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Supporting Information
Surface-Immobilized Conjugated Polymers Incorporating
Rhenium Bipyridine Motifs for Electrocatalytic and
Photocatalytic CO2 Reduction
Nicholas M. Orchanian, Lorena E. Hong, John A. Skrainka, Jacques A. Esterhuizen, Damir A.
Popov, and Smaranda C. Marinescu*
Department of Chemistry, University of Southern California, Los Angeles, California 90089,
United States
*email: [email protected]
Experimental Methods
Materials and Synthesis
All manipulations of air- and moisture-sensitive materials were conducted under nitrogen
atmosphere in a Vacuum Atmospheres glovebox or on a dual manifold Schlenk line with oven-
dried glassware. Water was deionized with the Millipore Synergy system (18.2 MΩ·cm). All
other solvents used were degassed with nitrogen, passed through activated alumina columns, and
stored over 4Å Linde-type molecular sieves. Proton NMR spectra were acquired using a Varian
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400-MR 2-Channel spectrometer at room temperature and referenced to the residual 1H
resonances of the deuterated solvent (1H: CD3CN, δ 1.95 ppm). The [2,2'-bipyridine]-5,5'-
diamine ligand was synthesized according to reported literature procedures.1 Complex 1 was
synthesized according to our previous report.2 All other chemical reagents were purchased from
commercial vendors and used without further purification.
Synthesis of 2
Complex 1 was recrystallized by slow diffusion of ether into a concentrated DMF
solution. Recrystallized complex 1 (45 mg) was suspended in acetonitrile (1.9 mL) and briefly
sonicated for 5 minutes. Separately, a solution of nitrosonium tetrafluoroborate (24 mg) was
dissolved in a minimal amount of acetonitrile (0.9 mL). Both solutions were cooled to -40 °C.
Once cooled, the suspension of 1 was added dropwise to the NOBF4 solution, leading to an
immediate color change from pale-yellow to dark blue. Addition of diethyl ether (6 mL) resulted
in the formation of a dark blue precipitate, which was collected by filtration, and stored in the
dark at -27 °C (1H in CD3CN: δ 10.10, 9.29 and 9.02 ppm).
Electrochemistry
Cyclic Voltammetry
Electrochemistry experiments were carried out in acetonitrile solution with 0.1 M
TBAPF6 electrolyte using a Pine potentiostat. The pseudo-reference electrode used was a Ag
wire purchased from VWR. The platinum wire used as a counter electrode was purchased from
Alfa Aesar. Ohmic drop was compensated using the positive feedback compensation
implemented in the instrument. All experiments in this paper were referenced relative to
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ferrocene (Fc) with the Fe3+/2+ couple at 0.0 V. Electrochemical experiments were carried out in
a three electrode configuration electrochemical cell under a nitrogen or CO2 atmosphere using
glassy carbon, graphite rod, carbon nanotubes, FTO, TiO2, or gold as the working electrode. The
reference and counter electrodes were isolated in glass capillaries with Vycor frits.
Estimation of Electrochemically-Active Coverage
The electrochemically-active catalyst loading was estimated by cyclic voltammetry. A
cathodic scan sweeping from Pi = -0.6 V to Pi = -2.25 V was performed for the modified
electrode under a nitrogen atmosphere. The resulting current-time plot was integrated for the film
redox feature at -1.95 V, which was used to determine and estimated catalyst loading based on
Equation S1 below. Q represents the total charge passed at the electrode for the cathodic wave
(C), F represents the Faraday constant (96,485 C mol-1), n represents the number of electrons for
the reduction event (2), and A represents the area of the electrode (cm2).
(1)
Controlled Potential Electrolysis and Gas Chromatography
CPE measurements were conducted in a two-chambered H cell. In the first chamber, the
working and reference electrodes were immersed in 40 mL of 0.1 M tetrabutylammonium
hexafluorophosphate (TBAPF6) in acetonitrile. The counter electrode (graphite rod) was placed
in the second chamber in 20 mL of 0.1 M TBAPF6 in acetonitrile. The two chambers were
separated by a fine porosity glass frit and the reference electrode was placed in a separate
compartment connected by a Vycor tip. Graphite rod electrodes (0.8 cm diameter; NAC Carbon
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Products, Inc.) were used as the working and auxiliary electrodes. For gas chromatography
experiments, 2 mL of gas were withdrawn from the headspace of the H cell with a gas-tight
syringe. This was injected into a gas chromatography instrument (Shimadzu GC-2010-Plus)
equipped with a BID detector and a Restek ShinCarbon ST Micropacked column. Faradaic
efficiencies were determined by dividing the amount of CO produced as measured by gas
chromatography by the amount of CO expected based on the total charge measured during
controlled potential electrolysis. For each experiment, the controlled-potential electrolysis
measurements were performed at least twice (with two electrodes prepared under identical
conditions), leading to similar behavior. The reported Faradaic efficiencies, TON, TOF, and
µmol of CO produced are average values.
Physical Methods
X-Ray Photoelectron Spectroscopy
XPS data were collected using a Kratos AXIS Ultra instrument. The monochromatic X-
ray source was the Al K α line at 1486.6 eV. Low-resolution survey spectra were acquired
between binding energies of 1–1200 eV. Higher-resolution detailed scans, with a resolution of
~0.1 eV, were collected on individual XPS lines of interest. The sample chamber was maintained
at < 2 × 10–9 Torr. The XPS data were analyzed using the CasaXPS software.
FT-IR
FT-IR spectra were acquired using a Bruker Vertex 80v spectrometer. Reflectance
spectra were collected using a VeeMAX III specular reflectance accessory from Pike
Instruments. Samples were positioned face-down over an aperture (3/8” diameter). All IRRAS
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measurements were collected with a 56° angle of incidence under vacuum pressure with 1 cm-1
resolution. Polarization studies were performed with a ZnSe polarizing lens purchased from Pike
Instruments. The spectra measured for unmodified substrates under identical experimental
parameters (angle, polarization, and resolution) were subtracted as background. Studies were
performed at 1 cm-1 resolution with 128 scans. ATR-FTIR measurements for complex 2 were
performed using a Bruker Optics Alpha FTIR spectrometer in the ATR mode.
UV-Vis
UV-Vis spectra were collected using a UV-1800 Shimadzu UV spectrophotometer. FTO
samples were studied in transmittance mode and the spectrum measured for an unmodified FTO
substrate was subtracted as background.
SEM
Scanning electron microscopy (SEM) was performed on a JEOL JSM 7001F scanning
electron microscope using an accelerating voltage of 15 kV.
AFM
Atomic force microscopy (AFM) topography images were collected in tapping mode
using an Agilent 5420 SPM instrument S3. The probe tips were Tap300-G Silicon AFM probes
(resonant frequency 300 kHz, force constant 40 N/m) purchased from Budgetsensors.com and
aligned prior to use. Images were collected with a scan rate of 0.25 lines per second and over an
area of 20 µm2. All samples were imaged under one atmosphere of air at room temperature. For
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each sample, three measurements were conducted and averaged to determine the root-mean-
square surface roughness.
ICP-OES
Inductively coupled plasma optical emission spectroscopy (ICP-OES) measurements
were performed using a Thermo Scientific iCAP 7000 ICP-OES.
Photocatalytic Studies
Mesoporous TiO2 (m-TiO2) electrodes were prepared by spin-coating a suspension of 20
mg TiO2 nanoparticles (anatase, ~20 nm) in 10 mL ethanol onto fluorine-doped tin oxide (FTO)
electrodes, which were then annealed at 450 °C for 30 minutes. All photocatalysis experiments
were conducted using a ThorLabs HPLS-30-03 solid state light source with a wavelength range
of 350 to 700 nm. For studies conducted with a filter, a 399 nm cutoff filter (purchased from
Schott Glass) was introduced. Using a gastight syringe, 2 mL of gas were withdrawn from the
headspace of the photocatalysis cell and injected into a gas chromatography instrument
(Shimadzu GC-2010-Plus) equipped with a BID detector and a Restek ShinCarbon ST
Micropacked column. TONs were determined by dividing the measured CO produced by the
catalyst loading determined by ICP-OES or CV analysis. All studies were conducted in 5:1
mixtures of DMF:TEOA (10 mL).
Computational Methods
All calculations were run using the Q-CHEM program package.7 Geometry optimizations
were run with unrestricted DFT calculations at the M06 level of theory with a composite basis
set.8 The Pople 6-31G* basis set was used for H, C, N, and O atoms and the Hay–Wadt VDZ
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(n+1) effective core potentials and basis sets (LANL2DZ) were used for Cl and Re atoms.9,10,11,12
All optimized geometries were verified as stable minima with frequency calculations at the same
level of theory. The M06 functional was used throughout this study, as it provides reduced
Hartree-Fock exchange contributions and includes empirical fitting for accuracy in
organometallic systems. Single point energy calculations were run with a larger 6-311G** basis
for H, C, N, and O atoms. Kohn-Sham orbital images are presented with isovalues of 0.05 for
clarity.
Figure S1. 1H NMR spectrum of 1 in acetonitrile-d3.
Figure S2. 1H NMR spectrum of 2 in acetonitrile-d3.
Figure S3. 19F NMR spectrum of 2 in acetonitrile-d3.
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Figure S4. ATR FTIR spectrum of complex 2.
Figure S5. Calculated vibrational spectrum of 2 at the LANL2DZ/M06 level of theory. Only stretching modes with
calculated intensity > 200 are included for clarity.
Figure S6. UV-Vis spectrum of 2 in an acetonitrile solution (0.5 mM 2).
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Figure S7. XPS survey scan for complex 2.
Figure S8. High-resolution XPS of the Re 4f region for complex 2.
Figure S9. High-resolution XPS of the Cl 2p region for complex 2.
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Figure S10. High-resolution XPS of the N 1s region for complex 2.
Figure S11. High-resolution XPS of the B 1s region for complex 2.
Figure S12. High-resolution XPS of the F 1s region for complex 2.
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Figure S13. Cyclic voltammetry of a glassy carbon electrode in 0.5 mM 2 in acetonitrile with 0.1 M TBAPF6
supporting electrolyte (ν = 100 mV/s).
Figure S14. Cyclic voltammetry of a FTO electrode in 0.5 mM 2 in acetonitrile with 0.1 M TBAPF6 supporting
electrolyte (ν = 100 mV/s).
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Figure S15. Cyclic voltammetry of a FTO electrode in 0.5 mM 2 in acetonitrile with 0.1 M TBAPF6 supporting
electrolyte (ν = 100 mV/s).
Figure S16. Estimated electroactive coverage as determined by cyclic voltammetry for FTO electrodes modified
with varying potential windows and scan rates. Initial potential (Pi), switching potential (Ps), and scan rate (ν) are
shown with the corresponding plots.
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Figure S17. XPS survey scan for FTO electrodes modified with a) n=1 b) n=5 c) n=10 and d) n=20.
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Figure S18. High resolution XPS of the Re 4f region for FTO electrodes modified with a) n=1 b) n=5 c) n=10 and
d) n=20.
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Figure S19. High resolution XPS of the Sn 2p region for FTO electrodes modified with a) n=1 b) n=5 c) n=10 and
d) n=20.
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Figure S20. High resolution XPS of the Cl 2p region for FTO electrodes modified with a) n=1 b) n=5 c) n=10 and
d) n=20.
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Figure S21. High resolution XPS of the P 2p region for FTO electrodes modified with a) n=1 b) n=5 c) n=10 and d)
n=20.
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Figure S22. High resolution XPS of the F 1s region for FTO electrodes modified with a) n=1 b) n=5 c) n=10 and d)
n=20.
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Figure S23. High resolution XPS of the C 1s region for FTO electrodes modified with a) n=1 b) n=5 c) n=10 and d)
n=20.
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Figure S24. SEM images of FTO films with varying thickness.
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Figure S25. SEM images of interfacial regions for FTO films.
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Figure S26. AFM data collected for FTO films with varying thickness.
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Figure S27. 3D projections of AFM data.
Table S1. RMS surface roughness of modified FTO electrodes.
n Sq (nm)
1 11.25±0.56
5 10.46±0.52
10 10.32±0.51
20 9.88±0.49
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Figure S28. PM-IRRAS of a modified FTO electrode (n = 20) with s- (red) and p- (black) polarization.
Figure S29. a) IRRAS of modified FTO electrodes with p polarization b) IRRAS peak height for the high-energy
carbonyl stretching mode as a function of the number of grafting scans applied.
Figure S30. UV-Vis spectra of FTO films with varying thickness.
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Figure S31. Cyclic voltammetry of a modified glassy carbon electrode (n = 5) in acetonitrile with 0.1 M TBAPF6
supporting electrolyte.
Figure S32. Cyclic voltammetry of a modified glassy carbon electrode (n = 1) in acetonitrile with 0.1 M TBAPF6
supporting electrolyte.
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Figure S33. Cyclic voltammetry of a modified glassy carbon electrode (n = 10) in acetonitrile with 0.1 M TBAPF6
supporting electrolyte.
Figure S34. Cyclic voltammetry of a modified glassy carbon electrode (n = 20) in acetonitrile with 0.1 M TBAPF6
supporting electrolyte.
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Figure S35. Four sequential cyclic voltammetry scans of a modified FTO electrode (n=5) from -0.6 V to -2.4 V.
The third and fourth scans begin with an anodic sweep to +0.6 V and lead to the stabilization of the current density
at the reduction event. The purple trace represents the same electrode after 24 hours of air exposure. All scans in
acetonitrile with 0.1 M TBAPF6 (ν = 100 mV/s).
Figure S36. A) Modified glassy carbon stick electrodes (n = 1, 5, 10, and 20) prepared with varying catalyst
loadings. b) Unmodified glassy carbon electrode (n = 0) and modified glassy carbon electrodes (n = 5) immediately
after grafting with CV scans to Ps = -2.60 V (blue coloration) and an identically-modified electrode after 5 minutes
of air exposure (orange coloration). c) A modified Au electrode (n = 10) with a portion of the electrode not modified
for visual comparison (n = 0).
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Table S2. Catalyst loading for FTO electrodes as determined by cyclic voltammetry (CV) and ICP-OES.
CV Loading ICP Bulk Loading
n C nmol/cm2 ppm nmol/cm2
1 0.00009 3.4±0.3 0.018 5.0±0.5
5 0.00037 13.7±1.4 0.026 6.9±0.7
10 0.00036 18.7±2.0 0.036 9.8±1.0
20 0.00065 26.8±2.7 0.040 10.8±1.1
Figure S37. Double-layer charging current density (ΔJ = Janodic - Jcathodic) at the open-circuit potential for a modified
glassy carbon electrode (n = 1) as a function of scan rate.
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Figure S38. Double-layer charging current density (ΔJ = Janodic - Jcathodic) at the open-circuit potential for a modified
glassy carbon electrode (n = 5) as a function of scan rate.
Figure S39. Double-layer charging current density (ΔJ = Janodic - Jcathodic) at the open-circuit potential for a modified
glassy carbon electrode (n = 10) as a function of scan rate.
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Figure S40. Double-layer charging current density (ΔJ = Janodic - Jcathodic) at the open-circuit potential for a modified
glassy carbon electrode (n = 20) as a function of scan rate.
Figure S42. Catalyst loading for modified graphite rod electrodes (n = 1, 5, 10, and 20) as determined by cyclic
voltammetry (red) and ICP (blue).
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Table S3. Summary of controlled potential electrolysis studies for modified graphite rod electrodes. TON and TOF
are calculated based on cyclic voltammetry (CV) estimated loading and ICP estimates. All experiments performed in
acetonitrile with 0.1 M TBAPF6 supporting electrolyte for 2 hours at -2.25 V. Modified graphite rod electrodes
served as the working electrodes, with a Ag wire reference and graphite rod counter electrode.
n
CV
ICP
C
CO
(µmol)
FE
(%)
Loading
(nmol) TON TOF (s-1)
Loading
(nmol) TON TOF (s-1)
1 1.33±0.1 3.32±0.3 48±5 4.1±0.4 806±80 0.112±0.01 2.9±0.3 1149±110 0.319±0.3
5 3.64±0.4 18.82±1.9 99±7 11.7±1.2 1606±160 0.223±0.02 5.3±0.5 3583±360 0.498±0.5
10 5.99±0.6 27.20±2.7 88±8 18.0±1.8 1508±150 0.210±0.02 7.5±0.8 3606±360 0.501±0.5
20 4.17±0.4 13.81±1.4 64±6 34.7±3.5 398±40 0.055±0.006 22.2±0.2 623±60 0.086±0.09
Figure S43. Catalyst loading for modified TiO2 electrodes (n = 1, 5, 10, and 20) as determined by cyclic
voltammetry (red) and ICP (blue).
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Table S4. Summary of photocatalytic studies for modified TiO2 electrodes. TON and TOF are calculated based on
cyclic voltammetry (CV) estimated loading and ICP estimates. All studies performed in 10 mL 5:1 DMF:TEOA
under illumination for 5 hours. *399 nm cut-on filter was introduced for this measurement.
n
CV
ICP
t (hr) CO (µmol)
Loading
(nmol)
TON
TOF
(hr-1)
Loading
(nmol)
TON
TOF (hr-
1)
1 5 0.41±0.04 4.0±0.4 103±10 20.6±2.1 5.8±0.6 70±7 14.0±1.4
5 5 0.31±0.03 7.9±0.8 39±4 7.8±0.8 10.9±1.1 28±3 5.6±0.6
5* 5 0.40±0.04 8.3±0.8 48±5 9.6±1.0 13.0±1.3 31±3 6.1±0.6
10 5 0.39±0.04 15.8±1.6 25±2 4.9±0.5 15.1±1.5 26±3 5.2±0.5
20 5 0.40±0.04 31.6±3.2 13±1 2.5±0.2 18.4±1.8 22±2 4.4±0.4
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Figure S44. High-resolution XPS of the Re 4f region for a modified FTO substrate (n = 20) before (blue) and after
(red) a 1 hour controlled potential electrolysis experiment at -2.25 V in acetonitrile solution with 0.1 M TBAPF6
supporting electrolyte under saturated CO2 atmosphere.
Figure S45. IRRAS studies of a modified FTO substrate (n = 20) before (black) and after (red) a 1 hour controlled
potential electrolysis experiment at -2.25 V in acetonitrile solution with 0.1 M TBAPF6 supporting electrolyte under
saturated CO2 atmosphere.
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Figure S46. UV-Vis studies of a modified FTO substrate (n = 20) before (blue) and after (red) a 1 hour controlled
potential electrolysis experiment at -2.25 V in acetonitrile solution with 0.1 M TBAPF6 supporting electrolyte under
saturated CO2 atmosphere.
Figure S47. Post-catalysis IRRAS results for a) a modified TiO2 device (n = 20) and b) a modified graphite rod
electrode (n = 20). After 5 hours of irradiation under photocatalytic conditions, the catalyst loading of the TiO2 film
has decreased by 66% as determined from the decrease in IRRAS intensity, while the loading on the graphite rod
electrode has decreased only by 5%.
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Figure S48. Electropolymerization scans in 0.5 mM 2 in acetonitrile with 0.1 M TBAPF6 supporting electrolyte (ν =
1 V/s, Pi = -0.6, Ps = -1.6) for a) glassy carbon, b) FTO, and c) graphite rod, d) TiO2, and e) gold working electrodes.
Only the first four grafting scans are shown for the gold electrode, as further scans exhibit sharp features indicating
scratching of the gold at the contact. Despite this behavior, continuous film growth is evident by visual coloration of
the films and growth of IRRAS signal.
Figure S49. XPS results for a bare FTO electrode. a) XPS survey scan b) High-resolution Re 4f region
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Figure S50. IRRAS characterization of modified TiO2 films with a) polarization-dependence studies of a modified
TiO2 film (n = 20) and b) IRRAS results from films of various catalyst loadings under s-polarization.
Figure S51. Catalyst loading for modified FTO electrodes (n = 1, 5, 10, and 20) as determined by cyclic
voltammetry (red) and ICP (blue).
Figure S52. Controlled potential electrolysis results for modified (n = 1, 5, 10, and 20) and bare graphite rod
electrodes in acetonitrile (with 0.1 M TBAPF6 supporting electrolyte) at -2.25 V.
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Figure S53. IRRAS results for modified gold electrodes prepared with varying numbers of grafting scans. All
exhibit enhanced carbonyl stretching modes under s-polarization relative to p-polarization.
Figure S54. IRRAS results for a modified graphite rod electrode (n = 10) indicating the presence of carbonyl
stretching modes, absence of diazonium stretches, and polarization dependence.
Figure S55. Side-on SEM image acquired for a modified FTO electrode (n = 20). The FTO + film layer is estimated
at 420 nm thickness. Based on the reported thickness of FTO (250 nm) by the manufacturer (MTI Corp.), the film
thickness is estimated as ~170 nm.
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Figure S56. Cyclic voltammograms of a modified graphite rod electrode (n = 10) in acetonitrile solution with 0.1 M
TBAPF6 supporting electrolyte under CO2 atmosphere before (red) and after (green) a two hour controlled potential
electrolysis experiment. The bare electrode under CO2 atmosphere is shown in black.
Figure S57. Cyclic voltammograms of modified graphite rod electrodes (n = 1, 5, 10, and 20) in acetonitrile solution
with 0.1 M TBAPF6 supporting electrolyte a) under CO2 atmosphere and b) under CO2 atmosphere with the addition
of 0.5 M TFE.
References
(1) Shinde, D. B.; Aiyappa, H. B.; Bhadra, M.; Biswal, B. P.; Wadge, P.; Kandambeth, S.;
Garai, B.; Kundu, T.; Kurungot, S.; Banerjee, R. A Mechanochemically Synthesized
Covalent Organic Framework as a Proton-Conducting Solid Electrolyte. J. Mater. Chem.
A 2016, 4 (7), 2682–2690.
Page 39
S-39
(2) Popov, D. A.; Luna, J. M.; Orchanian, N. M.; Haiges, R.; Downes, C. A.; Marinescu, S. C.
A 2,2'-Bipyridine-Containing Covalent Organic Framework Bearing Rhenium (I)
Tricarbonyl Moieties for CO2 Reduction. Dalton Trans., 2018, DOI:
10.1039/C8DT00125A.
(3) Savéant, J.-M. Elements of Molecular and Biomolecular Electrochemistry; Wiley-
Interscience: New York, NY, 2006.
(4) Costentin, C.; Saveant, J.-M. Cyclic Voltammetry Analysis of Electrocatalytic Films. J.
Phys. Chem. C 2015, 119 (22), 12174-12182.
(5) Costentin, C.; Savéant, J.-M. Multielectron, Multistep Molecular Catalysis of
Electrochemical Reactions: Benchmarking of Homogeneous Catalysts. ChemElectroChem
2014, 1 (7), 1226–1236.
(6) Rountree, E. S.; McCarthy, B. D.; Eisenhart, T. T.; Dempsey, J. L. Evaluation of
Homogeneous Electrocatalysts by Cyclic Voltammetry. Inorg. Chem. 2014, 53 (19),
9983–10002.
(7) Shao, Y.; Molnar, L.; Jung, Y.; Kussmann, J.; Ochsenfeld, C.; Brown, S.; Gilbert, A.;
Slipchenko, L.; Levchenko, S.; O'Neill, D.; DiStasio, R.; Lochan, R.; Wang, T.; Beran, G.;
Besley, N.; Herbert, J.; Lin, C.; Van Voorhis, T.; Chien, S.; Sodt, A.; Steele, R.; Rassolov,
V.; Maslen, P.; Korambath, P.; Adamson, R.; Austin, B.; Baker, J.; Byrd, E.; Dachsel, H.;
Doerksen, R.; Dreuw, A.; Dunietz, B.; Dutoi, A.; Furlani, T.; Gwaltney, S.; Heyden, A.;
Hirata, S.; Hsu, C.; Kedziora, G.; Khalliulin, R.; Klunzinger, P.; Lee, A.; Lee, M.; Liang,
W.; Lotan, I.; Nair, N.; Peters, B.; Proynov, E.; Pieniazek, P.; Rhee, Y.; Ritchie, J.; Rosta,
E.; Sherrill, C.; Simmonett, A.; Subotnik, J.; Woodcock, H.; Zhang, W.; Bell, A.;
Chakraborty, A.; Chipman, D.; Keil, F.; Warshel, A.; Hehre, W.; Schaefer, H.; Kong, J.;
Page 40
S-40
Krylov, A.; Gill, P.; Head-Gordon, M. Advances in Methods and Algorithms in a Modern
Quantum Chemistry Program Package. Phys. Chem. Chem. Phys. 2006, 8 (27), 3172-
3191.
(8) Zhao, Y.; Truhlar, D. G. The M06 Suite of Density Functionals for Main Group
Thermochemistry, Thermochemical Kinetics, Noncovalent Interactions, Excited States,
and Transition Elements: Two New Functionals and Systematic Testing of Four M06-
Class Functionals and 12 Other Function. Theor. Chem. Acc. 2008, 120 (1–3), 215–241.
(9) Ditchfield, R.; Hehre, W. J.; Pople, J. A. Self-Consistent Molecular-Orbital Methods. IX.
An Extended Gaussian-Type Basis for Molecular-Orbital Studies of Organic Molecules. J.
Chem. Phys. 1971, 54 (2), 724–728.
(10) Hehre, W. J.; Ditchfield, K.; Pople, J. A. Self-Consistent Molecular Orbital Methods. XII.
Further Extensions of Gaussian-Type Basis Sets for Use in Molecular Orbital Studies of
Organic Molecules. J. Chem. Phys. 1972, 56 (5), 2257–2261.
(11) Hay, P. J.; Wadt, W. R. Ab Initio Effective Core Potentials for Molecular Calculations.
Potentials for the Transition Metal Atoms Sc to Hg. J. Chem. Phys. 1985, 82 (1), 270–283.
(12) Wadt, W. R.; Hay, P. J. Ab Initio Effective Core Potentials for Molecular Calculations.
Potentials for Main Group Elements Na to Bi. J. Chem. Phys. 1985, 82 (1), 284–298.