JPS5940473A - Electrochemical power generating element made of acid electrolyte - Google Patents

Abstract

PURPOSE:To safely operate an electrochemical power generating element over a long period of time by partitioning a gas passage provided on a negative electrode with bank parts, providing closed grooves on the partitioning banks, and filling said grooves with paste from an electrolyte supply source. CONSTITUTION:In a porous carbon negative electrode substrate 10 bearing a negative electrode catalytic layer 5, outward and inward passages 11 for active material gas are partitioned with banks, and closed grooves 15, 16 are provided on these partitioning banks. Said closed grooves 15, 16 are filled with replenishing electrolyte paste 31 obtained by blending and kneading the heat resistant and phosphatic inorganic material fine powder and concentrated phosphoric acid. A unit power generating element is formed by allowing said negative electrode and the positive electrode of a substrate 20 bearing a positive electrode catalytic layer to face via an electrolyte matrix layer 6 and be closely united in a body. This electrochemical power generating element of acid electrolyte is excellent in its electrolyte bearing capability and durability.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to an electrochemical power generation element having an acidic electrolyte, using a gas mainly composed of hydrogen as a negative electrode active material, and using oxygen (air) as a positive electrode active material. The improvements include acid electrolyte electrochemical power generation that allows the reaction to proceed efficiently, maintains a high utilization rate of the negative electrode active material, and further enhances the electrolyte retention capacity to maintain commercial performance over a long period of time. Regarding elements.

[Technical background of the invention]

Gases that are easily converted to M such as hydrogen and oxidizing power such as oxygen Ω
An electrochemical power generation device that combines certain gases through an electrochemical reaction process and supplies the released free energy of the cast as DC power is an excellent power generation device with high efficiency, low noise, and low emissions that cause pollution. It is well known in the art that

The main unit of such a power generating element is generally made of porous carbon, which serves as the positive electrode, with an impregnated material layer having excellent chemical resistance, heat resistance, and oxidation resistance in the middle containing an electrolyte such as a concentrated sulfuric acid solution or a concentrated phosphoric acid solution. The plate and a porous carbon plate serving as a negative electrode are closely integrated with each other to form a unit power generation element. These electrodes are still coated with catalysts such as platinum and waterproofed with polytetrafluoroethylene to facilitate the reaction. However, in these power generating elements, even if the starting force of the unit element is high, it is 1v%.
To construct a practical power generation device, it is necessary to laminate tens or hundreds of elements.

One known method is to use a high-density grooved conductive carbon plate.

Gas flow passages in different directions are provided on the upper and lower surfaces of one conductive carbon plate, respectively, and the upper surface of P1 is in contact with the porous carbon plate forming the positive electrode (or negative electrode) of one power generation element. The lower surface is in contact with the porous carbon plate forming the negative electrode (or positive electrode) of the next power generating element, and the power generating elements are laminated, and each power generating element is connected via the groove of the laminated element. A reaction gas is supplied to the reactor, and reaction products are removed.

[Problems with background technology]

In the power generation element, in order to maintain a stable electromotive reaction over a long period of time while maintaining a high oil usage rate of the negative electrode active material, it is necessary to supply a sufficient amount of reaction gas to the electrode surface and to quickly release the reaction products. It is necessary to remove the

Furthermore, in order to maintain high power generation efficiency, it is important to ensure high electrode reactivity and to reduce ohmic loss inside the battery as much as possible.

The gas used for the negative electrode active material generally contains 60 to 90% hydrogen.
In many cases, hydrogen containing carbon dioxide gas and water vapor is used, but it is desired that this hydrogen be used efficiently as a power generating element.

In the oxidation of hydrogen by electrochemical reaction at the negative electrode, it is desirable that the path through which hydrogen participates in the reaction be as long as possible. For this purpose, it is effective to cause the reactive gas to return to a part of the electrode surface. However, in this gas flow, if the outgoing and returning paths are not completely separated, gas with a large hydrogen component will mix into the returning path midway, causing a decrease in the hydrogen utilization rate.

In addition, the ohmic loss of the electrolyte layer varies greatly depending on the amount of electrolyte in the matrix, so by storing electrolyte in addition to the electrolyte-retaining matrix layer, there is always enough electrolyte in the electrolyte layer even during long-term power generation. It is desirable to be able to maintain a state in which

However, in conventional electrochemical power generation devices that use graphite fiber thin plates as electrode bases, it is difficult to provide the electrode base with a function to separate the reactant gas into the outbound and return routes, and in the case of U-turn flow, a separator is installed on the interconnector side. 4411 had no choice but to be equipped. For this reason, the processing of the interconnector became costly and was an obstacle to the practical implementation of the fuel oil pond-based 1i plant.

Further, in the conventional power generation element, it is difficult to retain the electrolyte solution outside the IJ layer (electrolyte holding layer), and there is also a problem that it cannot withstand long-term operation.

[Purpose of the invention]

An object of the present invention is to provide an electrochemical power generating element that is highly efficient and capable of stable operation for a long period of time.

[Summary of the invention]

Specifically, by using a grooved porous carbon plate that serves as a gas flow path in the base of the negative electrode that constitutes the unit power generation element, the bank of the gas flow path not only maintains the electrolyte storage function, but also In order to smoothly proceed with the electrode reaction, a U-turn flow is adopted for supplying the negative electrode active material gas, and a dividing bank is provided to separate the outbound and return routes. Note that crossing grooves may be provided in the left and right groove groups of this partition bank, respectively, to make the gas flow uniform. A closed groove is provided in this partition bank, and this groove is filled with a paste of heat-resistant phosphoric acid inorganic material powder and concentrated phosphoric acid to serve as a replenishment source for the electrolyte. Note that Teflon may be added to this paste to give it binding properties.

Furthermore, if a closed groove is also provided on the bank at the end parallel to the gas flow groove and filled with paste for electrolyte replenishment,
Replenishment of electrolyte becomes easier, and low internal resistance can be maintained for a long period of time. Note that the bottom and side surfaces of the gas flow groove are preferably coated with a porous fluororesin membrane in order to facilitate the electrode reaction. Further, it is necessary to form a catalyst layer containing a platinum metal element on the back side of the groove surface in order to promote the electrolytic reaction. Electrochemical power generation consists of a negative electrode constructed in this way, a positive electrode using a thin substrate with a short diffusion path to support an electrode catalyst layer and easy gas permeation, and an acidic solute layer. It provides an element.

In addition, in the power generating element, a highly porous and thin carbon substrate must be used for the positive electrode. Particularly in power generation elements that use air as an oxidizing agent, the oxygen that can be used as an active material in the power generation element is about 20% in the atmosphere.
In addition, it only occupies q6, and its liquid content is higher than that of hydrogen, which is the negative electrode active material, so it faces strong resistance to diffusion. Furthermore, since most of the water produced by the electromotive reaction is removed via the positive electrode, it is important that the positive electrode allows gas to diffuse more easily than the negative electrode so as not to impede the permeation of the water.

Therefore, the present invention provides a power generation element that is improved so that the negative electrode side has an electrolyte storage effect, which has a relatively small burden on the permeation of the reactant gas.

In addition, since the electromotive force of a unit power generation element is at most about IV, a large number of power generation elements are used in a full-scale power generation unit by stacking them using electrically conductive laminated Ifi elements that have a positive electrode gas passage. .

In order to maintain a constant shape, the power generating element group is stacked and crimped and fastened together, but the electrode substrate on the negative electrode side of each unit element acts as a compressive force absorbing damper and mechanically adheres, resulting in fastening. Pressure is uniformly distributed among all units, and good electrical connection is maintained between the unit power generating elements and the laminated elements.

It is desirable that an electrochemical power generation element using a gas as an active material adopt a square or rectangular shape so that gas can be easily supplied and reaction products can be easily carried out.

[Embodiments of the invention]

An embodiment of the present invention will be described. Bulk specific gravity is 0.28~0
．． A porous graphite plate having a thickness between 78 and 2 to 4 mm, such as a felt-like carbon fiber board or a carbon fiber sheet board, or a sintered porous board whose main component is fibrous graphite, takes part in the electrode reaction. Gas supply width 1.2-2.5yu
A substrate formed by cutting grooves with a depth of 1.5 to 2.5 mm at a pitch of 4 to 5 mm is used as the negative electrode substrate. The end portion of this base body parallel to the groove has a width of 2.5 to 7.5 +++ m and a depth of 1.0 to 2.0 m. Provide Omyrt's closing groove. Furthermore, in order to improve the utilization rate of the negative electrode active material, it is effective to cause the negative electrode active material gas to flow in a U-turn. This U
When making a turn flow, a thick bank is provided to separate the outward and return paths, and a closed groove is also provided in this bank.

The left and right banks of the partition bank of the U-turn flow may be provided with grooves, respectively, in order to ensure a uniform flow of gas.

In addition, a porous fluororesin film such as tetrafluoroethylene is formed on the bottom and side surfaces of the grooves that form the gas flow path, and a catalyst layer is formed on the surface where the grooves are not provided to promote the electrode reaction. to form a negative electrode. This negative electrode and a carbon fiber sheet positive electrode supporting a positive electrode catalyst layer impregnated with M suspension of fluororesin and subjected to waterproof treatment are mixed with concentrated phosphoric acid in inorganic fine powder such as silicon carbide, tantalum oxide, and zirconia. (relaxant ma) impregnated with
A unit power generation element is formed by closely integrating the catalyst surfaces with the IIJx layer interposed therebetween so that they face each other.

Furthermore, fine powders of silicon carbide, tantalum oxide, zirconia, etc. or their phosphates are used alone or in combination, and after kneading concentrated phosphoric acid,
After filling the closed groove of the negative electrode, the bulk density is 1.6 to 1.
．． 95, phenolic resin is blended with graphite powder with a thickness of 3 to 6 mm, pressure molded, and one side has a width of 1.2 to 1.5 mm.
A groove with a depth of 1.3 to 2.5 mm is 4 to 6 m in urn.
Using laminated elements arranged at m pitches, the laminated elements and unit power generation elements are alternately stacked with the grooves acting as gas flow paths placed on the side in contact with the positive electrode of the laminated elements to generate power. form a unit. In a power generation unit constructed using this method, a portion of the electrolyte is not only stored on the bank of the negative electrode gas flow path, but also sufficiently stored in the closed groove, so that the electrolyte concentration in the matrix layer remains constant for a long time. It was uniform over a period of time, and almost no deterioration in performance over time due to ohmic loss in the electrolyte layer of the power generation element was observed.

The present invention will be explained using figures.

In the figure, the oxidant gas is flowing in the direction of B-B',
The reducing gas is flowing in the direction of A"→A"' via A-+A'. Closed grooves 15 and 16 for filling electrolyte paste for replenishment are provided, and reducing gas passages 11 waterproofed with fluororesin are provided on the side and bottom surfaces, and the thickness is 2 to 4. A negative electrode formed by supporting a negative electrode catalyst layer 5 on a porous carbon negative electrode substrate 10 and a fluororesin such as tetrafluoroethylene supporting a positive electrode catalyst layer that promotes the reaction of an oxidizing agent have a thickness Q. , a carbon fiber paper substrate of about 4 mm, that is, a positive electrode of a porous carbon fiber positive electrode substrate 20, and an electrolyte matrix in which powder of silicon carbide, tantalum oxide, zirconium oxato, etc. is impregnated with a concentrated phosphoric acid solution).
They are closely integrated with each other with the catalyst surfaces facing each other via the IJx layer 6 to form a unit power generation element. The closed grooves 15 and 16 are filled with a kneaded paste of a mixture of silicoco/carbide, tantalum oxide, zirconia fine powder, or zirconium phosphate powder and concentrated phosphoric acid solution. After filling the replenishing electrolyte 31, the B-B' force direction oxidizing gas flow path 2 is used to stack the unit power generating element groups.
A laminated element substrate 21 made of a carbon material is used, and the two are alternately stacked to form an electrochemical power generation unit. Note that the laminated element substrate 21 is formed of an air-liquid-tight conductive carbon plate.

Felt-like charcoal fiberboard with a bulk specific gravity of 0.52 to 0.56 and a thickness of 2.5 mm on both sides close to the closing edge and on banks with a width of 10 mm separating the U-turn flow of the negative electrode active material. A closed groove with a width of 5 mm and a depth of 1.5 mm is provided, and parallel to this groove there is a gas passage groove with a width of 1.5 mm, a width of 3.5 mm and a depth of 2 mm, and a gas passage groove with a width of 1.5 mm and a depth of 2 mm. The bottom surface of the gas flow groove of the electrode substrate with 9 grooves cut into it.

After coating the side surface with 10% polynato 2 fluoroethylene desverge solution and drying it, a layer of platinum catalyst supported on activated carbon was applied to the side without grooves, and then a layer of silicon carbide of several microns was applied. 5 Qwt% to 40wt%
A unit power generation element was formed using a paste prepared by kneading 105% phosphoric acid solution as a pacifier, and the closed groove was filled with a paste containing 40 wt% silicon carbide and 60 wt% 105% phosphoric acid solution. , the change in internal resistance per unit element of the stacked power generation unit over time is shown in Table 1.
As shown in Example 1, compared to the conventional power generation element using a rigid laminated element with grooves on both sides, which was manufactured for comparison, there was no change over a long period of time and stable performance was maintained. it is obvious. The electrode catalyst is platinum supported on activated carbon for both the negative and positive electrodes, and the amount applied is 0.6 m for the positive electrode.
Warm 2. The negative electrode is 0.3''/, L2.

Furthermore, as the negative electrode active material, 75 mol of hydrogen was used.

A mixed gas of 15 mol of carbon dioxide and 10 mol of water vapor was used, air was used as the positive electrode active material, and the temperature was 200°C + 2-5".
/cm2a, current density 250mA/, and continuous power generation at L2, as shown in Table 2, the terminal potential decreases little, and the power generation element according to the present invention has extremely superior performance compared to conventional power generation elements. have.

A second example was prepared in which the porous graphite plate used in the above example was constructed as follows and other things were the same, that is, chip-shaped graphite powder was kneaded with pulp material and a polyvinyl alcohol binder and heated to 1800''C. Bulk specific gravity 0.48 sintered with
A groove of width 1.8 * m depth 1.6 city pitch 4 was provided on a sintered porous plate with a thickness of ~0.56 and 2 mm, cross grooves of the same shape were provided every 20 cm, and a width 5 mm depth 1.5
A closed groove of m11I was provided, and it was filled with a paste prepared by kneading fine zirconium phosphate powder with a diameter of microns and phosphoric acid with a concentration of 100% in a weight ratio of 1 = 2, and the other parts were the same as the first groove. As shown in Tables 1 and 2, similar to the first example, the results were superior to the conventional type, and similar problems did not occur even when the power generating elements were stacked and fastened.

〔Effect of the invention〕

As shown above, the power generating element of the present invention is superior in performance, mechanical properties, and durability compared to conventional power generating elements. Similar Tib Table 1 Change in internal resistance of the power generating element of the present invention over time (200°C) Table 2 Change in potential during discharge of the power generating element of the present invention (200°C
) 2.5kli/crn2G 250re-10n
It is 2.

5... Negative electrode catalyst layer 6... Electrolyte matrix layer 10... Negative electrode 11 Negative electrode gas flow path 12.
14...Closed groove closing wall 15.16 Closed groove 13 - Wad! ll groove 20・
...Positive electrode 21...) Responsible element, 1 element 22
・Cathode active material flow path 31...Replenishment electrolyte paste Agent Patent attorney Norichika Kensuke (and one other person)

Claims (2)

[Claims] (1) In a military chemical generator that generates electricity by using hydrogen-based gas as the negative electrode active material and oxidizing gases as the positive electrode active material, the active material gas flows back and forth through the negative electrode. It is composed of a bank to separate the outbound and return paths, and a porous carbon plate with a group of gas channels parallel to the bank, and a closed groove in the partition bank. Acidic electrolyte electrochemical power generation characterized in that the IJ layer is filled with a paste of heat-resistant phosphoric acid-resistant inorganic material fine powder and concentrated phosphoric acid to replenish the electrolyte. element. (2) Acidic electrolyte electrochemistry according to claim 1, characterized in that closed grooves are provided in the banks at both ends parallel to the grooves of the negative electrode and filled with electrolyte paste for replenishing the electrolyte. Power generation element.