Low-temperature direct methanol reforming fuel cell

Abstract

The invention discloses a low-temperature direct methanol reforming fuel cell which comprises an anode plate, a CO conversion film electrode and a cathode plate which are arranged in sequence, and the CO conversion film electrode comprises an anode composite electrode, an electrolyte film and a cathode electrode which are arranged in sequence; the anode composite electrode is composed of an outer-layer anode electrode and an inner-layer anode electrode, and the inner-layer anode electrode is close to the electrolyte membrane; the outer anode electrode comprises a CO conversion catalyst, the inner anode electrode comprises an H2 reaction catalyst, and the cathode electrode comprises an O2 reaction catalyst. According to the methanol reforming low-temperature proton exchange membrane fuel cell, the outer-layer anode electrode of the anode composite electrode can directly convert and eliminate CO in methanol reforming gas, and the poisoning influence of CO on the inner-layer anode electrode and the cathode electrode is avoided, so that the problems that an existing methanol reforming low-temperature proton exchange membrane fuel cell needs multi-stage purification to remove CO, the specific power is low and the like are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of fuel cells, and in particular to a low-temperature direct methanol reforming fuel cell. Background Art

[0002] With the growing demand for energy and increasingly severe environmental problems, methanol fuel cells, as a clean and efficient energy conversion technology, have received widespread attention. Methanol fuel cell technology is mainly divided into three types: direct methanol fuel cells, methanol reforming low-temperature proton exchange membrane fuel cells and high-temperature methanol fuel cells. Among them, methanol reforming low-temperature proton exchange membrane fuel cells are an energy conversion system that combines methanol reforming technology with low-temperature proton exchange membrane fuel cells. Due to its high technical maturity and power level that can be expanded to megawatts, it has been widely used in many fields.

[0003] However, the existing methanol reforming low-temperature proton exchange membrane fuel cells have certain limitations. In addition to hydrogen used as fuel cell fuel, the hydrogen-rich gas produced by methanol reforming also contains 1% to 2% CO. At the operating temperature of the low-temperature proton exchange membrane fuel cell, CO easily poisons the platinum-based catalyst in the fuel cell and strongly adsorbs on the surface of the platinum-based catalyst, hindering the adsorption and reaction of hydrogen (H2) and oxygen (O2) on the catalyst surface. Therefore, the CO tolerance of the low-temperature proton exchange membrane fuel cell is limited to the ppm level. Therefore, when the methanol reforming chamber is connected to the low-temperature proton exchange membrane fuel cell, it is often necessary to undergo multi-stage purification components such as water vapor conversion and selective oxidation to remove CO from the methanol reforming gas, resulting in a relatively large system volume and complex system for the methanol reforming low-temperature proton exchange membrane fuel cell, resulting in low specific power and efficiency of the fuel cell. Summary of the invention

[0004] The purpose of the present invention is to provide a low-temperature direct methanol reforming fuel cell, which allows methanol reforming gas to be directly introduced into the low-temperature direct methanol reforming fuel cell, thereby eliminating the need for multiple purification steps and improving the specific power and efficiency of the methanol reforming low-temperature proton exchange membrane fuel cell.

[0005] In order to achieve the above object, the present invention provides a low-temperature direct methanol reforming fuel cell, comprising an anode plate, a CO conversion membrane electrode, and a cathode plate arranged in sequence, wherein:

[0006] The CO conversion membrane electrode comprises an anode composite electrode, an electrolyte membrane, and a cathode electrode arranged in sequence; the anode composite electrode consists of an outer anode electrode and an inner anode electrode, and the inner anode electrode is close to the electrolyte membrane; the outer anode electrode comprises a CO conversion catalyst, the inner anode electrode comprises a H2 reaction catalyst, and the cathode electrode comprises an O2 reaction catalyst;

[0007] Under working conditions, methanol reforming gas is introduced from the anode plate, and oxidizing gas is introduced from the cathode plate; wherein CO and water vapor in the methanol reforming gas react under the catalytic action of the CO conversion catalyst to produce outer protons; H2 in the methanol reforming gas reacts under the catalytic action of the H2 reaction catalyst to produce inner protons; the outer protons and the inner protons enter the cathode electrode through the electrolyte membrane, and react with the oxidizing gas under the catalytic action of the O2 reaction catalyst to produce water.

[0008] Furthermore, the CO conversion catalyst comprises a carbon-supported precious metal catalyst, and the precious metal comprises at least any one of iridium and rhodium.

[0009] Furthermore, the loading of precious metal in the CO conversion catalyst is 0.3 mg / cm 2 ~3mg / cm 2 .

[0010] Furthermore, the H2 reaction catalyst comprises a carbon-supported precious metal catalyst, and the precious metal comprises at least any one of platinum and ruthenium.

[0011] Furthermore, the loading of the noble metal in the H2 reaction catalyst is 0.3 mg / cm 2 ~3mg / cm 2 .

[0012] Furthermore, the O2 reaction catalyst at least comprises a carbon-supported platinum-based catalyst.

[0013] Furthermore, the platinum loading in the O2 reaction catalyst is 0.3 mg / cm 2 ~3mg / cm 2 .

[0014] Furthermore, the anode composite electrode and / or the cathode electrode further comprises a binder for fixing the catalyst.

[0015] Furthermore, the anode composite electrode and / or the cathode electrode further comprises an ionomer for conducting protons.

[0016] Furthermore, the oxidizing gas is oxygen or air.

[0017] Compared with the prior art, the beneficial effects of the present invention at least include:

[0018] (1) In the low-temperature direct methanol reforming fuel cell of the present invention, a CO conversion membrane electrode including an anode composite electrode is designed by research, wherein a low-temperature and high-activity CO conversion catalyst is integrated in the outer anode electrode of the anode composite electrode, which can directly convert and eliminate CO in the outer anode electrode, so that CO does not affect the platinum-based catalyst in the inner anode electrode and the cathode electrode, thereby ensuring the stable electrochemical reaction of the fuel cell and extending the service life of the fuel cell; at the same time, the CO conversion reaction produces additional protons and electrons, which is also beneficial to improving the fuel cell power. In the present invention, methanol reforming gas can be directly introduced into the low-temperature direct methanol reforming fuel cell without the need to remove CO through multiple purification steps, simplifying the fuel cell system and helping to improve the specific power and efficiency of the methanol reforming low-temperature proton exchange membrane fuel cell.

[0019] (2) Furthermore, the present invention regulates the loading amount of the CO conversion catalyst in the outer anode electrode of the anode composite electrode, thereby ensuring that the CO in the introduced methanol reforming gas can be completely converted and eliminated in the outer anode electrode. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic structural diagram of the low-temperature direct methanol reforming fuel cell of the present invention.

[0021] Figure 2 It is a schematic structural diagram of the CO conversion membrane electrode of the present invention.

[0022] Description of the accompanying drawings:

[0023] End plate 10, anode plate 20, anode gas diffusion layer 30, CO conversion membrane electrode 40, cathode gas diffusion layer 50, cathode plate 60, electrolyte membrane 41, anode composite electrode 42, outer anode electrode 421, inner anode electrode 422, cathode electrode 43. DETAILED DESCRIPTION

[0024] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0025] In the description of the present invention, it should be noted that the terms "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0026] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0027] The "methanol reforming gas" mentioned in this article refers to the hydrogen-rich gas produced by the reforming reaction of methanol to produce hydrogen, and the hydrogen-rich gas contains H2, CO2, CO, and water vapor; the volume percentage of H2 is 70%, and the volume percentage of CO is 1% to 2%.

[0028] As described in the background technology, for the existing methanol reforming low-temperature proton exchange membrane fuel cell, since the CO contained in the methanol reforming gas will have a poisoning effect on the platinum (Pt)-based catalyst in the low-temperature proton fuel cell, thereby hindering the normal electrochemical reaction of the fuel cell, the methanol reforming gas needs to undergo multiple stages of purification steps to remove CO before it can be introduced into the low-temperature proton exchange membrane fuel cell as fuel, resulting in the overall system size of the methanol reforming low-temperature proton exchange membrane fuel cell being bulky and complex, reducing the specific power and working efficiency of the fuel cell.

[0029] To solve the above problems, the present invention innovatively proposes for the first time a CO conversion membrane electrode comprising an anode composite electrode, wherein a low-temperature and high-activity CO conversion catalyst is integrated in the outer anode electrode of the anode composite electrode, which can directly promote the conversion reaction of CO in the outer anode electrode, so that CO does not affect the platinum-based catalyst in the inner anode electrode and the cathode electrode, and the conversion reaction produces additional protons and electrons to further maintain the stability of the electrochemical reaction of the fuel cell. In the present invention, for the first time, it is possible to directly introduce methanol reforming gas into a low-temperature direct methanol reforming fuel cell without going through a complex multi-stage purification step to remove CO, thereby simplifying the system, and it is expected to significantly improve the specific power and efficiency of the methanol reforming low-temperature proton exchange membrane fuel cell.

[0030] The specific implementation of the present invention is described in detail below with reference to the accompanying drawings and embodiments.

[0031] like Figure 1 As shown, the present invention provides a low-temperature direct methanol reforming fuel cell (hereinafter referred to as a "fuel cell"), comprising two end plates 10, an anode plate 20, an anode gas diffusion layer 30, a CO conversion membrane electrode 40, a cathode gas diffusion layer 50, and a cathode plate 60; wherein:

[0032] The end plate 10 is a stainless steel, aluminum, or titanium alloy plate with a gold-plated surface, which is used to provide mechanical support for the fuel cell, and to collect and export the electrons generated by the fuel cell to an external circuit. The end plate 10 is provided with a heating device for heating the end plate and starting the fuel cell. In this example, the end plate 10 is made of aluminum alloy, and the heating device is an electric heating plate. The end plate 10 is provided with an end plate inlet and an end plate outlet, which are used to pass reactants and discharge products, respectively. The reactants include fuel and oxidizing gas, and the products include water.

[0033] The anode plate 20 and cathode plate 60 are made of graphite or corrosion-resistant materials such as stainless steel, aluminum, and titanium alloy with gold plating on the surface. In this example, the anode plate 20 is a stainless steel plate with gold plating on the surface, and the cathode plate 60 is a titanium plate with gold plating on the surface. The anode plate 20. The anode plate 20 and cathode plate 60 are etched to form a multi-channel serpentine flow field. The inlet and outlet of the multi-channel serpentine flow field of the anode plate 20 are respectively connected to the end plate inlet and the end plate outlet of the anode side end plate, which are used for the introduction of fuel and the outflow of anode side products; the inlet and outlet of the multi-channel serpentine flow field of the cathode plate 60 are respectively connected to the end plate inlet and the end plate outlet of the cathode side end plate, which are used for the introduction of oxidizing gas and the outflow of cathode side products. In this example, the fuel is methanol reforming gas, and the oxidizing gas is oxygen (O2); a three-channel serpentine flow field is formed on the anode plate 20 by etching, and a five-channel serpentine flow field is formed on the cathode plate 60 by etching.

[0034] The anode gas diffusion layer 30 and the cathode gas diffusion layer 50 are carbon paper or carbon cloth. In this example, the anode gas diffusion layer 30 and the cathode gas diffusion layer 50 are SGL carbon paper with a thickness of 180 μm. In this example, the anode gas diffusion layer 30 is used to support the CO conversion membrane electrode 40, transmit the electrons generated by the anode reaction to the external circuit, and transmit the methanol reforming gas from the anode plate 20 to the CO conversion membrane electrode 40; the cathode gas diffusion layer 50 is used to support the CO conversion membrane electrode 40, transmit the electrons from the external circuit to the CO conversion membrane electrode 40, and transmit the oxygen from the cathode plate 60 to the CO conversion membrane electrode 40.

[0035] like Figure 2 As shown, the CO conversion membrane electrode 40 of the present invention comprises an electrolyte membrane 41 and an anode composite electrode 42 and a cathode electrode 43 respectively arranged on both sides of the electrolyte membrane 41. The anode composite electrode 42 is composed of an outer anode electrode 421 and an inner anode electrode 422. The outer anode electrode 421 is close to the anode gas diffusion layer 30, and the inner anode electrode 422 is close to the electrolyte membrane 41.

[0036] The outer anode electrode 421 includes a CO conversion catalyst. After the CO and water vapor in the methanol reformed gas from the anode gas diffusion layer 30 contact the CO conversion catalyst, an electrochemical oxidation reaction of CO occurs: CO+H2O→2H + +CO2+2e - , generating outer protons and electrons, the outer protons sequentially pass through the inner anode electrode 422 and the electrolyte membrane 41 into the cathode electrode 43; the electrons are conducted to the cathode electrode 43 through the external circuit to participate in the cathode reaction of the fuel cell. The CO conversion catalyst comprises a carbon-supported noble metal catalyst, wherein the noble metal comprises at least one of iridium and rhodium; wherein the loading of the noble metal is 0.3 mg / cm 2 ~3mg / cm 2 In this loading range, it is possible to ensure that the CO in the methanol reforming gas (CO concentration is usually 10 3 ppm to 10 4 ppm) is completely converted and eliminated in the outer anode electrode 421, so as not to affect the platinum-based catalyst in the inner anode electrode 422 or the cathode electrode 43. In this example, the CO conversion catalyst is a carbon-supported rhodium catalyst, wherein the rhodium loading is 0.3 mg / cm 2 .

[0037] The inner anode electrode 422 includes a H2 reaction catalyst. After the H2 in the methanol reformed gas from the anode gas diffusion layer 30 contacts the H2 reaction catalyst, an electrochemical oxidation reaction (anode reaction) of H2 occurs: H2→H + +e - , generating inner protons and electrons, which are respectively conducted to the cathode electrode 43 through the electrolyte membrane 41 and the external circuit to participate in the cathode reaction of the fuel cell. The H2 reaction catalyst comprises a carbon-supported noble metal catalyst, wherein the noble metal comprises at least one of platinum and ruthenium catalysts, wherein the loading of the noble metal is 0.3 mg / cm 2 ~3mg / cm 2 In this example, the H2 reaction catalyst is a carbon-supported platinum-ruthenium alloy catalyst, wherein the loading of platinum and ruthenium is 0.5 mg / cm 2 .

[0038] The electrolyte membrane 41 is used to conduct the protons generated in the anode composite electrode 42 to the cathode electrode 43, and is used to block the fuel on the anode side and the oxidizing gas on the cathode side. In this example, the electrolyte membrane 41 is a Nafion proton exchange membrane (provided by DuPont), with a thickness of 125 μm and an operating temperature of 60° C. to 95° C.

[0039] The cathode electrode 43 contains an O2 reaction catalyst. When the outer protons and inner protons from the anode composite electrode 42 and the O2 from the cathode gas diffusion layer 50 come into contact with the O2 reaction catalyst, an electrochemical reduction reaction (cathode reaction) occurs: O2+4H + +4e - →2H2O, water is produced. The O2 reaction catalyst comprises at least a carbon-supported platinum-based catalyst, wherein the platinum loading is 0.3 mg / cm 2 ~3mg / cm 2 In this example, the O2 reaction catalyst is a platinum-carbon catalyst, wherein the platinum loading is 0.5 mg / cm 2 .

[0040] The anode composite electrode 42 and / or the cathode electrode 43 also include 0-20% of a binder and 0-20% of an ionomer, measured in mass percentage; wherein the binder is used to fix the catalyst, and the ionomer is used to promote proton conduction. In the anode composite electrode 42, the outer anode electrode 421 or the inner anode electrode 422 may contain the binder and the ionomer, or both. In this example, the binder is polytetrafluoroethylene (PTFE); the ionomer is Nafion (provided by DuPont). In this example, the outer anode electrode 421 contains 20% by mass of PTFE and 5% by mass of Nafion; the inner anode electrode 422 contains 10% by mass of Nafion; and the cathode electrode 43 contains 10% by mass of Nafion. Nafion is a perfluorosulfonic acid polymer.

[0041] The working process of the low-temperature direct methanol reforming fuel cell described in this example is as follows: first, the end plate 10 is heated by an electric heating plate to start the low-temperature direct methanol reforming fuel cell. The methanol reforming gas enters the inlet of the three-channel serpentine flow field on the surface of the anode plate 20 through the end plate inlet of the anode side end plate in turn, flows along the three-channel serpentine flow field, and the methanol reforming gas further enters the anode composite electrode 40 through the SGL carbon paper, wherein CO and water vapor in the methanol reforming gas undergo a CO conversion reaction at the outer anode electrode 421 to produce H +, electrons; H2 in the methanol reforming gas undergoes a H2 conversion reaction at the inner anode electrode 422 to produce H + , electrons. The H generated by the reaction in the anode composite electrode 42 + , electrons enter the cathode electrode 43 through the Nafion proton exchange membrane and the external circuit respectively. At the same time, oxygen enters the entrance of the five-channel serpentine flow field on the surface of the cathode plate 60 through the end plate inlet of the cathode side end plate in turn, flows along the five-channel serpentine flow field, and further enters the cathode electrode 43 through the SGL carbon paper, and mixes with the H entering from the Nafion proton exchange membrane. + , the electrons entering from the external circuit undergo cathode reaction, realizing the conversion of chemical energy into electrical energy. In the above working process, CO in the methanol reformed gas can be directly converted and eliminated in the outer anode electrode 421 of the anode composite electrode 42, without affecting the electrochemical reaction in the inner anode electrode 422 and the cathode electrode 43, so there is no need to establish a multi-stage purification component between the methanol reforming chamber that produces the methanol reformed gas and the fuel cell. After the methanol reformed gas is generated, it can be directly introduced into the fuel cell for reaction, effectively reducing the overall system volume and the overall system startup time, thereby effectively improving the specific power and efficiency of the fuel cell system.

[0042] In summary, the present invention proposes a low-temperature direct methanol reforming fuel cell, which designs an anode composite electrode that integrates a low-temperature, high-activity CO conversion catalyst, and can directly convert and eliminate CO in the outer anode electrode of the anode composite electrode, avoiding the influence of CO on the platinum-based catalyst in the inner anode electrode and cathode electrode, and ensuring the stability of the electrochemical reaction. At the same time, the additional protons and electrons generated by the CO conversion reaction help to increase the battery power. In addition, the methanol reforming gas can be directly introduced into the battery without the need for multi-stage purification steps to remove CO, thereby simplifying the system and improving the specific power and efficiency of the methanol reforming low-temperature proton exchange membrane fuel cell.

[0043] Although the content of the present invention has been described in detail through the above preferred embodiments, it should be appreciated that the above description should not be considered as a limitation of the present invention. After reading the above content, it will be apparent to those skilled in the art that various modifications and substitutions of the present invention will occur. Therefore, the protection scope of the present invention should be limited by the appended claims.

Claims

1. A low-temperature direct methanol reforming fuel cell, characterized in that: It comprises an anode plate, a CO conversion membrane electrode, and a cathode plate arranged in sequence, wherein: The CO conversion membrane electrode comprises an anode composite electrode, an electrolyte membrane, and a cathode electrode arranged in sequence; the anode composite electrode consists of an outer anode electrode and an inner anode electrode, and the inner anode electrode is close to the electrolyte membrane; the outer anode electrode comprises a CO conversion catalyst, the inner anode electrode comprises a H2 reaction catalyst, and the cathode electrode comprises an O2 reaction catalyst; Under working conditions, methanol reforming gas is introduced from the anode plate, and oxidizing gas is introduced from the cathode plate; wherein CO and water vapor in the methanol reforming gas react under the catalytic action of the CO conversion catalyst to produce outer protons; H2 in the methanol reforming gas reacts under the catalytic action of the H2 reaction catalyst to produce inner protons; the outer protons and the inner protons enter the cathode electrode through the electrolyte membrane, and react with the oxidizing gas under the catalytic action of the O2 reaction catalyst to produce water.

2. The low-temperature direct methanol reforming fuel cell according to claim 1, characterized in that: The CO conversion catalyst comprises a carbon-supported noble metal catalyst, and the noble metal comprises at least one of iridium and rhodium.

3. The low-temperature direct methanol reforming fuel cell according to claim 2, characterized in that: The loading of precious metal in the CO conversion catalyst is 0.3 mg / cm 2 ~3mg / cm 2 .

4. The low-temperature direct methanol reforming fuel cell according to claim 1, characterized in that: The H2 reaction catalyst comprises a carbon-supported noble metal catalyst, and the noble metal comprises at least one of platinum and ruthenium.

5. The low-temperature direct methanol reforming fuel cell according to claim 4, characterized in that: The loading of precious metal in the H2 reaction catalyst is 0.3 mg / cm 2 ~3mg / cm 2 .

6. The low-temperature direct methanol reforming fuel cell according to claim 1, characterized in that: The O2 reaction catalyst at least comprises a carbon-supported platinum-based catalyst.

7. The low-temperature direct methanol reforming fuel cell according to claim 6, characterized in that: The platinum loading in the O2 reaction catalyst is 0.3 mg / cm 2 ~3mg / cm 2 .

8. The low-temperature direct methanol reforming fuel cell according to claim 1, characterized in that: The anode composite electrode and / or the cathode electrode further comprises a binder for fixing the catalyst.

9. The low-temperature direct methanol reforming fuel cell according to claim 1, characterized in that: The anode composite electrode and / or the cathode electrode further comprises an ionomer for conducting protons.

10. The low-temperature direct methanol reforming fuel cell according to claim 1, characterized in that: The oxidizing gas is oxygen or air.

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