The influence of temperature and structure of palladium surfaces on the adsorption of ethylene and hydrogenation of adsorption complexes by molecular and atomic hydrogen

1982 ◽  
Vol 47 (9) ◽  
pp. 2307-2322 ◽  
Author(s):  
Josef Kopešťanský
Keyword(s):  
Work Function ◽  
Atomic Hydrogen ◽  
Product Analysis ◽  
Influence Of Temperature ◽  
Adsorption Sites ◽  
Function Change ◽  
Surface Work ◽  
Ethylene Adsorption ◽  
Adsorption Complexes ◽  
Palladium Surface

A measurement of the work-function change, combined with the volumetric method and gas product analysis were used for investigation of the influence of temperature and palladium surface structure on the adsorption of ethylene and hydrogenation of its adsorption complexes by molecular and atomic hydrogen. It was verified that on palladium the highest activity for the C-H bond splitting of hydrocarbons is found on the adsorption sites corresponding to low-coordination surface atoms. The activation energy of the C-H bond dissociation is very low (ED ##i 2 kJ/mol); as a result, in the early stages of surface coverage, hydrogen appears on the surface - together with the formation of surface adsorption complexes. The presence of hydrogen is the main reason for the non-linearity of the work-function changes, observed for ethylene adsorption in the low-coverage region. Stable dehydrogenated surface particles are formed also by self-hydrogenation of ethylene in the higher-coverage region. With increasing temperature, the extent of dehydrogenation of the adsorbed complexes also increases - while the influence of molecular hydrogen on the work-function of the surface with pre-adsorbed ethylene becomes less significant. The interaction of atomic hydrogen with ethylene adsorption-complexes caused in all cases irreversible changes of the surface work-function.

Acetylene chemisorption at palladium: Effect of temperature and structure of the surface

1984 ◽  
Vol 49 (6) ◽  
pp. 1448-1458
Author(s):  
Josef Kopešťanský
Keyword(s):  
Work Function ◽  
Atomic Hydrogen ◽  
Effect Of Temperature ◽  
Thermally Stable ◽  
Template Effect ◽  
Temperature Range ◽  
Adsorbed Layers ◽  
Different Types ◽  
Adsorption Complexes ◽  
Low Coverage

The effect of temperature and structure of the palladium surfaces on acetylene chemisorption was studied along with the interaction of the adsorbed layers with molecular and atomic hydrogen. The work function changes were measured and combined with the volumetric measurements and analysis of the products. At temperature below 100 °C, acetylene is adsorbed almost without dissociation and forms at least two different types of thermally stable adsorption complexes. Acetylene adsorbed at 200 °C is partly decomposed, especially in the low coverage region. Besides the above mentioned effects, the template effect of adsorbed acetylene was studied in the temperature range from -80° to 25 °C. It has been shown that this effect is a typical phenomenon of the palladium-acetylene system which is not due to surface impurities.

scholarly journals Surface Work Function Change by Oxidation of Hydrogen-Terminated Chemical Vapor Deposited Diamond

Hyomen Kagaku ◽  
2005 ◽  
Vol 26 (9) ◽  
pp. 547-552
Author(s):  
Hidenori GAMO ◽  
Mikka N.-GAMO ◽  
Kiyoharu NAKAGAWA ◽  
Toshihiro ANDO
Keyword(s):  
Work Function ◽  
Chemical Vapor ◽  
Function Change ◽  
Surface Work ◽  
Chemical Vapor Deposited ◽  
Work Function Change ◽  
Oxidation Of Hydrogen ◽  
Surface Work Function

A Field Emission Microscopic Study of Hydrogen Adsorption on a Stepped Tungsten Plane: W(310)

1997 ◽  
Vol 11 (02n03) ◽  
pp. 63-71 ◽  
Author(s):  
D. S. Choi ◽  
S. M. Paik ◽  
J. H. Han ◽  
N. G. Park ◽  
K. S. Kim ◽  
...  
Keyword(s):  
Work Function ◽  
Field Emission ◽  
Hydrogen Adsorption ◽  
Indirect Comparison ◽  
Adsorption Sites ◽  
Function Change ◽  
Field Emission Current ◽  
Average Work ◽  
Work Function Change ◽  
Low Coverage

Using a newly developed Derivative Field Emission Current (DFEC) methods, the heat of desorption and the work-function-change of W(310) plane induced by hydrogen adsorption are measured. The average work function of the W(310) plane increases initially as the hydrogen dose increases for the low coverage region, decreases for the dose higher than about 0.7 Languimir, and saturates at about 4 Languimir. We find the eight hydrogen adsorption sites on the W(310) plane. Three of these sites are on the terrace (100) plane and the hydrogen adsorption on these sites lower the work function. The other three sites are on the step-wall (110) plane raising the work function. Last two sites are probably on the step-edge. The heats of desorption for these sites ranges from 16.6±2.0 kcal/mol for the γ2 state to 32.0±1.0 kcal/mol for the β6 state. An indirect comparison and analysis show that our findings are quite reasonable.

Work function studies of propylene, acetylene, hydrogen and nitrogen chemisorption on molybdenum

1982 ◽  
Vol 47 (11) ◽  
pp. 2996-3003
Author(s):  
Zdeněk Bastl
Keyword(s):  
Work Function ◽  
Surface Topography ◽  
Surface Coverage ◽  
Dissociative Chemisorption ◽  
Complete Coverage ◽  
Surface Sites ◽  
Function Change ◽  
Work Function Change

The work function changes of vacuum deposited molybdenum films caused by the chemisorption of propylene, acetylene, hydrogen and nitrogen were measured using the Kelvin vibrating capacitor method. During the hydrocarbon chemisorption, the work function increased in a low surface coverage region but decreased at the higher surface coverages. The saturation values of the work function changes corresponding to complete coverage of the surface by chemisorbed propylene and acetylene equal -0.08 eV and -0.42 eV, respectively. The observed dependences of the work function change on surface coverage are interpreted by the dissociative chemisorption of hydrocarbons on a limited number of surface sites which are simultaneously the sites of preferred adsorption. The extent of dissociation decreases in the adsorption with the increasing surface coverage. The results of the study of the work function changes induced by the hydrogen and nitrogen chemisorption enabled to draw several conclusions on the surface topography of the used films.

N-doped zeolite-templated carbon as a metal-free electrocatalyst for oxygen reduction

RSC Advances ◽  
2016 ◽  
Vol 6 (49) ◽  
pp. 43091-43097 ◽  
Author(s):  
Yonghyun Kwon ◽  
Kyoungsoo Kim ◽  
Ryong Ryoo
Keyword(s):  
Work Function ◽  
Oxygen Reduction ◽  
Catalytic Performance ◽  
Microporous Structure ◽  
Nitrogen Doped ◽  
Metal Free ◽  
Surface Work ◽  
Templated Carbon ◽  
Surface Work Function

Nitrogen-doped zeolite-templated carbon having 3-dimensionally microporous structure exhibited low surface work function and high catalytic performance for oxygen reduction.

Fundamental studies on SnO2 by means of simultaneous work function change and conduction measurements

2005 ◽  
Vol 490 (1) ◽  
pp. 43-47 ◽  
Author(s):  
T. Sahm ◽  
A. Gurlo ◽  
N. Bârsan ◽  
U. Weimar ◽  
L. Mädler
Keyword(s):  
Work Function ◽  
Function Change ◽  
Work Function Change

scholarly journals THE WORK-FUNCTION CHANGE OF K/Cu(111)

1990 ◽  
Vol 39 (12) ◽  
pp. 1989
Author(s):  
WANG GENG ◽  
LI HAI-YANG ◽  
XU YA-BO
Keyword(s):  
Work Function ◽  
Function Change ◽  
Work Function Change
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