Supporting Information Integrating Electrocatalytic 5 ...
Supporting Information
Integrating Electrocatalytic 5-Hydroxymethylfurfural Oxidation and Hydrogen Production via Co-P-Derived Electrocatalysts
Nan Jiang, Bo You, Raquel Boonstra, Irina M. Terrero Rodriguez and Yujie Sun* Department of Chemistry and Biochemistry, Utah State University, Logan, Utah 84322, United States
Materials Cobalt sulfate, sodium hypophosphite monohydrate, potassium hydroxide were purchased from commercial vendors and used as received. 5-hydroxymethylfurfural (HMF) and 2,5furandicarboxylic acid (FDCA) were purchased from Alfa Aesa and Chem-Impex, respectively, and used as received. 2,5-Diformylfuran (DFF) and 2-formyl-5-furancarboxylic acid (FFCA) were purchased from Ark Pharm. 5-Hydroxymethyl-2-furan-carboxylic acid (HMFCA) was purchased from Asta Tech. Copper foams were purchased from MTI Corporation. Water was deionized (18 Mcm) with a Barnstead E-Pure system and used in all the electrochemical studies. Electrochemical methods Electrochemical experiments were performed with Gamry Interface 1000 potentiostats. Aqueous Ag/AgCl reference electrodes (saturated KCl) were purchased from CH Instruments. The reference electrode in pH 7 phosphate buffer was calibrated with ferrocenecarboxylic acid (FcCOOH) whose EFe3+/2+ couple is 0.284 V vs SCE. All potentials reported in this paper were converted from vs Ag/AgCl to vs RHE by adding a value of 0.197 + 0.059 ×pH. iR (current times internal resistance) compensation was applied in all experiments to account for the voltage drop between the reference and working electrodes using the Gamary FrameworkTM Data Acquisition Software 6.11. All the electrochemical experiments were conducted in a two-compartment cell in which the anode and cathode compartments were separated by an anion exchange membrane. The anion exchange membrane (Fumasep FAA-3-PK-130) was purchased from Fuel Cell Store. Preparation of Co-P/CF Prior to electrodeposition, copper foams were rinsed with water and ethanol thoroughly to remove residual organic species. For the preparation of Co-P/CF, copper foam with a geometric area of 0.25 cm2 (4 cm2 for samples of electrolysis experiments) was exposed to the deposition solution (50 mM CoSO4 and 0.5 M NaH2PO2 in water). A platinum wire was used as the counter electrode and a Ag/AgCl (sat. KCl) electrode as the reference electrode. Nitrogen was bubbled through the electrolyte solution for at least 20 min prior to deposition and maintained during the entire deposition process. The potential of consecutive linear scans was cycled 15 times between -0.3 and -1.0 V vs Ag/AgCl at a scan rate of 5 mV/s under stirring. After deposition, the copper foam was removed from the deposition bath and rinsed with copious water gently. The as-prepared CoP/CF could be directly used for electrochemical experiments or stored under vacuum at room temperature for future use.
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HPLC analysis of oxidation products 10 μL aliquot was periodically collected from the electrolyte solution during chronoamperometry and diluted with 490 μL water. The sample solutions were then analysed via HPLC (Shimadzu Prominence LC-2030C system) at room temperature to calculate the HMF conversion and yields of oxidation products. The HPLC instrument was equipped with an ultraviolet-visible detector set at 265 nm and a 4.6 mm × 150 mm Shim-pack GWS 5 μm C18 column. The eluent solvent is a mixture of 5 mM ammonium formate aqueous solution and methanol. Separation was accomplished using a gradient elution by varying the volume percentage of methanol from 30% to 25% during 0 to 10 min and the flow rate was set at 0.5 mL/min. The quantification of HMF and its oxidation products were calculated based on the calibration curves of those standard compounds purchased from commercial vendors. Physical methods Scanning electron microscopy images and elemental mapping analysis were collected on a FEI QUANTA FEG 650 (FEI, USA) at the Microscopy Core Facility of USU. X-ray photoelectron spectroscopy analyses were done using a Kratos Axis Ultra instrument (Chestnut Ridge, NY). The samples were affixed on a stainless steel Kratos sample bar, loaded into the instrument’s load lock chamber, and evacuated to 5 10-8 torr before it was transferred into the sample analysis chamber under ultrahigh vacuum conditions (~10-10 torr). X-ray photoelectron spectra were taken using the monochromatic Al Kα source (1486.7 eV) at a 300 700 μm spot size. Low resolution survey and high resolution region scans at the binding energy of interest were taken for each sample. To minimize charging, samples were flooded with low-energy electrons and ions from the instrument’s built-in charge neutralizer. The samples were also sputter cleaned inside the analysis chamber with 1 keV Ar+ ions for 30 seconds to remove adventitious contaminants and surface oxides. Data were analyzed using CASA XPS software, and energy corrections on high resolution scans were done by referencing the C 1s peak of adventitious carbon to 284.5 eV. The generated hydrogen volume during electrolysis was quantified with a SRI gas chromatography system 8610C equipped with a Molecular Sieve 13 packed column, a HayesSep D packed column, and a thermal conductivity detector. The oven temperature was maintained at 60 C and argon was used as the carrier gas.
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Figure S1. A typical potentiodynamic deposition for the preparation of Co-P on copper foams (scan rate: 5 mV/s).
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Figure S2. SEM images of the as-prepared Co-P/CF.
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Figure S3. Elemental mapping images of the as-prepared Co-P.
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Figure S4. XPS survey spectra of (a) as-prepared Co-P/CF and (b) Co-P/CF after a 6-h controlled potential electrolysis of HMF oxidation at 1.423 V vs RHE in 1.0 M KOH.
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Figure S5. XRD patterns of Cu foam, as-prepared Co-P/CF, Co-P/CF post HER, and Co-P/CF post HMF oxidation.
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Figure S6. Linear sweep voltammograms of Co-P/CF (red) and blank copper foam (black) in 1.0 M KOH in the presence of 50 mM HMF at a scan rate of 2 mV/s.
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Figure S7. Controlled potential electrolysis of Co-P/CF in 1.0 M KOH containing 50 mM HMF at a potential of 1.423 V vs RHE. (Inset: the corresponding current change over time).
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Figure S8. HPLC traces of the electrocatalytic oxidation of HMF catalyzed by Co-P/CF at 1.423 V vs RHE.
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Figure S9. Carbon balance of HMF oxidation catalyzed by Co-P/CF in 1.0 M KOH with 50 mM HMF.
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Figure S10. 1H-NMR spectra of (a) commercial HMF, (b) an aliquot collected from the electrolyte before HMF oxidation, (c) commercial FDCA, and (d) the precipitate isolated from the acidified electrolyte of HMF oxidation after a controlled potential electrolysis at 1.423 V vs RHE for 6 h. All the NMR spectra were measured in D2O. 12
Figure S11. SEM images of Co-P/CF after the 6-h controlled potential electrolysis of HMF oxidation at 1.423 V vs RHE in 1.0 M KOH.
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Figure S12. Elemental mapping images of Co-P/CF after the 6-h controlled potential electrolysis of HMF oxidation at 1.423 V vs RHE in 1.0 M KOH.
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Figure S13. SEM images of Co-P/CF after the two-electrode electrolysis for HER in 1.0 M KOH.
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Figure S14. Elemental mapping images of Co-P/CF after the two-electrode electrolysis for HER in 1.0 M KOH.
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Integrating Electrocatalytic 5-Hydroxymethylfurfural Oxidation and Hydrogen Production via Co-P-Derived Electrocatalysts
Nan Jiang, Bo You, Raquel Boonstra, Irina M. Terrero Rodriguez and Yujie Sun* Department of Chemistry and Biochemistry, Utah State University, Logan, Utah 84322, United States
Materials Cobalt sulfate, sodium hypophosphite monohydrate, potassium hydroxide were purchased from commercial vendors and used as received. 5-hydroxymethylfurfural (HMF) and 2,5furandicarboxylic acid (FDCA) were purchased from Alfa Aesa and Chem-Impex, respectively, and used as received. 2,5-Diformylfuran (DFF) and 2-formyl-5-furancarboxylic acid (FFCA) were purchased from Ark Pharm. 5-Hydroxymethyl-2-furan-carboxylic acid (HMFCA) was purchased from Asta Tech. Copper foams were purchased from MTI Corporation. Water was deionized (18 Mcm) with a Barnstead E-Pure system and used in all the electrochemical studies. Electrochemical methods Electrochemical experiments were performed with Gamry Interface 1000 potentiostats. Aqueous Ag/AgCl reference electrodes (saturated KCl) were purchased from CH Instruments. The reference electrode in pH 7 phosphate buffer was calibrated with ferrocenecarboxylic acid (FcCOOH) whose EFe3+/2+ couple is 0.284 V vs SCE. All potentials reported in this paper were converted from vs Ag/AgCl to vs RHE by adding a value of 0.197 + 0.059 ×pH. iR (current times internal resistance) compensation was applied in all experiments to account for the voltage drop between the reference and working electrodes using the Gamary FrameworkTM Data Acquisition Software 6.11. All the electrochemical experiments were conducted in a two-compartment cell in which the anode and cathode compartments were separated by an anion exchange membrane. The anion exchange membrane (Fumasep FAA-3-PK-130) was purchased from Fuel Cell Store. Preparation of Co-P/CF Prior to electrodeposition, copper foams were rinsed with water and ethanol thoroughly to remove residual organic species. For the preparation of Co-P/CF, copper foam with a geometric area of 0.25 cm2 (4 cm2 for samples of electrolysis experiments) was exposed to the deposition solution (50 mM CoSO4 and 0.5 M NaH2PO2 in water). A platinum wire was used as the counter electrode and a Ag/AgCl (sat. KCl) electrode as the reference electrode. Nitrogen was bubbled through the electrolyte solution for at least 20 min prior to deposition and maintained during the entire deposition process. The potential of consecutive linear scans was cycled 15 times between -0.3 and -1.0 V vs Ag/AgCl at a scan rate of 5 mV/s under stirring. After deposition, the copper foam was removed from the deposition bath and rinsed with copious water gently. The as-prepared CoP/CF could be directly used for electrochemical experiments or stored under vacuum at room temperature for future use.
1
HPLC analysis of oxidation products 10 μL aliquot was periodically collected from the electrolyte solution during chronoamperometry and diluted with 490 μL water. The sample solutions were then analysed via HPLC (Shimadzu Prominence LC-2030C system) at room temperature to calculate the HMF conversion and yields of oxidation products. The HPLC instrument was equipped with an ultraviolet-visible detector set at 265 nm and a 4.6 mm × 150 mm Shim-pack GWS 5 μm C18 column. The eluent solvent is a mixture of 5 mM ammonium formate aqueous solution and methanol. Separation was accomplished using a gradient elution by varying the volume percentage of methanol from 30% to 25% during 0 to 10 min and the flow rate was set at 0.5 mL/min. The quantification of HMF and its oxidation products were calculated based on the calibration curves of those standard compounds purchased from commercial vendors. Physical methods Scanning electron microscopy images and elemental mapping analysis were collected on a FEI QUANTA FEG 650 (FEI, USA) at the Microscopy Core Facility of USU. X-ray photoelectron spectroscopy analyses were done using a Kratos Axis Ultra instrument (Chestnut Ridge, NY). The samples were affixed on a stainless steel Kratos sample bar, loaded into the instrument’s load lock chamber, and evacuated to 5 10-8 torr before it was transferred into the sample analysis chamber under ultrahigh vacuum conditions (~10-10 torr). X-ray photoelectron spectra were taken using the monochromatic Al Kα source (1486.7 eV) at a 300 700 μm spot size. Low resolution survey and high resolution region scans at the binding energy of interest were taken for each sample. To minimize charging, samples were flooded with low-energy electrons and ions from the instrument’s built-in charge neutralizer. The samples were also sputter cleaned inside the analysis chamber with 1 keV Ar+ ions for 30 seconds to remove adventitious contaminants and surface oxides. Data were analyzed using CASA XPS software, and energy corrections on high resolution scans were done by referencing the C 1s peak of adventitious carbon to 284.5 eV. The generated hydrogen volume during electrolysis was quantified with a SRI gas chromatography system 8610C equipped with a Molecular Sieve 13 packed column, a HayesSep D packed column, and a thermal conductivity detector. The oven temperature was maintained at 60 C and argon was used as the carrier gas.
2
Figure S1. A typical potentiodynamic deposition for the preparation of Co-P on copper foams (scan rate: 5 mV/s).
3
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Figure S2. SEM images of the as-prepared Co-P/CF.
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Figure S3. Elemental mapping images of the as-prepared Co-P.
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Figure S4. XPS survey spectra of (a) as-prepared Co-P/CF and (b) Co-P/CF after a 6-h controlled potential electrolysis of HMF oxidation at 1.423 V vs RHE in 1.0 M KOH.
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Figure S5. XRD patterns of Cu foam, as-prepared Co-P/CF, Co-P/CF post HER, and Co-P/CF post HMF oxidation.
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Figure S6. Linear sweep voltammograms of Co-P/CF (red) and blank copper foam (black) in 1.0 M KOH in the presence of 50 mM HMF at a scan rate of 2 mV/s.
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Figure S7. Controlled potential electrolysis of Co-P/CF in 1.0 M KOH containing 50 mM HMF at a potential of 1.423 V vs RHE. (Inset: the corresponding current change over time).
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Figure S8. HPLC traces of the electrocatalytic oxidation of HMF catalyzed by Co-P/CF at 1.423 V vs RHE.
10
Figure S9. Carbon balance of HMF oxidation catalyzed by Co-P/CF in 1.0 M KOH with 50 mM HMF.
11
Figure S10. 1H-NMR spectra of (a) commercial HMF, (b) an aliquot collected from the electrolyte before HMF oxidation, (c) commercial FDCA, and (d) the precipitate isolated from the acidified electrolyte of HMF oxidation after a controlled potential electrolysis at 1.423 V vs RHE for 6 h. All the NMR spectra were measured in D2O. 12
Figure S11. SEM images of Co-P/CF after the 6-h controlled potential electrolysis of HMF oxidation at 1.423 V vs RHE in 1.0 M KOH.
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Figure S12. Elemental mapping images of Co-P/CF after the 6-h controlled potential electrolysis of HMF oxidation at 1.423 V vs RHE in 1.0 M KOH.
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Figure S13. SEM images of Co-P/CF after the two-electrode electrolysis for HER in 1.0 M KOH.
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Figure S14. Elemental mapping images of Co-P/CF after the two-electrode electrolysis for HER in 1.0 M KOH.
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