Visible light photoreduction of CO;using heterostructured catalysts

• US 8,986,511 B1
• Filed: 10/13/2010
• Issued: 03/24/2015
• Est. Priority Date: 10/14/2009
• Status: Expired due to Fees

• Current Assignee: US Department of Energy (Government of the United States of America)
• Original Assignee: US Department of Energy (Government of the United States of America)
• Inventors: Wang, Congjun, Matranga, Christopher, Thompson, Robert L.
• Primary Examiner(s): Raphael, Colleen M
• Application Number:
  US12/903,282
• Time in Patent Office: 1,623 Days
• Field of Search: 204/157.52, 204/157.47, 204/157.15, 205/340
• US Class Current: 204/157.15
• CPC Class Codes: B01J 23/18 Arsenic, antimony or bismuth
• CPC Class Codes: B01J 27/04 Sulfides
• CPC Class Codes: B01J 27/0573 Selenium; Compounds thereof
• CPC Class Codes: B01J 27/0576 Tellurium; Compounds thereof
• CPC Class Codes: B01J 27/14 Phosphorus; Compounds thereof
• CPC Class Codes: B01J 35/30 characterised by their physical properties
• CPC Class Codes: B01J 35/39 Photocatalytic properties
• CPC Class Codes: C07C 1/12 from carbon dioxide with hydrogen
• CPC Class Codes: C07C 29/159 with reducing agents other than hydrogen or hydrogen-containing gases
• CPC Class Codes: C07C 31/04 Methanol
• CPC Class Codes: C07C 9/04 Methane production by treatment of sewage C02F11/04; natural gas, synthetic natural gas C10L3/06
• CPC Class Codes: Y02P 20/52 using catalysts, e.g. selective catalysts

Abstract

The method provides for use of sensitized photocatalyst for the photocatalytic reduction of CO₂ under visible light illumination. The photosensitized catalyst is comprised of a wide band gap semiconductor material, a transition metal co-catalyst, and a semiconductor sensitizer. The semiconductor sensitizer is photoexcited by visible light and forms a Type II band alignment with the wide band gap semiconductor material. The wide band gap semiconductor material and the semiconductor sensitizer may be a plurality of particles, and the particle diameters may be selected to accomplish desired band widths and optimize charge injection under visible light illumination by utilizing quantum size effects. In a particular embodiment, CO₂ is reduced under visible light illumination using a CdSe/Pt/TiO2 sensitized photocatalyst with H₂O as a hydrogen source.

Claims

1. A method of photocatalytically reducing CO₂ in the presence of water comprising:

producing a sensitized photocatalyst comprised of;

a wide band gap semiconductor material, where the valence band of the wide band gap semiconductor material has a more positive potential than the redox potential of H₂O,

a semiconductor sensitizer loaded on a surface of the wide band gap semiconductor material, where the semiconductor sensitizer comprises a binary semiconductor, where the binary semiconductor is InP, GaAs, PbS, PbSe, ZnTe, CdS, CdSe, or CdTe, such that the binary semiconductor has a band gap such that visible light produces photoexcitation in the binary semiconductor, and where the valence band of the wide band gap semiconductor material has a more positive potential than the redox potential of H₂O, and where the binary semiconductor has a band gap such that the binary semiconductor and the wide band gap semiconductor material form a heterojunction at an interface between the binary semiconductor and the wide band gap semiconductor material, where the heterojunction has a type II band alignment, and where the conduction band of the binary semiconductor has a more negative potential than the conduction band of the wide band gap semiconductor material,

a co-catalyst loaded on the wide band gap semiconductor material, where the co-catalyst is comprised of a transition metal;

and exposing the sensitized photocatalyst to CO₂ and H₂O, and exposing the sensitized photocatalyst to a visible light illumination, such that some portion of the CO₂ is photocatalytically reduced and such that product molecules are produced.

2. The method of claim 1 where the co-catalyst is selected based on the composition of the product molecules.

3. The method of claim 2 where the co-catalyst is Pt and the product molecules are hydrocarbons.

4. The method of claim 2 where the co-catalyst is Fe and the product molecules are diatomic hydrogen.

5. The method of claim 2 where the binary semiconductor is a semiconductor having a direct band gap.

6. The method of claim 5 where the where the wide band gap semiconductor material is TiO₂ or ZnO.

7. The method of claim 6 where the co-catalyst is Pt, the binary semiconductor is CdSe, and the product molecules are hydrocarbons.

8. The method of claim 6 where the co-catalyst is Fe, the binary semiconductor is CdSe, and the product molecules are H₂.

9. The method of claim 1 where the wide band gap semiconductor material is TiO₂, the co-catalyst is Pt, the binary semiconductor is CdSe, and the product molecules are hydrocarbons.

10. The method of claim 1 where the wide band gap semiconductor material is TiO₂, the co-catalyst is Fe, the binary semiconductor is CdSe, and the product molecules are H₂.

11. The method of claim 1 where the wide band gap semiconductor material is TiO₂ or ZnO.

12. The method of claim 1 where the wide band gap semiconductor material is comprised of a plurality of semiconductor particles, and where the co-catalyst is comprised of a plurality of co-catalyst particles, and where the co-catalyst is loaded on the wide band gap semiconductor when at least one of the co-catalyst particles is loaded on at least one of the semiconductor particles to form a catalyzed particle, and where the semiconductor sensitizer is comprised of a plurality of sensitizing particles, and where the semiconductor sensitizer contacts the wide band gap semiconductor material when at least one of the sensitizing particles contacts the catalyzed particle.

13. The method of claim 12 where charge injection occurs from the semiconductor sensitizer to the wide band gap semiconductor material when the sensitized photocatalyst is exposed to the visible light illumination, and where the at least one of the sensitizing particles has a sensitizing particle diameter and the sensitizing particle diameter is selected based on a desired rate of charge injection, and where the at least one of the semiconductor particles has a semiconductor particle diameter and the semiconductor particle diameter is selected based on a desired rate of charge injection.

14. The method of claim 12 where the at least one of the sensitizing particles has a sensitizing particle diameter and the sensitizing particle diameter is less than 10 nm and where the at least one of the semiconductor particles has a semiconductor particle diameter and the semiconductor particle diameter is less than 50 nm.

15. The method of claim 12 where the at least one of the sensitizing particles has a sensitizing particle diameter and the sensitizing particle diameter is selected in order to produce a desired band gap of the at least one of the sensitizing particles.

16. The method of claim 12 where a diameter of a at least one of the sensitizing particles is less than 50 nm and where a diameter of the at least one of the semiconductor particles particle is less than 100 nm.