Electrocatalytic conversion of carbon dioxide to methane and ...
Supplementary Materials:
Electrocatalytic conversion of carbon dioxide to methane and methanol on transition metal surfaces Kendra P. Kuhl, Toru Hatsukade, Etosha R. Cave, David N. Abram, Jakob Kibsgaard, and Thomas F. Jaramillo
Binding Strength of CO and O:
Table S1. Calculated binding strength in eV of CO(1, 2) and O(2) to the close-packed and stepped surfaces of the metals investigated in this study (* denotes surface bound species). The close-packed surface is the (111) surface for all metals except for Fe where a (110) surface is used. The stepped surface is the (211) surface for all metals except for Zn where a modified (10-15) is used and Fe where a (310) surface is used. For comparison is added a column with the range of experimental determined CO binding strength values from the literature (Zn: (3-5), Ag: (5, 6), Au: (7-10), Cu: (5, 11-15), Pt: (16-21), Ni: (22-28): Fe: (18, 29-31).
Mass transport limitations Figure S1a shows the average CO2RR current density over the course of one hour at constant potential. Note that the CO2RR current density on Au, Ag, and Zn levels out around -2.5 to -5 mA/cm2, which may indicate limitations from mass transport. A further indication of such effects may be the decrease in the absolute value of the CO2RR current density for these three metals at the highest overpotentials measured, where CO2 could have difficulty reaching the electrode surface due to intense hydrogen bubbling off the electrode surface. There could also be pH effects on the mass transport due to S1
changes in the concentration of buffer ions, such as hydroxide, bicarbonate, and carbonate, that could affect the delivery of CO2 to the surface. Of the four catalysts that show high current efficiency for the CO2RR – Au, Ag, Zn, and Cu – only Cu shows a current density whose magnitude continues to increase across the potential range without reaching a plateau. This can be explained by the very different product distribution on Cu compared to the other three metals. The main product of CO2RR on Au, Ag, and Zn is CO, a two electron product. On Cu, the main products are methane and ethylene, which require 8 and 12 electrons, respectively. To facilitate an analysis of mass transport, Figure S1b plots the total moles of CO2 reduced over the course of the one hour experiment. Au, Ag, and Zn plateau around the same number of moles reduced, but fewer moles of CO2 are reduced on Cu which explains why the CO2RR current density can continue to increase across the potential range without reaching a plateau. As Cu can transfer more electrons into each CO2 molecule, higher current densities for the CO2RR can be reached than for metals that mostly make two electron products. Design of an electrolysis cell with improved or better defined mass transport is needed to separate the effects of mass transport from inherent catalyst activity at the more cathodic potentials.
Figure S1: A Average CO2RR current densities over the course of one hour at constant potential. B Total moles of CO2 reduced over the course of one hour.
Minor products of CO2RR Table S2 compares the data reported by Hori et al. (32) (values with gray background) to the data collected in this study at: i) a similar potential, ii) a similar current density, and iii) the earliest potential where we observed the formation of hydrocarbons and/or alcohols on each metal. One experimental difference between the datasets is that previously reported data used galvanostatic electrolysis to generate measurable products and report the average, IR-corrected potential of each experiment run at -5 mA/cm2, while data present in this study was collected potentiostatically with IR-compensation and the current reported is the average current recorded at each potential. Performing the experiments potentiostatically has the advantage of offering more well-defined electrochemical conditions that govern reaction kinetics. Nevertheless, there still is some uncertainty to the voltage measurement due to the use of (and need for) IR-compensation, shown in Table S2. S2
Table S2: Data reported by Hori et al. (32) is shown for each metal in row with gray background. Date collected in this study is displayed on white background. i) Denotes data collected at similar potential, ii) denotes data collected a similar current density and iii) denotes data collected at the earliest potential where we observed the formation of hydrocarbons and/or alcohols. Detection of new products is highlighted with blue text.
S3
Isotope labeled 13CO2 reduction To rule out the possibility that liquid phase products observed in this study come from sources other than CO2 reduction, e.g. carbonaceous contamination (33, 34), isotope labeled 13CO2 was used to study the 13 CO2RR on each metal at a potential where novel minor products were observed. The incorporation of the 13C label into the products was confirmed by the peak splitting observed in 1H NMR, see Figure S2.
13
Figure S2: The incorporation of the C label into the product (A: formate and B: methanol) from 13 CO2 reduction confirmed by the peak splitting observed in 1H NMR.
Trace metal impurities It has been suggested that metal impurities can affect CO2RR activity.(35) Efforts were taken to minimize metal impurities so the CO2RR results reported would be truly representative of the activity of the elemental transition metals studied. All metal foils were purchased from Alfa Aesar and were of the highest purity available. Cu was considered the metal impurity most important to avoid because of its high activity for hydrocarbon formation during CO2RR. Table S3 shows the product and lot number for each metal, as well as the Cu concentration in each. Cu is present at the ppm level (as are many other metals). Assuming that the Cu impurities in each metal have the same CO2RR activity per site as bulk Cu, then the estimated partial current density for the major products, methane and ethylene, arising from Cu impurities would be 31 nA and 8 nA, which are below the detection limit for CO2RR products. To determine whether other trace metal impurities could arise from the foil or from any other source, X-ray photoelectron spectroscopy (XPS) was employed to study all surfaces before and after electrolysis experiments. No metals were observed other than the one transition metal under investigation for that particular study (Figure S3). While it is difficult to completely rule out the presence or impact of trace metal contamination, the fact that no other metals are present above the detection limits of XPS suggest that the activity and selectivity data presented to accurately reflect the nature of the elemental metal surfaces investigated.
S4
Table S3: Cu impurity levels in metal foils used for CO2RR in this study, data provided by the manufacturer. Additionally, to avoid cross-contamination between experiments performed on different metals, either dedicated polycarbonate electrolysis cells or Kel-F electrolysis cells washed in nitric acid were used for CO2RR. The use of the anion exchange membrane between the counter and working electrodes prevented dissolved Pt from counter electrode from reaching the working electrode compartment and depositing on the working electrode. X-ray photoelectron spectroscopy (XPS) performed both before and after CO2 electrolysis confirmed that metal impurities were below the detection limits of the technique (Figure S3). We ran additional electrolysis experiments using a gold counter electrode and found similar results to that of the Pt counter electrode, which further suggests that no contamination from the Pt counter electrode played a role in the observed chemistry.
S5
Figure S3: XPS spectra on the studied metal electrodes both before and after CO2 electrolysis. No metal impurities were observed in any of the spectra.
S6
Figure S4: A and D, Volcano plots of partial current density for CO2RR at -0.8 V vs. CO binding energy. B and E, Onset potential for the overall CO2RR (CO2 to any product) plotted vs. CO binding energy. C and F, Onset potential for methane and/or methanol plotted vs. CO binding energy. A-C: Theory CO binding energies, comparing close-packed surfaces with stepped surfaces, D-F: Experimental CO binding energies (see Table S1).
S7
References and Notes: 1.
2.
3.
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5.
6. 7. 8.
9.
10.
11. 12. 13. 14.
15.
T. Jiang, D. J. Mowbray, S. Dobrin, H. Falsig, B. Hvolbæk, T. Bligaard, J. K. Nørskov, Trends in CO Oxidation Rates for Metal Nanoparticles and Close‐Packed, Stepped, and Kinked Surfaces. The Journal of Physical Chemistry C 113, 10548‐10553 (2009); published online Epub2009/06/18 (10.1021/jp811185g). J. S. Hummelshøj, F. Abild‐Pedersen, F. Studt, T. Bligaard, J. K. Nørskov, CatApp: A Web Application for Surface Chemistry and Heterogeneous Catalysis. Angewandte Chemie International Edition 51, 272‐274 (2012)10.1002/anie.201107947). E. Giamello, B. Fubini, Heat of adsorption of carbon monoxide on zinc oxide pretreated by various methods. Journal of the Chemical Society, Faraday Transactions 1: Physical Chemistry in Condensed Phases 79, 1995‐2003 (1983)10.1039/F19837901995). A. F. Carley, M. W. Roberts, S. Yan, The influence of pre‐oxidation on the adsorption of CO at A Zn(0001) surface: Characterisation of a weakly chemisorbed species by XPS and UPS. Applied Surface Science 40, 289‐293 (1990); published online Epub1// (http://dx.doi.org/10.1016/0169‐ 4332(90)90026‐V). B. M. W. Trapnell, The Activities of Evaporated Metal Films in Gas Chemisorption. Proceedings of the Royal Society of London. Series A. Mathematical and Physical Sciences 218, 566‐577 (1953); published online EpubJuly 23, 1953 (10.1098/rspa.1953.0125). G. McElhiney, H. Papp, J. Pritchard, The adsorption of Xe and CO on Ag(111). Surface Science 54, 617‐634 (1976); published online Epub3// (http://dx.doi.org/10.1016/0039‐6028(76)90209‐0). G. McElhiney, J. Pritchard, The adsorption of Xe and CO on Au(100). Surface Science 60, 397‐410 (1976); published online Epub11/2/ (http://dx.doi.org/10.1016/0039‐6028(76)90324‐1). C. Ruggiero, P. Hollins, Interaction of CO molecules with the Au(332) surface. Surface Science 377–379, 583‐586 (1997); published online Epub4/20/ (http://dx.doi.org/10.1016/S0039‐ 6028(96)01451‐3). M. L. Kottke, R. G. Greenler, H. G. Tompkins, An infrared spectroscopic study of carbon monoxide adsorbed on polycrystalline gold using the reflection‐absorption technique. Surface Science 32, 231‐243 (1972); published online Epub7// (http://dx.doi.org/10.1016/0039‐ 6028(72)90131‐8). X. Xia, J. Strunk, W. Busser, M. Comotti, F. Schüth, M. Muhler, Thermodynamics and Kinetics of the Adsorption of Carbon Monoxide on Supported Gold Catalysts Probed by Static Adsorption Microcalorimetry: The Role of the Support. The Journal of Physical Chemistry C 113, 9328‐9335 (2009); published online Epub2009/05/28 (10.1021/jp809804v). J. Pritchard, Chemisorption on Copper. Journal of Vacuum Science & Technology 9, 895‐900 (1972)doi:http://dx.doi.org/10.1116/1.1317813). K. Horn, M. Hussain, J. Pritchard, The adsorption of CO on Cu(110). Surface Science 63, 244‐253 (1977); published online Epub3// (http://dx.doi.org/10.1016/0039‐6028(77)90341‐7). R. M. Dell, F. S. Stone, P. F. Tiley, The adsorption of oxygen and other gases on copper. Transactions of the Faraday Society 49, 195‐201 (1953)10.1039/TF9534900195). R. A. Beebe, E. L. Wildner, The Heat of Adsorption of Carbon Monoxide on Copper1. Journal of the American Chemical Society 56, 642‐645 (1934); published online Epub1934/03/01 (10.1021/ja01318a030). J. C. Tracy, Structural Influences on Adsorption Energy. III. CO on Cu(100). The Journal of Chemical Physics 56, 2748‐2754 (1972)doi:http://dx.doi.org/10.1063/1.1677603).
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D. A. W. D. P. King, The chemical physics of solid surfaces and heterogeneous catalysis. (Elsevier Scientific Pub. Co. ; Distributors for the U.S. and Canada, Elsevier North‐Holland, Amsterdam; New York; New York, 1981). R. M. Lambert, C. M. Comrie, The oxidation of CO by no on Pt(111) and Pt(110). Surface Science 46, 61‐80 (1974); published online Epub11// (http://dx.doi.org/10.1016/0039‐6028(74)90241‐ 6). D. Brennan, F. H. Hayes, The Adsorption of Carbon Monoxide on Evaporated Metal Films. Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences 258, 347‐373 (1965); published online EpubNovember 11, 1965 (10.1098/rsta.1965.0045). N. D. Gangal, N. M. Gupta, R. M. Iyer, Microcalorimetric Study of the Adsorption and Reaction of CO, O2, CO + O2, and CO2 on NaX Zeolite, Pt/NaX, and Platinum Metal: Effect of Oxidizing and Reducing Pretreatment. Journal of Catalysis 140, 443‐452 (1993); published online Epub4// (http://dx.doi.org/10.1006/jcat.1993.1097). A. D. Karmazyn, V. Fiorin, S. J. Jenkins, D. A. King, First‐principles theory and microcalorimetry of CO adsorption on the {2 1 1} surfaces of Pt and Ni. Surface Science 538, 171‐183 (2003); published online Epub7/20/ (http://dx.doi.org/10.1016/S0039‐6028(03)00726‐X). H. Steininger, S. Lehwald, H. Ibach, On the adsorption of CO on Pt(111). Surface Science 123, 264‐282 (1982); published online Epub12/2/ (http://dx.doi.org/10.1016/0039‐6028(82)90328‐ 4). G. Wedler, H. Papp, G. Schroll, Adsorption of carbon monoxide on polycrystalline nickel films. Surface Science 44, 463‐479 (1974); published online Epub8// (http://dx.doi.org/10.1016/0039‐ 6028(74)90131‐9). J. C. Tracy, Structural Influences on Adsorption Energy. II. CO on Ni(100). The Journal of Chemical Physics 56, 2736‐2747 (1972)doi:http://dx.doi.org/10.1063/1.1677602). H. H. Madden, J. Küppers, G. Ertl, Interaction of carbon monoxide with (110) nickel surfaces. The Journal of Chemical Physics 58, 3401‐3410 (1973)doi:http://dx.doi.org/10.1063/1.1679668). D. F. Klemperer, F. S. Stone, Heats of Adsorption on Evaporated Nickel Films. Proceedings of the Royal Society of London. Series A. Mathematical and Physical Sciences 243, 375‐399 (1958); published online EpubJanuary 14, 1958 (10.1098/rspa.1958.0006). M. M. Baker, E. K. Rideal, The adsorption of carbon monoxide by nickel. Transactions of the Faraday Society 51, 1597‐1601 (1955)10.1039/TF9555101597). O. Beeck, in Advances in Catalysis, V. I. K. W.G. Frankenburg, E. K. Rideal, Eds. (Academic Press, 1950), vol. Volume 2, pp. 151‐195. H. E. L. K. I. W. B. E. P. H. Ries, Catalysis Volume 1. (Reinhold, New York, 1954). G. Wedler, K. G. Colb, G. McElhiney, W. Heinrich, An investigation of the interaction of CO with polycrystalline iron films. Applications of Surface Science 2, 30‐42 (1978); published online Epub11// (http://dx.doi.org/10.1016/0378‐5963(78)90004‐1). D. Borthwick, V. Fiorin, S. J. Jenkins, D. A. King, Facile dissociation of CO on Fe{2 1 1}: Evidence from microcalorimetry and first‐principles theory. Surface Science 602, 2325‐2332 (2008); published online Epub7/1/ (http://dx.doi.org/10.1016/j.susc.2008.05.014). J. Bagg, F. C. Tompkins, Calorimetric heats of sorption of gases on evaporated iron films. Transactions of the Faraday Society 51, 1071‐1080 (1955)10.1039/TF9555101071). Y. Hori, Ed., Handbook of Fuel Cells: Fundamentals, Technology and Application, (VHC‐Wiley, Chichester, 2003), vol. 2, pp. 720‐733.
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Electrocatalytic conversion of carbon dioxide to methane and methanol on transition metal surfaces Kendra P. Kuhl, Toru Hatsukade, Etosha R. Cave, David N. Abram, Jakob Kibsgaard, and Thomas F. Jaramillo
Binding Strength of CO and O:
Table S1. Calculated binding strength in eV of CO(1, 2) and O(2) to the close-packed and stepped surfaces of the metals investigated in this study (* denotes surface bound species). The close-packed surface is the (111) surface for all metals except for Fe where a (110) surface is used. The stepped surface is the (211) surface for all metals except for Zn where a modified (10-15) is used and Fe where a (310) surface is used. For comparison is added a column with the range of experimental determined CO binding strength values from the literature (Zn: (3-5), Ag: (5, 6), Au: (7-10), Cu: (5, 11-15), Pt: (16-21), Ni: (22-28): Fe: (18, 29-31).
Mass transport limitations Figure S1a shows the average CO2RR current density over the course of one hour at constant potential. Note that the CO2RR current density on Au, Ag, and Zn levels out around -2.5 to -5 mA/cm2, which may indicate limitations from mass transport. A further indication of such effects may be the decrease in the absolute value of the CO2RR current density for these three metals at the highest overpotentials measured, where CO2 could have difficulty reaching the electrode surface due to intense hydrogen bubbling off the electrode surface. There could also be pH effects on the mass transport due to S1
changes in the concentration of buffer ions, such as hydroxide, bicarbonate, and carbonate, that could affect the delivery of CO2 to the surface. Of the four catalysts that show high current efficiency for the CO2RR – Au, Ag, Zn, and Cu – only Cu shows a current density whose magnitude continues to increase across the potential range without reaching a plateau. This can be explained by the very different product distribution on Cu compared to the other three metals. The main product of CO2RR on Au, Ag, and Zn is CO, a two electron product. On Cu, the main products are methane and ethylene, which require 8 and 12 electrons, respectively. To facilitate an analysis of mass transport, Figure S1b plots the total moles of CO2 reduced over the course of the one hour experiment. Au, Ag, and Zn plateau around the same number of moles reduced, but fewer moles of CO2 are reduced on Cu which explains why the CO2RR current density can continue to increase across the potential range without reaching a plateau. As Cu can transfer more electrons into each CO2 molecule, higher current densities for the CO2RR can be reached than for metals that mostly make two electron products. Design of an electrolysis cell with improved or better defined mass transport is needed to separate the effects of mass transport from inherent catalyst activity at the more cathodic potentials.
Figure S1: A Average CO2RR current densities over the course of one hour at constant potential. B Total moles of CO2 reduced over the course of one hour.
Minor products of CO2RR Table S2 compares the data reported by Hori et al. (32) (values with gray background) to the data collected in this study at: i) a similar potential, ii) a similar current density, and iii) the earliest potential where we observed the formation of hydrocarbons and/or alcohols on each metal. One experimental difference between the datasets is that previously reported data used galvanostatic electrolysis to generate measurable products and report the average, IR-corrected potential of each experiment run at -5 mA/cm2, while data present in this study was collected potentiostatically with IR-compensation and the current reported is the average current recorded at each potential. Performing the experiments potentiostatically has the advantage of offering more well-defined electrochemical conditions that govern reaction kinetics. Nevertheless, there still is some uncertainty to the voltage measurement due to the use of (and need for) IR-compensation, shown in Table S2. S2
Table S2: Data reported by Hori et al. (32) is shown for each metal in row with gray background. Date collected in this study is displayed on white background. i) Denotes data collected at similar potential, ii) denotes data collected a similar current density and iii) denotes data collected at the earliest potential where we observed the formation of hydrocarbons and/or alcohols. Detection of new products is highlighted with blue text.
S3
Isotope labeled 13CO2 reduction To rule out the possibility that liquid phase products observed in this study come from sources other than CO2 reduction, e.g. carbonaceous contamination (33, 34), isotope labeled 13CO2 was used to study the 13 CO2RR on each metal at a potential where novel minor products were observed. The incorporation of the 13C label into the products was confirmed by the peak splitting observed in 1H NMR, see Figure S2.
13
Figure S2: The incorporation of the C label into the product (A: formate and B: methanol) from 13 CO2 reduction confirmed by the peak splitting observed in 1H NMR.
Trace metal impurities It has been suggested that metal impurities can affect CO2RR activity.(35) Efforts were taken to minimize metal impurities so the CO2RR results reported would be truly representative of the activity of the elemental transition metals studied. All metal foils were purchased from Alfa Aesar and were of the highest purity available. Cu was considered the metal impurity most important to avoid because of its high activity for hydrocarbon formation during CO2RR. Table S3 shows the product and lot number for each metal, as well as the Cu concentration in each. Cu is present at the ppm level (as are many other metals). Assuming that the Cu impurities in each metal have the same CO2RR activity per site as bulk Cu, then the estimated partial current density for the major products, methane and ethylene, arising from Cu impurities would be 31 nA and 8 nA, which are below the detection limit for CO2RR products. To determine whether other trace metal impurities could arise from the foil or from any other source, X-ray photoelectron spectroscopy (XPS) was employed to study all surfaces before and after electrolysis experiments. No metals were observed other than the one transition metal under investigation for that particular study (Figure S3). While it is difficult to completely rule out the presence or impact of trace metal contamination, the fact that no other metals are present above the detection limits of XPS suggest that the activity and selectivity data presented to accurately reflect the nature of the elemental metal surfaces investigated.
S4
Table S3: Cu impurity levels in metal foils used for CO2RR in this study, data provided by the manufacturer. Additionally, to avoid cross-contamination between experiments performed on different metals, either dedicated polycarbonate electrolysis cells or Kel-F electrolysis cells washed in nitric acid were used for CO2RR. The use of the anion exchange membrane between the counter and working electrodes prevented dissolved Pt from counter electrode from reaching the working electrode compartment and depositing on the working electrode. X-ray photoelectron spectroscopy (XPS) performed both before and after CO2 electrolysis confirmed that metal impurities were below the detection limits of the technique (Figure S3). We ran additional electrolysis experiments using a gold counter electrode and found similar results to that of the Pt counter electrode, which further suggests that no contamination from the Pt counter electrode played a role in the observed chemistry.
S5
Figure S3: XPS spectra on the studied metal electrodes both before and after CO2 electrolysis. No metal impurities were observed in any of the spectra.
S6
Figure S4: A and D, Volcano plots of partial current density for CO2RR at -0.8 V vs. CO binding energy. B and E, Onset potential for the overall CO2RR (CO2 to any product) plotted vs. CO binding energy. C and F, Onset potential for methane and/or methanol plotted vs. CO binding energy. A-C: Theory CO binding energies, comparing close-packed surfaces with stepped surfaces, D-F: Experimental CO binding energies (see Table S1).
S7
References and Notes: 1.
2.
3.
4.
5.
6. 7. 8.
9.
10.
11. 12. 13. 14.
15.
T. Jiang, D. J. Mowbray, S. Dobrin, H. Falsig, B. Hvolbæk, T. Bligaard, J. K. Nørskov, Trends in CO Oxidation Rates for Metal Nanoparticles and Close‐Packed, Stepped, and Kinked Surfaces. The Journal of Physical Chemistry C 113, 10548‐10553 (2009); published online Epub2009/06/18 (10.1021/jp811185g). J. S. Hummelshøj, F. Abild‐Pedersen, F. Studt, T. Bligaard, J. K. Nørskov, CatApp: A Web Application for Surface Chemistry and Heterogeneous Catalysis. Angewandte Chemie International Edition 51, 272‐274 (2012)10.1002/anie.201107947). E. Giamello, B. Fubini, Heat of adsorption of carbon monoxide on zinc oxide pretreated by various methods. Journal of the Chemical Society, Faraday Transactions 1: Physical Chemistry in Condensed Phases 79, 1995‐2003 (1983)10.1039/F19837901995). A. F. Carley, M. W. Roberts, S. Yan, The influence of pre‐oxidation on the adsorption of CO at A Zn(0001) surface: Characterisation of a weakly chemisorbed species by XPS and UPS. Applied Surface Science 40, 289‐293 (1990); published online Epub1// (http://dx.doi.org/10.1016/0169‐ 4332(90)90026‐V). B. M. W. Trapnell, The Activities of Evaporated Metal Films in Gas Chemisorption. Proceedings of the Royal Society of London. Series A. Mathematical and Physical Sciences 218, 566‐577 (1953); published online EpubJuly 23, 1953 (10.1098/rspa.1953.0125). G. McElhiney, H. Papp, J. Pritchard, The adsorption of Xe and CO on Ag(111). Surface Science 54, 617‐634 (1976); published online Epub3// (http://dx.doi.org/10.1016/0039‐6028(76)90209‐0). G. McElhiney, J. Pritchard, The adsorption of Xe and CO on Au(100). Surface Science 60, 397‐410 (1976); published online Epub11/2/ (http://dx.doi.org/10.1016/0039‐6028(76)90324‐1). C. Ruggiero, P. Hollins, Interaction of CO molecules with the Au(332) surface. Surface Science 377–379, 583‐586 (1997); published online Epub4/20/ (http://dx.doi.org/10.1016/S0039‐ 6028(96)01451‐3). M. L. Kottke, R. G. Greenler, H. G. Tompkins, An infrared spectroscopic study of carbon monoxide adsorbed on polycrystalline gold using the reflection‐absorption technique. Surface Science 32, 231‐243 (1972); published online Epub7// (http://dx.doi.org/10.1016/0039‐ 6028(72)90131‐8). X. Xia, J. Strunk, W. Busser, M. Comotti, F. Schüth, M. Muhler, Thermodynamics and Kinetics of the Adsorption of Carbon Monoxide on Supported Gold Catalysts Probed by Static Adsorption Microcalorimetry: The Role of the Support. The Journal of Physical Chemistry C 113, 9328‐9335 (2009); published online Epub2009/05/28 (10.1021/jp809804v). J. Pritchard, Chemisorption on Copper. Journal of Vacuum Science & Technology 9, 895‐900 (1972)doi:http://dx.doi.org/10.1116/1.1317813). K. Horn, M. Hussain, J. Pritchard, The adsorption of CO on Cu(110). Surface Science 63, 244‐253 (1977); published online Epub3// (http://dx.doi.org/10.1016/0039‐6028(77)90341‐7). R. M. Dell, F. S. Stone, P. F. Tiley, The adsorption of oxygen and other gases on copper. Transactions of the Faraday Society 49, 195‐201 (1953)10.1039/TF9534900195). R. A. Beebe, E. L. Wildner, The Heat of Adsorption of Carbon Monoxide on Copper1. Journal of the American Chemical Society 56, 642‐645 (1934); published online Epub1934/03/01 (10.1021/ja01318a030). J. C. Tracy, Structural Influences on Adsorption Energy. III. CO on Cu(100). The Journal of Chemical Physics 56, 2748‐2754 (1972)doi:http://dx.doi.org/10.1063/1.1677603).
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16.
17.
18.
19.
20.
21.
22.
23. 24. 25.
26. 27. 28. 29.
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