JPH04314881A - Electrolytic device - Google Patents

Abstract

PURPOSE:To efficiently produce methane and the like by CO2 electrolytic reduction reaction without changing electrodes. CONSTITUTION:Hydrogen ions produced by electrolysis on the interface of a platinum plating film 4 as the positive electrode move through a proton- conductive solid electrolyte 3 to a copper plating film 5 as the negative electrode. In the film 5, hydrogen ions change into hydrogen to generate from the interface and act as the proton source.

Description

Description: FIELD OF INDUSTRIAL APPLICATION This invention relates to an electrolytic device for converting carbon dioxide gas into methane, methanol, etc. by an electrolytic reduction reaction. [0002] In recent years, global warming due to an increase in carbon dioxide gas in the atmosphere has been taken up as one of the global environmental problems.
To prevent this, attempts have been made to fix carbon dioxide gas by various methods. For example, it is known that when carbon dioxide gas is electrolytically reduced on a metal electrode, the carbon dioxide gas changes to carbon monoxide, methane, and methanol. The following conventional example is the 1990 Electrochemical Society of Japan Autumn Meeting (Proceedings P.1).
64), which is a report on the reduction of carbon dioxide gas CO2 using a Pd (palladium) electrode, which is a platinum group element and is known as a hydrogen storage metal. That is, Na
By cathodic electrolyzing in a 2SO4 aqueous solution, a Pd electrode that occluded hydrogen was heated to 0.1M NaClO4.
Reductive electrolysis was performed in a CO2-saturated aqueous solution containing 0.1M phosphate bacher, and methanol was produced with a current efficiency of 40.1%. Furthermore, methanol was similarly generated with high efficiency when a Ti (titanium) electrode that occluded hydrogen was used. The same report points out that these hydrogen storage electrodes serve as proton sources and contribute to improving methanol production efficiency. [0003] In the conventional carbon dioxide gas electrolytic reduction reaction, as described above, a hydrogen storage metal is used as a proton source supply electrode in order to increase the reaction efficiency. By the way, this hydrogen-absorbing metal captures and stores activated atomic hydrogen molecules in the gaps between the metal spoons, and there is a limit to the amount of hydrogen it can absorb. Therefore, in order to sustain the electrolytic reduction reaction of carbon dioxide gas over a long period of time, there was a problem in that the hydrogen storage metal used in the electrode had to be replaced one after another. The present invention was made to solve the above-mentioned problems, and an object of the present invention is to obtain an electrolytic device equipped with an electrode that can maintain its function as a proton source without being replaced. [Means for Solving the Problems] An electrolytic device according to the present invention includes a positive electrode and a negative electrode in a CO2 solution.
It performs an electrolytic reduction reaction, especially its negative electrode,
A positive electrode made of a porous platinum group electrode is formed on one side of a proton-conductive solid electrolyte, and a negative electrode made of a porous catalytic metal electrode for CO2 electrolytic reduction reaction is formed on the other side. [Operation] Water is decomposed on the positive electrode surface of the proton conductive solid electrolyte, and the hydrogen ions (protons) generated at this time move from the positive electrode to the negative electrode in the proton conductive solid electrolyte, and this negative electrode surface It acts as a proton source supply electrode and increases the production efficiency of methanol, etc. DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a sectional view showing the structure of an electrolysis device according to an embodiment of the present invention. In the figure, 1 is an electrolytic tank, 2
is a negative electrode, which includes a proton conductive solid electrolyte 3 in the center (for example, Nafion 117 manufactured by DuPont in the United States), a porous platinum plated film 4 formed by electroless plating on one side, and a proton conductive solid electrolyte 3. and a porous copper plating film 5 formed on the other surface by electroless plating. Then, a DC power source 6 of 1.0 to 1.5 volts is connected to use the platinum plating film 4 as a positive electrode and the copper plating film 5 as a negative electrode. 7 is a carbon electrode which is the positive electrode opposite to the negative electrode 2, 8 is a DC power supply connected between the negative electrode 2 and the positive electrode 7, and 9 is a carbon electrode that is a buffer solution containing 0.1 mol of potassium hydrogen carbonate. saturated electrolyte, 10
is a diaphragm that separates the negative electrode 2 and the positive electrode 7. Next, the operation will be explained. First, the following reaction proceeds at the interface of the platinum plating film 4, which is the positive electrode of the negative electrode 2, and water is electrolyzed to generate oxygen and hydrogen ions. H2 O→2H+ +1/2 O2 +2e- The hydrogen ions generated by this decomposition are transferred to the proton conductive solid electrolyte 3.
It moves through the interior and reaches the copper plating film 5, which is the negative electrode, and is released as hydrogen from its surface in the next reaction. 2H+ +2e- →H2 At this time, the copper plating film 5 is
When a constant current of 0.1 to 10 mA/cm2 is passed between the electrode 7 and the positive electrode 7, the CO2 dissolved in the electrolytic solution 9 is reduced on the copper plating film 5 to generate methane, methanol, ethane, etc. . That is, the copper plating film 5 acts as a proton source supply electrode, and the reaction in the above equation continues to proceed as long as a DC voltage is applied. The complexity of replacement etc. is eliminated. [0009] In the above embodiment, copper was used as the metal material of the porous catalyst electrode 5 for the CO2 electrolytic reduction reaction, but when producing aldehydes from CO2, for example, metals such as indium, tin, lead, etc. can be used. Furthermore, the metal material used for the positive electrode 4 is not limited to platinum, and other platinum group elements such as palladium may be used. Effects of the Invention As described above, in the present invention, a predetermined positive electrode and a negative electrode are formed on both sides of a proton-conductive solid electrolyte to form a negative electrode, so that hydrogen ions generated by decomposition at the positive electrode are is generated from the negative electrode through the proton-conductive solid electrolyte, and this continues to function as a proton source for the CO2 electrolytic reduction reaction. Therefore, an efficient CO2 reduction reaction can be achieved without requiring complicated electrode conversion as in the conventional method.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing the configuration of an electrolysis device according to an embodiment of the present invention.

[Explanation of symbols]

1 Electrolytic cell 2 Negative electrode 3. Proton conductive solid electrolyte 4 Platinum plating film as positive electrode 5 Copper plating film as negative electrode 6 DC power supply 7 Positive electrode 8 DC power supply 9 Electrolyte

Claims (1)

[Claims] Claim 1: A negative electrode comprising a positive electrode made of a porous platinum group electrode on one side of a proton-conductive solid electrolyte, and a negative electrode made of a porous catalytic metal electrode for carbon dioxide (hereinafter CO2) electrolytic reduction reaction on the other side. and a positive electrode serving as a counter electrode to the negative electrode, and an electrolytic device for carrying out a CO2 electrolytic reduction reaction in a CO2 solution.