Catalysis at the Sub-Nanoscale: Complex CO Oxidation Chemistry on a Few Au Atoms

Transcription

1 Electronic Supplementary Material (ESI) for Catalysis Science & Technology. This journal is The Royal Society of Chemistry 214 Catalysis at the Sub-Nanoscale: Complex CO Oxidation Chemistry on a Few Au Atoms Nima Nikbin a, Natalie Austin b, Dionisios G. Vlachos a, Michail Stamatakis c and Giannis Mpourmpakis b a Department of Chemical and Biomolecular Engineering, University of Delaware, Newark, Delaware 19716, USA b Department of Chemical Engineering, University of Pittsburgh, Pittsburgh, Pennsylvania 15261, USA c Department of Chemical Engineering, University College London, Torrington Place, London WC1E 7JE, UK Supporting Information KMC Methodology Details The Graph-Theoretical KMC framework was employed 1,2 as implemented in the software package Zacros. 3 The simulation requires a lattice structure, an energetics model and a reaction mechanism as input. These components are outlined below for each of the Au nanoclusters considered. Au 6 - Nanocluster Lattice Structure For Au - 6 both bridge and top sites are considered (Figure 1a in main manuscript). The different types of these sites are shown in the figure on the right. Thus, the corner top sites have coordination number 2 () whereas the edge top sites have coordination number 4 (topcn4). There are two different types of bridge sites as well, connecting two sites (bridge- 44), or a with a site (). The former are only included for completeness as the molecular species investigated do not bind therein. Page 1 of 21

2 Lattice Energetics Model Single- and two-body contributions to the total energy of the lattice were taken into account. The corresponding patterns are shown below. The ab-initio calculations showed that if an molecule is bound to the nanocluster, a second molecule cannot bind. This behavior was modelled by including the four pairwise patterns in the bottom of the figure whose energetic contributions were arbitrarily set to a high value (5 kcal/mol). C C kcal/mol kcal/mol kcal/mol kcal/mol O kcal/mol O CO kcal/mol kcal/mol CO kcal/mol CO 3 O OC O kcal/mol Page 2 of 21

3 12 o 5. kcal/mol bridge-44 bridge kcal/mol 5. kcal/mol 5. kcal/mol Reaction Mechanism The reaction mechanism consists of 12 reversible steps (24 elementary steps total) which are shown below. Reported are also the kinetic parameters: prefactor of the forward step, ratio of the forward versus reverse prefactors, as well as activation energy and reaction energy at the zero coverage limit. The latter is computed from the lattice energetics model. CO adsorption CO (gas) CO A fwd = bar -1 s -1, A fwd /A rev = bar -1, E =. kcal/mol, ΔE = kcal/mol CO (gas) CO A fwd = bar -1 s -1, A fwd /A rev = bar -1, E =. kcal/mol, ΔE = kcal/mol Page 3 of 21

4 adsorption (gas) A fwd = bar -1 s -1, A fwd /A rev = bar -1, E =. kcal/mol, ΔE = kcal/mol (gas) A fwd = bar -1 s -1, A fwd /A rev = bar -1, E =. kcal/mol, ΔE = kcal/mol C adsorption C(gas) C A fwd = bar -1 s -1, A fwd /A rev = bar -1, E =. kcal/mol, ΔE = kcal/mol C(gas) C A fwd = bar -1 s -1, A fwd /A rev = bar -1, E =. kcal/mol, ΔE = kcal/mol CO oxidation by CO C O A fwd = s -1, A fwd /A rev = , E = 11.4 kcal/mol, ΔE = kcal/mol CO 3 formation CO 3 CO O OC O Page 4 of 21

5 A fwd = s -1, A fwd /A rev = , E = 16.5 kcal/mol, ΔE = kcal/mol CO 3 decomposition CO 3 C(gas) O OC O O A fwd = s -1, A fwd /A rev = bar, E = kcal/mol, ΔE = 32.9 kcal/mol CO oxidation by O CO O C A fwd = s -1, A fwd /A rev = , E = kcal/mol, ΔE = kcal/mol CO O C A fwd = s -1, A fwd /A rev = , E = kcal/mol, ΔE = kcal/mol CO O CO 2 A fwd = s -1, A fwd /A rev = , E = kcal/mol, ΔE = kcal/mol Au 8 - Nanocluster Lattice Structure Similarly to the case of Au 6 -, Au 8 - has four different site types (Figure 1b in main manuscript), two top and two bridge as shown in the figure on the right. Thus, there are top sites with coordination numbers 2 () and 4 (), and bridge that connect two sites (bridge-44), or a with a site (). The former are only included for completeness as the molecular species investigated do not bind therein. Page 5 of 21

6 Lattice Energetics Model Single- and two-body contributions to the total energy of the lattice were taken into account. The corresponding patterns are shown below. The ab-initio calculations showed that if an molecule is bound to the nanocluster, a second molecule cannot bind. This behavior was modelled by including the pairwise additive - patterns whose energetic contributions were arbitrarily set to a high value (5 kcal/mol). Moreover, this cluster exhibits reconstruction for specific reaction pathways, which is implicitly taken into account in the binding energies of species. Thus, the subscript rc denotes species bound on the reconstructed structure. Finally, the gas species energies are 2.9 kcal/mol for CO, 2.7 kcal/mol for and kcal/mol for C. All energies incorporate zero point energy corrections. O O O O rc kcal/mol kcal/mol kcal/mol.98 kcal/mol -.2 kcal/mol Crc Crc CO CO CO O CO O kcal/mol kcal/mol kcal/mol kcal/mol CO CO 3 CO 3 CO 3rc O2CO O O CO kcal/mol kcal/mol kcal/mol kcal/mol kcal/mol +CO coads,rc CO rc O O CO O O CO kcal/mol kcal/mol 15 o bridge o 15 o bridge kcal/mol 5. kcal/mol Page 6 of 21

7 Reaction Mechanism The reaction mechanism consists of 22 reversible steps (44 elementary steps total) which are shown below. Reported are also the kinetic parameters: prefactor of the forward step, ratio of the forward versus reverse prefactors, as well as activation energy and reaction energy at the zero coverage limit. The latter is computed from the lattice energetics model. CO adsorption CO (gas) CO A fwd = bar -1 s -1, A fwd /A rev = bar -1, E =. kcal/mol, ΔE = kcal/mol CO (gas) CO A fwd = bar -1 s -1, A fwd /A rev = bar -1, E =. kcal/mol, ΔE = kcal/mol adsorption (gas) A fwd = bar -1 s -1, A fwd /A rev = bar -1, E =. kcal/mol, ΔE = kcal/mol C adsorption C (gas) Crc CO O A fwd = bar -1 s -1, A fwd /A rev = bar -1, E = 7.3 kcal/mol, ΔE = 2.9 kcal/mol C (gas) Crc CO O Page 7 of 21

8 A fwd = bar -1 s -1, A fwd /A rev = bar -1, E = kcal/mol, ΔE = 5.83 kcal/mol CO+ _coadsorption &_reconstruction (gas) +CO coads,rc CO O O CO A fwd = bar -1 s -1, A fwd /A rev = bar -1, E =. kcal/mol, ΔE = kcal/mol CO (gas) +CO coads,rc O O CO A fwd = bar -1 s -1, A fwd /A rev = bar -1, E =. kcal/mol, ΔE = kcal/mol CO formation (reconstructed) +CO coads,rc CO rc O O CO O O CO A fwd = s -1, A fwd /A rev = 1., E = 2.63 kcal/mol, ΔE = 1.2 kcal/mol CO decomposition (reconstructed) CO rc C(gas) O O CO O rc A fwd = s -1, A fwd /A rev = bar, E = kcal/mol, ΔE = kcal/mol CO oxidation by O Crc CO O rc CO O A fwd = s -1, A fwd /A rev = , E =. kcal/mol, ΔE = kcal/mol Page 8 of 21

9 Crc CO O rc CO O A fwd = s -1, A fwd /A rev = , E =. kcal/mol, ΔE = kcal/mol CO formation (gas) CO O2CO A fwd = bar -1 s -1, A fwd /A rev = bar -1, E =. kcal/mol, ΔE = kcal/mol CO tilting CO O2CO O O CO A fwd = s -1, A fwd /A rev = , E = 9.67 kcal/mol, ΔE = 7.87 kcal/mol CO decomposition CO C(gas) O O CO O A fwd = s -1, A fwd /A rev = bar, E = 9.45 kcal/mol, ΔE = kcal/mol O2CO O C(gas) A fwd = s -1, A fwd /A rev = bar, E = kcal/mol, ΔE = kcal/mol Page 9 of 21

10 CO oxidation by O CO O C(gas) A fwd = s -1, A fwd /A rev = bar, E = 3.92 kcal/mol, ΔE = kcal/mol CO O C(gas) A fwd = s -1, A fwd /A rev = bar, E = 1.6 kcal/mol, ΔE = kcal/mol CO 3 formation C(gas) O CO 3 A fwd = bar -1 s -1, A fwd /A rev = bar -1, E =.8 kcal/mol, ΔE = kcal/mol C(gas) O CO 3 A fwd = bar -1 s -1, A fwd /A rev = bar -1, E =.36 kcal/mol, ΔE = kcal/mol C(gas) O CO 3rc A fwd = bar -1 s -1, A fwd /A rev = bar -1, E = 1.54 kcal/mol, ΔE = kcal/mol Au 1 - Nanocluster Lattice Structure - The Au 1 cluster (Figure 1c, in main manuscript) has 4 different top site types: one with coordination number 4 (), two with coordination numbers equal to 3 (, topcn3γ), and one with coordination number 6 (top-cn6). Moreover, there are 6 bridge site types (, bridge-46,, bridge-3β6, bridge-3γ6, bridge-66). The internal sites (topcn6, bridge-46, bridge-3β6, bridge-3γ6, bridge-66) are only included for completeness as the molecular species investigated do not bind therein. Page 1 of 21

11 Lattice Energetics Model Single- and two-body contributions to the total energy of the lattice were taken into account. The corresponding patterns are shown below. The ab-initio calculations showed that if an molecule is bound to the nanocluster, a second molecule cannot bind. This behavior was modelled by including the pairwise additive - patterns whose energetic contributions were arbitrarily set to a high value (5 kcal/mol). Finally, the gas species energies are 2.9 kcal/mol for CO, 2.7 kcal/mol for and kcal/mol for C. All energies incorporate zero point energy corrections. O O kcal/mol kcal/mol kcal/mol kcal/mol O O O.8 kcal/mol 1.21 kcal/mol 2.13 kcal/mol O O b kcal/mol kcal/mol O O kcal/mol C CO O CO kcal/mol CO kcal/mol CO -9.5 kcal/mol kcal/mol C O CO C kcal/mol CO 3 O CO O kcal/mol C CO O kcal/mol CO 3 O CO O kcal/mol kcal/mol C kcal/mol CO O Page 11 of 21

12 5. kcal/mol 5. kcal/mol 5. kcal/mol O O 5. kcal/mol O O 5. kcal/mol O O 5. kcal/mol O O O O 5. kcal/mol O O O O 5. kcal/mol O O 5. kcal/mol O O Page 12 of 21

13 Reaction Mechanism The reaction mechanism consists of 45 reversible steps (9 elementary steps total) which are shown below. Reported are also the kinetic parameters: prefactor of the forward step, ratio of the forward versus reverse prefactors, as well as activation energy and reaction energy at the zero coverage limit. The latter is computed from the lattice energetics model. CO adsorption CO (gas) CO A fwd = bar -1 s -1, A fwd /A rev = bar -1, E =. kcal/mol, ΔE = kcal/mol CO (gas) CO A fwd = bar -1 s -1, A fwd /A rev = bar -1, E =. kcal/mol, ΔE = kcal/mol CO (gas) CO A fwd = bar -1 s -1, A fwd /A rev = bar -1, E =. kcal/mol, ΔE = kcal/mol CO diffusion CO CO A fwd = s -1, A fwd /A rev = 1.413, E = 6.19 kcal/mol, ΔE = kcal/mol CO CO A fwd = s -1, A fwd /A rev = 2.217, E = 2.13 kcal/mol, ΔE = -.5 kcal/mol Page 13 of 21

14 adsorption (gas) A fwd = bar -1 s -1, A fwd /A rev = bar -1, E =. kcal/mol, ΔE = kcal/mol (gas) A fwd = bar -1 s -1, A fwd /A rev = bar -1, E =. kcal/mol, ΔE = kcal/mol (gas) A fwd = bar -1 s -1, A fwd /A rev = bar -1, E =. kcal/mol, ΔE = kcal/mol (gas) O O A fwd = bar -1 s -1, A fwd /A rev = bar -1, E =. kcal/mol, ΔE = kcal/mol O O (gas) A fwd = bar -1 s -1, A fwd /A rev = bar -1, E =. kcal/mol, ΔE = kcal/mol tilting O O A fwd = s -1, A fwd /A rev = , E =.4 kcal/mol, ΔE = -7.9 kcal/mol Page 14 of 21

15 O O A fwd = s -1, A fwd /A rev = , E =.62 kcal/mol, ΔE = kcal/mol O O A fwd = s -1, A fwd /A rev = , E =.48 kcal/mol, ΔE = kcal/mol O O A fwd = s -1, A fwd /A rev = , E =.2 kcal/mol, ΔE = kcal/mol C adsorption C(gas) A fwd = bar -1 s -1, A fwd /A rev = bar -1, C E =. kcal/mol, ΔE =.57 kcal/mol C (gas) C CO O A fwd = bar -1 s -1, A fwd /A rev = bar -1, E =. kcal/mol, ΔE = kcal/mol C (gas) C CO O Page 15 of 21

16 A fwd = bar -1 s -1, A fwd /A rev = bar -1, E =. kcal/mol, ΔE =.48 kcal/mol C (gas) C CO O A fwd = s -1, A fwd /A rev = , E =. kcal/mol, ΔE = kcal/mol C (gas) C CO O A fwd = bar -1 s -1, A fwd /A rev = bar -1, E =. kcal/mol, ΔE = -.25 kcal/mol O diffusion O O A fwd = s -1, A fwd /A rev = , E =.38 kcal/mol, ΔE = kcal/mol O O A fwd = s -1, A fwd /A rev = , E = kcal/mol, ΔE = kcal/mol O O A fwd = s -1, A fwd /A rev = , E = 3.86 kcal/mol, ΔE = -8.5 kcal/mol Page 16 of 21

17 O O A fwd = s -1, A fwd /A rev = , E = kcal/mol, ΔE = kcal/mol CO oxidation by CO O C(gas) A fwd = s -1, A fwd /A rev = bar, E = 9.54 kcal/mol, ΔE = kcal/mol CO O C(gas) A fwd = s -1, A fwd /A rev = bar, E = kcal/mol, ΔE = kcal/mol CO O C(gas) A fwd = s -1, A fwd /A rev = bar, E = 1.5 kcal/mol, ΔE = kcal/mol CO O C(gas) A fwd = s -1, A fwd /A rev = bar, E = 11.8 kcal/mol, ΔE = kcal/mol CO O C(gas) A fwd = s -1, A fwd /A rev = bar, E = kcal/mol, ΔE = kcal/mol Page 17 of 21

18 CO A fwd = s -1, A fwd /A rev = bar, E = kcal/mol, ΔE = kcal/mol O C(gas) CO O O O C(gas) A fwd = s -1, A fwd /A rev = bar, E = kcal/mol, ΔE = kcal/mol O O 2 CO O O C(gas) A fwd = s -1, A fwd /A rev = bar, E = kcal/mol, ΔE = kcal/mol CO O O 2 O C(gas) O A fwd = s -1, A fwd /A rev = bar, E = kcal/mol, ΔE = kcal/mol CO oxidation by O CO O C(gas) A fwd = s -1, A fwd /A rev = bar, E = 2.98 kcal/mol, ΔE = kcal/mol Page 18 of 21

19 CO O C(gas) A fwd = s -1, A fwd /A rev = bar, E = 3.9 kcal/mol, ΔE = kcal/mol CO O C(gas) A fwd = s -1, A fwd /A rev = bar, E = 4.7 kcal/mol, ΔE = kcal/mol CO O C(gas) A fwd = s -1, A fwd /A rev = bar, E = 4.95 kcal/mol, ΔE = kcal/mol CO O C(gas) A fwd = s -1, A fwd /A rev = bar, E = 2.63 kcal/mol, ΔE = kcal/mol CO O C(gas) A fwd = s -1, A fwd /A rev = bar, E = 3.43 kcal/mol, ΔE = kcal/mol CO O C(gas) A fwd = s -1, A fwd /A rev = bar, E = 4.31kcal/mol, ΔE = kcal/mol Page 19 of 21

20 CO O C(gas) A fwd = s -1, A fwd /A rev = bar, E = 4.42 kcal/mol, ΔE = kcal/mol CO 3 formation C(gas) CO 3 O O OC O A fwd = bar -1 s -1, A fwd /A rev = bar -1, E =.3 kcal/mol, ΔE = kcal/mol C(gas) CO 3 O O OC O A fwd = bar -1 s -1, A fwd /A rev = bar -1, E =.29 kcal/mol, ΔE = kcal/mol C(gas) CO 3 O O OC O A fwd = bar -1 s -1, A fwd /A rev = bar -1, E =.42 kcal/mol, ΔE = kcal/mol C(gas) CO 3 O O OC O A fwd = bar -1 s -1, A fwd /A rev = bar -1, E =. kcal/mol, ΔE = kcal/mol Page 2 of 21

21 References 1 Stamatakis, M. & Vlachos, D. G. A Graph-Theoretical Kinetic Monte Carlo Framework for on-lattice Chemical Kinetics. J. Chem. Phys. 134, , doi:1.163/ (211). 2 Nielsen, J., d Avezac, M., Hetherington, J. & Stamatakis, M. Parallel Kinetic Monte Carlo Simulation Framework Incorporating Accurate Models of Adsorbate Lateral Interactions. J. Chem. Phys. 139, 22476, doi:1.163/ (213). 3 Stamatakis, M. Zacros: Advanced Lattice-KMC simulation Made Easy, < (213). 4 Stamatakis, M., Christiansen, M., Vlachos, D. G. & Mpourmpakis, G. Multiscale Modeling Reveals Poisoning Mechanisms of MgO-Supported Au Clusters in CO Oxidation. Nano Lett. 12, , doi:1.121/nl31318b (212). Page 21 of 21