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Supporting information

Enhance CO2-to-C2+ products yield through spatial management of CO transport in Cu/ZnO tandem electrodes

Tianyu Zhang, Zhengyuan Li, Jianfang Zhang, Jingjie Wu*

Department of Chemical and Environmental Engineering, University of Cincinnati, Cincinnati, OH, USA 45221

Figures S1-S14Reference S1.

Figure S1. Reaction rate of CO-to-C2H4 conversion as a function of CO partial pressure at -0.55 V vs. RHE. The data is adapted from reference.S1

Figure S2. The profile of the relationship between conversion (XA) and reaction volume of (a) CSTR, and (b) PFR.

Figure S3. A schematic of the customized flow cell.

Figure S4. (a) FE of various products and (b) jtotal of the Cu1.0&ZnO0.20 electrode as a function of applied potential. The performance was tested in a customized flow cell with 1 M KOH as electrolyte. The error bars represent the standard deviation from at least three independent samples.

Figure S5. (a) The j and (b) the FE of various products as a function of applied potential on the bare Cu electrode. The performance was tested in a customized flow cell with 1 M KOH as electrolyte.

Figure S6. (a) FE of C2H4, (b) jC2H4, (c) FE of C2+ products and (b) jC2+ as a function of applied potential on the bare Cu electrode, Cu1.0/ZnO0.20, and Cu1.0&ZnO0.20 tandem electrodes. The performance was tested in a customized flow cell with 1 M KOH as the electrolyte. The error bars represent the standard deviation from at least three independent samples.

Figure S7. (a) The current density and (b) the FE of H2 and CO as a function of applied potential on the bare ZnO electrode. The performance was tested in a customized flow cell with 1 M KOH as the electrolyte.

Figure S8. Demonstration of the overlapping of potential range for jCO on ZnO and jCO & jC2+

on Cu in two independent tests. The performance was tested in a customized flow cell with 1 M KOH as the electrolyte.

Figure S9. (a-e) The FE of various products as a function of applied potential on Cu1.0/ZnO0.05, Cu1.0/ZnO0.10, Cu1.0/ZnO0.15, Cu1.0/ZnO0.20, and Cu1.0/ZnO0.30 tandem electrodes. (f) The comparison of the total current density. The performance was tested in a customized flow cell with 1 M KOH as the electrolyte. The error bars represent the standard deviation from at least three independent samples.

Figure S10. (a) The FE of C2H4 and (b) the jC2H4 as a function of applied potential on the bare Cu and different Cu/ZnO tandem electrodes with Cu loading of 1 mg cm-2 and ZnO loading varying from 0.05 to 0.30 mg cm-2. The performance was tested in a customized flow cell with 1 M KOH as electrolyte. The error bars represent the standard deviation from at least three independent samples.

Figure S11. The (a, c, e) Faradaic efficiency and (b, d, f) production rate of (a, b) CH4, (c, d) C2H5OH, and (e, f) multi-carbon oxygenates as a function of applied potential on Cu/ZnO tandem electrodes with a constant Cu loading of 1.0 mg cm -2 and ZnO varies from 0.05 to 0.30 mg cm-2. The performance is tested in a custom flow cell with 1 M KOH as electrolyte. The error bars represent the standard deviation from at least three independent samples.

Figure S12. (a) The total CO generation rate and (b) the CO dimerization rate as a function of applied potential on the bare Cu, Cu1.0/ZnO0.05, Cu1.0/ZnO0.10, Cu1.0/ZnO0.15, Cu1.0/ZnO0.20 and Cu1.0/ZnO0.30 electrodes. The performance was tested in a customized flow cell with 1 M KOH as the electrolyte. The error bars represent the standard deviation from at least three independent samples.

Figure S13. A schematic of Cu/Pt/ZnO electrode.

Figure S14. The FE of various products on the bare Cu, Cu1.0/Pt0.10/ZnO0.15, Cu1.0/Pt0.01/ZnO0.15, and Cu1.0/CB0.10/ZnO0.15 electrodes. The performance was tested in a customized flow cell with 1 M KOH as the electrolyte.

Figure S15. The CO stripping cyclic voltammetry scan of the (a) Cu1.0/Pt0.10/ZnO0.15 and (b) Cu1.0/Pt0.01/ZnO0.15 electrodes after the CO2 reduction reaction.

References:

S1. Li, J.; Wang, Z.; McCallum, C.; Xu, Y.; Li, F.; Wang, Y.; Gabardo, C. M.; Dinh, C.-T.; Zhuang, T.-T.; Wang, L.; Howe, J. Y.; Ren, Y.; Sargent, E. H.; Sinton, D., Constraining CO Coverage on Copper Promotes High-Efficiency Ethylene Electroproduction. Nat. Catal. 2019, 2, 1124-1131.