The Role of Step Atom Density on the Binding and Reaction of Surface Species

Temperature-programmed desorption was used to examine the adsorption and reaction of CO, H2, O2, NO, CH3OH, and C2H4on several surfaces of platinum to see if there is a correlation between the atom density of step atoms and reactivity. Small variations in the desorption activation energy of hydrogen, oxygen, carbon monoxide, ethylene, and methanol were found the changing crystal face. However, on platinum surfaces, there was no correlation between the desorption activation energy and the step atom density. Reactivity was found to vary greatly with the crystal face. However, no correlation was found between the step atom density and the reactivity for the hydrogenolysis of ethylene to methane, for the decomposition of methanol to carbon monoxide, for the hydrogenolysis of methanol to methane, for the oxidation of methanol to carbon dioxide, for the oxidation of methanol to formaldehyde, or for the decomposition of nitric oxide to nitrogen and oxygen. Only for the self-hydrogenation of ethylene to ethane on platinum surfaces did the reactivity have any correlation with step atom density, and this correlation did not carry through to steady-state experiments. From our study, it appears that the active site for reaction is often not simply a step site. Rather, the active site consists of a special arrangement of step and terrace atoms that are aligned correctly to produce high reactivity.

[1]  P. Feibelman.  FRIEDEL OSCILLATIONS IN THE FORCE CONSTANTS OF METALS , 1997 .

[2]  Feibelman.  Energetics of steps on Pt(111). , 1995, Physical review. B, Condensed matter.

[3]  R. Masel,et al.  Methanol oxidation on (2 × 1)Pt(110): formaldehyde on a stepped surface , 1994 .

[4]  T. Einstein,et al.  Energies of steps, kinks, and defects on Ag?100? and Ag?111? using the embedded atom method, and some consequences , 1993 .

[5]  N. Kizhakevariam,et al.  Promotion and poisoning of the reaction of methanol on clean and modified platinum (100) , 1993 .

[6]  R. Masel,et al.  A comparison of electrochemical and gas-phase decomposition of methanol on platinum surfaces , 1992 .

[7]  R. Masel,et al.  Methanol adsorption and decomposition on (1 times 1)Pt(110) and (2 times 1)Pt(110): Identification of the active site for carbon-oxygen bond scission during alcohol decomposition on platinum , 1990 .

[8]  R. Masel,et al.  Coadsorption of ethylene and hydrogen on (2 × 1) Pt(110): Observation of a weakly bound form of ethylene , 1990 .

[9]  R. Masel,et al.  Ethylene adsorption and decomposition on (1 × 1) Pt(110): Chemistry of the coke formation site on platinum? , 1989 .

[10]  R. Masel,et al.  A TPD study of nitric oxide decomposition on Pt(100), Pt(411) and Pt(211) , 1989 .

[11]  J. Yates,et al.  Kinetics and energetics of oxygen adsorption on Pt(111) and Pt(112)- A comparison of flat and stepped surfaces , 1988 .

[12]  R. Masel,et al.  Structure sensitivity of ethylene adsorption on Pt(100): Evidence for vinylidene formation on (1×1) Pt(100) , 1987 .

[13]  R. Masel,et al.  A comparison of nitric oxide decomposition on Pt(210) and Pt(410): An example where an increase in step density has produced a decrease in reactivity , 1985 .

[14]  H. Kung,et al.  Temperature-Programmed Desorption Study of Ethylene on a Clean, a H-Covered, and an O-Covered Pt(111) Surface , 1985 .

[15]  R. Masel,et al.  Platinum (410), a face with unusual activity for the breaking of N-O and C-O bonds , 1984 .

[16]  G. Somorjai,et al.  Hydrogenation of ethylene over platinum (111) single-crystal surfaces , 1984 .

[17]  H. Ibach,et al.  Adsorption of oxygen on Pt(111) , 1982 .

[18]  B. Sexton,et al.  Decomposition pathways of C1C4 alcohols adsorbed on platinum (111) , 1982 .

[19]  B. Sexton.  Methanol decomposition on platinum (111) , 1981 .

[20]  J. Gland.  Molecular and atomic adsorption of oxygen on the Pt(111) and Pt(S)-12(111) × (111) surfaces , 1980 .

[21]  S. Davis,et al.  The effect of surface oxygen on hydrocarbon reactions catalyzed by platinum crystal surfaces with variable kink concentrations , 1980 .

[22]  D. Collins,et al.  The adsorption of CO, O2, and H2 on Pt: I. Thermal desorption spectroscopy studies☆ , 1977 .

[23]  G. Somorjai,et al.  The dehydrogenation and hydrogenolysis of cyclohexane and cyclohexene on stepped (high miller index) platinum surfaces , 1976 .

[24]  F. Netzer,et al.  The adsorption of hydrogen and the reaction of hydrogen with oxygen on Pt (100) , 1975 .

[25]  F. Netzer,et al.  Adsorption studies of oxygen and carbon monoxide on a Pt (100) surface , 1975 .

[26]  J. F. Nicholas,et al.  An Atlas of Models of Crystal Surfaces , 1965 .

[27]  P. Redhead.  Thermal desorption of gases , 1962 .

[28]  R. N. Pease,et al.  THE CATALYTIC COMBINATION OF ETHYLENE AND HYDROGEN IN THE PRESENCE OF METALLIC COPPER III. CARBON MONOXIDE AS A CATALYST POISON , 1925 .

[29]  H. Taylor.  A Theory of the Catalytic Surface , 1925 .

[30]  H. Taylor.  Fourth Report of the Committee on Contact Catalysis , 1923 .

[31]  Michael Faraday,et al.  V. Experimental researches in electricity.—Sixth series , 1834, Philosophical Transactions of the Royal Society of London.