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Supporting Information
Regulating the spin state of nickel in molecular catalysts for boosting
carbon dioxide reduction
Xiang Wang, Yubin Fu, Diana Tranca, Kaiyue Jiang, Jinhui Zhu, Jichao Zhang, Sheng Han,* Changchun Ke, Chenbao Lu,* Xiaodong Zhuang*
X. Wang, Prof. S. Han
College of Chemistry and Chemical Engineering, Shanghai University of Engineering Science, Shanghai 201620, China.
X. Wang, Dr. D. Tranca, K. Jiang, Dr. J. Zhu, Dr. C. Lu, Prof. X. Zhuang
The meso-Entropy Matter Lab, State Key Laboratory of Metal Matrix Composites, Shanghai Key Laboratory of Electrical Insulation and Thermal Ageing, School of Chemistry and Chemical Engineering, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, China. E-mail: [email protected] (C.L.), [email protected] (X.Z.)
Prof. S. Han
School of Chemical and Environmental Engineering, Shanghai Institute of Technology, Haiquan Road 100, Shanghai 201418, China. E-mail: [email protected]
Dr. Y. Fu
Center for Advancing Electronics Dresden (cfaed) & Department of Chemistry and Food Chemistry, Technische Universität Dresden 01062 Dresden, Germany
Dr. J. Zhang
Shanghai Synchrotron Radiation Facility, Zhangjiang Laboratory, Shanghai Advanced Research Institute, Chinese Academy of Sciences, No. 239, Zhangheng Road, Shanghai 201204, China. Prof. C. Ke
School of Mechanical Engineering, Shanghai Jiao Tong University, Shanghai 200240, China. Dr. C. Lu
College of Chemistry and Molecular Engineering, Zhengzhou University, Zhengzhou 450001, Henan, China.
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Experimental Procedures
Electrocatalysis measurements:
The electrocatalytic CO2 reduction was performed in a three electrode H-type cell, of which Ag/AgCl as the reference electrode, Pt plate as the counter electrode, and catalysts loaded on carbon paper as the working electrode. For preparation of working electrodes, typically, 1 mg of catalysts and 9 mg commercial carbon nanotube was blended with 1 mL of Nafion solution (0.5 wt. %) and stirred for 12 h to ensure uniform mixing catalyst ink. Then 100µL of catalyst ink was pipetted onto the carbon paper surface (1 cm−2), giving a catalyst loading of 1 mg cm−2. All potentials reported in this work were versus to reversible hydrogen electrode (RHE) using the following formula:
ERHE (V)=EAg/AgCl (V) + 0.197 V + 0.0591V * pH
The electrolyte was CO2 saturated 0.5 M KHCO3, and CO2 was continuously supplied to the cell (20 mL min-1) through a gas bubbling tube during the constant potential electrolysis. The LSV curves were obtained with a scan rate of 5 mV s−1, all potentials in this study were without iR compensated. The electrochemical double-layer capacitances (Cdl) of catalysts were calculated from CV curves. The CV curves were performed at scan rates varying from 10 to 50 mV s−1 in the region from -0.7 to -0.8 V. The capacitive currents of ΔJ (Janodic − Jcathodic) are plotted as a function of the CV against the scan rate. The slope of the fitting line is equal to twice the Cdl, which is linearly proportional to the electrochemically effective surface area of the electrode.
The gaseous products were monitored by an online gas chromatography (GC, Shimadzu GC-2014C), equipped with a thermal conductivity detector (TCD) detector for H2 and a flame ionization detector (FID) detector for CO quantification. A GC run repeats every 18 minutes. The GC was calibrated with standard gas mixtures (Air Liquide, CO, H2, CH4, C2H4 C2H6, C2H2 in N2) before the product measurements. The liquid products in the KHCO3 solution was analyzed and quantified through a Bruker 500 MHZ (AVANCE Ⅲ) NMR spectroscope with water suppression. After electrolysis, KHCO3 electrolyte (0.5 mL) was collected and mixed with D2O (0.1 mL) in an NMR tube and dimethyl sulfoxide (DMSO, 0.05 μL) as an internal standard.
Faradic efficiency (FE) calculation
Faradaic Efficiency (FE) of CO and H2 were calculated via the following equation: FE = 𝑄𝑖
𝑄𝑡𝑜𝑡𝑎𝑙=
2 × 𝑃𝑜 × F × × νi
R × T × I
where Qi is the quantity of electric charge needed to produce corresponding product i. Qtotal is the quantity of electric charge needed to produce all products. 2 is the number of electrons transferred per mole CO2 to CO or per mole H2O to H2. Po is atmospheric pressure (1.01 × 105 Pa), F is the faradaic constant (96485 C mol-1), v is the gas flow rate measured by flow meter, v
i is the volume
concentration of gas product in the exhaust gas from the cell determined by online GC. T is the reaction temperature (298.15 K), R is the idea gas constant (8.314 J mol-1 K-1), and I is the current at each potential.
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Evaluation of turnover frequency (TOF) (h-1)
The TOF (h-1) of product CO was evaluated as follows:
TOF =𝐹𝐸𝑐𝑜× 𝑗𝑡𝑜𝑡𝑎𝑙× 𝐴 × 𝑀𝑁𝑖× 𝑡 𝑛 × 𝐹 × 𝜔𝑁𝑖× 𝑚
where FE is the faradaic efficiency of CO, J is the total current density, A (1 cm2) is the electrode geometric area, ωNi is the mass fraction of nickel on the catalyst, m is the mass of catalyst coated on working electrode, and MNi is the atomic mass of Ni (59 g mol−1). F is the faradaic constant (96485 C mol−1), t is the reaction time (1 h/3600 s), n is the number of electron transferred for product formation, which is 2 for CO.
Calculations details:
All density functional theory (DFT) calculation was performed using the Gaussian 09 program.1The obtained structures were used for the final optimizations using 6-31G(d) basis sets.2， 3The results obtained with B3LYP/6-31G(d) method were used throughout the discussion. Analytical vibrational frequency computations at the optimized structures were done and the theoretical frequencies were scaled with the factor recommended by Scott and Radom.4
Characterization
X-ray photoemission spectroscopy (XPS) measurements were performed on a PHI–5000C ESCA system, the C 1s value was set at 284.8 eV for charge corrections. The Raman spectra of samples were obtained on Lab-RAM HR800 with excitation by an argon ion laser (532 nm). The physic sorption isotherms were measured via an Auto-sorb-iQA3200-4 sorption analyzer (Quantatech Co., USA) based on N2 adsorption/desorption at 77 K. XANES and EXAFS measurements were tested on the BL14W1 beamline at Shanghai Synchrotron Radiation Facility (SSRF). Fourier-transform infrared spectroscopy (FTIR) were recorded with a Spectrum 100 spectrometer (Perkin Elmer, Spectrum 100). Atomic force microscopy (AFM) measurements were performed on a Multimode Nanoscope IIIa atomic force microscope. Ultraviolet photoelectron spectroscopy (UPS) measurements were performed on ESCALAB 250xi with an unfiltered HeI (21.22 eV) gas discharge lamp under 2*10-8mbar. The cyclic voltammetry (CV) experiment was performed with recrystallized tetra-nbutyl-ammoniumhexafluorophosphate (TBAPF6, 0.1M) as supporting electrolyte at 298 K using the CH instrument (CHI 660E) electrochemical workstation. The conventional three electrode cell was used with a platinum working electrode (surface area of 0.3 mm2) and a platinum wire as the counter electrode. The band-gap (Eg) was calculated from the EHUMO and ELUMO from the first oxidation waves using EHUMO = -Eox1 – 4.80 eV and ELUMO = Ered1 – 4.80 eV.
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Figure S1. The first derivative XANES curves of NiPc and HS-NiPc. The first derivative XANES
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Figure S2. XPS results of NiPc and HS-NiPc. (a) XPS spectra of NiPc and HS-NiPc. (b)
High-resolution C 1s spectra of NiPc and NiPc. (c) High-High-resolution Ni 2p spectra of NiPc and HS-NiPc. (d) High-resolution N 1s spectra of NiPc and HS-HS-NiPc. In high-resolution C 1s spectra, two peaks locate at ~284.8 and ~286.2 eV for HS-NiPc and NiPc can be assigned to C=C/C-C and C-N, a weak at ~288.1 eV is attributed to the satellite peak. For Ni 2p spectra, two peaks locate at ~872.7 and ~855.6 eV for HS-NiPc and NiPc can be assigned to Ni 2p1/2 and Ni 2p3/2, respectively, indicating that the Ni valence state in HS-NiPc and NiPc is +2. For N 1s spectra, the main peak present at ~399.5 eV can be assigned to the pyrrolic N.
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Figure S3. (a) Raman spectra of NiPc and HS-NiPc. (b) FTIR spectra of NiPc and HS-NiPc. The
peaks locate at 244, 640, and 1610 cm-1 in Raman spectra can be attributed to the N-Ni, C-N, and C=N bond, respectively. In FTIR spectra, the strong absorption band at 1164 relate to the Ni-N, peaks at 1620,1524, and 1320 cm-1 represent benzene ring stretching, benzene in-plane deformation, and C=N–C at bridge sites, respectively. Typically, HS-NiPc and NiPc exhibit the similar characteristic features, indicating that hydrazine hydrate treatment doesn’t break the conjugated structure of phthalocyanine.
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Figure S4. 1/χm plots of NiPc and HS-NiPc. It can be seen that the para-magnetism of NiPc and HS-NiPc is independent of temperature.
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Figure S5. (a) AFM images of NiPc and HS-NiPc. (b) Work functions of NiPc and HS-NiPc. The
work function of HS-NiPc and NiPc is 5.01 and 5.57 eV, respectively, HS-NiPc possesses the lower work function.
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Figure S6. Schematic illustration of synthesize of HS-NiPor. The HS-NiPor was prepared via the
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Figure S7. XPS results of NiPor and HS-NiPor. (a) XPS spectra of NiPor and HS-NiPor. (b)
High-resolution of Ni 2 p spectra of NiPor and HS-NiPor. (c) High-High-resolution of C 1s spectra of NiPor and HS-NiPor. (d) High-resolution of N 1s spectra of NiPor and HS-NiPor. Two peaks locate at ~872.7 and ~855.5 eV for HS-NiPor and NiPor can be assigned to Ni 2 p1/2 and Ni 2 p3/2, indicating that the Ni valence state in HS-NiPor and NiPor is +2. For C 1s spectra, two peaks presented at ~284.8 and ~286.2 eV for HS-NiPor and NiPor can be assigned to C=C/C-C and C-N. In N 1s spectra, the main peak present at ~399.5 eV can be assigned to pyrrolic N.
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Figure S8. (a) Raman spectra of NiPor and HS-NiPor. (b) FTIR spectra of NiPor and HS-NiPor.
The peaks locate at 248, 645, and 1617 cm-1 in Raman spectra can be attributed to the N-Ni, C-N, and C=N bond, respectively. In FTIR spectra, the strong absorption band at 1164 related to Ni-N, peaks at 1625,1528, and 1326 cm-1 represent benzene ring stretching, benzene in-plane deformation, and C=N–C at bridge sites, respectively. HS-NiPor and NiPor exhibit the similar characteristic features, indicating that hydrazine hydrate treatment doesn’t break the conjugated structure of porphyrin.
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Figure S9. (a) UPS spectra of NiPor. (b) UPS of HS-NiPor. The work functions of NiPor and HS-NiPor calculated by UPS are 5.63 and 4.92 eV, respectively.
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Figure S10. (a) CV curves of NiPor and HS-NiPor measured in CH2Cl2 at a scan rate of 100 mV·s-1. (b) Magnification of CV curve of HS-NiPor. (c) Magnification of CV curve of NiPor. The band-gap (Eg) was calculated from the EHUMO and ELUMO from the first oxidation waves using EHUMO = -Eox1 – 4.80 eV and ELUMO = Ered1 – 4.80 eV. The band-gap of HS-NiPor and NiPor is calculated as 0.68 and 0.72 eV, respectively.
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Figure S11. (a) AFM images of NiPor and HS-NiPor. (b) Work functions of NiPor and HS-NiPor.
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Figure S12. (a) CV curves of HS-NiPc in Ar and CO2-saturated electrolyte. (b) CV curves of NiPc in Ar and CO2-saturated electrolyte. The current density in CO2-saturated electrolyte is considerable larger than that in Ar-saturated electrolyte.
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Figure S13. 1H NMR of product for HS-NiPc at -0.7 and -0.8 V. Except the water and solvent signal, no additional signal is detected, indicating that no liquid products formed during CO2RR.
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Figure S14. (a) H2 FE of NiPc and HS-NiPc at different applied potentials. It can be found that the FE of H2 for HS-NiPc is lower than that of NiPc. (b) The volume ratio of CO to H2 generate by HS-NiPc and HS-NiPc. The ratio of CO to H2 for HS-NiPc is much higher than that of NiPc, indicating the higher selectivity toward CO formation.
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Figure S15. (a) CV curves of NiPc, (b) CV curves of HS-NiPc at different scan rates (10-50 mV s -1).
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Figure S16. The corresponding capacitive current at -0.21 V vs. RHE as a function of scan rate.
The Cdl values of HS-NiPc and NiPc are measured as 14.28 and 9.75 mF cm-2, respectively. In general, the higher Cdl of HS-NiPc means the higher ECSA.
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Figure S17. (a) LSV curves of NiPor and HS-NiPor in CO2-saturated 0.5 M KHCO3 electrolyte, scan rate of 5 mV s–1. (b) CO FE of NiPor and HS-NiPor at different applied potentials. NiPor exhibits the poor activity toward CO2 reduction, however, HS-NiPor shows better activity. The CO FE increased from 0% to 25% at -0.6 V after hydrazine hydrate treatment.
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Figure S18. GC profiles of CO and H2 generated by HS-NiPor and NiPor. (a) Thermal conductivity detector (TCD) results for NiPor and NiPor. (b) Flame ionization detector (FID) results for HS-NiPor and HS-NiPor. No CO was generated by HS-NiPor, while generated by HS-HS-NiPor.
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Figure S19. (a) CV curves of NiPor. (b) CV curves of HS-NiPor at different scan rates (10-50 mV
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Figure S20. The corresponding capacitive current at -0.21 V vs. RHE as a function of scan rate.
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Figure S22. Singlet closed shell state of NiPc, the HOMO and LUMO of NiPc are -5.14 and -2.70
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Figure S23. Singlet closed shell state of NiPc + CO2, the HOMO and LUMO are calculated as -5.14 and -2.71 eV, respectively.
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Figure S24. Singlet closed shell state of NiPc + *COOH, the HOMO and LUMO are calculated as
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Figure S25. Singlet closed shell state of NiPc + *CO, the HOMO and LUMO are calculated as
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Figure S26. Triplet state of HS-NiPc, the SOMO and SUMO are calculated as -4.01 and -2.62 eV, respectively.
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Figure S27. Triplet state of HS-NiPc + CO2, the SOMO and SUMO are calculated as 4.05 and -2.59 eV, respectively.
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Figure S28. Triplet state of HS-NiPc + *COOH, the SOMO and SUMO are calculated as -1.68 and -0.22 eV, respectively.
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Figure S29. Triplet state of HSNiPc + *CO, the SOMO and SUMO are calculated as 5.07 and -2.70 eV, respectively.
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Table S1. Element contents of C, O, N, Ni for NiPc and HS-NiPc based on the XPS analysis.
C N Ni O NiPc 79.16 65.60 (EA) 17.17 19.70 (EA) 2.13 1.53 HS-NiPc 76.79 66.29 (EA) 17.74 19.54 (EA) 1.93 3.55
Table S2. The electrochemical data of obtained samples. Eox1 (V) Ered1 (V) HOMO (eV) LUMO (eV) Eg (eV) NiPc HS-NiPc 0.77 0.06 -0.74 -0.68 -5.57 -4.86 -4.06 -4.12 1.51 0.74 NiPor 0.96 -0.75 -5.76 -4.05 0.72 HS-NiPor 0.97 -0.71 -5.77 -4.09 0.68
Table S3. The calculated bandgap of NiPc and HS-NiPc.
status
Eg (eV)
Singlet closed shell state-Ni Phthalocyanine
2.44
Singlet closed shell state-Ni Phthalocyanine+CO
22.43
Singlet closed shell state-Ni Phthalocyanine+COOH
1.12
Singlet closed shell state-Ni Phthalocyanine+CO
2.43
Triplet state-Ni Phthalocyanine
1.39
Triplet state-Ni Phthalocyanine+CO
22.46
Triplet state-Ni Phthalocyanine+COOH
1.90
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Table S4. Comparison of CO2RR performance with reported molecular electrocatalysts. Catalyst Electrolyte (KHCO3) Potential (V vs. RHE） Current density （mA cm-2） FEco (%) Reference
CoPc 0.5M -0.80 8.0 99 Angew. Chem. Int. Ed. 2018,
57 (50), 16339-16342. CoPc 0.5M -0.67 18.10 93 Nat. Commun. 2019, 10 (1),
3844. CoPc-CN 0.1M -0.6 14.7 98 Nat. Commun. 2017, 8 (1), 14675. Ni-CNT-CC
0.5M -0.65 32.3 99 Angew. Chem. Int. Ed. 2020,
59 (2), 798-803. A-Ni-NSG 0.5M -0.61 12.6 98 Nat. Energy 2018, 3 (2), 140-147. Ni coordinat e CTF 0.5M -0.69 2 90 Chem. Sci. 2018, 9 (16), 3941-3947. NiPor-CTF
0.5M -0.79 52.9 97 Adv. Funct. Mater. 2019, 29
(10), 1806884.
COF-367-Co
0.5M -0.67 0.4 91 Science 2015, 349 (6253),
1208.
Co-MOF 0.1M -0.45 1 76 J. Am. Chem. Soc. 2015, 137
(44), 14129-14135. CoPP@C
NT
0.5M -0.6 25.1 98.3 Angew. Chem. Int. Ed. 2019,
58 (20), 6595-6599. Fe -PB 0.5M -0.63 0.5 100 Angew. Chem. Int. Ed. 2018,
57 (31), 9684-9688. Co-PMOF 0.5M -0.80 17 98.7 Nat. Commun. 2018, 9 (1), 4466. CoPc/Ox C
0.1M -0.73 -2.7 94 ACS Energy Lett. 2018, 3 (6),
1381-1386.
FeTMAP 0.1M KCl -0.54 1.68 98.7 Adv. Energy Mater. 2018, 8
(26), 1801280.
HS-NiPc 0.5M -0.7 2.7 98.5 This work
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HS-NiPor
0.5M -0.6 1.2 25 This work
NiPor 0.5M -0.6 1.1 0 This work
Reference:
1. Gaussian 09, Revision A.02, M. J. Frisch, G. W. Trucks, H. B. Schlegel, G. E. Scuseria, M. A. Robb, J. R. Cheeseman, G. Scalmani, V. Barone, G. A. Petersson, H. Nakatsuji, X. Li, M. Caricato, A. Marenich, J. Bloino, B. G. Janesko, R. Gomperts, B. Mennucci, H. P. Hratchian, J. V. Ortiz, A. F. Izmaylov, J. L. Sonnenberg, D. Williams-Young, F. Ding, F. Lipparini, F. Egidi, J. Goings, B. Peng, A. Petrone, T. Henderson, D. Ranasinghe, V. G. Zakrzewski, J. Gao, N. Rega, G. Zheng, W. Liang, M. Hada, M. Ehara, K. Toyota, R. Fukuda, J. Hasegawa, M. Ishida, T. Nakajima, Y. Honda, O. Kitao, H. Nakai, T. Vreven, K. Throssell, J. A. Montgomery, Jr., J. E. Peralta, F. Ogliaro, M. Bearpark, J. J. Heyd, E. Brothers, K. N. Kudin, V. N. Staroverov, T. Keith, R. Kobayashi, J. Normand, K. Raghavachari, A. Rendell, J. C. Burant, S. S. Iyengar, J. Tomasi, M. Cossi, J. M. Millam, M. Klene, C. Adamo, R. Cammi, J. W. Ochterski, R. L. Martin, K. Morokuma, O. Farkas, J. B. Foresman, and D. J. Fox, Gaussian, Inc., Wallingford CT, 2016
2. Chen, D.-M.; Liu, X.; He, T.-J.; Liu, F.-C., Density Functional Theory Study on the Geometric, Electronic and Vibrational Structures of Alkali Metal Porphyrin Complexes. Chem.
Phys. Lett. 2002, 361 (1), 106-114.
3. Rassolov, V. A.; Pople, J. A.; Ratner, M. A.; Windus, T. L., 6-31G* Basis Set for Atoms K through Zn. J. Chem. Phys. 1998, 109 (4), 1223-1229.
4. Scott, A. P.; Radom, L., Harmonic Vibrational Frequencies: An Evaluation of Hartree−Fock, Møller−Plesset, Quadratic Configuration Interaction, Density Functional Theory, and Semiempirical Scale Factors. J. Chem. Phys. 1996, 100 (41), 16502-16513.
5. Zhang, Z.; Xiao, J.; Chen, X.-J.; Yu, S.; Yu, L.; Si, R.; Wang, Y.; Wang, S.; Meng, X.; Wang, Y.; Tian, Z.-Q.; Deng, D., Reaction Mechanisms of Well-Defined Metal–N4 Sites in Electrocatalytic CO2 Reduction. Angew. Chem. Int. Ed. 2018, 57 (50), 16339-16342. 6. Yang, D.; Yu, H.; He, T.; Zuo, S.; Liu, X.; Yang, H.; Ni, B.; Li, H.; Gu, L.; Wang, D.; Wang, X., Visible-light-switched Electron Transfer over Single Porphyrin-metal Atom Center for Highly Selective Electroreduction of Carbon Dioxide. Nat. Commun. 2019, 10 (1), 3844. 7. Zhang, X.; Wu, Z.; Zhang, X.; Li, L.; Li, Y.; Xu, H.; Li, X.; Yu, X.; Zhang, Z.;
S-36
Liang, Y.; Wang, H., Highly Selective and Active CO2 Reduction Electrocatalysts Based on Cobalt Phthalocyanine/Carbon Nanotube Hybrid Structures. Nat. Commun. 2017, 8 (1), 14675.
8. Liu, S.; Yang, H. B.; Hung, S.-F.; Ding, J.; Cai, W.; Liu, L.; Gao, J.; Li, X.; Ren, X.; Kuang, Z.; Huang, Y.; Zhang, T.; Liu, B., Elucidating the Electrocatalytic CO2 Reduction Reaction over a Model Single-Atom Nickel Catalyst. Angew. Chem. Int. Ed. 2020, 59 (2), 798-803.
9. Yang, H. B.; Hung, S.-F.; Liu, S.; Yuan, K.; Miao, S.; Zhang, L.; Huang, X.; Wang, H.-Y.; Cai, W.; Chen, R.; Gao, J.; Yang, X.; Chen, W.; Huang, Y.; Chen, H. M.; Li, C. M.; Zhang, T.; Liu, B., Atomically Dispersed Ni(i) as the Active Site for Electrochemical CO2 Reduction. Nat. Energy 2018, 3 (2), 140-147.
10. Su, P.; Iwase, K.; Harada, T.; Kamiya, K.; Nakanishi, S., Covalent Triazine Framework Modified with Coordinatively-unsaturated Co or Ni Atoms for CO2 Electrochemical Reduction.
Chem. Sci. 2018, 9 (16), 3941-3947.
11. Lu, C.; Yang, J.; Wei, S.; Bi, S.; Xia, Y.; Chen, M.; Hou, Y.; Qiu, M.; Yuan, C.; Su, Y.; Zhang, F.; Liang, H.; Zhuang, X., Atomic Ni Anchored Covalent Triazine Framework as High Efficient Electrocatalyst for Carbon Dioxide Conversion. Adv. Funct. Mater 2019, 29 (10), 1806884.
12. Lin, S.; Diercks, C. S.; Zhang, Y.-B.; Kornienko, N.; Nichols, E. M.; Zhao, Y.; Paris, A. R.; Kim, D.; Yang, P.; Yaghi, O. M.; Chang, C. J., Covalent Organic Frameworks Comprising Cobalt Porphyrins for Catalytic CO2 Reduction in Water. Science 2015, 349 (6253), 1208.
13. Kornienko, N.; Zhao, Y.; Kley, C. S.; Zhu, C.; Kim, D.; Lin, S.; Chang, C. J.; Yaghi, O. M.; Yang, P., Metal–Organic Frameworks for Electrocatalytic Reduction of Carbon Dioxide. J. Am. Chem. Soc. 2015, 137 (44), 14129-14135.
14. Zhu, M.; Chen, J.; Huang, L.; Ye, R.; Xu, J.; Han, Y.-F., Covalently Grafting Cobalt Porphyrin onto Carbon Nanotubes for Efficient CO2 Electroreduction. Angew. Chem. Int. Ed. 2019,
58 (20), 6595-6599.
15. Smith, P. T.; Benke, B. P.; Cao, Z.; Kim, Y.; Nichols, E. M.; Kim, K.; Chang, C. J., Iron Porphyrins Embedded into a Supramolecular Porous Organic Cage for Electrochemical CO2 Reduction
S-37
in Water. Angew. Chem. Int. Ed. 2018, 57 (31), 9684-9688.
16. Wang, Y.-R.; Huang, Q.; He, C.-T.; Chen, Y.; Liu, J.; Shen, F.-C.; Lan, Y.-Q., Oriented Electron Transmission in Polyoxometalate-metalloporphyrin Organic Framework for Highly Selective Electroreduction of CO2. Nat. Commun. 2018, 9 (1), 4466.
17. Zhu, M.; Ye, R.; Jin, K.; Lazouski, N.; Manthiram, K., Elucidating the Reactivity and Mechanism of CO2 Electroreduction at Highly Dispersed Cobalt Phthalocyanine. ACS Energy Lett.
2018, 3 (6), 1381-1386.
18. Choi, J.; Wagner, P.; Jalili, R.; Kim, J.; MacFarlane, D. R.; Wallace, G. G.; Officer, D. L., A Porphyrin/Graphene Framework: A Highly Efficient and Robust Electrocatalyst for Carbon Dioxide Reduction. Adv. Energy Mater. 2018, 8 (26), 1801280.