RU2628760C1 - Electrochemical solid state fuel cell - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: fuel cell includes a housing 1, a gas-liquid path 2, electrodes 3 that can be made of activated carbon or carbon fibre or porous graphite and impregnated with a 20-60% aqueous solution of the heteropolyacid of 2-18 type of the H₆[P₂W₁₈O₆₂], are compressed on both sides by perforated metal plates 4 of stainless steel or chromium, or nickel, or copper with aperture diameter of 0.5-10 mm, which in turn can be made on the sides of the housing made of an inert dielectric material, the perforation is designed so that the holes in the housing are opposite the holes in the metal perforated plates of the electrodes. Two electrodes are placed in the housing opposite each other with a gap of 5-100 mm, through which the gas path 2 passes for supply and discharge of liquid or gas. Electrical terminals 5 and 6, which form a combined anode and a combined cathode, are attached to the metal plates of the electrodes 4.

EFFECT: expanding the range of used types of fuels, both liquid and gaseous, high cell efficiency, increasing the service life, simplicity in manufacturing and maintenance.

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Description

The invention relates to methods for the direct conversion of chemical energy of fuels into electrical energy using 2-18 rows of tungsten heteropoly acid as an active component and devices for their implementation. It can be used for the manufacture of fuel cells, which in turn can be used to create mobile and stationary sources of electrical energy.

Known electrochemical generator based on solid oxide fuel cells, including a housing, a chamber for mixing methane and air, a chamber for partial oxidation of methane, a chamber for electrochemical oxidation of fuel with a battery of fuel cells, and a chamber for surviving fuel (RU No. 2474929, publ. 02.10.2013). The methane partial oxidation chamber contains a plurality of tubes fixed to the tube plate with a methane partial oxidation catalyst deposited on their outer surfaces. Fuel cells in the form of tubes with open ends are coaxially connected to the tubes of the partial oxidation chamber. The survival chamber contains a set of perforated plates coated with a surviving catalyst. A catalyst for oxidizing fuel in excess of air is deposited on the inner surface of the tubes of the partial oxidation chamber.

This invention is designed to use methane as a fuel, operates at high temperatures, has a complex structure with a laborious method of its manufacture, which is its disadvantages.

A known method of manufacturing a catalytic electrode based on heteropoly compounds for hydrogen methanol fuel cells, including the manufacture of a composite catalyst based on heteropoly compounds and an active catalytic layer based on it with the addition of a hydrophobizing additive (RU No. 2561711, publ. 09/10/2015). The catalytic electrode is a porous nanostructured composite layer with a thickness of 5-15 μm, consisting of: a catalyst - a composite of a proton conductive heteropoly compound in the form of cesium salt of phosphoric tungsten acid and an electrically conductive additive of carbon material or doped tin dioxide, on which particles of a catalytic metal of a platinum group are chemically supported an average size of 3 nm, as well as 5-20% water repellent, preferably polytetrafluoroethylene. The content of the noble metal in the composite catalyst is from 5 to 30 wt. %, conductive components from 2 to 30 wt. %

Electrochemical fuel cells based on such electrodes are difficult to manufacture, noble metals with a high percentage are used as catalytically active materials, which leads to an increase in the cost of the product, and for the same reason, limits the life of the cell due to poisoning of the catalytically active components by contaminants, which can be contained in industrial hydrogen and methanol, which increases the requirements for fuel purity. Also, the proposed method limits the use of other liquid gaseous components due to the same poisoning of catalytically active substances.

Closest to the claimed technical solution is a fuel cell based on modified polyaniline with an efficiency of up to 90% and the possibility of using both gases and liquids as fuel (RU No. 144526, published on 08.27.2014). The fuel cell contains a housing that is simultaneously a cathode (made of copper, or titanium, or stainless steel, or aluminum), in the center of which is located an anode made in the form of a pipe having through holes 0.3-0.7 mm in diameter and located one another from each other with a pitch of 7 mm both horizontally and vertically, and on which a layer of modified conductive polyaniline is applied to the outer and inner sides by potentiostatic cycling. The anode is connected on one side to a tube for supplying liquid or gaseous fuel or air, and on the other hand, to a discharge tube for unreacted fuel, in addition, on the other hand, a tube for supplying air is placed in the housing, and on the opposite side is a tube for supplying air or liquid fuel, depending on the operating mode of the fuel cell, and a drain pipe is installed in the housing to change the unreacted liquid fuel. Current collectors are installed between the body and the metal parts of the anode.

It is known that fuel cells have different designs depending on the chemical and physical properties of the gas or liquid that are used as fuel.

The anode can be made of a dielectric material, on which a layer of one of the metals: chromium, gold, platinum, nickel, stainless steel, lead or graphite is sprayed on both sides, internal and external.

Additionally, in the case of using reducing gases — carbon monoxide or hydrogen, or a mixture of them — as fuel, an electrolyte is poured into the casing, which is a 0.5-1.0 molar aqueous solution of heteropoly acid of the 2-18 row having the chemical formula H ₆ [ P ₂ W ₁₈ O ₆₂ ] and which, for a better gas oxidation process, is saturated with oxygen by supplying air through an air supply pipe and / or air or liquid fuel supply pipe.

Additionally, in the case of using liquid fuel, an aqueous solution of ethanol, methanol or ammonia is poured into the housing.

Fuel cells are not of a simple design and are very difficult to manufacture. The use of liquid electrolyte greatly limits the use of various substances, for the same reason, the cell is inertial. When assembling fuel cells into the battery, it is necessary to create complex schemes for uniform fuel supply, which increases the overall dimensions of the product. The use of liquid electrolyte limits the operational use of this product. The use of a conductive polymer in aqueous solutions due to degradation of the latter limits the service life.

The problem to which the claimed invention is directed, is the creation of an electrochemical solid-state fuel cell for generating electricity of a simplified design without the use of expensive catalytically active materials and ion-separation membranes, where gaseous and liquid substances can be used as fuel.

This problem is solved due to the fact that the electrochemical solid-state fuel cell, including the housing 1, the electrodes 3 located therein, a gas-liquid path 2 used as the main catalytic substance, an aqueous solution of heteropoly acid 2-18 series H ₆ [P ₂ W ₁₈ O ₆₂ ] has two electrodes that can be made of activated carbon, carbon fiber, porous graphite, impregnated with a 20-60% aqueous solution of heteropoly acid H ₆ [P ₂ W ₁₈ O ₆₂ ], crimped on both sides with perforated metal plates 4 with a hole perforation diameter holes 0.5-10 mm, which can be made of stainless steel, chromium, nickel or copper, are placed in the housing 1, which can be made of inert dielectric materials and has perforations on the sides with a diameter of 0.5-10 mm in this way so that the holes in the housing are located opposite the holes in the metal perforated plates of the electrodes with a gap of 5-100 mm, through which the gas path 2 for supplying and discharging liquid or gas passes, and the electrical leads 5 and 6 are attached to the metal plates of the electrodes 4, forming bine combined anode and cathode.

The technical result provided by the given set of features is to expand the range of used types of fuels, both liquid and gaseous; high cell efficiency; increase the service life of the work; simplicity in manufacturing and maintenance.

The essence of the utility model is illustrated by drawings:

In FIG. 1 shows a general view of an electrochemical solid fuel cell, where 1 is a plastic dielectric body; 2 - plastic insert (gas-liquid path); 3 - porous carbon plate electrodes; 4 - perforated metal plates; 5 - electrical output of the combined anode; 6 - electrical output of the combined cathode; 7 - resistor; 8 - voltmeter.

The claimed electrochemical solid-state fuel cell includes a housing 1, a gas-liquid path 2, the use of an aqueous solution of a heteropoly acid of row 2-18 having the chemical formula H ₆ [P ₂ W ₁₈ O ₆₂ ], contains electrodes 3 of a thickness of 1-5 mm, which can be made of activated carbon, carbon fiber, porous graphite and impregnated with a 20-60% aqueous solution of heteropoly acid having the chemical formula H ₆ [P ₂ W ₁₈ O ₆₂ ], and crimped on both sides with perforated metal plates 4 with a hole perforation diameter of 0.5-10 mm which in their turn The core can be made of stainless steel, chrome, nickel or copper, and on the sides of the housing 1, which should be made of an inert dielectric material, such as fluoroplastic, plexiglass, polyethylene or various types of plastic, perforation is made with a diameter of 0.5 -10 mm so that the holes in the housing are opposite the holes in the metal perforated plates of the electrodes. Two electrodes 3 are placed in the housing opposite each other with a gap of 5-100 mm, through which a plastic insert passes - a gas path 2 for supplying and discharging liquid or gas. Electrical terminals 5 and 6 are attached to the metal plates of the electrodes 4, forming a combined anode and combined cathode.

The electrochemical fuel cell operates as follows. Gaseous or liquid fuel is passed through a gas-liquid path 2, which is oxidized by external oxygen, which in turn penetrates through the perforated holes in the housing and through the perforated holes in the metal plates of the electrodes. When an easily oxidizable liquid or gas is passed through the gas path, the anionic complex of the heteropoly acid of row 2-18 located in the porous carbon layer is restored and due to the capture of electrons from the oxidizable liquid or gaseous substance. Accordingly, the anionic complex of the heteropoly acid [P ₂ W ⁺⁵ O ₆₂ ] ^24- , in contact with, for example, hydrogen gas, is charged negatively during the redox reaction and charges negatively contacting internal plates of stainless steel, i.e. anode 5. However, the oxidation state of tungsten +5 is very unstable, therefore, from the side of the outer plates on the cathode 6, through which air oxygen enters, the reverse process of oxidation of the anionic complex [P ₂ W ⁺⁵ ₁₈ O ₆₂ ] ^6- to the initial state corresponding to oxidation state of tungsten +6.

As a result of such a redox reaction, a potential difference arises between the cathode and the anode. If between the electrodes 5 and 6 to establish an electrical load 7, then the current will flow through the circuit, respectively, there is an EMF.

Example. The use of hydrogen gas and an aqueous solution of ammonia as fuel in an electrochemical cell.

A 50% aqueous solution of a tungsten heteropoly acid of row 2-18 having the chemical formula H ₆ [P ₂ W ₁₈ O ₆₂ ] was prepared. Two identical plates of porous graphite with overall dimensions of 10 × 10 × 1 mm were impregnated with the prepared solution. The carbon plates thus prepared are sandwiched between perforated metal nickel plates 4 with a perforation diameter of 1.5 mm. Next, the manufactured electrodes were placed in a plastic case 1, on the sides of which a perforation with a diameter of 1.5 mm was also made, and the holes in the plastic case were combined with holes in the metal plates. The resulting gap between the electrodes was 7 mm. Then, a gas-liquid path 2 was inserted into this gap for supplying and discharging hydrogen gas and an ammonia solution. Electrical pins 5 and 6 were attached to the electrodes, which formed a combined anode and combined cathode, between which they set an electric load 7 in the form of a 50 Ω resistor, in parallel with which a voltmeter was installed 8. Next, a pure hydrogen cylinder was connected to gas-liquid path 2 and the flow rate was set 34 6 ml / h. After 30 s, the readings on the voltmeter stabilized, the voltmeter showed a voltage of 2.25 V. Therefore, the output power was approximately 102.6 mW. This process can be described by the following chemical reactions:

9H ₂ + H ₆ [P ₂ W ⁺⁶ ₁₈ O ₆₂ ] ^-6 = H ₂₄ [P ₂ W ⁺⁵ ₁₈ O ₆₂ ] ^-24

Then, the hydrogen supply was turned off, waited until the voltmeter readings returned to the initial value, and an 8% by mass aqueous solution of ammonia hydrate with a flow rate of 0.258 ml / h was applied to the cell, the density of aqueous 8% ammonia solution was 0.97 g / ml, reading the voltmeter was 1.7 V, therefore, the output power was about 57.8 mW.

6NH ₃ + H ₆ [P ₂ W ⁺⁶ ₁₈ O ₆₂ ] ^-6 = H ₂₄ [P ₂ W ⁺⁵ ₁₈ O ₆₂ ] ^-24 + 3N ₂

Approximate calculation of efficiency when using hydrogen as fuel in an electrochemical cell.

The density of hydrogen under normal conditions is 0.0000899 g / cm ^3, which is 0.0031 g. The calorific value of hydrogen is 120,000 J / g or 33 (Wh / h) / g or 10,820 kJ / m ³ or 10.82 J / cm ³ . Theoretical power at 100% efficiency with the consumption of pure hydrogen under normal conditions should have been 104 mW. The experimental maximum output power is 101.25 mW, thus the efficiency was approximately 97-98%.

An approximate calculation of the efficiency when using an ammonia solution as a fuel in an electrochemical cell.

At a flow rate of 0.258 ml / h of 8% ammonia solution (density of an 8% ammonia solution at 20 ° C = 0.97 g / ml), the mass flow rate of ammonia is 0.00256 g / h or the heat of combustion of ammonia is 20 790 J / g or 5, 775 (Wh) / g Therefore, at 100% efficiency for such conditions, the output power would be 115.7 mW. In practice, 2 times less was obtained, i.e. approximately 57.8 mW. Thus, we can conclude that the conversion efficiency for such given parameters was about 50%.

The example showed the possibility of using a solid-state electrochemical cell of a simplified design as a converter of chemical energy into electrical energy with high efficiency, using both gaseous and liquid fuels.

Claims (1)

An electrochemical solid-state fuel cell, comprising a housing 1, electrodes 3 located therein, a gas-liquid path 2 used as the main catalyst substance, an aqueous solution of heteropoly acid 2-18 of the H ₆ [P ₂ W ₁₈ O ₆₂ ] series, characterized in that there are two electrodes, which can be made of activated carbon or carbon fiber, or porous graphite, impregnated with a 20-60% aqueous solution of heteropoly acid H ₆ [P ₂ W ₁₈ O ₆₂ ], crimped on both sides with perforated metal plates 4 with a hole perforation diameter of 0.5-10 mm which They can be made of stainless steel or chromium, or nickel, or copper, placed in the housing 1, which can be made of inert dielectric materials and has perforations on the sides with a diameter of 0.5-10 mm so that the holes in the housing are located opposite the holes in the metal perforated plates of the electrodes with a gap of 5-100 mm, through which the gas path 2 for supplying and discharging liquid or gas passes, and the electrical leads 5 and 6 are attached to the metal plates of the electrodes 4, forming a combined th anode and combined cathode.

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