Thomas G. Kelly

Metal overlayer on metal carbide substrate: unique bimetallic properties for catalysis and electrocatalysis

Transition metal carbides often display electronic and catalytic properties that are similar to Pt-group metals. In this tutorial review, we describe the feasibility of replacing the Pt-group metal component in bimetallic systems with metal carbides. By supporting a metal monolayer on a carbide substrate, these bimetallic surfaces exhibit similar catalytic and electrocatalytic activity to the corresponding Pt-based bimetallic systems while demonstrating the advantages of lower cost and higher thermal stability. Another promising aspect is that the carbide substrates often promote the formation of small, flat metal particles with novel catalytic properties. We review the synthesis, characterization, and utilization of carbide-supported metal surfaces in heterogeneous catalysis and electrocatalysis. An overview is given for both theoretical and experimental investigations, and trends are drawn from the literature. We also discuss opportunities for future research on carbide-supported metal surfaces.

Controlling C–O, C–C and C–H bond scission for deoxygenation, reforming, and dehydrogenation of ethanol using metal-modified molybdenum carbide surfaces

For biomass-derived oxygenate molecules to be fully utilized for chemicals and fuels, control of the bond scission sequence is necessary. Particularly, the C–O, C–H, and C–C bonds must be selectively broken to produce hydrocarbons, aldehydes, and syngas, respectively. Molybdenum carbide (Mo2C) and metal-modified Mo2C may be used to tune the selectivity towards different bond scission pathways. We have investigated how the admetal modification of Mo2C can shift the selectivity towards breaking certain bonds, using ethanol as a probe molecule. Density functional theory (DFT) was used to predict the binding energies of ethanol and reaction intermediates on the Mo2C surfaces. Ultrahigh vacuum (UHV) techniques such as temperature programmed desorption (TPD) and high-resolution electron energy loss spectroscopy (HREELS) were used to verify the activity and reaction pathways on Mo2C and metal-modified Mo2C surfaces. It was seen that the bare Mo2C surface was active for C–O cleavage to produce ethylene. Surface modification with Ni resulted in the preferential C–C bond scission to form syngas, while modification by Cu led to the C–H scission to produce acetaldehyde.