CN109817990B - Unipolar plate for hydrogen fuel cell, preparation method of unipolar plate and hydrogen fuel cell - Google Patents
Unipolar plate for hydrogen fuel cell, preparation method of unipolar plate and hydrogen fuel cell Download PDFInfo
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Abstract
A unipolar plate for a hydrogen fuel cell, a preparation method thereof and the hydrogen fuel cell belong to the technical field of hydrogen fuel cell research. The method obtains the high density (2-2.1 g/cm) by adding the graphene layer into the unipolar plate and combining the in-situ densification means‑3) The expanded graphite/graphene/expanded graphite sandwich structure unipolar plate. Compared with the conventional unipolar plate for the hydrogen fuel cell, the conductivity of the middle graphene layer (8 x 10)5S/m) and thermal conductivity (up to 1500 Wm)‑ 1K‑1) The heat conduction and the electric conduction of the unipolar plate are greatly improved. The improvement of the conductivity of the unipolar plate can greatly improve the electron transmission speed of the bipolar plate, thereby improving the service efficiency of the whole hydrogen fuel cell. The improvement of the heat conduction performance can increase the service life of the hydrogen fuel cell.
Description
Technical Field
The invention belongs to the technical field of research of hydrogen fuel cells, and particularly relates to a unipolar plate for a hydrogen fuel cell, a preparation method of the unipolar plate and the hydrogen fuel cell.
Background
Under the large background of environmental storm, clean and sustainable energy development becomes an energy technology which is mainly developed by people. The fuel cell has the advantages of high power generation efficiency, less environmental pollution and the like, is gradually applied to the fields of aerospace, electric automobiles and the like, and has wide application prospect. A hydrogen fuel cell is a kind of fuel cell, and since a raw material thereof is hydrogen gas and a product thereof is water and carbon dioxide, there is no problem of environmental pollution and thus it is receiving attention. The core component of a hydrogen fuel cell is a bipolar plate. The bipolar plate is composed of two electrode plates, a proton exchange membrane is clamped between the two electrode plates, wherein the electrode plates play a role in supporting an oxidant and a reducer and guiding the oxidant and the reducer to flow on the surfaces of the electrodes in the battery. The redox reaction of hydrogen and oxygen is completed in the whole bipolar plate, and the heat generated by the reaction must be timely conducted out to ensure the normal operation of the battery, so that the bipolar plate not only requires good electrical conductivity, but also requires good heat-conducting property, and meanwhile, in order to improve the utilization rate of hydrogen and oxygen, the pair of single electrodes is required to have good gas barrier property.
However, the expanded graphite material is often used for the electrode of the conventional unipolar plate, the expanded graphite itself has low thermal conductivity, the thermal conductivity is 100W/m · K or less even if the density is increased by impregnating the resin, and the expanded graphite has poor gas barrier properties, resulting in low hydrogen gas utilization rate.
Disclosure of Invention
The invention provides a unipolar plate for a hydrogen fuel cell, a preparation method thereof and the hydrogen fuel cell, aiming at solving the problems of low thermal conductivity, low hydrogen utilization rate and the like of the unipolar plate in the hydrogen fuel cell.
In order to achieve the purpose, the technical scheme adopted by the invention is as follows:
the unipolar plate for the hydrogen fuel cell is prepared from expanded graphite and graphene.
A method for preparing the unipolar plate for the hydrogen fuel cell, the method comprising the following steps:
the method comprises the following steps: preparing a mould: preparing a corresponding graphite mold according to the shape and the size of the unipolar plate, wherein the mold is made of high-strength graphite;
step two: filling: uniformly spreading expanded graphite powder in a mould, and scraping the surface of the mould; then adding a layer of graphene powder, and leveling the surface; finally, adding expanded graphite powder, and scraping the surface;
step three: preforming: pressurizing the filler obtained in the step two, pressurizing at a constant speed of 5-20 mm/min by a press, maintaining the pressure for 1-5 min after the pressure reaches 0.5-1 MPa, preforming to obtain a sandwich structure, and taking out the sandwich structure from a mold;
step four: pre-sintering: sintering the preformed sandwich structure at 500-1000 ℃ for 1-2 h in vacuum;
step five: compacting and forming;
step six: machining into the final structure.
A hydrogen fuel cell comprising the above-described unipolar plate, said hydrogen fuel cell comprising at least one unipolar plate.
A method for preparing the unipolar plate for the hydrogen fuel cell, the method comprising the following steps:
the method comprises the following steps: preparing a mould: preparing a corresponding graphite mold according to the shape and the size of the unipolar plate, wherein the mold is made of high-strength graphite;
step two: filling: uniformly spreading expanded graphite powder in a mould, and scraping the surface of the mould; then adding a layer of graphene powder, and leveling the surface;
step three: preforming: pressurizing the filler obtained in the step two, pressurizing at a constant speed of 5-20 mm/min by a press, maintaining the pressure for 1-5 min after the pressure reaches 0.5-1 MPa, preforming to obtain a sandwich structure, and taking out the sandwich structure from a mold;
step four: pre-sintering: sintering the preformed sandwich structure at 500-1000 ℃ for 1-2 h in vacuum;
step five: compacting and forming;
step six: machining into the final structure.
A method for preparing the unipolar plate for the hydrogen fuel cell, the method comprising the following steps:
the method comprises the following steps: preparing a mould: preparing a corresponding graphite mold according to the shape and the size of the unipolar plate, wherein the mold is made of high-strength graphite;
step two: filling: adding a layer of graphene powder, and leveling the surface; then adding expanded graphite powder, and scraping the surface;
step three: preforming: pressurizing the filler obtained in the step two, pressurizing at a constant speed of 5-20 mm/min by a press, maintaining the pressure for 1-5 min after the pressure reaches 0.5-1 MPa, preforming to obtain a sandwich structure, and taking out the sandwich structure from a mold;
step four: pre-sintering: sintering the preformed sandwich structure at 500-1000 ℃ for 1-2 h in vacuum;
step five: compacting and forming;
step six: machining into the final structure.
Compared with the prior art, the invention has the beneficial effects that:
(1) the invention adds the graphene layer into the unipolar plate and combines in-situ densificationObtaining a high density (2 to 2.1 g/cm)-3) The expanded graphite/graphene/expanded graphite sandwich structure unipolar plate. Compared with the conventional unipolar plate for the hydrogen fuel cell, the conductivity of the middle graphene layer (8 x 10)5S/m) and thermal conductivity (up to 1500 Wm)-1K-1) The heat conduction and the electric conduction of the unipolar plate are greatly improved. The improvement of the conductivity of the unipolar plate can greatly improve the electron transmission speed of the bipolar plate, thereby improving the service efficiency of the whole hydrogen fuel cell. The improvement of the heat conduction performance can increase the service life of the hydrogen fuel cell.
(2) In the hot pressing process of the graphene powder, internal gas can be discharged, and under the action of the hydrodynamics of gas discharge, the two-dimensional material graphene can be directionally arranged perpendicular to the pressurizing direction. The graphene film which is arranged in an oriented mode has good gas barrier performance, after the bipolar plate is assembled, the existence of the graphene interlayer plays a role in packaging, hydrogen and oxygen are prevented from diffusing outwards to the bipolar plate (as shown in figure 3), the hydrogen and oxygen are enabled to fully react in the bipolar plate, the hydrogen utilization rate and the oxygen utilization rate of the hydrogen fuel cell are greatly improved, the waste of gas is reduced, and meanwhile the safety performance of the hydrogen fuel cell can also be improved.
(3) The invention has wide application. The graphene is a two-dimensional crystal material, the room-temperature in-plane thermal conductivity of the single-layer graphene with a perfect lattice is as high as 5300W/(m.K), and the electric conductivity is as high as 106S/m, and the film material with the oriented arrangement of the graphene has good gas barrier property, so that the gas barrier property of the hydrogen fuel cell can be greatly improved by using the graphene material in the unipolar plate. The unipolar plate has the advantages of good electrical conductivity and thermal conductivity, and can improve the utilization rate of hydrogen gas, thereby improving the energy conversion efficiency of the hydrogen fuel cell.
Drawings
Fig. 1 (a) is a front sectional view of a conventional bipolar plate, and (b) is a top sectional view of the conventional bipolar plate, in which upper and lower dotted line boxes represent an oxygen chamber and a hydrogen chamber, respectively;
fig. 2 is a side cross-sectional view of a hydrogen fuel cell of the present invention incorporating a sandwich-structured unipolar plate;
FIG. 3 is a schematic view of the principle of the present invention for improving gas barrier property;
the device comprises a bipolar plate 1, a gas and cooling liquid flow passage 2, an oxygen inlet 3, a cooling liquid inlet 4, a hydrogen inlet 5, a hydrogen outlet 6, a cooling liquid outlet 7, an oxygen outlet 8, a hydrogen outlet 9, a salient point at the hydrogen outlet 10, expanded graphite 11, a graphene layer 12, a hydrogen catalyst layer 13, an oxygen catalyst layer 14, a hydrogen unipolar plate 15, an oxygen unipolar plate 16, a proton exchange membrane 17, oxygen molecules 18, hydrogen protons 19 and hydrogen molecules 20.
Detailed Description
The technical solution of the present invention is not limited to the specific embodiments listed below, and includes any combination of the specific embodiments. The structure of the present invention will be described in detail below with reference to the accompanying drawings. The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the invention and not to limit the invention.
Referring to fig. 1, a conventional hydrogen fuel cell bipolar plate 1 mainly comprises a hydrogen unipolar plate 15, an oxygen unipolar plate 16 and a proton exchange membrane 17, gas and coolant flow channels 2 are formed on inner sides of the hydrogen unipolar plate 15 and the oxygen unipolar plate 16, hydrogen and oxygen respectively flow in from a hydrogen inlet 5 (see fig. 1) of the hydrogen unipolar plate 15 and an oxygen inlet 3 (see fig. 1) of the oxygen unipolar plate 16 and respectively flow through two sides of the proton exchange membrane 17, and hydrogen molecules 20 lose electrons under the action of a catalyst in a hydrogen catalyst layer 13, are oxidized into hydrogen protons 19, and pass through the proton exchange membrane 17 to react with oxygen molecules 18 in an oxygen chamber under the catalysis of the catalyst in the oxygen catalyst layer 14 to generate corresponding oxides. During the above reaction, a voltage is generated between the oxygen unipolar plate 15 and the hydrogen unipolar plate 16, and a current is generated after the load and the cell form a closed loop, which is the basic principle of the operation of the hydrogen fuel cell (as shown in fig. 3). Meanwhile, the heat generated by the oxidation-reduction reaction needs to be discharged in time, so that the gas of the hydrogen chamber and the oxygen chamber and the cooling liquid flow channel 2 can also introduce cooling liquid from the cooling liquid inlet 4 to cool the whole bipolar plate. Unreacted oxygen, hydrogen and cooling liquid respectively flow out from the oxygen outlet 8, the hydrogen outlet 6 and the cooling liquid outlet 7 and are recycled. Meanwhile, the hydrogen inlet and the hydrogen outlet are provided with a hydrogen inlet convex point 10 and a hydrogen outlet convex point 9 for regulating and controlling the air pressure in the hydrogen cavity, so that the danger caused by overhigh air pressure is prevented.
The traditional hydrogen unipolar plate 15 and oxygen unipolar plate 16 both adopt expanded graphite 11 as the main material, and the electrical conductivity and thermal conductivity of expanded graphite are not ideal, and the barrier property of gas is also poor. The graphene layer 12 consisting of high-thermal conductivity and high-electrical conductivity graphene is used as a packaging film covering the surface of the expanded graphite unipolar plate. The principle of gas barrier of the graphene thin film with highly oriented graphene (see fig. 2) is shown in fig. 3.
The first embodiment is as follows: the present embodiment describes a monopolar plate for a hydrogen fuel cell, in which a conventional bipolar plate for a hydrogen fuel cell is composed of two monopolar plates and a proton exchange membrane disposed between the two monopolar plates, one of the two monopolar plates being an oxygen monopolar plate and the other being a hydrogen monopolar plate; a hydrogen cavity is formed by the hydrogen unipolar plate and one side of the proton exchange membrane, a hydrogen inlet and a hydrogen outlet are respectively arranged at two ends of the hydrogen cavity, and a catalyst is filled in the hydrogen cavity; the oxygen unipolar plate and the other side of the proton exchange membrane form an oxygen chamber, and an oxygen inlet and an oxygen outlet are respectively arranged at two ends of the oxygen chamber; the two ends of the hydrogen unipolar plate and the two ends of the oxygen unipolar plate both comprise a cooling liquid inlet and a cooling liquid outlet, and the insides of the hydrogen cavity and the oxygen cavity are both composed of zigzag densely-arranged runners; the unipolar plate is prepared from expanded graphite and graphene.
The second embodiment is as follows: a method for manufacturing a unipolar plate for a hydrogen fuel cell according to a first embodiment, the method comprising the steps of:
the method comprises the following steps: preparing a mould: preparing a corresponding graphite mold according to the shape and the size of the unipolar plate, wherein the mold is made of high-strength graphite;
step two: filling: uniformly spreading expanded graphite powder in a mould, and scraping the surface of the mould; then adding a layer of graphene powder, and leveling the surface; finally, adding expanded graphite powder, and scraping the surface;
step three: preforming: pressing the filler obtained in the step two by using a press, uniformly pressing the filler at a constant speed of 5-20 mm/min, maintaining the pressure for 1-5 min after the pressure reaches 0.5-1 MPa, performing to obtain a sandwich structure, and taking out the sandwich structure from a mold;
step four: pre-sintering: vacuum sintering the preformed sandwich structure at 500-1000 ℃ for 1-2 h, and removing graphene dispersing agents and the like contained in the interior;
step five: compacting and forming;
step six: machining into the final structure.
The third concrete implementation mode: in the second embodiment, in the fifth step, the densification molding is performed by one of the following methods:
the method comprises the following steps: putting the sintered preformed body into a graphite mold, and carrying out hot-pressing sintering on the preformed body and the graphite mold in a hot-pressing sintering furnace; the hot-pressing sintering process comprises the following steps: heating from room temperature to 700-2500 ℃ at a heating rate of 8-20 ℃/min, pressurizing, wherein the pressure is 20-60 MPa, the heat preservation and pressure maintaining time is 30-120 min, and the whole hot-pressing sintering process is carried out in a vacuum environment;
the second method comprises the following steps: putting the sintered preformed body into a stainless steel mold, and pressurizing on a hydraulic press, wherein the pressure is 100-300 MPa, and the pressure maintaining time is 5-30 min; and after pressing, dipping in liquid, and then carrying out graphitization treatment at 2500-3000 ℃ for 30-120 min, wherein the whole densification forming process is carried out in a vacuum environment. The liquid is epoxy resin or other high polymers which can increase the density of the electrode plate after carbonization.
The fourth concrete implementation mode: in the second step of the preparation method of the unipolar plate for the hydrogen fuel cell, the graphene powder is a pure graphene material or a composite material in which 1 vt% -5 vt% of a highly conductive metal or alloy is added to the graphene powder as a matrix. The alloy is copper alloy, aluminum alloy or silver alloy and the like. The high-conductivity metal is silver, aluminum, copper and the like. In the third step, in the sandwich structure, the thickness of the graphene layer is 50-200 μm.
The fifth concrete implementation mode: a hydrogen fuel cell comprising the unipolar plates of embodiment one, said hydrogen fuel cell comprising at least one unipolar plate. Specifically, the hydrogen fuel cell may include a single-pole plate, a pair of single-pole plates, or a plurality of pairs of single-pole plates, and may further include a housing, a gas supply system, a coolant system, or the like.
The sixth specific implementation mode: a method for manufacturing a unipolar plate for a hydrogen fuel cell according to a first embodiment, the method comprising the steps of:
the method comprises the following steps: preparing a mould: preparing a corresponding graphite mold according to the shape and the size of the unipolar plate, wherein the mold is made of high-strength graphite;
step two: filling: uniformly spreading expanded graphite powder in a mould, and scraping the surface of the mould; then adding a layer of graphene powder, and leveling the surface;
step three: preforming: pressing the filler obtained in the step two by using a press, uniformly pressing the filler at a constant speed of 5-20 mm/min, maintaining the pressure for 1-5 min after the pressure reaches 0.5-1 MPa, performing to obtain a sandwich structure, and taking out the sandwich structure from a mold;
step four: pre-sintering: vacuum sintering the preformed sandwich structure at 500-1000 ℃ for 1-2 h, and removing graphene dispersing agents and the like contained in the interior;
step five: compacting and forming;
step six: machining into the final structure.
The seventh embodiment: in a fifth embodiment of the method for manufacturing a unipolar plate for a hydrogen fuel cell, in the step of densifying and forming, one of the following methods is adopted:
the method comprises the following steps: putting the sintered preformed body into a graphite mold, and carrying out hot-pressing sintering on the preformed body and the graphite mold in a hot-pressing sintering furnace; the hot-pressing sintering process comprises the following steps: heating from room temperature to 700-2500 ℃ at a heating rate of 8-20 ℃/min, pressurizing, wherein the pressure is 20-60 MPa, the heat preservation and pressure maintaining time is 30-120 min, and the whole hot-pressing sintering process is carried out in a vacuum environment;
the second method comprises the following steps: putting the sintered preformed body into a stainless steel mold, and pressurizing on a hydraulic press, wherein the pressure is 100-300 MPa, and the pressure maintaining time is 5-30 min; and after pressing, dipping in liquid, and then carrying out graphitization treatment at 2500-3000 ℃ for 30-120 min, wherein the whole densification forming process is carried out in a vacuum environment. The liquid is epoxy resin or other high polymers which can increase the density of the electrode plate after carbonization.
The specific implementation mode is eight: in the second step of the preparation method of the unipolar plate for the hydrogen fuel cell, the graphene powder is a pure graphene material or a composite material in which 1 vt% -5 vt% of a highly conductive metal or alloy is added to the graphene powder as a matrix. The alloy is copper alloy, aluminum alloy or silver alloy and the like. The high-conductivity metal is silver, aluminum, copper and the like. In the third step, in the sandwich structure, the thickness of the graphene layer is 50-200 μm.
The specific implementation method nine: a method for manufacturing a unipolar plate for a hydrogen fuel cell according to a first embodiment, the method comprising the steps of:
the method comprises the following steps: preparing a mould: preparing a corresponding graphite mold according to the shape and the size of the unipolar plate, wherein the mold is made of high-strength graphite;
step two: filling: adding a layer of graphene powder, and leveling the surface; then adding expanded graphite powder, and scraping the surface;
step three: preforming: pressing the filler obtained in the step two by using a press, uniformly pressing the filler at a constant speed of 5-20 mm/min, maintaining the pressure for 1-5 min after the pressure reaches 0.5-1 MPa, performing to obtain a sandwich structure, and taking out the sandwich structure from a mold;
step four: pre-sintering: vacuum sintering the preformed sandwich structure at 500-1000 ℃ for 1-2 h, and removing graphene dispersing agents and the like contained in the interior;
step five: compacting and forming;
step six: machining into the final structure.
The detailed implementation mode is ten: in a fifth embodiment of the method for manufacturing a unipolar plate for a hydrogen fuel cell, in the step of densifying and forming, one of the following methods is adopted:
the method comprises the following steps: putting the sintered preformed body into a graphite mold, and carrying out hot-pressing sintering on the preformed body and the graphite mold in a hot-pressing sintering furnace; the hot-pressing sintering process comprises the following steps: heating from room temperature to 700-2500 ℃ at a heating rate of 8-20 ℃/min, pressurizing, wherein the pressure is 20-60 MPa, the heat preservation and pressure maintaining time is 30-120 min, and the whole hot-pressing sintering process is carried out in a vacuum environment;
the second method comprises the following steps: putting the sintered preformed body into a stainless steel mold, and pressurizing on a hydraulic press, wherein the pressure is 100-300 MPa, and the pressure maintaining time is 5-30 min; and after pressing, dipping in liquid, and then carrying out graphitization treatment at 2500-3000 ℃ for 30-120 min, wherein the whole densification forming process is carried out in a vacuum environment. The liquid is epoxy resin or other high polymers which can increase the density of the electrode plate after carbonization.
The concrete implementation mode eleven: the method for manufacturing a unipolar plate for a hydrogen fuel cell according to the ninth embodiment is characterized in that: in the second step, the graphene powder is a pure graphene material or a composite material which takes graphene as a matrix and is added with 1-5 vt% of high-conductivity metal or alloy. The alloy is copper alloy, aluminum alloy or silver alloy and the like. The high-conductivity metal is silver, aluminum, copper and the like. In the third step, in the sandwich structure, the thickness of the graphene layer is 50-200 μm.
Example 1:
(1) high-strength graphite is used as a raw material, and a graphite mold is prepared according to the shape and the corresponding size of a single polar plate in the figure 1.
(2) Uniformly spreading the expanded graphite powder in a mould, scraping the surface, and adding the expanded graphite powder according to the final density of 2.0g/cm-3Calculating the thickness of 1 mm; then adding a layer of graphene/aluminum composite powder containing 1vt.% of pure aluminum powder, scraping the surface, wherein the adding amount is 50 mu m according to the thickness and the density is 2.0g/cm-3Calculating; finally adding expanded graphite powder, and scraping the surfaceThe amount added is the same as the amount added in the lowermost layer.
(3) And (3) applying a pressure of 0.5MPa to the filled material in the step (2) by using a press, uniformly pressurizing the material by using the press at a constant speed of 5mm/min, and keeping the pressure for 1min after the pressure reaches 0.5MPa to perform.
(4) The preformed sandwich structure was vacuum sintered at a temperature of 500 ℃ for 2 h.
(5) And (5) densifying and forming. And putting the sintered preformed body into a graphite mold, and performing hot-pressing sintering in a hot-pressing sintering furnace. The hot-pressing sintering process comprises the following steps: heating at a heating rate of 8 ℃/min, starting to pressurize at 60MPa after the temperature reaches 700 ℃, keeping the temperature and the pressure for 120min, and carrying out a vacuum environment.
(6) Machining into the final structure. Two identical unipolar plates prepared in the embodiment and a proton exchange membrane are assembled into a bipolar plate.
The performance of the bipolar plate is tested, and the result shows that: the density of the bipolar plate is 97%, the plane electric conductivity is 1905S/cm, the plane thermal conductivity is 1050W/m.K, and compared with the expanded graphite bipolar plate reported at present, the thermal conductivity and the electric conductivity are both improved by one order of magnitude. Airtightness: the permeability of high-purity hydrogen at 100MPa is 1.1X 10-10mol/m2S-1Pa-1。
Example 2:
(1) same as example 1 (1).
(2) Uniformly spreading the expanded graphite powder in a mould, scraping the surface, and adding the expanded graphite powder according to the final density of 2.0g/cm-3Calculating the thickness of 1 mm; then adding a layer of pure graphene powder, scraping the surface, wherein the adding amount is 200 mu m according to the thickness and the density is 2.0g/cm-3Calculating; and finally, adding expanded graphite powder, and scraping the surface, wherein the adding amount is the same as that of the lowest layer.
(3) And (3) applying a pressure of 1MPa to the filled material in the step (2) by using a press, uniformly pressurizing the material by using the press at a constant speed of 20mm/min, and keeping the pressure for 5min after the pressure reaches 1MPa to perform.
(4) The preformed sandwich structure was vacuum sintered at a temperature of 1000 ℃ for 1 h.
(5) And (5) densifying and forming. And putting the sintered preformed body into a graphite mold, and performing hot-pressing sintering in a hot-pressing sintering furnace. The hot-pressing sintering process comprises the following steps: heating at a heating rate of 10 ℃/min, starting to pressurize at 20MPa after the temperature reaches 2500 ℃, keeping the temperature and the pressure for 30min, and carrying out a vacuum environment.
(6) Machining into the final structure. Two identical unipolar plates prepared in the embodiment and a proton exchange membrane are assembled into a bipolar plate.
The performance of the bipolar plate is tested, and the result shows that: the density of the bipolar plate is 98%, the plane electric conductivity is 2065S/cm, the plane heat conductivity is 1189W/m.K, and compared with the expanded graphite bipolar plate reported at present, the heat conductivity and the electric conductivity are both improved by one order of magnitude. Airtightness: the permeability of high-purity hydrogen at 100MPa is 1.1X 10-10mol/m2S-1Pa-1。
Example 3:
(1) same as example 1 (1).
(2) The difference from example 2 (2) is that: the addition amount of the graphene powder is calculated according to the final thickness of 100 μm.
(3) And (3) applying a pressure of 0.8MPa to the filled material in the step (2) by using a press, uniformly pressurizing by using the press at a constant speed of 10mm/min, and keeping the pressure for 3min after the pressure reaches 0.8MPa to perform.
(4) The preformed sandwich structure was vacuum sintered at a temperature of 800 ℃ for 1.5 h.
(5) And (5) densifying and forming. And putting the sintered preformed body into a graphite mold, and performing hot-pressing sintering in a hot-pressing sintering furnace. The hot-pressing sintering process comprises the following steps: heating at a heating rate of 20 ℃/min, starting to pressurize at 40MPa after the temperature reaches 2000 ℃, keeping the temperature and the pressure for 60min, and carrying out a vacuum environment.
(6) Machining into the final structure. Two identical unipolar plates prepared in the embodiment and a proton exchange membrane are assembled into a bipolar plate.
The performance of the bipolar plate is tested, and the result shows that: the density of the bipolar plate is 98 percent, the plane electric conductivity is 1874S/cm, and the plane thermal conductivity is 1089WThe thermal conductivity and the electric conductivity are improved by an order of magnitude compared with the expanded graphite bipolar plate reported at present. Airtightness: the permeability of high-purity hydrogen at 100MPa is 1.0X 10-10mol/m2S-1Pa-1。
Example 4:
the difference between this example and example 2 is the densified shaped part of step (5). The densification forming process in this embodiment is as follows: and (3) putting the sintered preformed body into a stainless steel mold, and directly pressurizing on a hydraulic press under the pressure of 100MPa for 30 min. Impregnating epoxy resin after pressing is finished, and then carrying out graphitization treatment at the temperature of 3000 ℃, wherein the treatment time is 30min, and the vacuum environment is adopted.
The performance of the bipolar plate is tested, and the result shows that: the density of the bipolar plate is 94%, the plane electric conductivity is 1764S/cm, the plane thermal conductivity is 982W/m.K, and compared with the expanded graphite bipolar plate reported at present, the thermal conductivity and the electric conductivity are both improved by one order of magnitude. Airtightness: the permeability of high-purity hydrogen at 100MPa is 1.4X 10-10mol/m2S-1Pa-1。
Example 5:
the difference between this example and example 1 is the densified shaped part of step (5). The densification forming process in this embodiment is as follows: and (3) putting the sintered preformed body into a stainless steel mold, and directly pressurizing on a hydraulic press at the pressure of 300MPa for 5 min. And after pressing, impregnating epoxy resin, and then carrying out graphitization treatment at the temperature of 2500 ℃ for 120min in a vacuum environment.
The performance of the bipolar plate is tested, and the result shows that: the density of the bipolar plate is 95%, the plane electric conductivity is 1867S/cm, the plane thermal conductivity is 1022W/m.K, and compared with the expanded graphite bipolar plate reported at present, the thermal conductivity and the electric conductivity are both improved by one order of magnitude. Airtightness: the permeability of high-purity hydrogen at 100MPa is 1.2X 10-10mol/m2S-1Pa-1。
Example 6:
the difference between this example and example 1 is the densified shaped part of step (5). The densification forming process in this embodiment is as follows: and (3) putting the sintered preformed body into a stainless steel mold, and directly pressurizing on a hydraulic press under the pressure of 200MPa for 15 min. Impregnating epoxy resin after pressing is finished, and then carrying out graphitization treatment at the temperature of 2850 ℃, wherein the treatment time is 60min, and the vacuum environment is adopted.
The performance of the bipolar plate is tested, and the result shows that: the density of the bipolar plate is 95%, the plane electric conductivity is 1863S/cm, the plane thermal conductivity is 1005W/m.K, and compared with the expanded graphite bipolar plate reported at present, the thermal conductivity and the electric conductivity are both improved by one order of magnitude. Airtightness: the permeability of high-purity hydrogen at 100MPa is 1.3X 10-10mol/m2S-1Pa-1。
Example 7:
the present embodiment differs from embodiment 2 in that: the bipolar plate of this example is composed of the expanded graphite/graphene/expanded graphite sandwich hydrogen unipolar plate, the common expanded graphite oxygen unipolar plate, and the proton exchange membrane prepared by the method of example 2.
The performance of the bipolar plate is tested, and the result shows that: the density of the hydrogen unipolar plate is 98%, and the density of the oxygen unipolar plate is 81%. The planar electric conductivity of the hydrogen unipolar plate is 2065S/cm, and the planar thermal conductivity is 1189W/m.K. Airtightness: the permeability of high-purity hydrogen at 100MPa is 1.1X 10-10mol/m2S-1Pa-1。
Claims (5)
1. A preparation method of a unipolar plate for a hydrogen fuel cell is characterized by comprising the following steps: the unipolar plate is prepared from expanded graphite and graphene; the method comprises the following steps:
the method comprises the following steps: preparing a mould: preparing a corresponding graphite mold according to the shape and the size of the unipolar plate, wherein the mold is made of high-strength graphite;
step two: filling: uniformly spreading expanded graphite powder in a mould, and scraping the surface of the mould; then adding a layer of graphene powder, and leveling the surface; finally, adding expanded graphite powder, and scraping the surface;
step three: preforming: pressurizing the filler obtained in the step two, pressurizing at a constant speed of 5-20 mm/min by a press, maintaining the pressure for 1-5 min after the pressure reaches 0.5-1 MPa, preforming to obtain a sandwich structure, and taking out the sandwich structure from a mold;
step four: pre-sintering: sintering the preformed sandwich structure at 500-1000 ℃ for 1-2 h in vacuum;
step five: compacting and forming; the densification forming adopts one of the following methods:
the method comprises the following steps: putting the sintered preformed body into a graphite mold, and carrying out hot-pressing sintering on the preformed body and the graphite mold in a hot-pressing sintering furnace;
the second method comprises the following steps: putting the sintered preformed body into a stainless steel mold, and pressurizing and maintaining the pressure on a hydraulic machine; after pressing, dipping in liquid, and then carrying out graphitization treatment, wherein the whole densification forming process is carried out in a vacuum environment;
step six: machining into the final structure.
2. The method of manufacturing a unipolar plate for a hydrogen fuel cell according to claim 1, wherein: step five, in the method one: the hot-pressing sintering process comprises the following steps: heating from room temperature to 700-2500 ℃ at a heating rate of 8-20 ℃/min, pressurizing, wherein the pressure is 20-60 MPa, the heat preservation and pressure maintaining time is 30-120 min, and the whole hot-pressing sintering process is carried out in a vacuum environment; the second method specifically comprises the following steps: putting the sintered preformed body into a stainless steel mold, and pressurizing on a hydraulic press, wherein the pressure is 100-300 MPa, and the pressure maintaining time is 5-30 min; and after pressing, dipping in liquid, and then carrying out graphitization treatment at 2500-3000 ℃ for 30-120 min, wherein the whole densification forming process is carried out in a vacuum environment.
3. The method of manufacturing a unipolar plate for a hydrogen fuel cell according to claim 1, wherein: in the second step, the graphene powder is a pure graphene material or a composite material which takes graphene as a matrix and is added with high-conductivity metal or alloy, wherein the addition amount of the metal or alloy is 1-5 vt%.
4. The method of manufacturing a unipolar plate for a hydrogen fuel cell according to claim 1, wherein: in the third step, in the sandwich structure, the thickness of the graphene layer is 50-200 μm.
5. A hydrogen fuel cell comprising a unipolar plate produced by the production method according to claim 1, characterized in that: the hydrogen fuel cell includes at least one unipolar plate.
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