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Article
Geoffrey Ozin
University of Toronto
Corresponding Author
ORCiD: https://orcid.org/0000-0002-6315-0925
License:
This work is licensed under a CC BY 4.0 License. Read Full License
The surface frustrated Lewis pairs (SFLPs) on defect-laden metal oxides provide catalytic sites to activate H2 and CO2 molecules and enable efficient gas-phase CO2 photocatalysis. Lattice engineering of metal oxides provides a useful strategy to tailor the reactivity of SFLPs. Herein a one-step solvothermal synthesis is developed that enables isomorphic replacement of In3+ ions in UV-absorbing In2O3 by single-site Bi3+ ions to generate a new class of full-spectrum UV-Vis-NIR absorbing BixIn2-xO3 materials. Through compositional tuning, these materials prove to be three orders of magnitude more photoactive for the reverse water gas shift reaction (i.e., CO2 + H2 CO + H2O) than In2O3 itself, while also exhibiting notable photoactivity towards methanol production from carbon dioxide (i.e., CO2 + 3H2 CH3OH + H2O). The defective form of In2O3 containing oxygen vacancy sites can create SFLPs involving In3+ nearby the oxygen vacancy, which function as Lewis acidic sites, while lattice oxide O2- act as Lewis basic sites. In this study, it is discovered that the reactivity of these SFLPs can be further enhanced by single-site Bi3+ ion isomorphic substitution of Lewis acidic site In3+, thereby enhancing the propensity to activate CO2 molecules. In addition, the increased solar absorption efficiency and efficient charge separation and transfer of BixIn2-xO3 also contribute to the improved photocatalytic performance. These traits lead to enhanced binding and activation of CO2, exemplifying the opportunities that exist for atom-scale engineering in heterogeneous CO2 photocatalysis, another step towards the vision of the solar CO2 refinery.
Keywords
CO2 photocatalysis, surface frustrated Lewis pairs, Bismuth atom, Bi3, In3+ions
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This is a list of supplementary files associated with this preprint. Click to download.
- Supplementarymaterial.docx
Bismuth Atom Tailoring of Indium Oxide Surface Frustrated Lewis Pairs Boosts Heterogeneous CO2 Photocatalytic Hydrogenation
- TableS1.png
The molar contents of Bi in the series of BixIn2-xO3 nanocrystals determined by ICP-MS.
- TableS2.png
Fitting results of Bi L3-edge and In K-edge FT-EXAFS data.
- TableS3.png
The compared CO production rate of different catalysts for photocatalytic CO2 hydrogenation.
- TableS4.png
Specific surface area of pristine In2O3 and BixIn2-xO3 nanocrystals.
- FigureS1.png
(a) TEM, (b) HRTEM, (c) size distribution, and (d) SAED of pristine In2O3. The highlighted yellow ring in (a) shows one flower-like agglomerate. The red arrows in (b) represent the single nanocrystals, and the inset in (b) shows the lattice fringe with a spacing of 2.92 Å.
- FigureS2.jpg
(a) TEM, (b) HRTEM, (c) size distribution, and (d) SAED of 1.0% BixIn2-xO3 sample. (e) TEM and HRTEM of 3.0% BixIn2-xO3 sample. (f) TEM and HRTEM of 5.0% BixIn2-xO3 sample.
- FigureS3.jpg
Elemental mapping profiles of 1.0% BixIn2-xO3.
- FigureS4.jpg
In 3d and (b) Bi 4f XPS spectra of pure In2O3 and BixIn2-xO3 nanocrystals.
- FigureS5.jpg
EPR spectra of 1.0% BixIn2-xO3 nanocrystals recorded at room temperature and 77 K.
- FigureS6.jpg
Fitted Bi L3-edge and In K-edge FT-EXAFS spectra from (a) Bi2O3 and (b) In2O3 reference materials, as well as (c) 1.0% and (d) 5.0% BixIn2-xO3 samples.
- FigureS7.png
The actual reaction temperature tested by IR camera on (a) pristine In2O3 and (b) 1.0% BixIn2-xO3 nanocrystals.
- FigureS8.jpg
CO production rate as a function of absorption cut-off filter wavelength for pure In2O3 sample.
- FigureS9.jpg
(a) CH3OH production and (b) CO production as function of reaction time on pristine In2O3 and BixIn2-xO3 nanocrystals in the flow reactor at 230 C, with and without light irradiation.
- FIgureS10.jpg
(a) Plotted reaction rates demonstrating the long-term (50 h) catalytic stability of 1.0% BixIn2-xO3 nanocrystals during photocatalytic CO2 hydrogenation. (b) XRD patterns, (c) TEM image, and (d) Bi 4f XPS spectra of fresh and spent (i.e., after 50 h stability testing) 1.0% BixIn2-xO3 nanocrystals.
- FigureS11.jpg
(a) CH3OH production rates and (b) CO production rates of the top-performing catalyst 1.0% BixIn2-xO3 as a function of reaction temperatures.
- FigureS12.jpg
The color of pure In2O3 and substituted BixIn2-xO3 nanocrystals.
- FigureS13.jpg
Inferred band gaps of pristine In2O3 and various BixIn2-xO3 nanocrystals.
- FigureS14.jpg
Calculated DOS plots for (a) pristine In2O3 and (b) BixIn2-xO3 nanocrystals.
- FigureS15.jpg
High-resolution O 1s core-level XPS spectra of 1.0% BixIn2-xO3 nanocrystals. The O 1s core level XPS spectra could be fitted into three peaks at 529.3 eV, 530.9 eV, and 532.8 eV, which are assigned to oxides (OI), oxygen vacancies (OII), and hydroxyl groups (OIII), respectively.
- FigureS16.jpg
High-resolution O 1s core-level XPS spectra of pure In2O3 and BixIn2-xO3 nanocrystals.
- FigureS17.jpg
Time-resolved PL spectra of pristine In2O3 and 1.0% BixIn2-xO3 nanocrystals.
- FigureS18.jpg
Schematic of surface species contributing to the adsorption of CO2 on BixIn2-xO3 nanocrystals, as exemplified by monodentate carbonate-like species (m-CO32-), bidentate carbonate-like species (b-CO32-), bent adsorbed species (CO2-), and bicarbonate-like species (HCO3-).
- FigureS19.jpg
In-situ DRIFTS spectra for CO2 hydrogenation under (a) dark and (b) light conditions on 1.0% BixIn2-xO3.
- FigureS20.png
In-situ DRIFTS spectra for CO2 hydrogenation under (a) dark and (b) light conditions on pristine In2O3.
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This is a preprint. It has not completed peer review.
Article
Geoffrey Ozin
University of Toronto
Corresponding Author
ORCiD: https://orcid.org/0000-0002-6315-0925
Badges
Prescreen
This manuscript passed our Prescreen assessment
Complete author information
Appropriate declaration statements
Potential risks to human health
Prescreen
History
CURRENT STATUS: Posted
Version 1
Posted 04 Aug, 2020
License:
This work is licensed under a CC BY 4.0 License. Read Full License
The surface frustrated Lewis pairs (SFLPs) on defect-laden metal oxides provide catalytic sites to activate H2 and CO2 molecules and enable efficient gas-phase CO2 photocatalysis. Lattice engineering of metal oxides provides a useful strategy to tailor the reactivity of SFLPs. Herein a one-step solvothermal synthesis is developed that enables isomorphic replacement of In3+ ions in UV-absorbing In2O3 by single-site Bi3+ ions to generate a new class of full-spectrum UV-Vis-NIR absorbing BixIn2-xO3 materials. Through compositional tuning, these materials prove to be three orders of magnitude more photoactive for the reverse water gas shift reaction (i.e., CO2 + H2 CO + H2O) than In2O3 itself, while also exhibiting notable photoactivity towards methanol production from carbon dioxide (i.e., CO2 + 3H2 CH3OH + H2O). The defective form of In2O3 containing oxygen vacancy sites can create SFLPs involving In3+ nearby the oxygen vacancy, which function as Lewis acidic sites, while lattice oxide O2- act as Lewis basic sites. In this study, it is discovered that the reactivity of these SFLPs can be further enhanced by single-site Bi3+ ion isomorphic substitution of Lewis acidic site In3+, thereby enhancing the propensity to activate CO2 molecules. In addition, the increased solar absorption efficiency and efficient charge separation and transfer of BixIn2-xO3 also contribute to the improved photocatalytic performance. These traits lead to enhanced binding and activation of CO2, exemplifying the opportunities that exist for atom-scale engineering in heterogeneous CO2 photocatalysis, another step towards the vision of the solar CO2 refinery.
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