summarize the literature regarding FT synthesis on various cobalt model catalysts, ranging from well‐defined single crystals to nanoparticles dispersed on planar oxide supports. Fundamental issues such as structure sensitivity, surface restructuring, olefin readsorption, promoter effects, particle size effects, and the oxidation of nanoparticles are addressed.

C ₂ H ₄ /CO/H ₂ reaction is investigated on Rh/SiO ₂ model catalyst surfaces. Kinetic reactivity and infrared spectroscopic measurements are investigated as a function of Rh particle size under near atmospheric reaction conditions. Results show that propionaldehyde turnover frequency (TOF) (CO insertion pathway) exhibits a maximum activity near 〈 d _p 〉 = 2.5 nm. Polarization modulation infrared reflection absorption spectroscopy under CO and reaction (C ₂ H ₄ /CO/H ₂ ) conditions indicate the presence of Rh carbonyl species (Rh(CO) ₂ , Rh(CO)H) on small Rh particles, whereas larger particles appear resistant to dispersion and carbonyl formation. Combined these observations suggest the observed particle size dependence for propionaldehyde production via CO insertion is driven by two factors: ( i ) an increase in propionaldehyde formation on undercoordinated Rh sites and ( ii ) creation of carbonyl hydride species (Rh(CO)H)) on smaller Rh particles, whose presence correlates with the lower activity for propionaldehyde formation for 〈 d _p 〉 < 2.5 nm.

Microscopic and spectroscopic techniques at near-atmospheric pressures have been used in recent years to investigate CO oxidation over Pt-group metals. New insights have been obtained that allow broadening of the understanding of this reaction beyond the ultrahigh vacuum regime where it is well-understood. However, new issues also have arisen that need clarification. In this paper, we review recent work in our laboratory, using polarization modulation infrared reflection absorption spectroscopy (PM-IRAS) and reaction kinetics measurements from ultrahigh vacuum to near-atmospheric pressures. These studies reveal a continuity of this reaction with respect to pressure over Pt, Pd, and Rh; that is, Langmuir−Hinshelwood kinetics is exhibited over a wide pressure range with no apparent “pressure gap”. The difference between Ru(0001) and other noble metals is well-understood with respect to higher oxygen binding energies and reduced CO inhibition. It is concluded that for all Pt-group metals the most active phase is one saturated with chemisorbed oxygen and with low CO coverages. The significance of oxide phases under most industrially relevant catalytic conditions suggested recently in the literature is not consistent with the experimental data.