Patent Application
20250084546
This application is based on and claims the benefit of priority from Japanese Patent Application No. 2023-146462, filed on 8 Sep. 2023, the content of which is incorporated herein by reference.
The present invention relates to a catalyst, a cathode, and an electrolytic device used for electrolytic reduction of carbon dioxide and/or carbon monoxide.
Conventionally, approaches aiming at mitigating or reducing influence of climate changes have been continued to be carried out, and in order to achieve the approaches, research and development for reducing carbon dioxide emission have been carried out.
Patent Document 1 describes an abrupt interface CO2 electroreduction catalyst for converting CO2 into a multi-carbon compound. The abrupt interface CO2 electroreduction catalyst includes a porous gas diffusion layer having a gas-contact side configured to come into contact with CO2 gas and allow the CO2 gas to pass toward a reaction interface side at the opposite side, and a catalyst layer disposed on a reaction interface side of the porous gas diffusion layer, covering the reaction interface side of the porous gas diffusion layer, and having an electrolytic solution-contact side configured to come into contact with an aqueous electrolytic solution. The porous gas diffusion layer is made of a hydrophobic material. The catalyst layer is hydrophilic so as to allow the aqueous electrolytic solution to pass through the catalyst layer to form a gas-liquid interface on the reaction interface side opposite to the catalyst layer, is composed of one or more metals selected to convert CO2 into the multi-carbon compound under determined electrolytic reduction conditions, and is thin enough to prevent diffusion limitations of CO2 in the aqueous electrolytic solution and enhance selectivity for the multi-carbon compound. Herein, the catalyst layer includes Cu.
Patent Document 1: PCT International Publication No. WO2018/232515
However, the abrupt interface CO2 electroreduction catalyst described in Patent Document 1 has low Faradaic efficiency of a C2 compound and/or a C3 compound.
The present invention has an object to provide a catalyst capable of improving the Faradaic efficiency of a C2 compound and/or a C3 compound.
A first aspect of the present disclosure relates to a catalyst used for electrolytic reduction of carbon dioxide and/or carbon monoxide, including copper particles supported on a surface of a diamond-like carbon particle, a part of the surface of the diamond-like carbon particle being covered with the copper particles.
A second aspect of the present disclosure relates to the catalyst as described in the first aspect, in which coverage on the diamond-like carbon particle with the copper particles is 30% or more and 70% or less.
A third aspect of the present disclosure relates to the catalyst as described in the first or second aspect, in which an average particle diameter of the diamond-like carbon particles is 5 nm or more and 50 nm or less.
A fourth aspect of the present disclosure relates to the catalyst as described in any one of the first to third aspects, in which an average particle diameter of the copper particles is 0.5 nm or more and 1.2 nm or less.
A fifth aspect of the present disclosure relates to a cathode including the catalyst as described in any one of the first to fourth aspects, the catalyst being supported on a surface of a gas diffusion layer.
A sixth aspect of the present disclosure relates to an electrolytic device including the cathode as described in the fifth aspect.
The present invention can provide a catalyst capable of improving the Faradaic efficiency of a C2 compound and/or a C3 compound.
Hereinafter, embodiments of the present invention will be described with reference to drawings.
A catalyst 10 is used for electrolytic reduction of carbon dioxide and/or carbon monoxide. The catalyst 10 includes copper particles 12 supported on the surface of a diamond-like carbon particle 11, and a part of the diamond-like carbon particle 11 is covered with the copper particles 12.
In an electrolytic reduction reaction of carbon dioxide, the number of electrons required for formation of a C2compound and/or a C3 compound is larger than the number of electrons required for the formation of a C1 compound, but in the catalyst 10, electrons are supplied to groups derived from carbon dioxide and/or carbon monoxide bonded to the surface of the copper particles 12 via the surface of the diamond-like carbon particle 11 not covered with the copper particles 12. Accordingly, a carbon-carbon bond is formed. As a result, the Faradaic efficiency of the C2 compound and/or the C3 compound is improved. On the other hand, when the diamond-like carbon particle 11 is absent, or the entire surface of the diamond-like carbon particle 11 is covered with the copper particles 12, electrons are not easily to be supplied to groups derived from carbon dioxide and/or carbon monoxide bonding to the surface of the copper particles 12. Accordingly, the carbon-carbon bond is not easily formed. As a result, the Faradaic efficiency of the C2 compound and/or the C3 compound is deteriorated. Furthermore, electrolytic reduction of water easily occurs, and the Faradaic efficiency of hydrogen is improved.
Herein, specific examples of the electrolytic reduction reaction of carbon dioxide generated by the C1 compound are shown below.
CO2+2H++2e−→CO+H2O
CO2+2H++2e−→HCOOH
CO2+6H++6e−→CH3OH+H2O
CO2+8H++8e−→CH4+2H2O
Furthermore, specific examples of the electrolytic reduction reaction of carbon dioxide generated by the C2 compound and/or C3 compound are shown below.
2CO2+8H++8e−→CH3COOH+2H2O
2CO2+12H++12e−→CH3CH2OH+3H2O
2CO2+12H++12e−→C2H4+4H2O
2CO2+14H++14e−→C2H6+4H2O
3CO2+18H++18e−→CH3CH2CH2OH+5H2O
Furthermore, the electrolytic reduction reaction of water is shown below.
2H2O+2e−→H2+2OH−
The coverage on the diamond-like carbon particle 11 with the copper particles 12 is preferably 30% or more and 70% or less, and more preferably 40% or more and 60% or less. When the coverage on the diamond-like carbon particle 11 with the copper particles 12 is 30% or more and 70% or less, the Faradaic efficiency of the C2 compound and/or the C3 compound is improved. Note here that the coverage on the diamond-like carbon particle 11 with the copper particles 12 is measured by energy-dispersive X-ray spectroscopy (TEM-EDX).
An average particle diameter of the diamond-like carbon particles 11 is preferably 5 nm or more and 50 nm or less, and more preferably 5 nm or more and 10 nm or less. When the average particle diameter of the diamond-like carbon particles 11 is 5 nm or more and 50 nm or less, the Faradaic efficiency of the C2 compound and/or the C3 compound is improved.
The average particle diameter of the copper particles 12 is preferably 0.5 nm or more and 1.2 nm or less, and preferably 0.5 nm or more and 0.8 nm or less. When the average particle diameter of the copper particles 12 is 0.5 nm or more and 1.2 nm or less, the Faradaic efficiency of the C2 compound and/or the C3 compound is improved.
Note here that the average particle diameters of the diamond-like carbon particles 11 and the copper particles 12 are measured, for example, as the average value of the Fere diameter of 100 particles arbitrarily selected from a scanning electron microscope (SEM) image.
The catalyst 10 is produced, for example, as follows. Firstly, an aqueous solution of copper acetate is prepared. At this time, the concentration of the aqueous solution of copper acetate is not particularly limited, but it is, for example, 0.05 M or more and 2 M or less. Next, an aqueous dispersion of diamond-like carbon is prepared. At this time, the concentration of the aqueous dispersion of diamond-like carbon is not particularly limited, but it is, for example, 4% by mass or more and 6% by mass or less, and pH of the aqueous dispersion of the diamond-like carbon is not particularly limited, but it is, for example, 3 or more and 4 or less. Next, the aqueous solution of copper acetate and the aqueous dispersion of diamond-like carbon are stirred using, for example, a magnetic stirrer. At this time, the mixing time is not particularly limited, but is, for example, 0.5 hours to 5hours. Next, rinsing with distilled water is carried out to settle diamond-like carbon particles the surface of which is supported by copper acetate particles, followed by drying under an inert gas atmosphere, for example, at 500° C. for 3hours. At this time, the inert gas is not particularly limited, and examples thereof include helium gas and nitrogen gas. Furthermore, annealing is carried out for 3 hours at a temperature of, for example, 500° C. or more and 1050° C. or less under a reducing gas atmosphere to obtain a catalyst 10 including copper particles 12 supported on the surface of the diamond-like carbon particles 11. At this time, the reducing gas is not particularly limited, and examples thereof include a mixed gas of argon gas and hydrogen gas.
Commercial products of the diamond-like carbon include, for example, Diamond nanopowder (manufactured by Sigma-Aldrich).
Note here that the catalyst 10 can be used for a cathode for an electrolytic device of carbon dioxide and/or carbon monoxide by disposing the catalyst 10 on, for example, a gas diffusion layer 21.
A cathode 20 includes a catalyst 10 supported on a surface of a gas diffusion layer 21.
The gas diffusion layer 21 is not particularly limited as long as it is a porous layer capable of permeating a raw material gas including carbon dioxide and/or carbon monoxide, a gas produced by electrolytic reduction of carbon dioxide and/or carbon monoxide, and hydrogen produced by the electrolytic reduction of water.
Commercial products of the gas diffusion layer 21 include, for example, Sigracet 39 BB (manufactured by SGL carbon).
Note here that the cathode 20 can be applied to well-known electrolytic devices of carbon dioxide and/or carbon monoxide.
As mentioned above, embodiments of the present invention are described, but the present invention is not limited to the above-mentioned embodiment, and can be appropriately changed within the scope of the present invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2023-146462 | Sep 2023 | JP | national |
