JPH04311586A - Device for electrolytically reducing carbon dioxide - Google Patents

Abstract

PURPOSE:To efficiently electrolytically reduce CO2 for a long time at the time of electrolyzing an electrolyte contg. CO2 to reduce the CO2 to CH4, etc., by irradiating the electrolyte with an ultrasonic wave. CONSTITUTION:A proton conductive solid electrolyte 3 is arranged in the electrolyte 2 saturated with 0.1mol of potassium bicarbonate as the buffer soln., and a porous Pt-plated electrode 4 as the first positive electrode is provided on the one side and a porous Cu-plated electrode 5 as the negative electrode on the other side. A carbon electrode 6 as the second positive electrode is furnished with a diaphragm 9 in between, and a DC voltage of 1.0-1.5V is impressed between the electrodes 4 and 5 to generate O2 gas on the electrode 4 by the electrolysis of water. H ion migrates in the solid electrolyte 3 and is liberated from the surface of the electrode 5, and a current is applied to the electrodes 5 and 6 from a power source 8. The CO2 dissolved in the electrolyte 2 is reduced on the electrode 5 to generate methane and ethane. In this case, the electrolyte is vibrated by an ultrasonic vibrator 10, and the formation of methane, etc., on the electrode 5 is accelerated.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrolytic reduction device for carbon dioxide, which converts carbon dioxide gas into methane, methanol, etc. by an electrolytic reduction reaction.

0002

[Prior Art] In recent years, in order to prevent global warming caused by an increase in carbon dioxide gas in the atmosphere, which is one of the global environmental problems,
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, or ethane.

[0003] Figure 3 is a quote from a report presented at the 1990 Fall Conference on Electrochemistry.
It is related to the reduction of In this figure, 0.1M
Electrolytic reduction of CO2 is performed in KHCO3 solution, and 2
This shows that methane and ethane were produced at a current efficiency of 0 to 40%.

0004

[Problems to be Solved by the Invention] In the conventional method for reducing carbon dioxide gas by electrolytic reaction, the activity of the catalytic metal electrode decreases when electrolysis is carried out for a long time, and the electrolytic reduction reaction of CO2 progresses on the surface of the catalytic metal electrode. As a result, CO2 near the electrode
Because the concentration decreased, there were problems such as a decrease in the production efficiency of ethane and ethylene.

[0005] This invention was made with the aim of solving the above-mentioned problems, and it is possible to prevent a decrease in the activity of the catalytic metal electrode, and also to reduce the concentration of CO2 in the vicinity of the catalytic metal electrode. An object of the present invention is to obtain an electrolytic reduction device for carbon dioxide that can prevent carbon dioxide from decreasing and efficiently electrolytically reduce carbon dioxide over a long period of time.

[0006]

[Means for Solving the Problems] A carbon dioxide electrolytic reduction device according to the present invention is one in which an ultrasonic irradiation means for irradiating ultrasonic waves into an electrolytic solution is provided in an electrolytic cell.

[0007]

[Operation] In this invention, the electrolytic solution is vibrated by irradiating ultrasonic waves into the electrolytic solution, thereby preventing retention of reaction products on the surface of the negative electrode and generation of a concentration gradient of CO2.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a carbon dioxide electrolytic reduction apparatus according to an embodiment of the present invention. In the figure, reference numeral 1 denotes an electrolytic cell containing an electrolytic solution 2, which is saturated with carbon dioxide gas using, for example, 0.1 mol of potassium bicarbonate as a buffer solution. 3 is a proton conductive solid electrolyte provided in the electrolytic cell 1; for example, Nafion 117 manufactured by DuPont is used. 4 is a porous platinum-plated electrode as a first positive electrode formed by electroless plating on one side of the proton-conductive solid electrolyte 3;
is a porous copper-plated electrode as a negative electrode formed by plating on the other surface of the proton-conductive solid electrolyte 3.

Reference numeral 6 denotes a carbon electrode as a second positive electrode provided in the electrolytic cell 1 as a counter electrode to the copper-plated electrode 5. Reference numeral 7 denotes a second carbon electrode for applying direct current between the platinum-plated electrode 4 and the copper-plated electrode 5. 1 a DC power source; 8 a second DC power source for applying DC between the copper plating electrode 5 and the carbon electrode 6; 9;
1 is a diaphragm provided between the copper-plated electrode 5 and the carbon electrode 6, and 10 is an ultrasonic vibrator attached to the electrolytic cell 1 as an ultrasonic irradiation means.

In the electrolytic reduction apparatus configured as described above, the first DC power source 7 is used to apply vibration to the electrolyte 2 by the ultrasonic vibrator 10, and the electrodes on both sides of the proton-conductive solid electrolyte 3 are heated. Apply voltage. That is, with the platinum-plated electrode 4 as the positive electrode and the copper-plated electrode 5 as the negative electrode, the
Apply a voltage of ~1.5 volts. As a result, electrolysis of water occurs on the surface of the platinum-plated electrode 4, oxygen is generated on the surface of the platinum-plated electrode 4, and hydrogen that has moved in the proton-conductive solid electrolyte 3 is generated from the surface of the copper-plated electrode 5. Ions are released. Therefore, the copper-plated electrode 5 acts as a proton source electrode. At this time, when a constant current of 0.1 to 10 mA/cm2 is applied between the copper plating electrode 5 and the carbon electrode 6 using the second DC power supply 8, the CO2 dissolved in the electrolyte 2 is transferred to the copper plating electrode 5.
is reduced above, resulting in the production of methane and ethane.

In such an electrolytic reduction apparatus, since ultrasonic vibration is applied to the electrolytic solution 2 by the ultrasonic vibrator 10, retention of reaction products on the surface of the copper-plated electrode 5 is prevented, and The generation of a CO2 concentration gradient near the copper-plated electrode 5 is eliminated. Therefore, for example, as shown in FIG. 2, methane and ethane are efficiently produced over a long period of time.

[0012] In the above embodiment, the copper plated electrode 4 was shown as the negative electrode, that is, the catalytic metal electrode, but other materials may be used as long as they serve as a catalyst for the CO2 electrolytic reduction reaction. Not limited. Further, the second positive electrode is not limited to the carbon electrode 6 either.

[0013]

Effects of the Invention As explained above, in the carbon dioxide electrolytic reduction device of the present invention, an ultrasonic irradiation means is provided in the electrolytic cell and ultrasonic waves are irradiated into the electrolyte, so that the electrolyte is vibrated. It is possible to prevent a decrease in the activity of the catalytic metal electrode, that is, the negative electrode, due to the retention of reaction products, and also to prevent a decrease in the concentration of CO2 near the negative electrode. The effect is that electrolytic reduction can be carried out efficiently over a period of time.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing a carbon dioxide electrolytic reduction apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram showing the relationship between current efficiency and time when methane is produced by the apparatus in FIG. 1;

FIG. 3 is a diagram showing the relationship between current efficiency and time when methane is produced by a conventional device.

[Explanation of symbols]

1 Electrolytic cell 2 Electrolyte 3 Proton conductive solid electrolyte 4 Platinum plated electrode (first positive electrode) 5 Copper plated electrode (negative electrode) 6 Carbon electrode (second positive electrode)

Claims (1)

[Claims] 1. An electrolytic cell containing an electrolytic solution in which carbon dioxide is dissolved; a first positive electrode made of a porous platinum group metal;
and a negative electrode made of a porous metal that serves as a catalyst for the electrolytic reduction reaction of carbon dioxide, and a proton conductive solid electrolyte provided in the electrolytic solution, and a proton conductive solid electrolyte provided in the electrolytic solution opposite to the negative electrode. a second positive electrode provided in the electrolytic cell;
An apparatus for electrolytically reducing carbon dioxide, comprising: ultrasonic irradiation means for irradiating ultrasonic waves into the electrolytic solution.