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Title: Light-driven synthesis of C2H6 from CO2 and H2O on a bimetallic AuIr composite supported on InGaN nanowires Open Access Deposited

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Methodology
  • Epitaxial growth of InGaN NWs. InGaN NWs were grown using a Veeco Gen II MBE system equipped with a radio frequency plasma-assisted nitrogen source. 3-inch silicon wafer was used as the substrate. Prior to loading into the MBE chamber, the silicon wafer was washed with acetone and methanol for eliminating organic contaminants, followed by rinsing with 10% hydrofluoric acid to remove silicon oxides. The growth conditions for these nanowires include a Ga beam equivalent pressure (BEP) of 5 × 10-8 Torr, In BEP of 4 × 10-8 Torr, and forward plasma power of 350 W. The nitrogen flow rate is set to be 1.0 standard cubic centimeter per minute (sccm), ensuring nitrogen-rich atmosphere to promote the formation of N-terminated lateral surface (m-plane) of the nanowires. In addition, the use of Ga seeding layer to promote the formation of a Ga-polar basal plane is also critical for N-termination. The substrate temperature for the growth is ~700 oC. Typically, a bottom GaN layer was first in situ grown to serve as the template of InGaN NWs. Subsequently, five segments of InGaN were deposited on GaN nanowires with a growth duration of 40 minutes. A GaN spacing layer was grown with 10 minutes between InGaN segments. Mg doping was employed throughout the structure to tune the surface band bending of the NWs. The assembly of Au NPs@InGaN NWs/Si. InGaN NWs/Si was immersed into 1 mol/L HCl for 10 minutes to remove the surface impurities. The pretreated InGaN NWs/Si (geometry surface area ~0.2 cm2) was rinsed with distilled water and then placed into a 400 mL glass chamber equipped with a top quartz window. 60 mL CH3OH/H2O mixture (10/50) was poured into the chamber, followed by the addition of a desired volume of gold precursor (H2AuCl4, 0.2 mol/L). The chamber was then vacuumed for approximately 20 minutes to remove air in the system. 300 W xenon lamp (Cermax, PE300BUV) was utilized as the light source for Au photo-deposition with an illumination time of 30 minutes. The assembled Au NPs@InGaN NWs/Si was rinsed with distilled water to remove carbon residuals. The assembly of AuIr@InGaN NWs/. Using Au@InGaN NWs as the parental template, Ir was further deposited onto Au@p-InGaN NWs/Si using the above-mentioned procedure in various concentrations of iridium chloride aqueous solution. Finally, the as-synthesized AuIr@InGaN NWs/Si was rinsed with distilled water to remove carbon residual and dried by nitrogen again. AuIr/Si was prepared for comparison by the same procedure in the absence of InGaN NWs. Characterization of the devices. The STEM work was conducted using a JEOL 3100R05 double-corrected S/TEM operated at 300 kV. Energy-dispersive X-ray spectroscopy (EDS) elemental mapping was carried out on a Thermo Fisher Scientific Talos F200X S/TEM equipped with a Super-X detector. The SEM characterization was performed on a FEI Helios 650 NanoLab at Materials Characterizations Center of University of Michigan. The loading density of AuIr was evaluated by an inductively coupled plasma-atomic emission spectroscopy (Perkin-Elmer Nexion 2000 Series). The samples were dissolved in Aqua regia (HNO3: HCl = 1:3) for 2 hours prior to the testing. The optical property measurements were analyzed using UV-VIS-NIR spectroscopy (Thermo Scientific Evolution 600). The X-ray photoelectron spectroscopies of artificial photosynthesis devices were collected using a Kratos Axis Ultra XPS with a monochromatic Al source at ~10 mA and ~15 V. The binding energy of Ga3d was used for the internal calibration. The room-temperature photoluminescence spectroscopy measurements were conducted using either a 325-nm He-Cd laser or a 405-nm laser as the excitation source. The X-ray diffraction profile data were collected on Rigaku Ultima IV in a grazing incident mode with an incident angle of 0.5°. Cu K-alpha line was utilized for the irradiation and the diffraction/scattering signals were recorded using a scintillation count detector. AES data were collected on a PHI 680 Auger nanoprobe which is equipped with a field emission electron gun and a cylindrical mirror energy analyzer. The transient reflection spectroscopy was recorded at an excitation wavelength of 350 nm with an excitation power of 40 nJ per pulse and probe wavelength of 650 nm. Photocatalytic reactions. If not specifically noted, photocatalytic reactions of CO2 with H2O were performed in a home-made sealed glass chamber (diameter, 5cm; volume, 400 mL) equipped with a top quartz lip under 300 W xenon lamp illumination without filter. Prior to illumination, 30 mL distilled water was purged with high-purity CO2 (PurityPlus, 99.8%) for 30 minutes and poured into the chamber. Subsequently, the chamber was completely vacuumed to remove air in the system. The vacuumed chamber was further filled with high-purity CO2 (99.9%) to 2 atm, followed by an illumination step with a light intensity of 3.5 W‧cm-2. By contrast, to clarify the origin of the carbonaceous products, a control experiment was conducted by illuminating the vacuum distilled water (30 mL) in the absence of CO2 with a 300 W Xenon lamp at light intensity of 3.5 W‧cm-2 without varying other conditions. The gaseous products were qualitatively and quantitatively analyzed by a gas chromatograph with a FID detector (GC 2014, Shimadzu) and a thermal conductivity detector (GC 2010, Shimadzu). The liquid reaction mixtures were analyzed by nuclear magnetic resonance spectroscopy (NMR 500M, Bruker) using 1,3,5-trioxane as an internal standard. During the long-term operation of 60 hours the chamber was vacuumed and then purged with CO2 again before the next run at intervals of 6, 9 or 12 hours. The performance was evaluated on the basis of accumulated data. Calculation of activity and selectivity of H2, CO, CH4, and C2H6 and LTFs efficiency "Activity = " "Yield " /(("Surface × W × T" ) ) (1) "Selectivity of ethane = " "Rateethane " /(("RateH2 + RateCO + Ratemethane + Rateethane" ) ) (2) "TON = " "Yield " /(("Surface × Loading Density" ) ) (3) "TOF = " "Yield" /(("Surface × Loading Density × T" ) ) (4) "LTFs = " "ΔHH2×YieldH2+ΔHCO×YieldCO+ΔHmethane×Yieldmethane+ΔHethane×Yieldethane" /(("Light intensity × Surface × T" ) ) (5) where Surface is the geometric surface of the sample, ~0.3 cm2. W is the total weight of the epitaxial of InGaN NWs, which is estimated to be ~0.17 mg/cm2, without considering the trace amount of the cocatalysts. Rate is the evolution rate of each product. Yield is the produced amount of each product. T is the illumination time. TON is the turnover number. TOF is the turnover frequency. Loading Density of the AuIr cocatalyst is evaluated to be 0.012 µmol‧cm-2 by ICP-AES. LTF is light-to-fuels energy efficiency. 𝞓H represents the standard molar enthalpy of combustion of specific products. DRIFT Spectroscopy Characterization. In-situ diffuse reflectance infrared Fourier-transform spectroscopy analysis was conducted using a Bruker IFS 66v Fourier transformation spectrometer with a Harrick diffuse reflectance accessory at the Infrared Spectroscopy and Microspectroscopy Endstation (BL01B) in the National Synchrotron Radiation Laboratory (NSRL), Hefei. Each spectrum was recorded by averaging 128 scans at a resolution of 2 cm−1. The nanowire arrays are placed horizontally in the sample chamber. Prior to exposure to CO2 (99.9999%) atmosphere and illumination, a spectrum is collected as background. During the in-situ characterization, water vapor saturated CO2 is introduced into the sample chamber; and a xenon lamp (PLS-SXE300, Perfect Light) is used as a full-spectrum light source. The spectra are recorded in dark and under illumination for a certain time. Transient Reflection Spectroscopy. Optical pump-optical probe transient absorption spectroscopy was performed using a 100 fs, 1 kHz, Ti:Sapphire regenerative amplifier (Coherent Libra). A portion of the laser output was coupled to an optical parametric amplifier (Coherent OPerA Solo) for generating the 350 nm pump beam with a diameter of 0.3 mm and pulse energy of 0.8 μJ at the sample. The super continuum probe in the visible region was generated using a sapphire crystal. The incident angle of the probe beam was approximately 8° with respect to the sample surface normal. An ultrafast transient absorption system, equipped with two sets of fiber-coupled grating spectrometers plus Si CMOS detector arrays, was used for data collection. Density functional theory calculations. Density functional theory (DFT) calculations were performed with Perdew-Burke-Ernzerhof exchange-correlation functional47 as implemented in Vienna Ab initio Simulation Package (VASP)48, 49 Plane-wave cutoff energy of 450 eV with a 3 × 3 × 1 Γ-centered k-point sampling generated by the Monkhorst-Pack scheme50 were used for all calculations. A threshold of 10−5 eV was used for the convergence of the electronic structure. Optimized structures were obtained by minimizing the forces on each ion until they fell below 0.01 eV/Å. The long-range dispersion correction was considered by the zero damping DFT-D3 method of Grimme 51. During the structural relaxation, all atoms in the bottommost two layers were fixed to their bulk positions whereas the remaining atoms together with the adsorbates were allowed to relax. Prior theoretical studies52, 53 have shown that the binding energies are predominantly affected by the local bonding environment. Therefore, we focused on surface ensembles that exhibit different local bonding environments but with same alloying concentration. Specifically, we considered triatomic ensembles described in the form of AuxIry where x + y = 3, x ≥ 0, y ≥ 0, being Au3, Au2Ir1, Au1Ir2, and Ir3, as illustrated in Fig. 4c in the manuscript. These triatomic ensembles were modeled in a 4-layer 3 × 3 AuIr(111) slab models with Au:Ir ratio fixed to 1:1. For each triatomic ensemble, we randomly generated 10 different structures by maintaining the structure of the examined triatomic ensembles and varying the atoms around this structure. Then the adsorption energies of reaction intermediates in CO2 reduction and HER on these different structures were calculated, based on which the average values and corresponding error bars of adsorption energies can be determined. Similar to these triatomic ensembles, pure Au and Ir were also modeled 4-layer 3 × 3 Au(111) and Ir(111) slab models for comparison.
Description
  • Generation of C2+ compounds using sunlight, carbon dioxide, and water provides a promising path for carbon neutrality. The exploration of a catalyst to break the bottleneck of C-C coupling, for constructing a rational artificial photosynthesis integrated device, is at the core. Herein, based on operando spectroscopy measurements, theoretical calculations, and feedstock experiments, it is discovered that gold, in conjunction with iridium, can catalyze the reduction of CO2, achieving C-C coupling by insertion of CO2 into -CH3. Owing to a combination of optoelectronic and catalytic properties, the assembly of AuIr with InGaN nanowires on silicon (AuIr@InGaN NWs/Si) enables the achievement of a C2H6 activity of 58.8 mmol‧g-1‧h-1 with a turnover number of 54,595 over 60 hours. A light-to-fuels efficiency of ~0.59% for solar fuels production from CO2 and H2O is achieved without any other energy inputs. This work provides a carbon-negative path for producing higher order C compounds.
Creator
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  • zwye@umich.edu
Contact information
Discipline
Keyword
Date coverage
  • 2023-07-20
Resource type
Last modified
  • 07/28/2023
Published
  • 07/28/2023
Language
DOI
  • https://doi.org/10.7302/w8ep-0g79
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To Cite this Work:
Ye, Z., Mi, Z. (2023). Light-driven synthesis of C2H6 from CO2 and H2O on a bimetallic AuIr composite supported on InGaN nanowires [Data set], University of Michigan - Deep Blue Data. https://doi.org/10.7302/w8ep-0g79

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Thumbnailthumbnail-column Title Original Upload Last Modified File Size Access Actions
Fig.2a-Au-loading-Activity.xlsx 2023-07-23 2023-07-23 9.5 KB Open Access
Fig.2b-Au-loading-Select..xlsx 2023-07-23 2023-07-23 8.41 KB Open Access
Fig.2c-Au-Time_course.xlsx 2023-07-23 2023-07-23 8.61 KB Open Access
Fig.2d-AuIr-loading-Activity..xlsx 2023-07-23 2023-07-23 8.67 KB Open Access
Fig.2e-AuIr-loading-Select..xlsx 2023-07-23 2023-07-23 8.52 KB Open Access
Fig.2f-AuIr-loading-LTF.xlsx 2023-07-23 2023-07-23 8.55 KB Open Access
Fig.3a-TOF-C2H6.xlsx 2023-07-23 2023-07-23 8.41 KB Open Access
Fig.3b-TOF-CH4.xlsx 2023-07-23 2023-07-23 8.42 KB Open Access
Fig.3c-TOF-CO.xlsx 2023-07-23 2023-07-23 8.41 KB Open Access
Fig.3d-Yield-C2H6.xlsx 2023-07-23 2023-07-23 9.51 KB Open Access
Fig.3e-Yield-CH4.xlsx 2023-07-23 2023-07-23 9.51 KB Open Access
Fig.3f-Yield-CO.xlsx 2023-07-23 2023-07-23 9.51 KB Open Access
Fig.4a-TOF-feedstock_experiments.xlsx 2023-07-23 2023-07-23 8.4 KB Open Access
Supplementary_Data_1.txt 2023-07-23 2023-07-23 88.2 KB Open Access
Supplementary_Figure_12.xlsx 2023-07-23 2023-07-23 9.16 KB Open Access
Supplementary_Figure_14.xlsx 2023-07-23 2023-07-23 8.98 KB Open Access
Supplementary_Figure_15.xlsx 2023-07-23 2023-07-23 11.3 KB Open Access
Supplementary_Figure_16.xlsx 2023-07-23 2023-07-23 9.15 KB Open Access
Supplementary_Figure_17.xlsx 2023-07-23 2023-07-23 8.96 KB Open Access
Supplementary_Figure_18.xlsx 2023-07-23 2023-07-23 12.7 KB Open Access
Supplementary_Figure_19.xlsx 2023-07-23 2023-07-23 8.96 KB Open Access
Supplementary_Figure_21.xlsx 2023-07-23 2023-07-23 8.97 KB Open Access
Supplementary_Figure_22.a-TON-C2H6.xlsx 2023-07-23 2023-07-23 8.43 KB Open Access
Supplementary_Figure_22.b-TON-CH4.xlsx 2023-07-23 2023-07-23 8.43 KB Open Access
Supplementary_Figure_22.c-TON-CO.xlsx 2023-07-23 2023-07-23 8.43 KB Open Access
Supplementary_Figure_23.a-C2H6_rate.xlsx 2023-07-23 2023-07-23 9.5 KB Open Access
Supplementary_Figure_23.b-CH4_rate.xlsx 2023-07-23 2023-07-23 9.51 KB Open Access
Supplementary_Figure_23.c-CO_rate.xlsx 2023-07-23 2023-07-23 9.51 KB Open Access
readme.txt 2023-07-28 2023-07-28 4.59 KB Open Access

Access note: Some figures may not display correctly on Mac computers. If this occurs, try a Windows PC. Further details regarding the data are available from the authors upon reasonable request.
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The dataset provided contains the relevant data necessary to construct the listed figures in the manuscript titled 'Light-driven synthesis of C2H6 from CO2 and H2O on a bimetallic AuIr composite supported on InGaN nanowires.' The figures are based on the information and results gathered from this dataset.

Fig. 2. Photocatalytic activity of AuIr decorated InGaN NWs. a, b, Evolution rate (a) and selectivity (b) of different products from photocatalytic CO2 reduction over Au NPs@InGaN NWs/Si decorated with various amounts of Au. c, Time course of CO and CH4 evolved from CO2 reduction reaction over Au2@InGaN/Si. d-f, Evolution rate (d) and Selectivity (e), and LTFs efficiencies (f) of various products from photocatalytic CO2 reduction over AuIr@InGaN NWs/Si with various Au/Ir ratios. Experimental conditions: 30 mL distilled water, CO2, 300 W Xenon lamp, 3.5 W‧cm-2. (The data has a 5-10% error bar during sampling.)

Fig. 3. Stability testing of various CO2 reduction products. a-c, TOF of C2H6 (a), CH4 (b), and CO (c) from photocatalytic CO2 reduction over Au0.44Ir0.56@InGaN NWs/Si in water. d-f, yield of C2H6 (d), CH4 (e), and CO (f) from photocatalytic CO2 reduction over Au0.44Ir0.56@InGaN NWs/Si in water. Experimental conditions: 30 mL distilled water, CO2, 300 W Xenon lamp, 3.5 W‧cm-2.

Fig. 4. Mechanism investigation. a, The TOF of C2H6 of various feedstocks in water over Au0.44Ir0.56@InGaN/Si. Experimental conditions: 30 mL distilled water, 300 W Xenon lamp, 3.5 W‧cm-2. b, DRIFT spectra recorded from photocatalytic CO2 reduction over Au0.44Ir0.56@InGaN NWs/Si. c, Calculated reaction energy (orange column) and energy barrier (blue column) of different C-C coupling mechanisms on Au2Ir2(111) facet, including *CH + *CH → *C2H2, *CH2 + *CH2 → *C2H4, *CH3 + *CH3 → C2H6(g), and CO2 insertion into *CH3, i.e., *CH3 + CO2(g) → *CH3COO. d, Free energy diagram of the reaction pathway before C-C coupling on Au2Ir2(111) facet. Yellow, blue, red, grey, and white spheres represent the atoms of gold, iridium, oxygen, carbon, and hydrogen, respectively. e, Schematic of light-driven C-C coupling from CO2 and H2O over Au0.44Ir0.56@InGaN/Si.

Supplementary Figure 12 | The influence of light intensity on photocatalytic CO2 reduction over AuIr@InGaN NWs/Si. Experimental conditions: 30 mL distilled water, CO2, 300 W Xenon lamp. The light intensity is changed by adjusting the distance between xenon lamp and reaction chamber without temperature control.

Supplementary Figure 14 | The temperature-illumination time at various light intensities. Experimental conditions: 30 mL distilled water, CO2, 300 W Xenon lamp. The light intensity is changed by adjusting the distance between xenon lamp and reaction chamber. The temperature measurement was conducted by attaching heat dipole to the back of the InGaN NWs wafer.

Supplementary Figure 15 | The influence of temperature over different light intensity on CO2 reduction over AuIr@InGaN NWs/Si. a) The illumination intensity was 1.5 W‧cm-2. b) The illumination intensity was 2.5 W‧cm-2. c) The illumination intensity was 3.5 W‧cm-2.

Supplementary Figure 16 | Temperature-dependent CO2 solubility in distilled water. The data was collected from Lange’s Handbook of chemistry.1

Supplementary Figure 17 | The performance of CO2 reduction over AuIr@InGaN NWs/Si under ultraviolet light illumination.

Supplementary Figure 18 | GC-MS measurement of photocatalytic CO2 reduction reaction with 12CO2 and 13CO2 over Au0.44Ir0.56@InGaN NWs/Si.

Supplementary Figure 19 | Evolution rate of different products and oxygen of these products from photocatalytic CO2 reduction over Au0.44Ir0.56@InGaN NWs/Si.

Supplementary Figure 21 | Time course of O2 consumption in the O2/CO2 mixture under different illumination spectra without wafer sample.

Supplementary Figure 22 | Turnover number of C2H6 a), CH4 b), and CO c) from CO2 reduction over Au0.44Ir0.56@InGaN NWs/Si under a long-term illumination of 60 hours. Experimental conditions: CO2, 30 mL distilled water, 300 W Xenon lamp, 3.5 W‧cm-2.

Supplementary Figure 23 | Activity of photocatalytic CO2RR toward C2H6 a), CH4 b), and CO c) under a long-term operation of 60 hours. Experimental conditions: CO2, 30 mL distilled water, 300 W Xenon lamp, 3.5 W‧cm-2.

Supplementary data 1.txt include the DFT original data involved in the manuscript.

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