High Resolution Electron Energy Loss Spectroscopy Study Research Articles

Nitrogen bonding, work function and thermal stability of nitrided graphite surface: An in situ XPS, UPS and HREELS study

In this study, we investigate the chemical and electronic properties of nitrogen incorporated highly oriented pyrolytic graphite (N–HOPG) surface. The N–HOPG surfaces were prepared by three methods: radio frequency N2 (RF(N2)) plasma, microwave N2 (MW(N2)) plasma and N2+ ion implantation. The surface chemical states of carbon–nitrogen bonds on the N–HOPG surfaces, evolution of defects and thermal stability were investigated by X-ray photoelectron spectroscopy, high-resolution electron energy loss spectroscopy (HREELS) and ultraviolet photoelectron spectroscopy. Nitrogen exists in graphitic–N bonding state predominantly on the low damage N–HOPG surfaces (RF(N2) plasma at 9.3 Pa and 200 eV N2+ ion implantation) and in pyridine–N bonding state on high damage N–HOPG surfaces (RF(N2) plasma at 4.0 Pa and 500 eV N2+ ion implantation). Partial structural recovery is possible for low damage N–HOPG surfaces upon annealing. HREELS analysis revealed preferential bonding of hydrogen to defect sites and retention of graphite lattice structure for N–HOPG surfaces with low-level of surface damage. Furthermore, low damage N–HOPG surfaces exhibited low work function due to incorporation of nitrogen at graphitic sites. HCN temperature programmed desorption spectra showed a broad peak positioned at 550 °C which is associated with desorption of pyrrolic–N content.

Influence of RF(N2) plasma conditions on the chemical interaction and stability of activated nitrogen with polycrystalline diamond surfaces: A XPS, TPD and HREELS study

In this study, the chemical interaction of nitrogen with polycrystalline diamond surfaces is investigated. The interaction of nitrogen with the diamond surface was activated using a non-line of sight interaction RF(N2) plasma source equipped with a neutralizer placed at the exit of the plasma source to decrease the density of the high energetic nitrogen species arriving at the surface. Nitridation process has been carried out for different N2 plasma exposure time (20 and 30 min) and pressure (3 × 10−2 and 7 × 10−2 Torr) at plasma power of 36 W. The chemical and structural properties of nitrided (as-processed, annealed to different temperatures and hydrogenated) diamond surfaces were evaluated using X-ray photoelectron spectroscopy, high-resolution electron energy loss spectroscopy (HREELS) and temperature programmed desorption (TPD). The HREELS analysis of nitrided diamond surfaces suggests that the plasma processing pressure and the exposure time play a crucial role in controlling surface structural quality. The presence of the optical phonon (∼300 meV), which is a signature feature of well-defined and defects-free diamond surface; confirms the crystalline quality of nitride surfaces and nitrogen present in different bonding configurations: CNH2 and CN. Further, the HREELS analysis shows that NH surface bonds stability is below 700 °C. TPD spectra show N2 and HCN peaks at ∼600 °C that are associated with nitrogen surface bonded species. Hydrogenation of annealed surfaces revealed that the surface structural recovery is possible with the low level of structural damage.

Furfuryl alcohol deoxygenation, decarbonylation, and ring-opening on Pt(111)

The adsorption and decomposition of furfuryl alcohol on Pt(111) was studied using temperature-programmed desorption (TPD) and high-resolution electron energy loss spectroscopy (HREELS). TPD studies showed that furfuryl alcohol underwent decarbonylation to furan, propylene, carbon monoxide, and hydrogen, as well as hydrodeoxygenation to produce methylfuran and water. Benzene was also produced as an unexpected ring decomposition product. Experiments conducted on deuterium-precovered Pt(111) were used to determine the extent of hydrogen exchange between the surface and organic intermediates during TPD. These experiments suggested that furan was likely evolved in part through dehydrogenated C4H2O intermediates. In contrast to earlier observation of furfuryl alcohol chemistry on Pd(111), deoxygenation of furfuryl alcohol only occurred via hydrogenation by surface hydrogens and not through an interadsorbate hydrogen exchange. The HREELS studies revealed that at low coverages, the furyl ring was adsorbed in a flat-lying configuration on the Pt(111) surface, while at higher coverages intermediates with more upright structures were observed. Furfuryl alcohol decomposed through a furfural intermediate, which underwent decarbonylation and decomposition at relatively low temperatures to produce propylene and benzene. These results elucidate key differences between Pt and Pd surfaces important for designing catalysts to have high selectivity towards a given process.

TPD and HREELS study of the reaction of guaiacol on Zn-decorated Pt(111)

Temperature programmed desorption (TPD) and high resolution electron energy loss spectroscopy (HREELS) were used to characterize the adsorption and reaction of guaiacol on Pt(111) and Zn-modified Pt(111) surfaces. It was found that the guaiacol molecule binds to the Pt(111) surface via the aromatic ring which facilitates unselective decomposition to produce CO, H2 and small hydrocarbon fragments at relatively low temperatures. In contrast, on Zn-modified Pt(111) surfaces, guaiacol was found to bond to surface Zn sites via the oxygen atoms in the molecule producing a bonding configuration in which the aromatic ring is tilted away from the surface. Such a binding configuration facilitates the desired CO bond cleavage while keeping the aromatic nature of the molecule intact.

HR-EELS study of hydrogen bonding configuration, chemical and thermal stability of detonation nanodiamond films

Nano-diamond films composed of 3–10 nm grains prepared by the detonation method and deposited onto silicon substrates by drop-casting were examined by high resolution electron energy loss spectroscopy (HR-EELS), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and secondary ion mass spectroscopy (SIMS). The impact of (i) ex-situ ambient annealing at 400 °C and (ii) ex-situ hydrogenation on hydrogen bonding and its thermal stability were examined. In order to clarify the changes in hydrogen bonding configuration detected on the different surfaces as a function of thermal annealing, in-situ hydrogenation by thermally activated atomic hydrogen was performed and examined. This study provides direct evidence that the exposure to ambient conditions and medium temperature ambient annealing have a pronounced effect on the hydrogen-carbon bonding configuration onto the nano-diamond surfaces. In-situ 1000 °C annealing results in irreversible changes of the film surface and partial nano-diamond silicidation.

Deuterium adsorption on (and desorption from) SiC(0 0 0 1)-(3 × 3), R30°, R30° and quasi-free-standing graphene obtained by hydrogen intercalation

We present a comparative high-resolution electron energy-loss spectroscopy study on the interaction of atomic hydrogen and deuterium with various reconstructions of SiC(0 0 0 1). We first show that on both the (3 × 3) and reconstructions, deuterium atoms only bind to silicon atoms, thereby confirming the silicon-rich appellation of these reconstructions. Deuterium passivation of the (3 × 3) is only reversible when exposed to atomic deuterium at a surface temperature of 700 K since tri- and dideuterides, necessary precursors for silicon etching, are not stable. On the other hand, we show that the deuteration of the is always reversible because precursors to silicon etching are scarce on the surface. Then, we demonstrate that hydrogen (deuterium) adsorption at 300 K on both the (buffer-layer) and the quasi-free-standing graphene occurs on carbon atoms justifying their carbon-rich appellation. Comparison of the deuterium binding in the intercalation layer of quasi-free-standing graphene with the deuterated surface provides some indication on the bonding structure at the substrate intercalation layer. Finally, by measuring C–H (C–D) vibrational frequencies and hydrogen (deuterium) desorption temperatures we suggest that partial sp2-to-sp3 rehybridization occurs for the carbon atoms of the buffer-layer because of the corrugation related to covalent bonding to the SiC substrate. In contrast, on quasi-free-standing graphene hydrogen (deuterium) atoms adsorb similarly to what is observed on graphite, i.e. without preferential sticking related to the underlying SiC substrate.

The adsorption and reaction of ethylene glycol and 1,2-propanediol on Pd(111): A TPD and HREELS study

The reactions of ethylene glycol and 1,2-propanediol have been studied on Pd(111) using temperature programmed desorption (TPD) and high resolution electron energy loss spectroscopy (HREELS). Both molecules initially decompose through O–H activation, forming ethylenedioxy (–OCH 2CH 2O–) and 1,2-propanedioxy (–OCH 2CH(CH 3)O–) surface intermediates. For ethylene glycol, increases in thermal energy lead to dehydrogenation and formation of carbonyl species at both oxygen atoms. The resulting glyoxal (O═CHCH═O) either desorbs molecularly or reacts through one of two competing pathways. The favored pathway proceeds via C–C bond scission, dehydrogenation, and decarbonylation to form carbon monoxide and hydrogen. In a minor pathway, small amounts of glyoxal undergo C–O bond scission and recombination with surface hydrogen to form ethylene and water. The same reaction mechanism occurs for 1,2-propanediol after methyl elimination and formation of glyoxal. However, this is accompanied by a minor pathway involving a methylglyoxal (O=CHC(CH 3)=O) intermediate. The prevalence of the dehydrogenation/decarbonylation pathway in the current work is consistent with the high selectivity for C–C scission in the aqueous phase reforming of polyols on supported Pd catalysts.

Vibrational spectroscopy of oxygen on the (100) and (111) surfaces of lanthanum hexaboride

Reflection absorption infrared spectroscopy (RAIRS) and high resolution electron energy loss spectroscopy (HREELS) have been used to study the adsorption of oxygen on the (100) and (111) surfaces of lanthanum hexaboride. Exposure of the surface at temperatures of 95 K and above to O 2 produces atomic oxygen on the surface and yields vibrational peaks in good agreement with those observed in previous HREELS studies. On the La-terminated (100) surface, RAIRS peaks correspond to vibrations of the boron lattice that gain intensity due to a decrease in screening of surface dipoles that accompanies oxygen adsorption. A sharp peak at ∼ 734 cm − 1 in the HREEL spectrum shows isotopic splitting with RAIRS into two components at 717 and 740 cm − 1 with full widths at half maxima of only 12 cm − 1. The sharpness of this mode is consistent with its interpretation as a surface phonon that is well separated from both the bulk phonons and other surface phonons of LaB 6. On the boron-terminated LaB 6(111) surface, broad and weak features are assigned to both vibrations of the boron lattice and of boron oxide. On the (100) surface, oxygen blocks the adsorption sites for CO, and adsorbed CO prevents the dissociative adsorption of O 2.

HREELS study of graphene formed on hexagonal silicon carbide

AbstractUsing high resolution electron energy loss spectroscopy (HREELS) in conjunction with low energy electron diffraction (LEED) and X‐ray induced photoelectron spectroscopy (XPS), we have studied surface reconstructions from Si‐rich to C‐rich surfaces up to graphene formation. It is shown that the coupling between the longitudinal optical phonons and the carrier plasmons that originate from the presence of the layered semimetallic character of graphene and few layer graphene (FLG) drastically influence the HREELS‐spectra. For the hydrogen smoothened SiC‐samples, which have been subsequently annealed under high Ar‐pressure [1], the Fuchs‐Kliewer surface phonon ω0 is completely screened and two other losses ω‐ and ω+, called plasmarons, appear. They originate from the coupling between surface optical phonons and plasma oscillations of free‐electrons resulting from the graphene/SiC interface. For the heated SiC‐samples under ultra‐high‐vacuum (UHV) conditions, the situation is different, which indicates cluster formation of graphene / graphite at the surface. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Ethanol and ethylene glycol on Ni/Pt(1 1 1) bimetallic surfaces: A DFT and HREELS study

The reactions of ethanol and ethylene glycol have been studied on Ni/Pt(1 1 1) bimetallic surfaces using density functional theory (DFT) and high resolution electron energy loss spectroscopy (HREELS). A linear correlation has been observed between the binding energies of ethanol, ethoxy, and ethylene glycol species and the surface d-band center, with increasing binding energy as the d-band center shifts closer to the Fermi level. HREELS measurements have identified the bond scission sequence of ethanol and ethylene glycol on Ni/Pt(1 1 1) bimetallic surfaces. Two bimetallic surfaces can be formed that possess very different chemical properties: one with a monolayer of Ni atoms on top of Pt(1 1 1) designated Ni–Pt–Pt(1 1 1), and the other with the Ni atoms diffusing into the subsurface region, designated Pt–Ni–Pt(1 1 1). At 120 K ethanol adsorbs molecularly with the O–H bond intact on Pt(1 1 1) and Pt–Ni–Pt(1 1 1), while dissociative adsorption is observed on Ni–Pt–Pt(1 1 1) and Ni(1 1 1) film surfaces. Ethylene glycol adsorbs molecularly with the O–H bond intact on all four surfaces at 200 K, and desorbs reversibly from Pt(1 1 1) and Pt–Ni–Pt(1 1 1). In contrast, ethylene glycol undergoes decomposition on Ni–Pt–Pt(1 1 1) and Ni(1 1 1) film surfaces through O–H bond cleavage, forming an ethylenedioxy (–OCH 2CH 2O–) intermediate. This intermediate reacts by further dehydrogenation and C–C bond scission to eventually form CO. Overall, the HREELS results are consistent with TPD studies that show the reforming activities of ethanol and ethylene glycol follow the trend Ni–Pt–Pt(1 1 1) > Ni(1 1 1) film > Pt(1 1 1) > Pt–Ni–Pt(1 1 1).

A comparative study of the adsorption and hydrogenation of acrolein on Pt(1 1 1), Ni(1 1 1) film and Pt–Ni–Pt(1 1 1) bimetallic surfaces

In this study we have investigated the reaction pathways for the decomposition and hydrogenation of acrolein (CH 2 CH−CH O) on Ni/Pt(1 1 1) surfaces under ultra-high vacuum (UHV) conditions using temperature programmed desorption (TPD) and high-resolution electron energy loss spectroscopy (HREELS). While gas-phase hydrogenation products are not observed from clean Pt(1 1 1), the subsurface Pt–Ni–Pt(1 1 1), with Ni residing below the first layer of Pt, is active for the self-hydrogenation of the C O bond to produce unsaturated alcohol (2-propenol) and the C C bond to produce saturated aldehyde (propanal), with the latter being the main hydrogenation product without the consecutive hydrogenation to saturated alcohol. For a thick Ni(1 1 1) film prepared on Pt(1 1 1), the self-hydrogenation yields for both products are lower than that from the Pt–Ni–Pt(1 1 1) surface. The presence of pre-adsorbed hydrogen further enhances the selectivity toward C O bond hydrogenation on the Pt–Ni–Pt(1 1 1) surface. In addition, HREELS studies of the adsorption of the two hydrogenation products, 2-propenol and propanal, are performed on the Pt–Ni–Pt(1 1 1) surface to identify the possible surface intermediates during the reaction of acrolein. The results presented here indicate that the hydrogenation activity and selectivity of acrolein on Pt(1 1 1) can be significantly modified by the formation of the bimetallic surfaces.

Adsorption and reaction of SiH 4 and oxygen on Pd(1 1 1)

Coadsorption of SiH 4 and oxygen on Pd(1 1 1) has been studied via temperature programmed desorption (TPD), high resolution electron energy loss spectroscopy (HREELS), and Auger electron spectroscopy (AES). These techniques indicate that surface Si and O react at <200 K to form a surface SiO X layer that is stable to at least 950 K. TPD studies show trends indicating that surface Si reacts rapidly with surface O on Pd(1 1 1), such that Si–O bond formation occurs preferentially over H 2O formation from reaction of surface H and O. HREELS studies provide direct evidence of Si and O bonding on the surface through characteristic Si–O vibrations. Some of these vibrations observed after high-temperature annealing may indicate a network of bonded Si–O atoms on the surface rather than isolated molecular adsorbates. AES gives further details of Si–O bonding through fine structure in the Si LVV spectra. CO was used as a probe molecule in both TPD and HREELS studies to study the effect of the SiO X partial overlayer on a well-characterized adsorbate on the Pd(1 1 1) surface. The annealed SiO X layer was found to primarily function by decreasing the number of CO desorption sites, rather than altering the CO adsorption state.

HREELS study of the adsorption and evolution of diethylamine (DEA) on Si(1 0 0) surfaces

The adsorption of diethylamine (DEA) on Si(1 0 0) at 100 K was investigated using high-resolution electron energy loss spectroscopy (HREELS) and electron stimulated desorption (ESD). The thermal evolution of DEA on Si(1 0 0) was studied using temperature programmed desorption (TPD). Our results demonstrate DEA bonds datively to the Si(1 0 0) surface with no dissociation at 100 K. Thermal desorption of DEA takes place via a β-hydride elimination process leaving virtually no carbon behind. Electronic processing of DEA/Si(1 0 0) at 100 K results in desorption of ethyl groups; however, carbon and nitrogen are deposited on the surface as a result of electron irradiation. Thermal removal of carbon and nitrogen was not possible, indicating the formation of silicon carbide and silicon nitride.

Structural characterization, magnetic behavior and high-resolution EELS study of new perovskites Sr 2Ru 2−xCo xO 6−δ (0.5⩽ x⩽1.5)

New oxides of general formula Sr 2Ru 2− x Co x O 6− δ (0.5⩽ x⩽1.5) have been synthesized as polycrystalline materials and characterized structurally by X-ray diffraction. For 0.5⩽ x<0.67 the orthorhombic, Pnma, perovskite structure of the end member, SrRuO 3, is found. At x=0.67 a phase separation into an Ru-rich Pnma phase and a Co-rich I2/ c phase occurs. The I2/ c form is also found for x=1.0 but another orthorhombic phase, Imma, obtains for x=1.33 and 1.5. Reductive weight losses indicate negligible oxygen non-stoichiometry, i.e., δ∼0, for all compositions even those rich in Co. High-resolution electron energy loss spectroscopy (EELS) indicates that cobalt is high-spin Co 3+ or high-spin Co 4+ for all x. Appropriate combinations of Ru 4+, Ru 5+, HS Co 3+ and HS Co 4+ are proposed for each x which are consistent with the observed Ru(Co)–O distances. Significant amounts of Co 4+ must be present for large x values to explain the short observed distances. Broad maxima in the d.c. susceptibilities are found between 78 and 97 K with increasing x, along with zero-field-cooled (ZFC) and field-cooled (FC) divergences suggesting glassy magnetic freezing. A feature near 155 K for all samples indicates a residual amount of ferromagnetic SrRuO 3 not detected by X-ray diffraction.

Sequential Reactions with Amine‐Terminated Monolayers and Isolated Molecules on H/Si(111)

A simple method for preparing monolayers with terminal amine functionality is demonstrated. A gas-phase photochemical reaction of 1,3-diaminopropane with a H-terminated Si(111) surface results in the molecules covalently attaching to the surface, primarily through the formation of a Si--N bond. These monolayers are characterized by scanning tunneling microscopy (STM) and high-resolution electron energy loss spectroscopy (HREELS). The reactivity of the terminal amine is confirmed by exposing the monolayer to benzaldehyde, resulting in the formation of an imine link and the grafting of phenyl rings onto the surface. For short irradiation times, this reaction leads to the formation of isolated amine groups on an otherwise pristine H-terminated surface. STM and HREELS studies of the benzaldehyde reaction on these low-coverage surfaces (less than 0.005 monolayers) indicate that the reaction is restricted to the reactive amine groups, leaving the remainder of the surface unaffected. This simple approach for a sequential coupling reaction is expected to facilitate attachment of more complex molecules (molecular switches, biomolecules) for single-molecule STM studies.

Trends in the adsorption and decomposition of hydrogen and ethylene on monolayer metal films: A combined DFT and experimental study

The combination of density functional theory (DFT) modeling with surface science experiments offers the potential to design catalysts with improved activity and selectivity. In the current paper we report theoretical and experimental studies of the adsorption and decomposition of hydrogen and ethylene on several bimetallic surfaces. DFT calculations predicted that Pd/Mo(1 1 0) and Pt/W(1 1 0) bimetallic surfaces would bind hydrogen and ethylene more weakly than do the corresponding surfaces of the parent metals. The adsorption and decomposition of hydrogen and ethylene on Pd/Mo(1 1 0) and Pt/W(1 1 0) bimetallic systems were investigated using temperature-programmed desorption (TPD), Auger electron spectroscopy (AES), and high-resolution electron energy loss spectroscopy (HREELS) to test the DFT predictions. On the 0.5 and 1.0 ML Pd/Mo(1 1 0) surfaces, the binding strength and the degree of dissociation of hydrogen and ethylene were significantly reduced as compared to Mo(1 1 0) and thick Pd films. Similarly, on 0.5 and 1.0 ML Pt/W(1 1 0) surfaces, TPD results indicated that the degree of dissociation of hydrogen and ethylene was substantially reduced as compared to clean W(1 1 0). HREELS studies of C 2H 4 and C 2D 4 revealed that the adsorption of ethylene on Pt/W(1 1 0) occurred via the weakly π-bonded configuration, which was different from the di-σ bonding on clean W(1 1 0) or Pt(1 1 1).

High-resolution EELS study of the vacancy-doped metal/insulator system, Nd 1−xTiO 3, [formula omitted] to 0.33.

High-resolution electron energy loss spectroscopy (EELS) spectra have been obtained for several members of the vacancy-doped metal/insulator perovskite system Nd 1− x TiO 3 where NdTiO 3 ( x = 0 ) is a Mott–Hubbard insulator and Nd 2/3TiO 3 ( x = 0.33 ), a band insulator. The insulator to correlated-metal transitions occur at x ≈ 0.20 and x ≈ 0.10 . Both O K- and Ti L 2,3-edge data were obtained on the title materials and the related d 0 perovskites, CaTiO 3, SrTiO 3 and BaTiO 3. The crystal structure of Nd 0.70TiO 3 ( x = 0.30 ) was refined from powder neutron data in Cmmm which is taken as a model for the structure of Nd 2/3TiO 3 ( x = 0.33 ) as well. The L-edge spectra for Nd 1− x TiO 3 show systematic changes consistent with the valence state evolution from all Ti 3+ ( x = 0.0 ) to all Ti 4+ ( x = 0.33 ). Octahedral crystal fields of 1.5 and 2.0 eV were inferred from the L-edge data for NdTiO 3 and Nd 2/3TiO 3 by comparison with calculated spectra from the literature. Broader L 3 and L 2 peak widths for Nd 2/3TiO 3 than for the other d 0 perovskites are attributed to the more complex crystal structure of this material which includes two Nd sites with partial occupation and a more distorted Ti–O environment with low site symmetry. A markedly different O K-edge spectrum for Nd 2/3TiO 3 is attributed to the involvement of Nd 5 d levels.

A combined SNMS and EFTEM/EELS study on focused ion beam prepared vanadium nitride thin films

We investigated the diffusion profiles and core-loss fine-structures (ELNES) of thin vanadium nitride films by electron energy-loss spectroscopy (EELS) and energy filtering transmission electron microscopy (EFTEM). The nitride layers have been produced by rapid thermal processing in a NH 3 or N 2 atmosphere and have then been cross-sectioned with a focused ion beam instrument (FIB) under mild milling conditions to maintain crystallography. For the high-resolution electron energy-loss spectroscopy studies (HREELS), a recently developed TEM gun monochromator, implemented into a 200 kV field emission gun column was used in combination with a new post-column spectrometer. It was found that, dependent on substrate and atmosphere, layers with different vanadium and nitrogen content were formed, showing distinct differences in their ELNES. With an energy resolution at the 0.2 eV level and a TEM beam spot size of approximately 2 nm these layers could be unambiguously identified when compared to theoretical ELNES simulations from the literature.

Me-PTCDI thin film deposition on InSb(1 1 1)A

The evolution of N, N′-dimethylperylene-3,4,9,10-dicarboxyimide (Me-PTCDI) thin films formed by vapour deposition on InSb(1 1 1)A substrates has been studied by X-ray photoelectron spectroscopy (XPS), high-resolution electron energy loss spectroscopy (HREELS) and low energy electron diffraction (LEED). XPS studies of the Me-PTCDI covered surface indicate that no significant interaction occurs at sub-monolayer coverage when compared to multilayer Me-PTCDI films. HREELS studies suggest only a weak interaction as evidenced by very small changes in the frequencies of several molecular vibrational modes. LEED patterns show the Me-PTCDI overlayer adopts a structure commensurate with the underlying InSb(1 1 1)A substrate surface and that can be rationalised by van der Waals intermolecular energy calculations for the Me-PTCDI unit cell. The results are consistent with a weak interaction at the Me-PTCDI/InSb interface, the formation of the commensurate structure being sufficient to overcome the small energetic penalty associated with deviation from the calculated intermolecular interaction energy minimum.

The determination of binding energies and preexponential factors: a time resolved HREELS study on Fe(1 1 1)/CO 2

Characteristic high-resolution-electron-energy-loss-spectroscopy (HREELS) intensities of the linear CO 2-state on Fe(1 1 1) have been measured for several different CO 2 pressures as function of surface temperature (temperature programmed HREELS). Taking these isobaric data as input into the Clausius-Clapeyron equation yields a set of isosteric binding energies as function of coverage, which follow the linear relation E b = E b0 ∗ (1 − 0.168 ∗ θ) quite closely. In order to achieve a complete description of the system, the isothermal response to CO 2 pulses was monitored versus time for temperatures between 100 K and 135 K (time resolved HREELS). From these data the adsorption—and the desorption coefficients were determined as function of temperature and coverage by fitting the experimental data to an adsorption model. With the isosteric binding energies as input into the Arrhenius parameterisation of the desorption coefficients a set of preexponentials has been determined as function of temperature. Their values range between 2 × 10 13/s to 10 15/s.