Characterization of Molybdenum Carbide Nanoparticles Formed on Au(111) Using Reactive-Layer Assisted Deposition

Abstract

Temperature programmed desorption (TPD), Auger electron spectroscopy (AES), X-ray photoelectron spectroscopy (XPS), and scanning tunneling microscopy (STM) have been used to characterize molybdenum carbide nanoparticles prepared on a Au(111) substrate. The MoC(x) nanoparticles were formed by Mo metal deposition onto a reactive multilayer of ethylene, which was physisorbed on a Au(111) substrate at low temperatures (<100 K). The resulting clusters have an average diameter of approximately 1.5 nm and aggregate in the fcc troughs located on either side of the elbows of the reconstructed Au(111) surface. Core level XPS shows that the electronic environment of the Mo and C atoms in the nanoparticles is similar to that found in Mo(2)C(0001) single crystals and carburized Mo metal surfaces. Peak intensities in XPS and AES spectra were used to estimate an average Mo/C atomic ratio of 1.2 +/- 0.3 for nanoparticles annealed above 600 K.

Boosting the activity of transition metal carbides towards methane activation by nanostructuring

“…22 On a Au(111) substrate, with the characteristic herringbone (22×√3) reconstruction structure, inverse carbide/gold, sulfide/gold and oxide/gold systems have been generated for fundamental studies in catalysis. 22,[26][27][28][29] In this case, the MoC y nanoparticles were generated by deposition of Mo metal onto a reactive multilayer of ethylene, which was physisorbed on a Au(111) surface at 100 K. 22 The amount of Mo deposited was estimated using XPS and Mo/Au ratios seen in previous studies for the deposition of Mo on the herringbone structure of Au(111). 22,30 The Au(111) substrate does not react with ethylene but the deposited Mo does for form carbide nanoparticles.…”

“…22,[26][27][28][29] In this case, the MoC y nanoparticles were generated by deposition of Mo metal onto a reactive multilayer of ethylene, which was physisorbed on a Au(111) surface at 100 K. 22 The amount of Mo deposited was estimated using XPS and Mo/Au ratios seen in previous studies for the deposition of Mo on the herringbone structure of Au(111). 22,30 The Au(111) substrate does not react with ethylene but the deposited Mo does for form carbide nanoparticles. Upon heating to 750 K, the unreacted ethylene desorbed and MoC y nanoparticles were left on the gold substrate (Figure S1).…”

“…In this article, we use a combination of experimental and theoretical techniques to investigate the reactivity of MoC y nanoparticles towards CH 4 activation and dissociation. In particular, we focus on molybdenum carbide (MoC y ) nanoparticles which are growth on an inert Au(111) substrate 22 and employ X-ray photoelectron spectroscopy (XPS), thermal desorption mass spectroscopy (TDS), and density functional theory (DFT) based calculations to examine the interaction of methane with the supported MoC y nanoparticles. We provide compelling evidence that the MoC y /Au(111) systems are able to dissociate methane at room temperature.…”

In Situ CO2-Emission Assisted Synthesis of Molybdenum Carbonitride Nanomaterial as Hydrogen Evolution Electrocatalyst

“…The Mo 3d spectra were deconvoluted into six peaks, assignable to Mo 2+ (228.1 and 231.2 eV), Mo 3+ (228.9 and 231.9 eV), and Mo 6+ (232.5 and 235.2 eV) species. 13,31,32 Mo 6+ is assigned to molybdenum oxides, 31 whereas Mo 2+ and Mo 3+ are thought to be molybdenum carbides and nitrides, 13,32 respectively, which are known to serve as active sites for HER. 15 The total concentrations of Mo species in PDAP-MoCN and PDAP-MoCN-CO 2 exceeded 14 mol % (Table 1), which are much higher than that in PANI-MoCN (8 mol %).…”

Preparation and olefin-metathesis activity of cyclopentylidene-oxo initiator sites on a molybdenum carbide surface

“…Similarly, the selective formation of terminal alkylidenes on b-Mo 2 C shows that interstitial carbide formation leads to single Mo site surface chemistry [10,18,19]. The latter observation is especially interesting in that formation of carbide phases from molybdenum nanoparticles can occur in the presence of hydrocarbons at relatively low temperatures [20]. Work by Chen and co-workers on molybdenum carbide surface films clearly shows that subsurface carbon is required to obtain chemisorption properties characteristic of bulk carbides [21][22][23].…”