Interactions among 18O2, C2H4, and NO on the surface of stepped Pt(332)

2008 ◽  
Vol 86 (1) ◽  
pp. 39-49 ◽  
Author(s):  
Yuhai Hu ◽  
Keith Griffiths
Keyword(s):  
Thermal Desorption ◽  
Annealing Temperature ◽  
Catalytic Reduction ◽  
Thermal Desorption Spectroscopy ◽  
Blocking Effect ◽  
No Adsorption ◽  
Infrared Reflection Absorption Spectroscopy ◽  
Infrared Reflection ◽  
Site Blocking

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.

ADSORPTION DYNAMICS OFCO2ON HYDROGEN PRECOVEREDZn-ZnO(0001): A MOLECULAR BEAM STUDY

2004 ◽  
Vol 11 (06) ◽  
pp. 521-529 ◽  
Author(s):  
J. WANG ◽  
U. BURGHAUS
Keyword(s):  
Monte Carlo ◽  
Binding Energy ◽  
Thermal Desorption ◽  
Impact Energy ◽  
Atomic Hydrogen ◽  
Molecular Beam ◽  
Thermal Desorption Spectroscopy ◽  
Adsorption Dynamics ◽  
Site Blocking ◽  
The Impact

Presented are initial, S0, and coverage, Θ, dependent, S(Θ), adsorption probability measurements, respectively, of CO2adsorption on a hydrogen precovered, polar, Zn -terminated surface of ZnO , parametric in the impact energy, Ei, and atomic hydrogen precoverage, ΘH. Furthermore, CO2Thermal Desorption Spectroscopy has been used to estimate ΘHas well as the binding energy of CO2on H / Zn - ZnO . The S(Θ) curves are below Ei=0.56 eV , consistent with precursor-mediated adsorption (S~ const ), and above that impact energy with adsorbate-assisted adsorption (S increases with Θ). Although a decrease in the CO2binding energy from 32.5 to 28.8 kJ/mol with ΘHis present, S(Θ, ΘH) curves are consistent with a physical site blocking, as demonstrated by Monte Carlo Simulations.

scholarly journals Investigation of the Pressure Dependent Hydrogen Solubility in a Martensitic Stainless Steel Using a Thermal Agile Tubular Autoclave and Thermal Desorption Spectroscopy

Metals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 231
Author(s):  
Patrick Fayek ◽  
Sebastian Esser ◽  
Vanessa Quiroz ◽  
Chong Dae Kim
Keyword(s):  
Stainless Steel ◽  
Thermal Desorption ◽  
Hydrogen Diffusion ◽  
Martensitic Stainless Steel ◽  
Thermal Desorption Spectroscopy ◽  
Hydrogen Uptake ◽  
Hydrogen Solubility ◽  
Automotive Components ◽  
Set Up ◽  
Service Application

Hydrogen is nowadays in focus as an energy carrier that is locally emission free. Especially in combination with fuel-cells, hydrogen offers the possibility of a CO2 neutral mobility, provided that the hydrogen is produced with renewable energy. Structural parts of automotive components are often made of steel, but unfortunately they may show degradation of the mechanical properties when in contact with hydrogen. Under certain service conditions, hydrogen uptake into the applied material can occur. To ensure a safe operation of automotive components, it is therefore necessary to investigate the time, temperature and pressure dependent hydrogen uptake of certain steels, e.g., to deduct suitable testing concepts that also consider a long term service application. To investigate the material dependent hydrogen uptake, a tubular autoclave was set-up. The underlying paper describes the set-up of this autoclave that can be pressurised up to 20 MPa at room temperature and can be heated up to a temperature of 250 °C, due to an externally applied heating sleeve. The second focus of the paper is the investigation of the pressure dependent hydrogen solubility of the martensitic stainless steel 1.4418. The autoclave offers a very fast insertion and exertion of samples and therefore has significant advantages compared to commonly larger autoclaves. Results of hydrogen charging experiments are presented, that were conducted on the Nickel-martensitic stainless steel 1.4418. Cylindrical samples 3 mm in diameter and 10 mm in length were hydrogen charged within the autoclave and subsequently measured using thermal desorption spectroscopy (TDS). The results show how hydrogen sorption curves can be effectively collected to investigate its dependence on time, temperature and hydrogen pressure, thus enabling, e.g., the deduction of hydrogen diffusion coefficients and hydrogen pre-charging concepts for material testing.

The Role of Cr in H Desorption Kinetics in Rapidly Solidified Al

2014 ◽  
Vol 783-786 ◽  
pp. 264-269 ◽  
Author(s):  
Iya I. Tashlykova-Bushkevich ◽  
Keitaro Horikawa ◽  
Goroh Itoh
Keyword(s):  
High Temperature ◽  
Thermal Desorption ◽  
High Purity ◽  
Thermal Desorption Spectroscopy ◽  
Secondary Phase ◽  
Hydrogen Desorption ◽  
Oxide Surface ◽  
Desorption Kinetics ◽  
Hydrogen Trapping ◽  
Rapidly Solidified

Hydrogen desorption kinetics for rapidly solidified high purity Al and Al-Cr alloy foils containing 1.0, 1.5 and 3.0 at % Cr were investigated by means of thermal desorption analysis (TDA) at a heating rate of 3.3°C/min. For the first time, it was found that oxide inclusions of Al2O3 are dominant high-temperature hydrogen traps compared with pores and secondary phase precipitates resulted in rapid solidification of Al and its alloys. The correspondent high-temperature evolution rate peak was identified to be positioned at 600°C for high purity Al and shifted to 630°C for Al-Cr alloys. Amount of hydrogen trapped by dislocations increases in the alloys depending on Cr content. Microstructural hydrogen trapping behaviour in low-and intermediate temperature regions observed here was in coincidence with previous data obtained for RS materials using thermal desorption spectroscopy (TDS). The present results on hydrogen thermal desorption evolution indicate that the effect of oxide surface layers becomes remarkable in TDA measurements and show advantages in combinations of both desorption analysis methods to investigate hydrogen desorption kinetics in materials.

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