CN102044679B - Method for preparing membrane electrode catalytic layer and gas sensor, and gas sensor - Google Patents
Method for preparing membrane electrode catalytic layer and gas sensor, and gas sensor Download PDFInfo
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- CN102044679B CN102044679B CN200910205510.1A CN200910205510A CN102044679B CN 102044679 B CN102044679 B CN 102044679B CN 200910205510 A CN200910205510 A CN 200910205510A CN 102044679 B CN102044679 B CN 102044679B
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Abstract
The embodiment of the invention discloses a method for preparing a membrane electrode catalytic layer and a method for preparing a gas sensor. The invention has the technical scheme that because the hydrophilic treatment is carried out on a carbon-carried catalyst, carbon powder grains are tightly piled, thus the prepared catalytic layer has better heat and electricity conductivity and simultaneously lays the foundation for reasonably filling organic proton conductors. The weight of the organic proton conductors filled in the gaps of all the carbon powder grains is calculated according to the duty ratio after the carbon powder grains are tightly piled, so that the unreasonable problem in the course of allocating the ratio of each composite material according to the method tried in the experiment in the prior art is overcome when the ratio of each raw material in the catalytic layer is allocated.
Description
Technical field
The present invention relates to membrane electrode technical field, be specifically related to preparation method and the gas sensor of a kind of membrane electrode catalytic layer, gas sensor.
Background technology
Fuel cell is clean, portable and the advantages such as the reproducible energy can be provided with it, in military field, and heat and power supply field, field of space technology, communication equipment has field of power supplies, transport field, and more and more important effect is being brought into play in portable electronics field etc.Wherein, Proton Exchange Membrane Fuel Cells (PEMFC, Proton Exchange Membrane Fuel Cell) is the fastest a kind of in the development of current fuel cell field.And membrane electrode (MEA, Membrane ElectrodeAssembly) is the key components of Proton Exchange Membrane Fuel Cells, its performance has very important impact to the overall performance of PEMFC.How by the main direction that low cost fabrication goes out efficiently, MEA is present stage research reliably.
As shown in Figure 1, the structural representation of MEA, comprising: diffusion layer 1, regulating course 2, Catalytic Layer 3, proton exchange membrane (PEM, Proton Exchange Membrane) 4, Catalytic Layer 5, regulating course 6, and diffusion layer 7 conventionally.Wherein, take proton exchange membrane 4 as boundary, MEA is divided into negative and positive the two poles of the earth.Needing explanation, in presents, is with diffusion layer 1, regulating course 2, and Catalytic Layer 3 one sides are anode, and with Catalytic Layer 5, regulating course 6, and diffusion layer 7 one sides are that negative electrode describes.Proton exchange membrane 4 can be so that the proton that anode produces passes, and prevents electronics that negative electrode produces through (preventing cathode and anode short circuit) and prevent that proton exchange membrane 4 both sides gases from passing self.Diffusion layer 1 and diffusion layer 7 be normally by carbon paper, or the material of carbon cloth and so on makes, and plays the effect of support, conduction, granule proliferation, discrete particles; Regulating course 2 and regulating course 6 are normally comprised of carbon dust and polytetrafluoroethylene (PTFE, i.e. Teflon), play passage and reproduce, the effects such as gas, moisture adjusting; Catalytic Layer 3 and Catalytic Layer 5 mainly by catalyst carbon, carry platinum (Pt/C) and Nafion resin forms, and is the core of chemical reaction in fuel cell.
Prior art provides a kind of method of preparing Proton Exchange Membrane Fuel Cells MEA Catalytic Layer, comprises the following steps:
Step 1: catalyst and organic proton conductor, heteropolyacid salt, organic solvent are mixed into slip; The mass ratio of catalyst, organic proton conductor, heteropolyacid salt and organic solvent is 10: 1～10: 1～10: 100～1000;
Step 2: this slip is produced on uniformly on the surface of a side of gas diffusion layers or proton exchange membrane, forms the electrode precursor body with Catalytic Layer;
Step 3: the electrode precursor soma by this with Catalytic Layer is dry, supported proton exchange film fuel cells electrode.
In the slurry that wherein prepared by above-mentioned prior art, catalyst is one or more in platinum (Pt), aluminium (Au), ruthenium (Ru), rubidium (Rh), silver (Ag), iridium (Ir), palladium (Pd), cobalt (Co), iron (Fe), titanium (Ti), manganese (Mn); Or be more than one carbon supported catalyst in them, the loading of catalytic active component is 20～80wt.%; Described heteropolyacid salt is for being preferably insoluble heteropoly acid, and molecular formula is YnH3-nXM12O40, YnH6-nXM18O62 (Y=Cs; X=p, Si; M=Mo, W) as the various cesium salts of the various cesium salts of phosphomolybdic acid, phosphotungstic acid.The cesium salt of silicomolybdic acid, the various cesium salts of silico-tungstic acid etc.
In above-mentioned prior art, organic proton conductor is perfluor or partially fluorinated SOLID ORGANIC proton electrolyte, as come from the Nafion solution of Dupont (DuPont) company, from Flemion solution or the Aciplex solution of Japanese Asahi Chemical company.Described catalyst, organic proton conductor are 1: 2～5: 2～5: 50～500 with the preferred mass ratio of heteropolyacid salt.
In the research and practice process to prior art, the present inventor finds: in prior art, it is the method for MEA Catalytic Layer in a kind of PEMFC of preparation finding out by great many of experiments, the consumption of the various raw materials that use in preparation process is that operating personnel repeatedly attempt summing up by experiment, this technology does not have reliable theoretical foundation, in the Catalytic Layer that makes to prepare, some material is in the use of MEA, do not perform to effect, cause Catalytic Layer chemical reaction efficiency not high, and, cause the part waste of material in Catalytic Layer, increased the cost of preparation Catalytic Layer.
Summary of the invention
The embodiment of the present invention provides a kind of preparation method of membrane electrode catalytic layer, makes in preparation Catalytic Layer more efficiently, has reduced the cost of Kaolinite Preparation of Catalyst layer.
The embodiment of the present invention provides a kind of preparation method of membrane electrode catalytic layer, comprising: configuration packet is containing the slip of catalyst, by the Catalytic Layer of the Pulp preparation membrane electrode configuring; Described configuration packet specifically comprises containing the slip of catalyst:
Carbon supported catalyst is added to water moistening;
Carbon powder particle is carried out to hydrophilic treated, make between described carbon powder particle tightly packed;
Duty ratio after tightly packed according to carbon powder particle, the mass ratio of carbon supported catalyst, and the quality of the carbon supported catalyst of current use, calculate the quality of filling organic proton conductor of hole between described closelypacked carbon powder particle;
Organic proton conductor of the quality of the organic proton conductor calculating described in quality is greater than or equal to, joins in the mixed slurry after hydrophilic treated;
Stir current mixed slurry, thereby described in obtaining, comprise the slip of catalyst.
The embodiment of the present invention also provides a kind of method of preparing gas sensor, comprises for the preparation of the gas compartment that fills tested gas, for the preparation of the gas compartment of dress calibrating gas, and prepares the external circuit of membrane electrode and described membrane electrode; The described method of preparing the Catalytic Layer in membrane electrode specifically comprises the preparation method of above-mentioned a kind of membrane electrode catalytic layer.
The embodiment of the present invention also provides a kind of gas sensor, comprises, and the first gas compartment, the second gas compartment, membrane electrode and external circuit, the Catalytic Layer in described membrane electrode adopts the preparation method as above-mentioned a kind of membrane electrode catalytic layer;
Described the first gas compartment, for filling tested gas;
Described the second gas compartment, for filling predefined calibrating gas;
Described membrane electrode is between described the first gas compartment and described the second gas compartment, and described tested gas and described calibrating gas carry out electrochemical reaction on described membrane electrode;
Described external circuit, arrives negative electrode for the electric transmission that the electrochemical reaction Anodic carrying out on described membrane electrode is produced, for the electrochemical reaction of carrying out in cathode side Catalytic Layer provides electronics.
The embodiment of the present invention adopts carries out hydrophilic treated to carbon supported catalyst, make between carbon powder particle tightly packed, thereby make can possess better heat conduction and conduction in the Catalytic Layer of preparation, for rationally filling organic proton conductor, lay the foundation simultaneously; Duty ratio after employing is tightly packed according to carbon powder particle, calculate the quality that is filled in organic proton conductor of hole between all carbon powder particles, make in configuration Catalytic Layer during each raw-material ratio, reduce the unreasonable problem that ratio that way that available technology adopting experiment attempts configures each composition material occurs, reduced the cost of Kaolinite Preparation of Catalyst layer.
Accompanying drawing explanation
In order to be illustrated more clearly in the embodiment of the present invention or technical scheme of the prior art, to the accompanying drawing of required use in embodiment or description of the Prior Art be briefly described below, apparently, accompanying drawing in the following describes is only some embodiments of the present invention, for those of ordinary skills, do not paying under the prerequisite of creative work, can also obtain according to these accompanying drawings other accompanying drawing.
Fig. 1 is the structural representation sketch of membrane electrode;
Fig. 2 is the simplified schematic diagram of the chemical reaction that carries out of the Catalytic Layer of the negative electrode of membrane electrode in the Five-channel principle of embodiment of the present invention institute foundation;
Fig. 3 is preparation method's general flow chart of a kind of membrane electrode catalytic layer of providing of the embodiment of the present invention one;
Fig. 4 is preparation method's general flow chart of a kind of membrane electrode catalytic layer of providing of the embodiment of the present invention two;
Fig. 5 is the locus of tightly packed rear each composition of Catalytic Layer of carbon ball that provides of the embodiment of the present invention;
Fig. 6 is the structural representation of the gas sensor that provides of the embodiment of the present invention three;
Fig. 7 is the method flow sketch of the gas sensor of the preparation that provides of the embodiment of the present invention four.
Embodiment
Below in conjunction with the accompanying drawing in the embodiment of the present invention, the technical scheme in the embodiment of the present invention is clearly and completely described, obviously, described embodiment is only the present invention's part embodiment, rather than whole embodiment.Embodiment based in the present invention, those of ordinary skills, not making the every other embodiment obtaining under creative work prerequisite, belong to the scope of protection of the invention.
The embodiment of the present invention provides a kind of preparation method of membrane electrode catalytic layer, the method is on the basis of the clear understanding of the chemical reaction carrying out in MEA based on inventor, the Five-channel method that instructs fuel cell exploitation summing up, in MEA, possesses rational proton channel, aquaporin, electron channel, the passage of heat, during with this five passages of gas passage, can so that in the Catalytic Layer in this MEA, can continue carry out electrochemical reaction.And, because inventor clearly recognizes the relation between each composition and structure in Catalytic Layer, solved a difficult problem that how to acquire theoretically the best in quality ratio of Catalytic Layer in the situation that various composition materials are definite, with in prior art owing to not understanding core reaction rule in Catalytic Layer, and the method for the Catalytic Layer of preparing membrane electrode of finding out according to experimental result is compared, the method of preparing Catalytic Layer that adopts the embodiment of the present invention to provide, can reduce on the basis of catalyst material waste, greatly increase the incidence of effective electrochemical reaction in Catalytic Layer.
Before the method that the present embodiment is provided explains, first five-way Dow process is explained, as shown in Figure 2, in the embodiment of the present invention, the electrochemical reaction in illustrated membrane electrode refers to the chemical reaction (being the chemical reaction carrying out in Catalytic Layer 5 in Fig. 1) that the Catalytic Layer of the negative electrode of membrane electrode is carried out.In the Catalytic Layer of negative electrode, from proton exchange membrane conduction, enter the H this Catalytic Layer
+, under the catalytic action of catalyst Pt, be combined with electronics, and with the oxygen reaction that enters this Catalytic Layer, finally generate water.The place that above-mentioned reaction occurs in this Catalytic Layer can be called reflecting point (or be called " reaction singular point ").Therefore,, in order to guarantee that fuel cell can provide lasting, electric energy reliably, in the Catalytic Layer of the negative electrode of MEA, need to reasonably address the problem:
(1), how by the proton transport of conducting from proton exchange membrane to reaction singular point;
(2), how by the electric transmission of carrying on external circuit to reaction singular point;
(3), how oxygen is transferred on reaction singular point by gas passage;
(4), how the water producing due to chemical reaction on reaction singular point is discharged from Catalytic Layer;
(5), how the heat producing due to chemical reaction on reaction singular point is discharged from Catalytic Layer.
When reasonably solved above-mentioned five problems in Catalytic Layer, on microcosmic, can find out, the chemical reaction carrying out in Catalytic Layer (is more fully in the Catalytic Layer of same volume, it is more than the reaction singular point in the Catalytic Layer rationally not addressing the above problem in Catalytic Layer after rationally addressing the above problem, to react singular point), and reasonably dredge water and heat that chemical reaction produces, make Catalytic Layer safety and reliability.
Problem based on required solution in above-mentioned Catalytic Layer, can be from selecting rational Catalytic Layer composition material, and the angle of understanding the relation between each component structure in Catalytic Layer is explored.For example: in Catalytic Layer, adopt Pt/C catalyst, wherein, carbon powder particle has good conductivity and thermal conductivity, carbon can be used as conducting medium and heat-conducting medium, therefore, the conducting medium that can comprise from selective catalysis layer for deal with problems (2) and (4) and the material of heat-conducting medium are started with, then, consider again how in Catalytic Layer, to distribute between carbon powder particle, make conduction and heat conduction more efficient; For (1) problem of solution, make Catalytic Layer have the ability of good proton conducting, therefore, in Catalytic Layer, need to consider to add the material with proton conducting ability, as the Nafion resin of du pont company's production, in order to guarantee the unimpeded of proton channel, also need to consider the distributed architecture between carbon powder particle and Nafion resin.In the explanation of follow-up specific embodiment, can more describe the embodiment of the present invention in detail when preparation Catalytic Layer according to above-mentioned thinking, how to address the above problem.
Also it should be noted that, the material in the Catalytic Layer shown in Fig. 2 is Pt/C and Nafion resin, and wherein, Pt/C is as catalyst, and Nafion resin (is the H shown in Fig. 2 as the medium of proton conducting
+).Also it will be appreciated that, the catalyst using in the embodiment of the present invention can be not limited to the Pt/C of above-mentioned explanation, can also be carbon carry silver (Ag/C), carbon carry titanium (Ti/C), carbon carry the carbon supported catalysts such as manganese (Mn/C) wherein any one; Medium (being organic proton conductor) for proton conducting in the embodiment of the present invention can be not limited to Nafion resin, can also be other material as the DOW film of DOW chemical company, the aciplex film of Ashaichemical company etc.
It will be appreciated that, the catalyst of below mainly take in Catalytic Layer in the specific embodiment of explanation is Pt, organic proton conductor is that Nafion resin describes, the preparation method of the Catalytic Layer that catalyst, organic proton conductor are other, can be Pt according to catalyst, organic proton conductor be that the method for preparing Catalytic Layer of Nafion resin easily draws.
Technical scheme the invention process being provided below in conjunction with specific embodiment is elaborated.
Embodiment mono-,
The embodiment of the present invention provides a kind of preparation method of membrane electrode catalytic layer, and the method comprises two stages, and first stage is the slip that configuration packet contains catalyst; Second stage is according to the slip of configuration, prepares the Catalytic Layer of membrane electrode.Wherein, the first stage configuration packet in the method, containing the slip of catalyst, as shown in Figure 3, specifically comprises:
Step S1: carbon supported catalyst is added to water moistening;
Wherein, in step S1, the mass ratio of carbon supported catalyst is known, refer to because the concrete purposes of MEA is different, and to the requirement of the mass ratio of carbon supported catalyst, be different, be A designer person determined according to actual needs.For example: the Pt/C that normally used mass ratio is 30% (mass ratio that is Pt and C is: 3: 7), mass ratio can be also 35% or 28% in another embodiment certainly, the embodiment of the present invention is not done special restriction.
Step S2: carbon powder particle is carried out to hydrophilic treated, make between described carbon powder particle tightly packed;
It should be noted that, carbon powder particle is due to manufacture craft, is all not regular, identical spherical, because carbon dust primary particle is in nanoscale, having nanoscale effect, is mutually exclusive between carbon powder particle, and this is also the main cause that carbon powder particle density is very little.Although this phenomenon has guaranteed specific area, but, unavoidably increased the contact internal resistance between carbon dust, in macroscopic view, internal resistance is less, but on microcosmic, consider that the contact internal resistance difference between variable grain is very large, from the micro-reaction zone of electrochemistry, different tiny area reaction heat is different, can cause the consistency of reaction very poor, and then cause the life-span of compartmentalization different.And owing to being mutually exclusive between carbon powder particle, causing between carbon powder particle can not close contact, makes carbon in Catalytic Layer fail to reach best for the performance of heat conduction and conduction.
Therefore, need to carry out hydrophilic treated to carbon powder particle, take Pt/C as example, concrete hydrophilic treated step can be: to adding in the Pt/C after water, add isopropyl alcohol.Thereby guarantee that between Pt/C particle, close contact is piled up.It should be noted that, due to the volume of Pt particle, compare very littlely with C particle volume, can ignore the volume of Pt particle, therefore, can think that after hydrophilic treated, carbon powder particle is tightly packed.
Step S3: the duty ratio after tightly packed according to carbon powder particle, the mass ratio of carbon supported catalyst, and the quality of the carbon supported catalyst of current use, calculate the quality of filling organic proton conductor of hole between described closelypacked carbon powder particle;
It will be appreciated that, theoretical according to Five-channel, need to guarantee to have in catalyst the medium of proton conducting, and guarantee the common of proton channel, in above-mentioned steps S2, carbon powder particle is carried out after hydrophilic treated, between carbon powder particle, be closelypacked, make proton channel unobstructed, just the material of proton conducting need to be filled in the hole between all carbon powder particles.
Therefore, the duty ratio after tightly packed according to carbon powder particle in above-mentioned steps S3, and the carbon of described preset mass ratio carries the quality of platinum, easily calculates the quality of the Nafion resin that is filled in hole between all carbon powder particles.
Step S4: the organic proton conductor calculating described in quality is greater than or equal to organic proton conductor of quality, join in the mixed slurry after hydrophilic treated;
Wherein, the Nafion resin of the quality of the Nafion resin calculating described in quality being greater than or equal in step S4, join including in the mixed solution that carbon carries platinum after hydrophilic treated, ensure first in quality enough Nafion resins and can be filled in the hole between all carbon powder particles.In the situation that carbon supported catalyst mass ratio is definite, can determine the mass ratio of the Nafion resin of selection, by really realizing in follow-up step S5 Nafion resin filling in the hole between all carbon powder particles.
Step S5: stir current mixed slurry, thereby comprise the slip of catalyst described in obtaining.
Wherein, on the basis of the Nafion resin of the enough quality that provide in step S4, specifically can fully stir by high-shear homogenizer, can realize Nafion resin filling in the hole between all carbon powder particles.
Also it should be noted that, because Nafion resin has hydrophily, make when this Catalytic Layer is carried out chemical reaction, the passage of water that one of can action-reaction product.And in Five-channel theory is thought, matter field is as same electric field, matter stream is as electric current, as long as there is potential difference to exist, the transmission of proton is as electronics transmission, and only symbol is different different with conductive medium for the two, as long as after proton exchange membrane saturated aqueous, sulfonate radical wherein becomes movable, and this is the key that matter field is set up.Once proton A of hydrogen gas side produces in course of reaction, the proton B of air side in Nafion resin will participate in reaction immediately simultaneously, do not exist so-called proton A participating in reaction afterwards through film.Therefore, in Catalytic Layer, can be used as the Nafion resin of aquaporin, after saturated aqueous, make proton conductivity better.
The explanation of preparation method by above-mentioned a kind of membrane electrode catalytic layer that the embodiment of the present invention one is provided, the method adopts carries out hydrophilic treated to carbon powder particle, make between described carbon powder particle tightly packed, thereby make in the Catalytic Layer of preparation better heat conduction and conduction (or, be interpreted as transmission electronic);
Simultaneously, duty ratio after employing is tightly packed according to carbon powder particle, the mass ratio of carbon supported catalyst, quality with the carbon supported catalyst of current use, calculate the quality that is filled in organic proton conductor of hole between all carbon powder particles, while making in configuration Catalytic Layer the ratio of each material, overcome available technology adopting experiment and attempted configuring the unreasonable problem that the ratio of each composition material occurs, reduced the cost of Kaolinite Preparation of Catalyst layer.
Embodiment bis-,
The embodiment of the present invention provides a kind of preparation method of membrane electrode catalytic layer, and the method is similar to the method that embodiment mono-provides, and the preparation method of a kind of membrane electrode catalytic layer that the present embodiment provides is a kind of preparation method more specifically.The method also comprises two stages, and first stage is the slip that configuration packet contains catalyst; Second stage is according to the slip of configuration, prepares the Catalytic Layer of membrane electrode.Wherein, in this Catalytic Layer, catalyst is Pt, and organic proton conductor is Nafion resin, and the first stage configuration packet in the method, containing the slip of catalyst, as shown in Figure 4, specifically comprises:
Step 401: the hydroxyl on carbon powder particle is carried out to homogenizing processing; Carbon dust after homogenizing is processed adds and includes Pt
2+cushioning liquid in, prepare carbon and carry platinum;
Wherein, it should be noted that, catalyst granules is evenly distributed on carbon powder particle, can guarantee the effective ratio of catalyst in Catalytic Layer, thereby effectively play catalytic action.Therefore, need to obtain satisfactory carbon and carry platinum in step 401, Pt particle equally distributed carbon around C particle carries platinum.
Take Pt/C as example, specifically can the comprising of step 401: the hydroxyl on carbon powder particle is carried out to homogenizing processing, hydroxyl is evenly distributed on each carbon powder particle; Carbon powder particle after homogenizing is processed adds and includes Pt
2+cushioning liquid in, make Pt
2+with hydroxy combining, will with Pt
2+in conjunction with hydroxyl reduction, thereby guarantee that platinum grain is uniformly distributed at described carbon powder particle around.
Step 402: similar to embodiment mono-step S1, being about to carbon supported catalyst, to add water moistening, describes in detail and please refer to embodiment mono-;
Step 403: similar to embodiment mono-step S2, that is: carbon powder particle is carried out to hydrophilic treated, make between described carbon powder particle tightly packedly, describe in detail and please refer to embodiment mono-;
Step 404: the duty ratio after tightly packed according to carbon powder particle six sides is 74.1: 25.9, and the carbon of described preset mass ratio carries the quality of platinum, calculates the quality of filling the Nafion resin of hole between described closelypacked carbon powder particle;
Wherein, carbon powder particle six sides tightly packed can to get duty ratio by Mathematical Modeling be 74.1: 25.9.
It should be noted that, it because six sides are tightly packed, is a kind of theoretic value, due to carbon powder particle size heterogeneity, cause porosity to reduce, therefore, hole after can also be tightly packed according to six sides is 1.1 times of hole after reducing, and it is 23.5 that above-mentioned porosity value 25.9 is obtained to porosity value divided by 1.1, thereby the duty ratio obtaining after tightly packed is (100-23.5): 23.5=3.26; According to described duty ratio after tightly packed, be 3.26, and the carbon of described preset mass ratio carries the quality of platinum, calculate the quality of filling the Nafion resin of hole between described closelypacked carbon powder particle.This scheme can be used as the alternative operation of step 404.
It should be noted that, the hole after six sides that mention are here tightly packed is the numerical value 1.1 in 1.1 times of hole after reducing, is an empirical value.In another embodiment, can also be other numerical value such as 1.15 times, 1.09 times, 1.2 times, when being other numerical value, duty ratio is corresponding difference again, and the embodiment of the present invention is not done special restriction.
For example: when the carbon supported catalyst of preset mass ratio is: 30% Pt/C can calculate the optimal proportion (or quality) of used Nafion resin in step 404.Specifically comprise:
According to given data: Φ
pt(platinum grain diameter)=2.5nm; Φ
c(carbon powder particle diameter)=40nm; Φ
nafion(Nafion particle diameter)=2～4nm;
ρ
pt(platinum density)=43 ρ
c(carbon density)=21.45g/cm
3, toner density=0.5g/cm
3;
Density=the 1.25g/cm of Nafion resin
3;
V
c(carbon powder particle volume)=4000V
pt(platinum grain volume)=4000V
nafion(Nafion particle diameter)
By above data, can be inferred if Pt is dispersed on C carrier, there are 40 Pt balls on each carbon ball surface, but due to volume great disparity, therefore when considering Nafion consumption, need not consider the volume of Pt, and illustraton of model (carbon ball is tightly packed) as shown in Figure 5.
According to as previously mentioned, duty ratio: V
carbon ball: V
hole=3.26: 1; Follow again according to the density of carbon ball and the density of Nafion and show that the mass ratio of the two is M
c: M
nafion=1.3: 1.Suppose that Nafon volume is 1cm
3, the volume of carbon dust is 3.26cm
3, Nafion quality is 1.25g, the quality of carbon be 1.63g (wherein, 1.63=3.26*0.5); The quality of Pt/C be 2.33g (wherein, 2.33=1.63/70%); Finally show in Catalytic Layer that the theoretical optimal proportion of Nafion is 34.9% (wherein, Nafion quality/(Nafion quality+Pt/C quality)=1.25g/ (1.25g+2.33g)=34.9%), when adopting 30% catalyst in many documents, the record that Nafion optimal proportion is 35% is very identical.
Step 405: similar to embodiment mono-step S4, that is: the Nafion resin of the quality of the Nafion resin calculating described in quality is greater than or equal to, join including in the mixed solution that carbon carries platinum after hydrophilic treated, describe in detail and please refer to embodiment mono-;
Step 406: similar to embodiment mono-step S5, that is: stir current mixed slurry, thereby described in obtaining, comprise the slip of catalyst, describe in detail and please refer to embodiment mono-.
Explanation according to above-mentioned steps 401 to step 406, can prepare the slip that comprises the various materials of Catalytic Layer, need to carry out to this slip the processing of second stage, according to the slip of configuration, prepares the Catalytic Layer of membrane electrode.
Wherein, according to the slip of configuration, the operation of preparing the Catalytic Layer of membrane electrode can adopt operation same as the prior art, this operation can specifically comprise: by configuration described slip 30～90 ℃ of heating, make described slip retrogradation, the slip after retrogradation is directly coated in the proton exchange membrane of described membrane electrode, or, directly be coated on the regulating course of described membrane electrode, thereby formed the Catalytic Layer of membrane electrode.
Also it should be noted that, can adopt slip coating is dried, and the thickness of controlling the Catalytic Layer that is dried the rear membrane electrode forming is at 0.5～5 micron.
In aforesaid operations, by the THICKNESS CONTROL of Catalytic Layer, the reason of 0.5～5 micron, be why, in Five-channel theory, to guarantee that the smooth and easy of gas passage is the problem should be noted that when preparation Catalytic Layer.Transmission rate according to gas in Nafion resin and the impact of considering current density and concentration polarization, catalyst is too thick or too inhomogeneous, Catalytic Layer can not be too thick, gas diffusion is difficult to, cause concentration polarization (wherein, concentration polarization, refers to the phenomenon of the voltage drop causing when air feed speed is fast not), thus can cause the performance of Catalytic Layer to reduce.Therefore, the concrete manufacture craft of Catalytic Layer can adopt catalyst to be directly coated in (CCM, Catalyst Coated Membrane) on film, not only can reduce the consumption of catalyst, can also improve the performance of Catalytic Layer.
The explanation of preparation method by above-mentioned a kind of membrane electrode catalytic layer that the embodiment of the present invention two is provided, the method adopts carries out hydrophilic treated to carbon powder particle, make between described carbon powder particle tightly packed, thereby make in the Catalytic Layer of preparation better heat conduction and conduction (or, be interpreted as transmission electronic); Duty ratio after employing is tightly packed according to carbon powder particle, the quality of carrying platinum with the carbon of described preset mass ratio, calculate the quality of the Nafion resin that is filled in hole between all carbon powder particles, while making in configuration Catalytic Layer the ratio of each material, overcome available technology adopting experiment and attempted configuring the unreasonable problem that the ratio of each composition material occurs.
Further, the method adopts and obtains, there is catalyst granules equally distributed carbon supported catalyst (as: Pt uniform particles is distributed in the circumgranular Pt/C of C) around carbon powder particle, guarantee the effective ratio of catalyst in Catalytic Layer, thereby effectively play catalytic action.
Further, in the method, limit the thickness of the Catalytic Layer of preparing, made gas passage more reasonable, more unobstructed.Not only the consumption of catalyst can be reduced, the performance of Catalytic Layer can also be improved.
Embodiment tri-,
The embodiment of the present invention provides a kind of gas sensor, as shown in Figure 6, is the structural representation sketch of this gas sensor, and this gas sensor comprises the first gas compartment 10 and 20, two gas compartments of the second gas compartment, membrane electrode (MEA) 30 and external circuit 40.As shown in Figure 6, MEA is between two gas compartments.
The first gas compartment 10, for filling tested gas;
The second gas compartment 20, for filling predefined calibrating gas;
Membrane electrode 30, between the first gas compartment 10 and the second gas compartment 20, described tested its body and many core calibrating gas carry out electrochemical reaction on described membrane electrode;
External circuit 40, arrives negative electrode for the electric transmission that the electrochemical reaction Anodic carrying out on membrane electrode 30 is produced, for the electrochemical reaction of carrying out in cathode side Catalytic Layer provides electronics.
In one embodiment, the first gas compartment is for filling tested gas, and the second gas compartment is used for filling calibrating gas.This calibrating gas can preset as required, and as in one embodiment, if this gas sensor is hydrogen gas sensor, calibrating gas is oxygen, and tested gas can can also be also the mist of hydrogen and other gas for air for hydrogen.
It should be noted that, in this MEA, the preparation method of Catalytic Layer adopts the method for preparing Catalytic Layer in MEA that embodiment mono-or embodiment bis-provide.
For the ease of understanding the method for this gas sensor of preparation, need to do necessary explanation to the operation principle of gas sensor, in tested gas, include the gas of proton required in can providing MEA, as: can be hydrogen in one embodiment.And calibrating gas in the second gas compartment of MEA opposite side, as being oxygen in one embodiment, refers to the gas that flows to Catalytic Layer in MEA in five-way Dow process in gas passage.The voltage that user can produce according to MEA gets in measurement gas can put forward for MEA the concentration of protogenic gas, thereby realizes the effect of gas sensing.
Further, when preparing gas sensor, in the MEA using at gas sensor, needed is mainly magnitude of voltage, can there is no electric current, or electric current is very little.Therefore, can on external circuit, strengthen resistance.
Further, when preparing gas sensor, the diffusion layer of MEA is had relatively high expectations to gas diffusivity, therefore, the gas diffusion layers of MEA can add the Teflon (PTFE) (wherein, PTFE has hydrophobicity) of high concentration, thereby guarantees the quick through diffusion layer of gas.
For example, can adopt in one embodiment concentration is 20%～60% PTFE.Can adopt in one embodiment concentration is 20% PTFE, can adopt in one embodiment concentration and be 60% PTFE, can also adopt in another embodiment concentration is 40% PTFE, and can also adopt in another embodiment concentration is 50% PTFE.
The gas sensor that the present embodiment provides, compare with the gas sensor that existing method is prepared, reducing on the cost basis of Catalytic Layer, greatly improved the performance of Catalytic Layer, thereby made gas sensor can record more accurately the concentration of hydrogen in tested gas.
Embodiment tetra-
Accordingly, as shown in Figure 7, the embodiment of the present invention provides the method for the gas sensor in Preparation Example three in, comprising:
Step 501, for the preparation of the gas compartment that fills tested gas;
Step 502, for the preparation of the gas compartment of dress calibrating gas;
Step 503, prepares the external circuit of membrane electrode and this membrane electrode.
The method of preparing Catalytic Layer in MEA that the method for the Catalytic Layer in membrane electrode specifically adopts embodiment mono-or embodiment bis-to provide is provided.
Further, when preparing gas sensor, the diffusion layer of MEA is had relatively high expectations to gas diffusivity, therefore, the gas diffusion layers of MEA can add the Teflon (PTFE) (wherein, PTFE has hydrophobicity) of high concentration, thereby guarantees the quick through diffusion layer of gas.
For example, can adopt in one embodiment concentration is 20%～60% PTFE.Can adopt in one embodiment concentration is 20% PTFE, can adopt in one embodiment concentration and be 60% PTFE, can also adopt in another embodiment concentration is 40% PTFE, and can also adopt in another embodiment concentration is 50% PTFE.
The gas sensor that the method that the present embodiment provides is prepared, compare with the gas sensor that existing method is prepared, reducing on the cost basis of Catalytic Layer, greatly improved the performance of Catalytic Layer, thereby made gas sensor can record more accurately the concentration of hydrogen in tested gas.
A kind of the membrane electrode catalytic layer above embodiment of the present invention being provided, preparation method and the gas sensor of gas sensor are described in detail, applied specific case herein principle of the present invention and execution mode are set forth, the explanation of above embodiment is just for helping to understand method of the present invention and core concept thereof; , for one of ordinary skill in the art, according to thought of the present invention, all will change in specific embodiments and applications, in sum, this description should not be construed as limitation of the present invention meanwhile.
Claims (10)
1. a preparation method for membrane electrode catalytic layer, comprising: configuration packet is containing the slip of catalyst, by the Catalytic Layer of the Pulp preparation membrane electrode configuring; It is characterized in that, described configuration packet specifically comprises containing the slip of catalyst:
Carbon is carried to platinum, and to add water moistening, and described catalyst is specially platinum;
Carbon is carried to platinum and carry out hydrophilic treated, make described carbon carry platinum grain evenly distributed;
Suppose that it is that the tightly packed computed duty cycle of six sides is 74.1 that evenly distributed described carbon carries between platinum grain
:25.9;
According to described duty ratio, carbon carries the mass ratio of platinum, and the carbon of current use carries the quality of platinum, calculates and fills the quality that described closelypacked carbon carries organic proton conductor of hole between platinum grain; Wherein, the mass ratio that carbon carries platinum is the percentage of the quality of platinum and carbon dust, and organic proton conductor is Nafion resin;
Described in quality is equaled, calculate the Nafion resin of quality, join in the mixed slurry after hydrophilic treated;
Stir current mixed slurry, thereby described in obtaining, comprise the slip of catalyst.
2. the preparation method of a kind of membrane electrode catalytic layer according to claim 1, is characterized in that, described carbon carries in platinum, and catalyst platinum uniform particles is distributed in around carbon powder particle.
3. the preparation method of a kind of membrane electrode catalytic layer according to claim 1, is characterized in that, described by carbon carry platinum add water moistening before, described method also comprises:
Hydroxyl on carbon powder particle is carried out to homogenizing processing;
Carbon dust after homogenizing is processed adds and includes pt
2+cushioning liquid in, prepare carbon and carry platinum.
4. the preparation method of a kind of membrane electrode catalytic layer according to claim 1, is characterized in that, the Catalytic Layer of the described Pulp preparation membrane electrode with configuration, specifically comprises:
Slip coating is dry, and the thickness of controlling the Catalytic Layer that is dried the rear membrane electrode forming is at 0.5～5 micron.
5. the preparation method of a kind of membrane electrode catalytic layer according to claim 1, is characterized in that
Due to described carbon powder particle size heterogeneity, cause the hole between the carbon powder particle after tightly packed to reduce, wherein, the hole after six sides are tightly packed is 1.1 times of hole after reducing, thus the duty ratio obtaining after tightly packed is 3.26;
According to described duty ratio after tightly packed, be 3.26, carbon carries the mass ratio of platinum, and the carbon of current use carries the quality of platinum, calculates the quality of filling the Nafion resin of hole between described closelypacked carbon powder particle.
6. the preparation method of a kind of membrane electrode catalytic layer according to claim 5, is characterized in that, the percentage that carbon carries the quality of platinum and carbon dust in platinum is 30%;
Described duty ratio is 3.26, and carbon carries the mass ratio of platinum, and the carbon of current use carries the quality of platinum, knows the volume in the space of hole between described closelypacked carbon powder particle, and wherein, the volume of Pt particle is ignored;
According to Nafi
othe density of n resin, and the volume in the space of hole between described closelypacked carbon powder particle, know and fill the required Nafi of all holes
othe quality of n resin.
7. the preparation method of a kind of membrane electrode catalytic layer according to claim 1, is characterized in that, the Catalytic Layer of the described Pulp preparation membrane electrode with configuration, specifically comprises:
The described slip of configuration, 30～90 ℃ of heating, is directly coated in the slip after retrogradation in the proton exchange membrane of described membrane electrode, or, be directly coated on the regulating course of described membrane electrode, form the Catalytic Layer of membrane electrode.
8. a method of preparing gas sensor, comprises for the preparation of the gas compartment that fills tested gas, for the preparation of the gas compartment of dress calibrating gas, and prepares the external circuit of membrane electrode and described membrane electrode; It is characterized in that, the described method of preparing the Catalytic Layer in membrane electrode is the preparation method as described in claim 1 to 7 any one specifically.
9. a kind of method of preparing gas sensor according to claim 8, is characterized in that, the diffusion layer in membrane electrode, specifically comprises:
The Teflon that employing concentration is 20%～60% is as diffusion layer material, and the Teflon that described concentration is 20%～60% refers to that the mass percent of Teflon and water is 20%～60%.
10. a gas sensor, comprises, the first gas compartment, the second gas compartment, membrane electrode and external circuit, is characterized in that, the Catalytic Layer in described membrane electrode adopts the method preparation as described in claim 1 to 7 any one;
Described the first gas compartment, for filling tested gas;
Described the second gas compartment, for filling predefined calibrating gas;
Described membrane electrode is between described the first gas compartment and described the second gas compartment, and described tested gas and described calibrating gas carry out electrochemical reaction on described membrane electrode;
Described external circuit, arrives negative electrode for the electric transmission that the electrochemical reaction Anodic carrying out on described membrane electrode is produced, for the electrochemical reaction of carrying out in cathode side Catalytic Layer provides electronics.
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| CN1560949A (en) * | 2004-02-20 | 2005-01-05 | �人����ѧ | Catalyst coated membrane fuel cell by indirect method ultrathin core assembly for synthetising |
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