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Molecular adsorption at a well defined gas-solid interphase: Statistical rate theory approach
A558 438 QUANTUM
Surface Science 176 (1986) 438-444 North-Holland, Amsterdam STICKING
A. Y O S H I M O R I
THEORY
ON A SIMPLIFIED
MODEL
and K. CHO
Department of Material Physics, Faculty of Engineering Science, Osaka University, Toyonaka, Osaka 560, Japan Received 21 April 1986; accepted for publication 4 June 1986 An analysis is made on the "transmission problem" in a simplified one-dimensional model. In the model, a short range force is assumed between a gas atom and a solid surface with modulation due to solid phonons, and space is discretized for the quantum mechanical motion of the atom. The rigorous conclusion is obtained that the atom with vanishing kinetic energy does not stick to the surface.
Surface Science 176 (1986) 445-456 North-Holland, Amsterdam
445
A MOLECULAR ORBITAL ANALYSIS OF THE PRECURSOR AND THE ACTIVATION BARRIER FOR CHEMISORPTION
STATE
I. C O adsorbed on nickel (111) E.L. G A R F U N K E L
and Xinghong FENG
Department of Chemistry, Rutgers - The State University, New Brunswick, NJ 08903, USA Received 23 December 1985; accepted for publication 28 May 1986 The precursor state and the activation barrier for the associative chemisorption of carbon monoxide on nickel (111) has been investigated using semi-empirical molecular orbital (MO) calculations. Results show a weakly bound precursor state when CO is oriented parallel to the metal surface, and no precursor state for the perpendicular orientation. It is also shown that there is an activation barrier between the precursor and chemisorption states. The results are generally consistent with recent experimental observations of precursor-like states. A qualitative molecular orbital analysis is developed to explain the precursor state and the barrier for chemisorlation.
457
Surface Science 176 (1986) 457-475 North-Holland, Amsterdam MOLECULAR
ADSORPTION
INTERPHASE: C.A. WARD
STATISTICAL
AT A WELL DEFINED GAS-SOLID RATE THEORY
APPROACH
and M. ELMOSELHI
Kinetics and Thermodynamics Laboratory, Department of Mechanical Engineering, University of Toronto, Toronto, Canada M5S 1A4 Received 25 February 1986; accepted for publication 6 June 1986 The objective of Statistical Rate Theory is to derive explicitly the coverage dependence of the expression for the rate of adsorption. The other parameters in the rate expression can then be viewed as material properties of a gas-solid surface combination, since they have no coverage dependence. After these properties have been tabulated, they can be used with Statistical Rate
A559 Theory to predict the rate of adsorption in independent circumstances. This hypothesis is examined by considering CO adsorbing on Ni(1,1,1). The properties of this well defined gas-solid surface are first established from the EELS spectrum, ellipsometric isotherms, and an ultraviolet photoemission spectroscopic study of the desorption rate. These studies were conducted in different laboratories. After these material properties are measured, they are used with Statistical Rate Theory to predict the rate of CO adsorption on Ni(1,1,1) and the result is compared with a set of measurements. Close agreement was found throughout the experimental period. It had been previously reported that Absolute Rate Theory could not describe these results unless both the pre-exponential factor and the activation energy were allowed to depend on coverage.
476
Surface Science 176 (1986) 476-490 North-Holland, Amsterdam
A PHOTOEMISSION STUDY OF BENZOTRIAZOLE COPPER AND CUPROUS OXIDE Bo-Shung FANG
ON CLEAN
*, C l i f f o r d G . O L S O N a n d D a v i d W . L Y N C H
Ames Laboratory-USDOE ** and Department of Physics, lowa State University, Ames, IA 50011, USA Received 20 February 1986; accepted for publication 21 May 1986 Photoemission spectra of benzotriazole (BTA) chemisorbed on clean Cu and on cuprous oxide were compared with the spectra of condensed- and gas-phase BTA. Chemisorbed BTA bonds to both Cu and Cu20 via lone-pair orbitals on the nitrogen ring. The lack of a chemical shift for the ~r orbitals indicates that BTA does not lie flat on the surface. We propose a model for the geometry and bonding of chemisorbed BTA which accounts for its corrosion inhibition on Cu, and for the corrosion inhibition, or lack of inhibition, by molecules similar to BTA.
491
Surface Science 176 (1986) 491-504 North-Holland, Amsterdam ADSORPTION OF METHANOL, FORMALDEHYDE AND FORMIC ACID ON Pd(100) SURFACES MODIFIED BY A SODIUM AND SODIUM
OXIDE OVERLAYER
Chikashi EGAWA,
Ichiro DOI, Shuichi NAITO
and Kenzi TAMARU
Department of Chemistry, Faculty of Science, University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113, Japan Received 3 February 1986; accepted for publication 13 June 1986 The effect of a sodium and sodium oxide overlayer on a Pd(100) surface has been investigated by AES, LEED, XPS, UPS and TPRS methods. Ordered surface structures of (4 x 4), (2 × 2) and c(2 x 2) were observed for a sodium overlayer, which was contracted by the adsorption of oxygen. The increase of bonding energy of CO, H 2 as well as CO 2 was confirmed on both sodium and sodium oxide covered surfaces, and three adsorption states were distinguished for CO 2 on these surfaces. For the adsorption of methanol, formaldehyde and formic acid, the interaction was also strengthened on the sodium covered surface. As a result, the concentration as well as the stability of surface methoxide and formate was significantly increased and the strong interaction between formaldehyde and surface oxygen was confirmed.
Surface Science 176 (1986) 438-444 North-Holland, Amsterdam STICKING
A. Y O S H I M O R I
THEORY
ON A SIMPLIFIED
MODEL
and K. CHO
Department of Material Physics, Faculty of Engineering Science, Osaka University, Toyonaka, Osaka 560, Japan Received 21 April 1986; accepted for publication 4 June 1986 An analysis is made on the "transmission problem" in a simplified one-dimensional model. In the model, a short range force is assumed between a gas atom and a solid surface with modulation due to solid phonons, and space is discretized for the quantum mechanical motion of the atom. The rigorous conclusion is obtained that the atom with vanishing kinetic energy does not stick to the surface.
Surface Science 176 (1986) 445-456 North-Holland, Amsterdam
445
A MOLECULAR ORBITAL ANALYSIS OF THE PRECURSOR AND THE ACTIVATION BARRIER FOR CHEMISORPTION
STATE
I. C O adsorbed on nickel (111) E.L. G A R F U N K E L
and Xinghong FENG
Department of Chemistry, Rutgers - The State University, New Brunswick, NJ 08903, USA Received 23 December 1985; accepted for publication 28 May 1986 The precursor state and the activation barrier for the associative chemisorption of carbon monoxide on nickel (111) has been investigated using semi-empirical molecular orbital (MO) calculations. Results show a weakly bound precursor state when CO is oriented parallel to the metal surface, and no precursor state for the perpendicular orientation. It is also shown that there is an activation barrier between the precursor and chemisorption states. The results are generally consistent with recent experimental observations of precursor-like states. A qualitative molecular orbital analysis is developed to explain the precursor state and the barrier for chemisorlation.
457
Surface Science 176 (1986) 457-475 North-Holland, Amsterdam MOLECULAR
ADSORPTION
INTERPHASE: C.A. WARD
STATISTICAL
AT A WELL DEFINED GAS-SOLID RATE THEORY
APPROACH
and M. ELMOSELHI
Kinetics and Thermodynamics Laboratory, Department of Mechanical Engineering, University of Toronto, Toronto, Canada M5S 1A4 Received 25 February 1986; accepted for publication 6 June 1986 The objective of Statistical Rate Theory is to derive explicitly the coverage dependence of the expression for the rate of adsorption. The other parameters in the rate expression can then be viewed as material properties of a gas-solid surface combination, since they have no coverage dependence. After these properties have been tabulated, they can be used with Statistical Rate
A559 Theory to predict the rate of adsorption in independent circumstances. This hypothesis is examined by considering CO adsorbing on Ni(1,1,1). The properties of this well defined gas-solid surface are first established from the EELS spectrum, ellipsometric isotherms, and an ultraviolet photoemission spectroscopic study of the desorption rate. These studies were conducted in different laboratories. After these material properties are measured, they are used with Statistical Rate Theory to predict the rate of CO adsorption on Ni(1,1,1) and the result is compared with a set of measurements. Close agreement was found throughout the experimental period. It had been previously reported that Absolute Rate Theory could not describe these results unless both the pre-exponential factor and the activation energy were allowed to depend on coverage.
476
Surface Science 176 (1986) 476-490 North-Holland, Amsterdam
A PHOTOEMISSION STUDY OF BENZOTRIAZOLE COPPER AND CUPROUS OXIDE Bo-Shung FANG
ON CLEAN
*, C l i f f o r d G . O L S O N a n d D a v i d W . L Y N C H
Ames Laboratory-USDOE ** and Department of Physics, lowa State University, Ames, IA 50011, USA Received 20 February 1986; accepted for publication 21 May 1986 Photoemission spectra of benzotriazole (BTA) chemisorbed on clean Cu and on cuprous oxide were compared with the spectra of condensed- and gas-phase BTA. Chemisorbed BTA bonds to both Cu and Cu20 via lone-pair orbitals on the nitrogen ring. The lack of a chemical shift for the ~r orbitals indicates that BTA does not lie flat on the surface. We propose a model for the geometry and bonding of chemisorbed BTA which accounts for its corrosion inhibition on Cu, and for the corrosion inhibition, or lack of inhibition, by molecules similar to BTA.
491
Surface Science 176 (1986) 491-504 North-Holland, Amsterdam ADSORPTION OF METHANOL, FORMALDEHYDE AND FORMIC ACID ON Pd(100) SURFACES MODIFIED BY A SODIUM AND SODIUM
OXIDE OVERLAYER
Chikashi EGAWA,
Ichiro DOI, Shuichi NAITO
and Kenzi TAMARU
Department of Chemistry, Faculty of Science, University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113, Japan Received 3 February 1986; accepted for publication 13 June 1986 The effect of a sodium and sodium oxide overlayer on a Pd(100) surface has been investigated by AES, LEED, XPS, UPS and TPRS methods. Ordered surface structures of (4 x 4), (2 × 2) and c(2 x 2) were observed for a sodium overlayer, which was contracted by the adsorption of oxygen. The increase of bonding energy of CO, H 2 as well as CO 2 was confirmed on both sodium and sodium oxide covered surfaces, and three adsorption states were distinguished for CO 2 on these surfaces. For the adsorption of methanol, formaldehyde and formic acid, the interaction was also strengthened on the sodium covered surface. As a result, the concentration as well as the stability of surface methoxide and formate was significantly increased and the strong interaction between formaldehyde and surface oxygen was confirmed.