The Role of Surface Oxophilicity in Copper-catalyzed Water Dissociation

Transcription

1 Supporting Information The Role of Surface Oxophilicity in Copper-catalyzed Water Dissociation Wesley Luc, 1 Zhao Jiang, 2,3 Jingguang G. Chen,*,3 and Feng Jiao*,1 [1] Center for Catalytic Science and Technology, Department and Biomolecular Engineering, University of Delaware, Newark, DE USA [2] Xi an Jiaotong University, Xi an, Shaanxi, China [3] Department of Chemical Engineering, Columbia University, New York, NY USA *Corresponding authors: jgchen@columbia.edu & jiao@udel.edu Table of Contents Index Table S1: Calculated HBEs and OBEs for Cu-M (111) surfaces Table S2: Calculated HBEs and OBEs for Pt (111) surface Figure S1: Sub-layer substitution surface Table S3: Calculated HBEs and OBEs for sub-layer substitution surface Figure S2: Metal oxide cluster on Cu(111) surfaces Table S4: Calculated HBEs and OBEs for metal oxide cluster on Cu(111) surfaces Table S5: Calculated HBEs with different U values for Ti 3 O 6 /Cu(111) Figure S3: Photograph images of the synthesis of Cu-M bimetallic RDE disks Table S6: Calculated lattice constants from the FCC (111) peak positions Figure S4: XPS characterization of as-prepared Cu-M bimetallics Figure S5: Surface roughness characterization Figure S6: Catalytic testing of Cu-M bimetallic and Cu replicates Figure S7: Independent long-term stability testing of Cu-M bimetallics Figure S8: Post-reaction XPS characterization of Cu-M bimetallics Figure S9: XPS characterization of as-prepared Cu/MO/OH catalysts Figure S10: SEM images of Cu/MO/OH catalysts Figure S11: Catalytic testing of Cu/MO/OH bimetallic and Cu replicates Figure S12: HER activity of Cu with higher loading of TiO 2 clusters Page S3 S4 S5 S6 S7 S8 S9 S10 S11 S12 S13 S14 S15 S16 S17 S18 S19 S20 S1

2 Figure S13: Independent long-term stability testing of Cu/MO/OH catalysts Figure S14: Post-reaction XPS characterization of Cu/MO/OH catalysts Figure S15. Electrochemical characterization of Pt References S21 S22 S23 S24 S2

3 Table S1. Calculated HBEs and OBEs for Cu-M (111) surfaces [#]: Corresponding adsorption site on Figure 1. S3

4 Table S2. Calculated HBEs and OBEs for Pt (111) surface Note: Site [1] and [2] are FCC and HCP sites, respectively S4

5 Figure S1: Sub-layer substitution surface model with Cu and M = Ti, Co, or Ni atoms represented in orange and blue, respectively. S5

6 Table S3. Calculated HBEs and OBEs for sub-layer substitution surface model. [#]: Corresponding adsorption site on Figure S1. S6

7 Figure S2. Metal oxide cluster on Cu (111) surface model: a) Ti 3 O 6 /Cu (111) surface where Cu, Ti, and O atoms are represented in orange, grey, and red, respectively. b) Ni 3 O 3 /Cu (111) surface with Cu, Ni, and O atoms represented in orange, blue, and red, respectively. It must be noted that a CoO x /Cu (111) was not examined due to the intensive computational power that was needed. S7

8 Table S4. Calculated HBEs and OBEs for metal oxide cluster on Cu (111) surface model. (#): Corresponding adsorption site on Figure 2S. S8

9 Table S5. Calculated HBEs under different U values on the Ti 3 O 6 /Cu(111) interface U (ev) HBEs on Ti 3 O 6 /Cu(111) (ev) S9

10 Figure S3. a) Photograph image of as-synthesized Cu-M ingot using arc melting, b) as-machined Cu-M RDE disks, c) Cu-M RDE disks sealed in quartz tube under Ar atmosphere, and d) Cu-M disks inserted into E4 Series RDE tips. S10

11 Table S6. Calculated lattice constants from the FCC (111) peak positions. S11

12 Figure S4. XPS characterization of as-prepared Cu-M bimetallics. a&b) Cu 2p 3/2 and Ti 2p spectra of Cu-Ti. c&d) Cu and Co 2p 3/2 spectra of Cu-Co. e&f) Cu and Ni 2p 3/2 spectra of Cu- Ni. Partial surface oxidation was observed. Peak positions were obtained from various published works. 1-4 S12

13 Figure S5. Surface roughness characterization. Typical AFM images of Cu-M bimetallic surface in a) amplitude, b) phase, c) height, and d) line scans of the height fluctuations for the three indicated lines in c). S13

14 Figure S6. Cu-M bimetallic and Cu replicates were also independently tested in H 2 saturated 0.1 M KOH solution with a rotation speed of 1800 rpm at room temperature with a scan rate of 10 mv sec -1. The 5 th scan of each Cu-M bimetallic and Cu replicates are shown. a) Three sets of polarization curves including data already presented in Figure 3. b) The average Tafel slopes and exchange current densities with standard deviations. S14

15 Figure S7. Independent long-term stability testing of Cu-M bimetallics. HER polarization curves at the 5 th scan and after 1000 scans with a scan rate of 10 mv sec -1 in H 2 saturated 0.1 M KOH solution with a rotation speed of 1800 rpm at room temperature. The scans in between were scanned at 25 mv sec -1. After 1000 scans, the electrode surface was cleared of residual bubbles and then immediately rescanned. The reported XPS elemental at.% includes the oxidized and non-oxidized states. S15

16 Figure S8. Long-term stability testing post-reaction XPS characterization of Cu-M bimetallics. a&b) Cu 2p 3/2 and Ti 2p spectra of Cu-Ti. c&d) Cu and Co 2p 3/2 spectra of Cu-Co. e&f) Cu and Ni 2p 3/2 spectra of Cu-Ni. Again, partial oxidation was observed. S16

17 Figure S9. XPS characterization of as-prepared Cu/MO/OH catalysts. a&b) Cu 2p 3/2 and Ti 2p spectra of Cu/TiO 2. c&d) Cu and Co 2p 3/2 spectra of Cu/Co(OH) 2. e&f) Cu and Ni 2p 3/2 spectra of Cu/Ni(OH) 2. S17

18 Figure S10. SEM images of a) Cu/TiO 2, b) Cu/Co(OH) 2, and c) Cu/Ni(OH) 2 S18

19 Figure S11. Cu/MO/OH replicates were also independently tested in H 2 saturated 0.1 M KOH solution with a rotation speed of 1800 rpm at room temperature with a scan rate of 10 mv sec -1. The 5 th scan of each Cu/MO/OH and Cu replicates are shown. a) Three sets of polarization curves including data already presented in Figure 4. b) The average Tafel slopes and exchange current densities with standard deviations. S19

20 Figure S12. a) SEM imaging of Cu with higher loading of TiO 2. b) Electrocatalytic performance of Cu with higher loadings of TiO 2. S20

21 Figure S13. Independent long-term stability testing of Cu/MO/OH catalysts. HER polarization curves at the 5 th scan and after 1000 scans with a scan rate of 10 mv sec -1 in H 2 saturated 0.1 M KOH solution with a rotation speed of 1800 rpm at room temperature. The scans in between were scanned at 25 mv sec -1. After 1000 scans, the electrode surface was cleared of residual bubbles and then immediately rescanned. S21

22 Figure S14. Long-term stability testing post-reaction XPS characterization of Cu/MO/OH catalysts. a&b) Cu 2p 3/2 and Ti 2p spectra of Cu/TiO 2. c&d) Cu and Co 2p 3/2 spectra of Cu/Co(OH) 2. e&f) Cu and Ni 2p 3/2 spectra of Cu/Ni(OH) 2. S22

23 Figure S15. Electrochemical characterization of Pt. HER activity of bulk Pt in H 2 -saturated 0.1 M KOH after ir-correction, determined with a sweep rate of 10 mv s -1 and a rotation rate of 1800 rpm at room temperature. b) Corresponding Tafel plot with a Tafel slope of 121 mv dec -1. c) HER/HOR kinetic currents on bulk Pt surface and corresponding Bulter-Volmer fit (α a = 0.48). The kinetic currents were corrected for ir loss, and the HOR branch was corrected for H 2 mass transport limitation. The exchange current was determined to be 610 µa cm -2 as consistent with similar reported values. 5 S23

24 References 1. Druska, P.; Strehblow, H.-H., Quantitative determination of the passive layer on Cu Ni alloys. Surface and Interface Analysis 1995, 23, Gaskell, K. J.; Starace, A.; Langell, M. A., ZnxNi1-xO Rocksalt Oxide Surfaces: Novel Environment for Zn2+ and Its Effect on the NiO Band Structure. The Journal of Physical Chemistry C 2007, 111, Biesinger, M. C.; Lau, L. W. M.; Gerson, A. R.; Smart, R. S. C., Resolving surface chemical states in XPS analysis of first row transition metals, oxides and hydroxides: Sc, Ti, V, Cu and Zn. Applied Surface Science 2010, 257, Biesinger, M. C.; Payne, B. P.; Grosvenor, A. P.; Lau, L. W. M.; Gerson, A. R.; Smart, R. S. C., Resolving surface chemical states in XPS analysis of first row transition metals, oxides and hydroxides: Cr, Mn, Fe, Co and Ni. Applied Surface Science 2011, 257, Sheng, W.; Gasteiger, H. A.; Shao-Horn, Y., Hydrogen Oxidation and Evolution Reaction Kinetics on Platinum: Acid vs Alkaline Electrolytes. Journal of The Electrochemical Society 2010, 157, B1529-B1536. S24