SOx poisoning has been a critical problem in the chemistry of selective catalytic reduction of NOx, and many fundamental issues surrounding the reactions remain unclear. In this paper, reactions taking place in the (C2H5OH)-C-13-NO-(SO2)-O-18-O-2 system on a platinum single crystal surface were studied. Oxidation of (C2H5OH)-C-13 by (SO2)-O-18 proceeds mainly through O-18-H reaction, and oxidation of the backbone carbon atoms can occur at high (SO2)-O-18 exposures, e.g., 1.6 Ls of (SO2)-O-18 for 0.4 L of (C2H5OH)-C-13. Thus, the presence of (SO2)-O-18 only slightly suppresses the catalytic reduction of NO by (C2H5OH)-C-13. Co-adsorbed O-2 evidently exerts a suppressive effect. When oxygen is lean (relative to (SO2)-O-18), the (SO2)-O-18-O-2 reactions mainly give rise to surface sulphoxy species at temperatures between 400 and 500K and thus, the NO-(C2H5OH)-C-13 reactions can still proceed. The NO reduction reaction is completely suppressed when oxygen is rich, a result of the Pt surface being passivated. This finding provides a valuable guide for optimizing the reaction atmosphere to improve the efficiency of the selective catalytic reduction of NO by hydrocarbons (or oxygen-containing fragments from oxidation of hydrocarbons in this case). (C) 2017 Elsevier B.V. All rights reserved.

The catalytic reduction of NO by hydrocarbons (C2H4 and its derivatives) in the presence of both (SO2)-O-18 and O-2 on Pt(332) was investigated. (SO2)-O-18-C2H4 interactions are much stronger than NO-C2H4 interactions. Coadsorbeol (SO2)-O-18 molecules consume most of the H atoms from C2H4 dissociation before NO dissociation, a major cause for suppressing the NO-C2H4 reaction. The (SO2)-O-18 molecules also reduce the reactivity of Pt(332) toward NO-C2H4 reaction by passivating the metal surface and by blocking the step sites for NO adsorption. NO-C2H4 reactions are also suppressed by coadsorbed 0(ads) atoms due to the stronger Pt-O interaction and facile H-O reaction. However, when the coverage of O atoms is appropriate, the O atoms effectively lifts the suppressive effect of (SO2)-O-18, a result of the facile O-(SO2)-O-18 reaction, which scavenges the (SO2)-O-18 related species and consequently gives the Pt(332) surface a more reactive pathway toward the NO dissociation (compared to that covered with sulfur oxides).

The photochemical and thermal reactivity of a number of acyl azide-substituted pyridine compounds, namely nicotinyl azide, isonicotinyl azide, picolinyl azide and dinicotinyl azide with investigated as saturated monolayers on a single-crystal Pt(111) surface in an ultrahigh vacuum chamber. Multilayers of the substrates exhibited a maximum rate of desorption at 270 K, above which, stable saturated monolayers formed as characterized by reflection-absorption infrared spectroscopy by observation of C=O and N3 bands at 1700 cm(-1), and 2100 and 1300 cm(-1) respectively. The monolayers were stable up to 400 K. Photolysis of the monolayer (or heating above 400 K) results in the formation of the respective isocyanate intermediate after loss of nitrogen as evidenced by the appearance of a new infrared band at 2260 cm(-1) with concomitant loss of the azide bands. The resulting isocyanate saturated monolayer is stable in absence of nucleophiles, but can be quenched with appropriate nucleophiles.

The paper reviews recent advances in the understanding of hydrogen adsorption on the Si (100)−(2 × 1) surface. Absolute measurement of deuterium coverage over a wide range of exposure allow us to identify different reaction process. Channeling analysis sees changes of surface structure down several layers below the surface on various hydride terminated Si(100) surfaces.

Irradiation of saturated monolayers of 3- and 4-substituted pyridyl diazoacetates on single-crystal Pt surfaces leads to either the corresponding reactive carbene or stable ketene intermediate with the chemoselectivity determined by the position of the photoreactive substituent on the pyridyl ring, which ultimately directs the available interactions with neighboring substrates.

The influence of (SO2)-O-18, O-2 and their reaction products, surface sulphoxy species, on NO-D-2 reactions on the surface of stepped Pt(332) was studied. Oxidation of (SO2)-O-18 by O-2 proceeds to a very slight extent on Pt(332), taking place as the surface temperature is increased to 300 K and higher. The oxidation reaction gives rise to surface sulphoxy species ((SOx)-O-18, x>2) that persist on the surface up to 500 K but desorb completely at 600 K. The surface sulphoxy species desorb mainly as (SO2)-O-18 (predominantly) and (SO3)-O-18. On the other hand, co-adsorbed (SO2)-O-18 molecules render the desorption of O atoms, (which otherwise occurs at 700 K and higher from a clean Pt(332) surface), undetectable. Such oxygen desorption reappears and gains a considerable intensity as the sulphoxy species covered Pt(332) surface was further exposed to NO molecules. However, NO dissociation is suppressed in the presence of (SO2)-O-18, O atoms and surface sulphoxy species; the suppressive effect from O atoms and surface sulphoxy species is much more significant than that from (SO2)-O-18. No N-2 desorption resulting from NO dissociation is detected under some conditions.The suppressive effect exerted by O atoms and surface sulphoxy species also holds for the NO-D reaction, but is highly dependent on the exposures of O-2 and (SO2)-O-18. The NO-D reaction is not suppressed on the Pt(332) surface which has been pre-exposed to 0.4 L O-2 at 90 K and then annealed to 200 K, due to rapid removal of O atoms (including those from NO dissociation) as a result of the facile reaction between O and D. On the Pt (332) surface, pre-exposed to O-2 and (SO2)-O-18 and then annealed to 400 K, the efficiency of the NO-D reaction (manifested by N-2 production) is obviously lower than that on a clean surface (without surface sulphoxy species); however, the suppressive effect becomes significant only as the exposures of O-2 and (SO2)-O-18 are >= 0.4 L.Surface sulphoxy species-induced suppression of the NO-D reaction on Pt(332) mainly results from NO-Pt interactions being weakened and a lack of D atom supply at the surface temperatures where NO dissociation becomes significant. O-2 desorption from the Pt(332) surface finishes at similar to 350 K, at which temperature surface sulphoxy species and O atoms persist and NO dissociation just becomes appreciable. As such, the NO-D reaction evolves into NO dissociation on the surface sulphoxy species covered Pt(332).The present results also suggest that the site blocking effect of surface sulphoxy species and O atoms does not evidently contribute to their suppression of NO-D reaction. (C) 2010 Elsevier B.V. All rights reserved.

Interactions between S18O2 and NO on the surface of stepped Pt(332) were studied using Fourier transform infra red reflection-absorption spectroscopy (FTIR-RAS) combined with thermal desorption spectroscopy (TDS). Adsorbed S18O2 does not seem to have a preference for step sites on Pt(332). As such, the presence of S18O2 molecules following exposures of ⩽1.6L does not significantly block the subsequent adsorption of NO (⩽0.8L) on these step sites. Adsorbed S18O2 molecules undergo dissociation (S18O2(a)→S18O(a)+18O(a)) as the surface temperature is increased to 250K and above, but the resultant 18O(a) further reacts with sulfur oxides (S18O2(a) and S18O(a)) to form S18Ox (x>2) species at ∼400K and above. The S18Ox species desorb as S18O2. Even though the presence of co-adsorbed S18O2 suppresses NO dissociation and subsequent N2 production, this effect is not significantly enhanced with increasing the exposures of S18O2 in the range ⩽1.6L; N2 desorption is still detectable at an exposure of 1.6L S18O2, at which a considerable amount of S18O2 desorption is detected.

It has previously been shown that experimental infections of the parasitic trematode Schistosoma mansoni, the adult worms of which reside in the blood stream of the mammalian host, significantly reduced atherogenesis in apolipoprotein E gene knockout (apoE−/−) mice. These effects occurred in tandem with a lowering of serum total cholesterol levels in both apoE−/− and random-bred laboratory mice and a beneficial increase in the proportion of HDL to LDL cholesterol. To better understand how the parasitic infections induce these effects we have here investigated the involvement of adult worms and their eggs on lipids in the host. Our results indicate that the serum cholesterol-lowering effect is mediated by factors released from S. mansoni eggs, while the presence of adult worms seemed to have had little or no effect. It was also observed that high levels of lipids, particularly triacylglycerols and cholesteryl esters, present in the uninfected livers of both random-bred and apoE−/−mice fed a high-fat diet were not present in livers of the schistosome-infected mice.

NO dissociation and subsequent N-2 production in the presence of co-adsorbed (SO2)-O-18 and D-2 on the surface of stepped Pt(332) were studied using Fourier transform infra red reflection-absorption spectroscopy (FTIR-RAS) combined with thermal desorption spectroscopy (TDS). Reduction of NO by D (D-2 is adsorbed dissociatively on Pt surfaces) proceeds to a limited extent, because this reaction is rate-controlled by NO dissociation and the supply of D atoms at the higher surface temperatures at which NO dissociation becomes significant (350 K and higher). NO-D reaction is suppressed in the presence Of (SO2)-O-18, depending significantly on the (SO2)-O-18 coverage and the competition between the reactions NO-D and (SO2)-O-18-D. When the supply of D-2 is limited, e.g., 0.1 L in this study, the presence Of (SO2)-O-18 suppresses the NO-D reaction. With a sufficient supply of D-2, e.g., 0.4 L and higher, D-atom competing reactions do not play a role any more because the reactions of both NO and (SO2)-O-18 with D proceed only to a very limited extent. As such, generation of O atoms from (SO2)-O-18 dissociation is the main reaction that leads to the suppression in NO dissociation and consequently, N-2 production.It is also concluded that the presence of (SO2)-O-18 does not seriously poison the active sites on the Pt surface, providing that there is a sufficient D supply to remove O atoms from both NO dissociation and (SO2)-O-18 dissociation. (C) 2009 Elsevier B.V. All rights reserved.

Interactions between (SO2)-O-18 and NO on the surface of stepped Pt(332) were studied using Fourier transform infra red reflection-absorption spectroscopy (FTIR-RAS) combined with thermal desorption spectroscopy (TDS). Adsorbed (SO2)-O-18 does not seem to have a preference for step sites on Pt(332). As such, the presence of (SO2)-O-18 molecules following exposures of <= 1.6 L does not significantly block the subsequent adsorption of NO (<= 0.8 L) on these step sites. Adsorbed (SO2)-O-18 molecules undergo dissociation ((SO2)-O-18(a) -> (SO)-O-18(a) + O-18(a)) as the surface temperature is increased to 250 K and above, but the resultant O-18(a) further reacts with sulfur oxides ((SO2)-O-18(a) and (SO)-O-18(a)) to form (SOx)-O-18 (x > 2) species at similar to 400 K and above. The (SOx)-O-18 species desorb as (SO2)-O-18. Even though the presence of co-adsorbed (SO2)-O-18 suppresses NO dissociation and subsequent N-2 Production, this effect is not significantly enhanced with increasing the exposures of (SO2)-O-18 in the range <= 1.6 L; N-2 desorption is still detectable at an exposure of 1.6 L (SO2)-O-18, at which a considerable amount of (SO2)-O-18 desorption is detected. (C) 2008 Elsevier B.V. All rights reserved.

Oxidation of (C2H5OH)-C-13 by NO and O-2 on the surface of stepped Pt(332) was studied using Fourier transform infrared reflection-absorption spectroscopy combined with thermal desorption spectroscopy. Upon annealing, adsorbed (C2H5OH)-C-13 molecules undergo stepwise dissociation. Desorption of H-2, released from the scission of O-H, C-13-H (alpha-C-13), and C-13-H (beta-C-13) bonds in sequence, covers a broad temperature range from similar to 260 to similar to 550 K. Desorption of (CO)-C-13 gives rise to a peak at 500-510 K. This surface process does not change greatly in the presence of O-2. Oxidation of (C2H5OH)-C-13 and, consequently, the generation of the products are strongly dependent on the pretreatment of (C2H5OH)-C-13. Thermal desorption spectra of H-2 and (CO2)-C-13 indicate that oxidation of (C2H5OH)-C-13 to H2O and (CO2)-C-13 is a primary process in most cases. However, when (C2H5OH)-C-13 adsorbed at 90 K is preannealed to 250 K before being exposed to O-2, reaction of O with H predominates. Consequently, oxidation of carbon-related species to (CO2)-C-13 is completely suppressed. (C2H5OH)-C-13 dissociation, in particular, the cleavage of the C-13-C-3 bonds, is suppressed in the presence of NO. Desorption of H-2, released from dehydrogenation of (13)CHx (beta-C) at surface temperatures above 400 K, is not detectable from the co-adlayers following the adsorptions of (C2H5OH)-C-13 and NO at 90 K. Oxidation of (C2H5OH)-C-13 related species with NO to (CO)-C-13 and (CO2)-C-13 proceeds to a much smaller extent compared to that with O-2. The presence of (C2H5OH)-C-13, irrespective of whether it is preadsorbed or postadsorbed, results in more NO desorption from terraces (at 350-360 K), due to a site-swapping effect exerted by (C2H5OH)-C-13 derivatives ((CO)-C-13 and (13)CHx). Nonetheless, NO reduction and subsequent N-2 production is promoted in the presence of (C2H5OH)-C-13. This effect, however, does not strongly depend on the exposure of (C2H5OH)-C-13. It is concluded that reduction of NO and subsequent N-2 production proceeds through a mechanism of NO dissociation and subsequent O removal, NO dissociation on the steps of the Pt(332) being a rate-limiting step. The reaction of (C2H5OH)-C-13-related species with O effectively scavenges O atoms arising from NO dissociation, therefore giving rise to vacant sites that accommodate O atoms from further NO dissociation. This accounts for the (C2H5OH)-C-13-induced enhancement in N-2 production.

Selective catalytic reduction (SCR) of NOx is one of the important strategies in regulating NOx emissions. In the past several decades, the reactions of NOx (mainly NO) with H-2, CO, NH3 and hydrocarbons have been extensively investigated under ambient conditions and have been summarized in numerous reviews. Nonetheless, many questions appear to be difficult to answer under ambient conditions, e.g., the pathways through which the reactions proceed. The introduction and development of modern surface science technology has played an indispensable role and is widely employed in the studies of the SCR of NOx, greatly helping to elucidate the mechanisms of the reactions with CO, H-2, and NH3. However, so far, there are few review papers systematically summarizing the progress of such studies.Recently, systematic surface science studies have been conducted on the mechanisms of SCR of NO with organic molecules including ethylene, benzene, and ethanol, which are much more complicated than those with H-2, CO and NH3 and have drawn much less attention before. It is confirmed that these reactions can be reliably and most importantly, reproducibly probed by surface science technology, but a great deal of work remains to be done.Since Delmon et al. have provided a very thorough review of the researches on catalytic removal of NO (reactions with H-2, CO and NH3) UP to 1998, in which the reactions conducted both under ambient and UHV conditions were included, this review mainly concentrates on the progress made since 1998. (C) 2009 Elsevier B.V. All rights reserved.

The catalytic reduction of NO in the presence of benzene on the surface of Pt(3 3 2) has been studied using Fourier transform infra red reflection-absorption spectroscopy (FTIR-RAS) and thermal desorption spectroscopy (TDS). IR spectra show that while the presence of benzene molecules at low coverage (e.g., following an exposure of just 0.25 L) promotes NO-Pt interaction, the adsorption of NO on Pt(3 3 2) at higher benzene coverages is suppressed. It is also shown that there are no strong interactions between the adsorbed NO molecules and the benzene itself or benzene-derived hydrocarbons, which can lead to the formation of intermediate species that are essential for N-2 production.TDS results show that the adsorbed benzene molecules undergo dehydrogenation accompanied by hydrogen desorption starting at 300 K and achieving a maximum at 394 K. Subsequent dehydrogenation of the benzene-derived hydrocarbons then begins with hydrogen desorption starting at 500 K. N-2 desorption from NO adlayers on clean Pt(3 3 2) surface becomes significant at temperatures higher than 400 K, giving rise to a peak at 465 K. This peak corresponds to N2 desorption from NO dissociation on step sites. The presence of benzene promotes N-2 desorption, depending on the benzene coverage. When the benzene exposure is 0.25 L, the N-2 desorption peak at 459 K is dramatically increased. Increasing benzene coverage also results in the intensification of N-2 desorption at similar to 410 K. At benzene exposures of 2.4 L, N-2 desorption develops as a broad peak with a maximum at similar to 439 K.It is concluded that the catalytic reduction of NO by platinum in the presence of benzene proceeds by NO decomposition and subsequent oxygen removal at temperatures lower than 500 K, and NO dissociation is a rate-limiting step. The contribution of benzene to N-2 desorption is mainly attributed to providing a source of H, which quickly reacts with NO-derived atomic 0, leaving the surface with more vacant sites for further NO dissociation. (c) 2007 Elsevier B.V All rights reserved.

Oxidation of C213H5OH by NO and O2 on the surface of stepped Pt(332) was studied using Fourier transform infrared reflection-absorption spectroscopy combined with thermal desorption spectroscopy. Upon annealing, adsorbed C213H5OH molecules undergo stepwise dissociation. Desorption of H2, released from the scission of O–H, C13–H (α-C13), and C13–H (β-C13) bonds in sequence, covers a broad temperature range from ∼260to∼550K. Desorption of C13O gives rise to a peak at 500–510K. This surface process does not change greatly in the presence of O2. Oxidation of C213H5OH and, consequently, the generation of the products are strongly dependent on the pretreatment of C213H5OH. Thermal desorption spectra of H2 and C13O2 indicate that oxidation of C213H5OH to H2O and C13O2 is a primary process in most cases. However, when C213H5OH adsorbed at 90K is preannealed to 250K before being exposed to O2, reaction of O with H predominates. Consequently, oxidation of carbon-related species to C13O2 is completely suppressed. C213H5OH dissociation, in particular, the cleavage of the C13–C3 bonds, is suppressed in the presence of NO. Desorption of H2, released from dehydrogenation of C13Hx (β-C) at surface temperatures above 400K, is not detectable from the co-adlayers following the adsorptions of C213H5OH and NO at 90K. Oxidation of C213H5OH related species with NO to C13O and C13O2 proceeds to a much smaller extent compared to that with O2. The presence of C213H5OH, irrespective of whether it is preadsorbed or postadsorbed, results in more NO desorption from terraces (at 350–360K), due to a site-swapping effect exerted by C213H5OH derivatives (C13O and C13Hx). Nonetheless, NO reduction and subsequent N2 production is promoted in the presence of C213H5OH. This effect, however, does not strongly depend on the exposure of C213H5OH. It is concluded that reduction of NO and subsequent N2 production proceeds through a mechanism of NO dissociation and subsequent O removal, NO dissociation on the steps of the Pt(332) being a rate-limiting step. The reaction of C213H5OH-related species with O effectively scavenges O atoms arising from NO dissociation, therefore giving rise to vacant sites that accommodate O atoms from further NO dissociation. This accounts for the C213H5OH-induced enhancement in N2 production.

The influence of pre-dosed oxygen on NO-C2H4 interactions on the surface of stepped Pt(3 3 2) has been investigated using Fourier transform infrared reflection-absorption spectroscopy (FTIR-RAS) and thermal desorption spectroscopy (TDS). The presence of oxygen significantly suppresses the adsorption of NO on the steps of Pt( 3 3 2), leading to a very specific adsorption state for NO molecules when oxygen-NO co-adlayers are annealed to 350 K (assigned as atop NO on step edges). An oxygen-exchange reaction also takes place between these two kinds of adsorbed molecules, but there appears to be no other chemical reaction, which can result in the formation of higher-valence NOx.C2H4 molecules which are post-dosed at 250 K to adlayers consisting of O-18 and NO do not have strong interactions with either the NO or the O-18 atoms. In particular, interactions which may result in the formation of new surface species that are intermediates for N-2 production appear to be absent. However, C2H4 is oxidized to (CO2)-O-18 by O-18 atoms at higher annealing temperature. This reaction scavenges surface O-18 atoms quickly, and the adsorption of NO molecules on step sites is therefore quickly restored. As a consequence, NO dissociation on steps proceeds very effectively, giving rise to N-2 desorption which closely resembles that following only NO exposure on a clean Pt( 3 3 2), both in peak intensity and desorption temperature. It is concluded that the presence of O-18(2) in the selective catalytic reduction (SCR) of NO with C2H4 on the surface of Pt(3 3 2) does not play a role of activating reactants. (C) 2008 Elsevier B.V. All rights reserved.

Fourier transform infra red reflection–absorption spectroscopy (FTIR-RAS), thermal desorption spectroscopy (TDS), and auger electron spectroscopy (AES), were employed to explore the mechanism of NO reduction in the presence of C2H4 on the surface of stepped Pt(332). Both NO–Pt and C2H4–Pt interactions are enhanced when NO and C2H4 are co-adsorbed on Pt(332). As a result, C2H4 is dissociated at surface temperatures as low as 150K, and the N–O stretch band is weakened. The presence of post-exposed C2H4 leads NO desorption from steps to decrease significantly, but the same effect on NO desorption from terraces becomes appreciable only at higher post-exposures of C2H4, e.g., 0.6L and 1.2L, and proceeds to a much slighter extent. Auger spectra indicate that as a result of the reaction with O from NO dissociation, the amount of surface C species is greatly reduced when NO is post-exposed to a C2H4 adlayer. It is concluded that reduction of NO in the presence of C2H4 proceeds very effectively on the surface of the Pt(332), through a mechanism of NO dissociation and subsequent O removal. Following this mechanism, the significant dissociation of adsorbed NO molecules on steps at surface temperatures below 400K, and subsequent rapid reaction between the resultant O and C-related species, accounts for the considerable amount of N2 desorption at temperatures below 400K.

The influence of co-adsorbed 18O2 (18O) on NO/C2H4 reactions on the surface of stepped Pt(332) has been investigated using Fourier transform infrared reflection–absorption spectroscopy (FTIR-RAS) and thermal desorption spectroscopy (TDS). The presence of 18O2 (18O) results in changes in C2H4 dissociation behavior, with formation of ethylidyne taking place at surface temperature much higher than that in the absence of 18O2 (18O). Pre-annealing 18O2/C2H4 co-adlayers to 250 and 300 K does not lead to significantly different IR spectra, but a variety of spectra are observed when the 250 K and 300 K 18O/C2H4 co-adlayers are further exposed to 0.8 L NO at 90 K, depending on the 18O2 pre-exposure. NO adsorption in bridge sites, both on steps and on terraces is more significantly suppressed for the co-adlayers in which 18O2/C2H4 is pre-annealed to 250 K. This site-blocking effect is enhanced with increasing 18O2 exposure. However, no new surface species, which are intermediates for N2 production, are detected. Thermal desorption spectra indicate that various species are produced, but only N2 and H2 desorption have intensities that can be reliably analyzed (that is to be able to quantitatively elucidate how the yields of these two species vary with change in the ratios of NO to C2H4 and 18O2). Desorption of both N2 and H2 is more strongly dependent on 18O2 exposure than on the temperature to which 18O2/C2H4 adlayers are pre-annealed. The presence of 18O2, irrespective of the dosing sequence, suppresses N2 desorption, but this effect is much weaker when 18O2 is post-dosed. For the case with 18O2 pre-dosed, irrespective of the annealing temperature (250 K or 300 K), N2 desorption is greatly suppressed at an 18O2 exposure of 0.2 L, but thereafter remains almost unchanged with increasing 18O2 exposure from 0.4 to 1.6 L. This feature of N2 desorption is explained by the restoration of the adsorption of NO onto steps and the subsequent NO dissociation on these sites. In contrast, H2 desorption decreases continuously and disappears at 0.8 L 18O2 and higher. It is concluded that the presence of 18O2 in the reaction of NO with C2H4 on the surface of Pt(332) does not play any role of activating the surface reactants.Key words: NO, platinum, C2H4, deNOx, hydrocarbon, selective catalytic reduction.

On metals such as Zr, during hydrogen exposure, dissolution competes with desorption; this competition call be probed by thermal desorption at different heating rates. In the case of desorption from preadsorbed hydrogen, only similar to 1% of the hydrogen call be desorbed even at heating rates of >10(10) K s(-1). Recent measurements of the dynamics of hydrogen released by water dissociation on Zr(0 0 0 1) [G. Bussiere, M. Musa, P.R. Norton, K. Griffiths, A.G. Brolo, J.W. Hepburn, J. Chem. Phys. 124 (2006) 124704] have shown that the desorbing hydrogen originates from the recombinative desorption of adsorbed H-atoms and that over 25% of the water collisions lead to hydrogen desorption. To gain further insight into the desorption and dissolution of hydrogen and in all attempt to resolve the paradox of the different desorption yields from H, vs. H2O exposures, we report new measurements of the laser induced thermal desorption (LITD) of hydrogen from Zr(0 0 0 1) at initial temperatures down to 90 K. The low temperature was chosen because work function measurements suggested that hydrogen adsorbed into only the outermost (surface site) of the two available adsorption sites (surface and subsurface). from which we postulated much more efficient desorption at high heating rates compared to desorption from the sub-surface sites. However, hydrogen desorption by LITD from Zr(000 1) at 90 K still only accounts for 1%) of the adsorbed species. the remainder dissolving into the bulk at LITD heating rates. The different yields alluded to above remain unexplained (Bussiere, 2006). (c) 2007 Elsevier B.V. All rights reserved.

The influence of pre-dosed O-2 On he catalytic reduction of NO with (C2H5OH)-C-13 on the surface of stepped Pt(332) was investigated using Fourier transform infra red reflection-absorption spectroscopy (FTIR-RAS) and thermal desorption spectroscopy (TDS). We show that the oxidation of (C2H5OH)-C-13 with O-2 is a very effective reaction, occurring at 150 K and giving rise to acetate. The presence of NO does not lead to any evident oxidation of (C2H5OH)-C-13 irrespective of the annealing temperature. For the case of O-2 + (C2H5OH)-C-13 + NO co-adlayers, oxidation (C2H5OH)-C-13 also takes place at 150 K. However, no new surface species that are supposed to be an intermediate for the production of N-2 are detected.The influence of O-2 on the production and desorption of N-2 is intimately related to both O-2 and (C2H5OH)-C-13 coverage. The presence of pre-dosed O-2 does not greatly promote N-2 desorption. In fact, N-2 desorption is suppressed quantitatively with increasing O-2, coverage, after which unreacted, or left-over O atoms appear and remain on steps. It is concluded that the presence of pre-dosed O-2 does not play a role of activating reactants in the catalytic reduction of NO with (C2H5OH)-C-13 on the surface of Pt(332). (C) 2007 Elsevier B.V. All rights reserved.