JP2003213472A - Electrode for electrochemical conversion of carbon dioxide into hydrocarbon gas - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To use a Cu-Sn-P alloy as a working electrode for producing, with high current efficiency, hydrocarbon gases relatively insoluble in aqueous solution, such as methane and ethylene, as substitutes for petroleum in electrochemical reduction of carbon dioxides. <P>SOLUTION: For the purpose of producing hydrocarbon gases relatively insoluble in aqueous solution, such as methane and ethylene, with high current efficiency in the electrochemical reduction of carbon dioxides, it is necessary to allow the adsorption of CO to occur simultaneously with the generation of hydrogen by water electrolysis on an electrode used. In order to solve this problem, copper is alloyed with heteroatoms to change the surface energy of the electrode and control the CO adsorption and the hydrogen generation by water electrolysis. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to electrochemical immobilization of carbon dioxide.

[0002]

2. Description of the Related Art Conventionally, in order to produce a hydrocarbon gas by converting carbon dioxide by electrolytic reduction, copper of good purity has been used as an electrode. Moreover, the sum of the current generation rates of methane and ethylene was 63.1%, and the total current generation efficiency of gases by electrolytic reduction of carbon dioxide, which was easy to separate from the electrolytic solution, was 67%. In addition, the production of hydrogen at this time was 82%, and the others were soluble in water such as formic acid and ethanol.

[0003]

When carbon dioxide is electrolytically reduced by a copper electrode to be converted into hydrocarbon, carbon monoxide (CO) is produced as a reduction intermediate product of carbon dioxide and is adsorbed on the copper electrode. To do. The amount of adsorption is important and therefore
It is necessary to control that amount. For that purpose, it was necessary to alloy with copper and a dissimilar metal to increase the adsorption of CO.

[0004]

The relationship between CO and metal surface energy is important in order to increase the amount of CO adsorbed. Therefore, an attempt was made to solve the adsorption problem between CO and the metal electrode by alloying copper and a heteroatom.

[0005]

DETAILED DESCRIPTION OF THE INVENTION Hydrogen is required to convert carbon dioxide into hydrocarbons by electrolytic reduction of carbon dioxide. In this case, it is desirable that the potential at which CO is adsorbed on the copper electrode is close to the hydrogen generation potential due to the electrolysis of water. It can also be said that a balance between the amount of CO adsorbed on the electrode and the amount of hydrogen generated is necessary. Optimizing these relationships is important for immobilizing carbon dioxide to hydrocarbon gases.

[0006]

The present invention will be described in more detail by way of examples, which should not be construed as limiting the invention thereto.

Example 1 Pulsed electrolysis was applied, and cathode potential (Ec) =-2100 mV vs. Cu / Sn / P (phosphor bronze) using 0.1 MKHCO ₃ as an electrolyte. The anodic potential (Ea) was changed with Ag / AgCl, and the production current efficiency of gases such as methane and ethylene was measured. The result is shown in FIG.
As can be seen from FIG. 1, Ea = −900 mV vs. Ag /
In AgCl, the maximum value of both was 68.7%. At this time, the current generation efficiency of methane was 61.6% and the current generation efficiency of ethylene was 7.1%. In this case, if the anode potential is from -500 mV to -900 mV, the conventional value, the sum of methane and ethylene production efficiency is 63.1%.
It shows a higher value.

Example 2 Pulse electrolysis was applied, using 0.1 MKHCO ₃ as an electrolyte and Cu / Sn / P (phosphor bronze) as the cathode potential (Ec) =-2100 mVvs. By changing the anode potential (Ea) with Ag / AgCl, together with methane and ethylene,
Hydrogen and carbon monoxide were measured. In this way, the total efficiency of methane, ethylene and CO generated current was 75% or more. Conventionally, the production current efficiency of the above-mentioned three kinds of gases was 67%, and the total production current efficiency of gases containing hydrogen was 95% or more. Others, such as formic acid and ethanol, are soluble in water. This means that the gases can be easily separated from the electrolytic solution, so that the electrolytic solution can be used for a long time without replacement.

Example 3 Similarly, pulse electrolysis was applied to Cu / Ag and Cu having different concentrations of three kinds of Cu in 0.1 MKHCO ₃ .
/ Ni, Cu / Zn, Cu / Be, the cathode potential (Ec) is -1650 mV vs. From Ag / AgCl-
2200 mV vs. The anodic potential (Ea) from -50 mV to -700 mV vs. Ag / AgCl. Ag / A
The production efficiency of hydrocarbons such as methane and ethylene was measured while changing to gCl. FIG. 2 shows a plot diagram of the maximum production current efficiency of methane and ethylene with respect to the copper content in each alloy. However, since the maximum production efficiency potentials of methane and ethylene are different, the sum of the production current efficiencies of methane and ethylene is smaller than the sum of methane and ethyl in this figure at the same potential. It is naturally smaller than the value of 68.7%.

[0010]

Industrial Applicability The present invention contributes to the prevention of global warming by fixing carbon dioxide to carbon dioxide with high current efficiency, and provides a petroleum substitute. According to the literature, the production current efficiency of methane and ethylene when the copper electrode is used is 63.1, which is considerably smaller than when the Cu / Sn / P electrode of the present invention is used. Among the products other than these, there are water-soluble components such as ethanol and formic acid. These increase with electrolysis time, and as a result, they undergo an electrode reaction or cause an increase in the resistance of the electrolytic solution, which lowers the current efficiency of the hydrocarbon gas, so that it is necessary to replace the electrolytic solution frequently. Considering these matters, it is necessary to produce a large amount of water-insoluble substances, and the effect of the present invention is great.

[Brief description of drawings]

FIG. 1 Cathode potential-21 at Cu / Sn / P electrode
00 mV. Graph showing the relationship between the anodic potential and the generation current efficiency of methane, ethylene, carbon monoxide and hydrogen in Ag / AgCl.

FIG. 2 is a graph showing the relationship between the copper content rate in various copper alloys and the production current efficiency of methane and ethylene.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Miyuki Kawanami             1-1-1 Kazumigaoka, Higashi-ku, Fukuoka City Fukuoka Women             Inside the university (72) Inventor, Brush Tanaka             1-1-1 Kazumigaoka, Higashi-ku, Fukuoka City Fukuoka Women             Inside the university (72) Inventor Makoto Aihara             1-1-1 Kazumigaoka, Higashi-ku, Fukuoka City Fukuoka Women             Inside the university F-term (reference) 4K011 AA68 DA10                 4K021 AA09 AC02 BA17 BB03 DA13

Claims (2)

[Claims] 1. An all-hydrocarbon gas-immobilized electrode. 2. A carbon dioxide conversion electrode having a production current efficiency including claim 1 and a CO production current efficiency of 75% or more.