Electrochemical reduction of carbon dioxide
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Publication Number
US-11878279-B2
Publication Date
2024-01-23
Expiration Date
Abstract
Disclosed herein is a method for selectively reducing, using electrical energy, CO2 to formic acid, a catalyst for use in the method, and an electrochemical reduction system. The method for producing formic acid by electrochemically reducing carbon dioxide of the present invention includes (a) reacting carbon dioxide with a metal complex represented by formula (1), and (b) applying a voltage to a reaction product of the carbon dioxide and the metal complex represented by formula (1):
Core Innovation
The invention relates to electrochemical reduction of carbon dioxide (CO2) to carbon monoxide or formic acid using metal-complex catalysts. The catalytic step involves reacting CO2 with a metal complex represented by a formula that uses M1 as ruthenium or iron and defines ligand structures that form a nitrogen-containing heterocycle having a 2,2′-bipyridine structure, optionally having one to four substituents selected from alkyl, alkoxy, aryloxy, or halogen.
The method proceeds by applying a voltage to the reaction product obtained after CO2 is reacted with the defined metal complex. Selective CO or formic-acid release is obtained by voltage application to the CO2 adducts formed during the reaction of CO2 with the metal complex. CO2 adduct formation and behavior are supported by characterization such as IR spectrum, MS spectrum, and NMR spectrum.
The document further describes electrochemical CO2 reduction efficiency even at low CO2 concentration, including ambient-air level CO2. A system concept is described for producing products from CO2-containing gas, including an electrochemical cell, CO2 injection, a potentiostat, and CO discharge/detection.
Claims Coverage
The provided content includes one independent claim directed to producing formic acid by electrochemically reducing CO2 using a defined ruthenium or iron metal complex followed by voltage application. The dependent claims refine the inventive concept by constraining the electrochemical setup, CO2 delivery, CO2 concentration range, and substituent group scope.
Formic acid production by voltage-applied CO2 adduct from defined ruthenium or iron metal complex
A method for producing formic acid by electrochemically reducing carbon dioxide, comprising reacting carbon dioxide with a metal complex represented by formula (2a) wherein M1 represents ruthenium or iron; rings A and B form a nitrogen-containing heterocycle having a 2,2′-bipyridine structure optionally having one to four substituents selected from alkyl, alkoxy, aryloxy, or halogen; and applying a voltage to the reaction product.
Electrochemical cell with working and counter electrodes and negative and positive voltage application
Performing the method in an electrochemical cell with a working electrode and a counter electrode by introducing carbon dioxide into a solution containing the metal complex and applying a negative voltage to the working electrode and a positive voltage to the counter electrode.
Carbon dioxide introduced as a carbon dioxide-containing gas into solution containing metal complex
Introducing carbon dioxide into a solution containing the metal complex as a carbon dioxide-containing gas in the production method.
Specified carbon dioxide concentration range in the carbon dioxide-containing gas
Providing carbon dioxide to be reacted as a gas containing 0.03% to 100% carbon dioxide.
Substituent scope for X1, X2, and X3
Specifying that each of X1, X2, and X3 is independently an alkyl, alkenyl, cycloalkyl, cycloalkenyl, or aromatic hydrocarbon group optionally having one to three substituents selected from a defined set of functional groups.
The claim coverage centers on reacting CO2 with a ruthenium or iron metal complex defined by a 2,2′-bipyridine nitrogen-containing heterocycle and applying voltage to the reaction product to produce formic acid. Dependent claims further define the electrochemical cell arrangement, CO2 delivery as a gas, a CO2 concentration range, and the permitted substituent scope.
Stated Advantages
Electrochemical CO2 reduction proceeds efficiently even at low CO2 concentration, including ambient-air level CO2.
Selective CO/formic-acid release is obtained by applying voltage to CO2 adducts.
High faradaic efficiency for CO generation with the rhenium complex.
Selective generation of formic acid (HCOOH) using the manganese complex.
Documented Applications
Producing formic acid and CO or formic acid release from a CO2-containing gas using an electrochemical reduction system.
Operation at low CO2 concentration, including ambient-air level CO2, in the context of CO2-containing gas processing.
Electrochemical conversion of carbon dioxide to CO using a rhenium complex.
Electrochemical conversion of carbon dioxide to formic acid (HCOOH) using a manganese complex.
CO2 addition to coordinated amines in solution and with ambient air to form CO2 adduct complexes for characterization.
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