Solar powered CO2 conversion

Patent metadata

Field	Value
Publication number	US-9528192-B1
Application number	US-201313956218-A
Country	US
Kind code	B1
Filing date	Jul 31, 2013
Priority date	Jan 16, 2013
Publication date	Dec 27, 2016
Grant date	Dec 27, 2016

Abstract

Methods and devices for reducing CO 2 to produce hydrocarbons are disclosed. A device comprises a photoanode capable of splitting H 2 O into electrons, protons, and oxygen; an electrochemical cell cathode comprising an electro-catalyst capable of reducing CO 2 ; H 2 O in contact with the surface of the photoanode; CO 2 in contact with the surface of the cathode; and a proton-conducting medium positioned between the photoanode and the cathode. Electrical charges associated with the protons and the electrons move from the photoanode to the cathode, driven in part by a chemical potential difference sufficient to drive the electrochemical reduction of CO 2 at the cathode. A light beam is the sole source of energy used to drive chemical reactions. The photoanode can comprise TiO 2 nanowires or nanotubes, and can also include WO 3 nanowires or nanotubes, quantum dots of CdS or PbS, and Ag or Au nanostructures. The cathode can comprise a conductive gas diffusion layer with nanostructures of an electro-catalyst such as Cu or Co.

First claim

What is claimed is:

1. A system for converting CO 2 , to one or more hydrocarbons, comprising:
first and second photovoltaic (PV) electrodes, spaced apart and configured to provide at least one channel, defined by at least two nanostructures that are aligned approximately perpendicular to a surface of said first PV electrode, he nanostructures comprising at least one of nanotubes and nanowires, extending between the first and second PV electrodes, where at least one of the first and second electrodes comprises a conductive electrode, partly or fully transparent at a channel end, where the at least one channel receives a light beam, receives at least two H 2 O molecules and causes the at least two H 2 O molecules to dissociate into at least four H+ ions, at least four electrons, and at least one oxygen-containing molecule;
wherein the light beam has at least one wavelength in a range of at least one of 260-600 nm and 700-1500 nm;
wherein the second PV electrode also serves as a first electrochemical cell electrode (ECE) of an electrochemical cell;
a second electrochemical cell electrode (ECE), spaced apart from the first ECE and comprising an electrocatalyst that is configured to receive at least one CO 2 molecule, at least four H+ ions and at least four electrons and to reduce the at least one molecule of CO 2 to provide at least one hydrocarbon molecule that is at least one of CH 4 , C 2 H 4 and C 2 H 6 , with a total branching ratio of at least about 10 percent; and
a proton-conducting electrolyte, positioned between and connected to the first ECE and the second ECE;
wherein the second ECE has an associated positive chemical potential relative to a chemical potential of the first ECE;
wherein the second ECE comprises nanostructures comprising at least one of Cu and C, distributed over a gas diffusion layer, the gas diffusion layer comprises at least one of (i) carbon fibers and a hydrophobic binder and (ii) an intrinsically conducting polymer that comprises polythiophene;
wherein electrical charges associated with the H+ ions and with the electrons move in the electrolyte from the first ECE toward the second ECE; and
wherein the device has no battery or other source of electrical power.

2. The system of claim 1 , wherein said at least one channel comprises nanostructures comprising TiO 2 , and at least one of WO 3 , CdS, CdSe, CdTe, Au and Ag.

3. The system of claim 1 , wherein said at least one channel comprises nanostructures comprising at least one quantum dot of at least one of PbS and CdS.

4. The system of claim 1 , wherein said second PV electrode comprises carbon paper.

5. The system of claim 1 , wherein said transparent conductive electrode comprises at least one of indium tin oxide, fluorine-doped tin oxide, carbon nanotubes and graphene.

6. The system of claim 1 , wherein said second ECE comprises an electro-catalyst capable of enhancing reduction of said at least one CO 2 molecule.

7. The system of claim 1 , wherein said electrolyte comprises at least one of NAFION®, Na 2 SO 4 , KHSO 3 and KOH and has a thickness in a range of about 1-20 μm.

8. The system of claim 1 , wherein said H 2 O molecules comprise a buffered electrolyte having a pH greater than about 7.

9. The system of claim 1 , wherein said second ECE has said chemical potential that is greater than said chemical potential of said first ECE by at least about +0.5 eV.

10. The system of claim 1 , wherein said second ECE has a porosity up to about 80 percent.

11. An integrated photovoltaic cell and electrochemical cell, comprising:
a photovoltaic (PV) cell comprising first and second spaced apart electrodes and at least one light-receiving channel, which together comprise a photoanode, that receives a light beam, having at least one wavelength in a range of at least one of 260-600 nm and 700-1500 nm, where the channel receives at least two H 2 O molecules and exposes the at least two H 2 O molecules to the light beam and dissociates the at least two H 2 O molecules into at least four H+ ions, at least four electrons and at least one oxygen-containing molecule; and
an electrochemical cell, comprising the second electrode and a third electrode, spaced apart from each other by a proton-conducting electrolyte, where the third electrode has an associated positive chemical potential ΔCP relative to the second electrode and the third electrode is configured to receive at least one CO 2 molecule and to permit the at least one CO 2 molecule to interact with the H+ ions and the electrons, and to thereby become reduced, and to produce at least one hydrocarbon,
wherein operation of the integrated photovoltaic cell and electrochemical cell does not use a battery or equivalent source of electrical power; and
wherein said third electrode comprises at least one of Cu nanoparticles and Co nanoparticles, which are passivated with at least one of polyvinylpyrrolidone (PVP) nanoparticles, Au nanoparticles and Ag nanoparticles.

12. The integrated cells of claim 11 , wherein said first electrode comprises TiO 2 nanostructures, doped or impregnated or coated with at least one of WO 3 , ZnO, CdS, CdSe, CdTe, Au nanoparticles, Ag nanoparticles, PbS quantum dots and CdS quantum dots.

13. The integrated cells of claim 11 , wherein said at least one hydrocarbon molecule produced comprises at least one of CH 4 , C 2 H 4 and C 2 H 6 .

Assignees

• The Us Administrator Of The Nat Aeronautics & Space Administration (Nasa)
• Nasa

Inventors

• Chen Bin

Classifications

• C25B3/04

  Chemistry & Metallurgy · mapped topic

• C25B9/18 Primary

  Chemistry & Metallurgy · mapped topic

• C25B1/003

  Chemistry & Metallurgy · mapped topic

• C25B3/25 Primary

  Reduction · CPC title

• C25B1/55

  Photoelectrolysis · CPC title