Achieving Selective and Efficient Electrocatalytic Activity for CO 2 Reduction Using Immobilized Silver Nanoparticles

Transcription

1 Supporting Information Achieving Selective and Efficient Electrocatalytic Activity for CO 2 Reduction Using Immobilized Silver Nanoparticles Cheonghee Kim, a Hyo Sang Jeon, a,b Taedaehyeong Eom, c Michael Shincheon Jee, a,d Hyungjun Kim, c Cynthia M. Friend, e Byoung Koun Min, a,b,f * and Yun Jeong Hwang a,b * a Clean Energy Research Center, Korea Institute of Science and Technology, Seoul 2792, Republic of Korea b Korea University of Science and Technology, Daejeon 34113, Republic of Korea c Graduate School of Energy, Environment, Water, and Sustainability (EEWS), Korea Advanced Institute of Science and Technology (KAIST), Daejeon, 34141, Republic of Korea d Department of Chemical and Biological Engineering, Korea University, Seoul 2841, Republic of Korea e Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts 2138, United States f Green School, Korea University, Seoul 2841, Republic of Korea *Corresponding author: [ ] bkmin@kist.re.kr [Tel] [Fax] (Prof. B. K. Min) [ ] yjhwang@kist.re.kr [Tel] [Fax] (Prof. Y. J. Hwang) S1

2 Table of Contents XRD data of... S3 TEM images of Ag nanoparticles... S4 XPS spectra of prepared Ag/C... S5 Estimation of the relative cysteamine amount... S6 CO partial current densities with error bars... S7 CO partial current densities depending on overpotential... S7 Electrochemical surface area measurement... S8 Total current densities... S9 CO Faradaic efficiency with error bars... S1 H 2 and CO Faradaic efficiencies of... S11 Durability test of Ag foil and... S12 13 C isotope experiments... S13 CO Tafel plots... S14 Summary of particle size and electrochemical properties... S15 Comparison of different silver electrocatalysts... S16 Reference... S17 S2

3 Intensity (a. u.) (111) (2) (22) (311) (222) degree) Figure S1. XRD data of with only crystalline face centered cubic Ag peaks present. S3

4 Figure S2. TEM images of Ag nanoparticles synthesized on carbon support without cysteamine showing Ag nanoparticles are neither size-controlled nor immobilized on the carbon support. S4

5 Intensity (a.u.) Intensity (a.u.) 3 nm Ag/C S 2p 3 nm Ag/C Ag 3d 1 nm Ag/C a 1 nm Ag/C b Binding Energy (ev) Binding Energy (ev) Figure S3. XPS spectra of prepared 3, 5, and 1 nm Ag/C for a; S 2p and b; Ag 3d. S5

6 Estimation of relative cysteamine amount The relative cysteamine amount was calculated using the following equation: Area (S Ag S bond )/ASF S Area (Ag total )/ASF Ag 1 (%) where ASF S, and ASF Ag are atomic sensitivity factors of sulfur and silver, respectively, Area (S Ag S bond ) is the peak area associated with Ag-S bond in S 2p spectra, and Area (Ag total ) is the peak area in Ag 3d spectra. Ag-S bond signal was taken from S 2p spectra not from Ag 3d spectra because S 2p spectra showed a more distinct peak evolution associated with Ag-S bond. The ratios were 18.6, 22., and 16.3 % for 3, 5, and 1 nm Ag/C samples, respectively, indicating relatively larger cysteamine amount in 5 nm Ag/C sample compared to the other two. S6

7 CO Current Density (ma/cm 2 ) nm Ag/C 1 nm Ag/C Ag foil Potential (V, E vs RHE) Figure S4. CO partial current densities of various silver electrodes depending on applied potentials with error bars. CO Current Density (ma/cm 2 ) nm Ag/C 1 nm Ag/C Ag foil Overpotential (, V) Figure S5. CO partial current densities depending on overpotentials. S7

8 Current (ma) Current (ma) Current (ma) Current (ma) Electrochemical surface area measurement: lead underpotential deposition (UPD).6.4 Bulk Pb Submonolayer UPD of Pb nm Ag/C Potential (V, E vs Ag/AgCl) Potential (V, E vs Ag/AgCl) nm Ag/C Potential (V, E vs Ag/AgCl) Ag foil Potential (V, E vs Ag/AgCl) Figure S6. Cyclic voltammograms of UPD and bulk deposition of Pb in 5 mm Pb(NO 3 ) 2, 1 mm HNO 3 and 1 mm KCl solution. Cyclic voltammetry was performed from. V to -.5 V (vs. Ag/AgCl) with a scan rate 1 mv/s or 1 mv/s in 5 mm Pb(NO 3 ) 2, 1 mm HNO 3 and 1 mm KCl solution. The electrochemical surface area was calculated by area of Pb UPD corresponding to a charge of 1.67 x 1-3 cm 2 /μc. R3 S8

9 Current Density (ma/cm 2 ) Carbon black Cysteamine-C 3 nm Ag/C 1 nm Ag/C Ag foil Potential (V, E vs RHE) Figure S7. Total current densities depending on applied potential. S9

10 Faradaic Efficiency (%) nm Ag/C Ag foil 3 nm Ag/C Potential (V, E vs RHE) Figure S8. CO Faradaic efficiency depending on applied potential with error bars. S1

11 Faradaic Efficiency (%) 1 8 H 2 CO Potential (V, E vs RHE) Figure S9. H 2 and CO Faradaic efficiencies of depending on applied potential. S11

12 Faradaic Efficiency (%) Faradaic Efficiency (%) a CO H 2 Ag foil Time (hour) Current Density (ma/cm 2 ) b CO H Time (hour) Current Density (ma/cm 2 ) Figure S1. Durability test with a; Ag foil and b; samples for 5 hours. Durability test was performed at -1.1 V (vs. RHE) and -.8 V (vs. RHE) for Ag foil and 5 nm Ag/C, respectively. S12

13 Air CO Chromatogram 12 CO 2 m/z : 28 ( 12 CO) Mass-spectrum a Air Chromatogram CO 13 CO 2 m/z : 29 ( 13 CO) Mass-spectrum b Figure S11. GC-MS chromatograms of a; normal CO 2 reduction products and b; 13 CO 2 isotope products for. S13

14 (V) nm Ag/C 1 nm Ag/C Ag foil Log (j CO, ma cm 2 ) Figure S12. CO Tafel plots of prepared 3, 5, 1 nm Ag/C, and Ag foil. S14

15 Table S1. Summary of particle size and electrochemical properties of prepared 3, 5, 1 nm Ag/C and Ag foil. Catalyst Size (nm) Overpotential.1 1. ma/cm 2 ma/cm 2 (mv) (mv) Mass activity at -.8 V (ma/mg) Tafel slope (mv/dec) Exchange current density (ma/cm 2 ) 3 nm Ag/C 3.4 ± E-5 5. ± E-4 1 nm Ag/C 1.6 ± E-5 Ag foil n/a n/a E-6 S15

16 Table S2. Comparison of different silver electrocatalysts for CO 2 reduction. Sample Ag loading amount (mg/cm 2 ) Electrolyte ph Overpotential (η, mv) J CO a (ma/cm 2 ) Mass activity J CO b (ma/mg) Ref.9.5 M KHCO 3 /CO This work Nanoporous Ag ~4.5 M KHCO 3 /CO R1 Ag Nanoparticle 1..5 M KHCO 3 /CO R1 Ag Nanocoarals N/A c.1 M KHCO 3 /CO N/A R2 5 nm Ag Nanoparticle 1. EMIN-BF 4 N/A N/A ~.95(-1.14 V vs. SHE) ~.95(-1.14 V vs. SHE) R3 Ag nanoparticle 6.7 EMIN-BF 4 N/A 17 ~ R4 Ag Pyrazole/ Carbon 1. 1 M KOH / CO 2 N/A N/A ~3 (-1.4 V vs. Ag/AgCl) ~3 (-1.4 V vs. Ag/AgCl) R5 Polycrystalline Ag N/A.5 M KHCO 3 /CO ~ N/A This work a CO partial current density under the overpotential noted in the left column unless the bias potential is noted. b Mass activity of CO production under the overpotential noted in the left column unless the bias potential is noted. c Ag loading amount is not applicable because nano-corals were prepared on the polycrystalline Ag foil. S16

17 Reference R1. Lu, Q.; Rosen, J.; Zhou, Y.; Hutchings, G. S.; Kimmel, Y. C.; Chen, J. G.; Jiao, F. Nat. Commun. 214, 5, R2. Hsieh, Y.; Senanayake, S. D.;, Zhang, Y.; Xu, W.; Polyansky, D. E. ACS Catal. 215, 5, R3. Salehi-Khojin, A.; Jhong, H. M.; Rosen, B. A.; Zhu, W.; Ma, S.; Kenis, P. J. A.; Masel, R. I. J. Phys. Chem. C 213, 117, R4. Rosen, B. A.; Salehi-Khojin, A.; Thorson, M. R.; Zhu, W.; Whipple, D. T.; Kenis, P. J. A.; Masel, R. I. Science 211, 334, 643 R5. Tornow, C. E.; Thorson, M. R.; Ma, S.; Gewirth, A. A.; Kenis, P. J. J. Am. Chem. Soc. 212, 134, S17