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INVENTION
Patent of the Russian Federation RU2262161
NEW TYPES OF FUEL
The name of the inventor: PELED Emanuel (IL); DUVDEVANI Tahir (IL); MELMAN Avi (IL); Aharon Adi (IL)
The name of the patent holder: TEL-AVIV UNIVERSITY FUTURE TECHNOLOGY DEVELOPMENT LP. (IL)
Address for correspondence: 129010, Moscow, ul. B. Spasskaya, 25, p. 3, LLC "Law firm Gorodissky & Partners", Pat. EE Nazina
Date of commencement of the patent: 2001.01.18
The invention relates to fuel cells and organic fuels intended for use in fuel cells. The technical result of the invention is the choice of the most active organic fuels. According to the invention, the use of dimethyl oxalate, ethylene glycol, its oxalic acid esters, glyoxalic acid and formic acid, glyoxylic acid and its methyl esters, glyoxyalkaldehyde and polyethylene oxalate for fueling fuel cells, fuel cells supplied as fuel with these compounds, a hybrid source Energy, containing these fuel cells, and a method for determining their concentration in solution.
DESCRIPTION OF THE INVENTION
The invention relates to fuel cells and organic fuels intended for use in fuel cells.
Hydrocarbons and aliphatic alcohols with great difficulty undergo electrolytic oxidation completely (J. Wong, S. Wosmus and RFSavinell (J. Wang, S. Wasmus, RFSavinell), Journal of the Electrochemical Society (J. Electrochem. Soc.) 142, 4218 (1995)), the basic oxidation products of aliphatic alcohols are aldehydes or ketones, CO 2 and acids or esters. Even at a temperature of 190 ° C, ethanol oxidation is not complete in a fuel cell with a polymer electrolyte membrane (TEM), the main oxidation product (over 60%) is ethanol, while CO 2 is less than 40% of oxidation products. A compound that does not give an electrooxidation of up to 80% or more can not be considered an effective fuel. As is well known to the inventors, there have never been reports of complete electrooxidation of a compound having a C-C bond, except for oxalic acid (BC Bagotsky and IB Vasiliev, Elec-trochemica Acta 9, 869 (1964)). There are several publications that offer fuel for use in fuel cells. Among them, US Pat. No. 5,599,638 mentions the use of methanol, formaldehyde, formic acid, dimethoxymethane, trimethoxymethane and trioxane. Looking at approximately 150 organic compounds as a potential fuel for fuel cells carried out by NASA (NASA report No. SP-120 (1967), chapter 15, page 225 and the following), only methanol was tested for suitability as an efficient fuel. Other organic molecules were examined in acid, neutral or basic solutions for their half-cell potential, the electrode voltage was measured at different currents and temperatures, and the maximum power per cm 2 was calculated, assuming a theoretical oxygen electrode. All the molecules that were screened showed some maximum power in the range of 1-250 mW / cm 2 . However, this parameter does not indicate whether the connection is a good candidate as a fuel. For example, methanol, which is considered a good organic fuel, and ethanol, which can hardly be considered as a fuel, have demonstrated similar values of maximum power in an acid medium (13 and 15 mW / cm 2, respectively). In SP-120 (Chapter 16, p. 262 et seq.), It was reported that ethylene glycol and urea have poor performance (in a 30% KOH fuel cell). Some of the other molecules mentioned in this NASA report are glycerol, glyoxal aldehyde and glyoxylic acid.
The present invention provides organic fuels for fuel cells. The organic fuels of the present invention are selected from the group consisting of dimethyl oxalate, ethylene glycol, its esters of oxalic acid, glyoxalic acid and formic acid, glyoxylic acid and its methyl esters, glyoxyalkaldehyde and polyethylene oxalate, wherein the latter is a polyester of oxalic acid And ethylene glycol. The organic fuels of the invention are subjected to pure and efficient oxidation in non-alkaline fuel cells, especially acidic fuel cells. Preferred fuels according to the present invention are dimethyl oxalate, ethylene glycol, formic acid ester, ethylene oxalate and polyethylene oxalate. The most preferred fuels according to the present invention are ethylene glycol and dimethyl oxalate. Preferred fuels of the invention are those fuels more than 80% of which are converted to CO 2 and leave only minor amounts of non-volatile by-products when used as fuel in the fuel cell.
Non-limiting examples of fuel cells that can work satisfactorily with the fuel of the invention include fuel cells with liquid feed, fuel cells with gaseous starting material, high temperature fuel cells, solid oxide fuel cells, molten carbonate fuel cells and fuel cells , Which use proton-exchange or proton-conducting membranes. Preferred are fuel cells that use proton exchange or proton-conducting membranes, or fuel cells with a solid oxide.
In addition, the invention provides mixtures of the fuels of the invention, as well as mixtures of fuels of the invention with known organic fuels such as methanol for use as fuel in fuel cells.
Some of the fuels of the invention may be useful in use with alkaline fuel cells, especially at elevated temperatures. However, when an alkaline electrolyte is used, it may be necessary to replace it from time to time due to incomplete electro-oxidation of fuel in the main environment and the accumulation of carbonates or other organic salts caused by this incomplete electro-oxidation.
When the fuel cells function with the fuel of the invention, they exhibit a transient current density that is lower than the transition current density exhibited by the fuel cells when working with methanol, which is currently the most widely used fuel in such cells. A low transient current leads to high efficiency. In order not to be bound to theory, it can be assumed that low transient currents are due to the large size of the fuel molecules of the invention, as compared to the size of methanol molecules. The large size of the molecules correlates with a small diffusion coefficient, which leads to a low density of the transient current.
In addition, the fuels of the invention have higher boiling points than methanol, thus passing through the proton-conducting membrane mainly in their liquid phase. Naturally, the diffusion coefficient in the liquid phase is less than in the gas phase.
Solid fuels of the invention, such as dimethyl oxalate and polyethylene oxalate, can have advantages over liquid fuels like methanol for several reasons, for example, their easier handling and lower solubility in water. Thus, they maintain a low concentration, which helps in maintaining a low transient current. In addition, it is possible to store their saturated solutions, for example, in the anode chamber of the fuel cell, together with a significant amount of solid fuel that dissolves when the element is functioning and the fuel is consumed, while the undissolved solid fuel serves as a fuel reserve.
In accordance with another of its aspects, the invention provides a direct oxidation fuel cell having an anode, a cathode, a proton-conducting membrane disposed between said anode and said cathode, means for supplying organic fuel to the anode, and means for supplying oxygen to the cathode, wherein said organic fuel Is selected from the group consisting of dimethyl oxalate, ethylene glycol, oxalic acid esters, glyoxalic acid and formic acid, glyoxylic acid and its methyl esters, glyoxyalkaldehyde and polyethylene oxalate. Preferred elements according to this aspect of the invention are those in which the fuel is selected from the group consisting of dimethyl oxalate, ethylene glycol, its oxalic acid esters and formic acid and polyethylene oxalate. The most preferred fuel cells according to this aspect of the present invention are those in which the fuel is selected from the group consisting of ethylene glycol and dimethyl oxalate.
In accordance with one embodiment, the fuel cell according to this aspect of the present invention is further characterized in that the CO 2 generated during its operation is discharged through a thin hydrophobic porous matrix placed in the anode compartment or into a fuel tank, thereby enabling gas removal Without loss of solution.
In accordance with another of its embodiments, the present invention provides a fuel cell that is specifically adapted to operate with the fuel of the invention. Such a fuel cell is characterized by the presence of a cathode comprising, in addition to the oxygen reduction catalyst, a fuel oxidation catalyst not limited to Pt-Ru, Pt-Sn, Pt-Ru-Sn, Pt-Ag-Ru, Pt-Os or A combination of these catalysts. The oxidation catalyst of the fuel in the cathode improves the oxidation of the fuel that passes through the membrane and prevents deactivation of the oxygen reduction catalyst at the cathode, which is usually a Pt catalyst or a Pt alloy. The practical relationship between the reduction catalyst and the oxidation catalyst is between 1% and 50%, preferably 5% and 20% (percent by weight), or between 0.01 and 5 mg, preferably between 0.05 and 0.2 mg of the oxidation catalyst at 1 cm 2 of the oxygen electrode.
The invention further provides, according to another of its aspects, a method for estimating the concentration of new fuels at a predetermined temperature, the method comprising the following steps:
(A) preparing calibration curves of the transient current as a function of the fuel concentration at said predetermined temperature in the fuel cell;
(B) measuring the transient current at said predetermined temperature in said fuel cell; and
(C) determining the fuel concentration based on the current measured in step (b) and the calibration curve prepared in step (a).
This method is based on the work of inventors who have discovered that the transient current in the fuel cells of the invention is directly proportional to the fuel concentration. For example, it was found that the density of the transient current of 1 g-mole (gram-molecule) of ethylene glycol at 80 ° C was twice as large as the density of the transient current of 0.5 g-mole ethylene glycol at the same temperature (41 and 19 mA / cm 2, respectively), and the density of the transition current of 0.25 gmole of dimethyl oxalate at 60 ° C was approximately 2.5 times greater than the transition current density of 0.1 gmole of dimethyl oxalate at the same temperature (2.5 and 0, 9 mA / cm 2, respectively). This conclusion is valid under conditions that ensure that the measured current does not depend on the voltage at which it is measured.
The method of the invention can be used to measure fuel concentration in a fuel solution in a running fuel cell. It can be performed by measuring the transient current in a functioning fuel cell. Alternatively, it is possible to provide an auxiliary small fuel cell for performing the measurement. This alternative embodiment enables measurement in accordance with the invention without having to operate the entire fuel cell with the voltage required for the measurement. The auxiliary fuel cell may be physically separated from the fuel cell, integrated therein, attached to it or attached to a fuel reservoir.
The present invention provides a hybrid power source comprising at least one fuel cell according to the present invention, a DC converter and a rechargeable battery.
The methanol fuel cell of direct action (MTEPD) and fuel cells with liquid starting material (TEMP) are low power sources. However, devices such as mobile phones, computers and small electric vehicles need high power for a short time. For these and similar applications, it is possible to combine the fuel cell according to the invention with a small, powerful rechargeable battery that provides more power when required. Such a combination is beneficial for all currently used hybrid energy sources, among other things, thanks to a small transient current. Currently, DC converters can start operating at 0.7 V, since only two or three fuel cells can be combined (in series) via a DC-to-battery converter. If the density of the transient current is small enough, say 15 mA / cm 2 or less, preferably 5 mA / cm 2 or less, such a hybrid power source does not need very frequent fuel supply. Therefore, this hybrid power source is preferred with a low-density fuel cell of the transition type of the fuel cell type of the invention. The fuel cell charges the battery and provides little power consumption, while a high-power battery provides a high load. This small amount of required fuel cells makes it possible to use a flat and thin fuel cell system.
The present invention provides such hybrid power sources that are provided with the fuel of the present invention. Fueling such hybrid power sources with the solid fuel of the present invention is most advantageous.
For example, a hybrid power source consisting of two thin fuel cells connected in series and supplied with a liquid fuel according to the invention of the ethylene glycol type or a solid fuel of the invention of the dimethyl oxalate type, a DC converter and a small element on high-power lithium ions can be used to power a cellular phone.
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In order to better understand the invention and see how it can work in practice, several embodiments of the invention will be described in detail with reference to the drawings in which: 1 is a graph showing the polarization curves of some fuels according to the present invention and some currently used fuels; and 2 is a schematic illustration of an organic fuel cell with a solid feed material in accordance with the invention. |
Detailed Description of Certain Embodiments
Example 1 : Preparation of polarization curves for several types of fuel
The fuel cell was made using pure metal catalysts instead of catalysts supported on a carbon substrate. Cathodic catalytic paint was prepared by the following process.
Pt nanopowder (platinum black purchased from Johnson Matthey), TeflonTM emulsion and 5% NafionTM solution were combined in the following weight ratios: 60% Pt, 25% Teflon (Teflon) emulsion and 15% Nafion. First, the Pt powder and the Teflon emulsion were mixed by ultrasonic treatment for 15 minutes. After two periods of ultrasonic treatment, the resulting ink was placed in a magnetic stirrer for at least one night.
The anodic catalytic paint was prepared by the following process: Pt: Ru nanopowder (50% Pt: Ru carbon black purchased from Johnson Matthey) and polyvinyl-idenfluoride (PVDF) were mixed in the following weight ratios: 91% catalyst powder and 9 % Of polyvinylidene fluoride. Propylene carbonate was added in an amount equal to 30-70% of the volume of the catalyst, then cyclopentanone was added and the resulting paint was stirred for at least one night.
Preparation of the electrodes: Cathodic catalytic paint was applied to carbon fiber coated Teflon Tehflon paper, forming a layer of 4 mg Pt / cm 2 . The paint (in the form of a paste) was applied in layers, allowing each layer to dry for about one hour before applying the next layer. This operation was repeated until the required amount of catalyst was obtained. In the same way, the anodic catalytic paint was applied to carbon fiber-free Teflon-coated Teflon paper until a layer of 5-10 mg catalyst / cm 2 was obtained. Both electrodes were washed in 3 grams of sulfuric acid and then in water.
The cathode and the anode were placed on both sides of the PCM (proton-conducting membrane) 100-300 μm thick parallel to each other and subjected to hot pressing under a pressure of 10-70 kg / cm 2 at a temperature of 85-130 ° C. 1 illustrates the polarization curves for this type of fuel cell under the following conditions: a fuel solution and 3 grams of H 2 SO 4 were circulated through the anode at a flow rate of 9 ml / min. Oxygen circulated past the cathode under a pressure of 0.25 atm above atmospheric pressure. The temperature of the element was 65 ° C. The PPM had a thickness of 300 μm and consisted of a 16% SiO 2 powder with nanoparticles, 24% polyvinylideneforide, and 60% pore volume with a typical diameter of 1.5 nm. The element demonstrated more than 100 hours of stable operation at a voltage of 0.4 V. The investigated fuels were methanol (1 g-mol), 0.1 g-mole of oxalic acid with 1 g-mole of methanol, 0.1 g-mole of oxalic acid, 0.1 gmole of dimethyl oxalate, 0.1 gm of ethylene glycol and 0.5 g of mole of glycerol. (Of these, glycerol, oxalic acid and methanol are not n in accordance with the present invention). As shown in the graph, under these conditions, dimethyl oxalate and ethylene glycol had better characteristics. However, one must bear in mind that none of the conditions in this experiment have been optimized, so that other concentrations and / or other catalysts can lead qualitatively to differing observations.
The fuel was determined by electrochemical titration with 50 ml of a fuel solution at constant voltage until the current decreased to 3 mA. It is estimated that at this current only a few percent of the fuel remained unoxidized. The application was calculated by comparing the experimental performance with the theoretical value. An additional correction was made by extrapolating the titration curves to zero current. This correction increases the usage values by a value of 3 to 6% (see Table 1).
It was found that the application of fuel at 0.2 V was 95% for dimethyl oxalate, 94% for ethylene glycol and only 85% for methanol (see Table 1). At a more practical voltage of 0.4 V, fuel utilization was found to be 89% for ethylene glycol, 67% for dimethyl oxalate and 81% for methanol.
As fuel passes to the cathode side, these high values of fuel use suggest that there is almost 100% electrical oxidation of the fuel.
Fuel transfer measurements were performed at several temperatures by supplying nitrogen instead of oxygen to the cathode compartment (under ambient pressure) and feeding the organic fuel-acid solution to the anode compartment. The voltage of the element was reversed; Hydrogen was released on the fuel electrode, while the fuel that passed to the cathode side was oxidized. It was found that the current flowing at a voltage of 1 V was the current limitation for the oxidation of all fuel.
Table 2 summarizes the results of the fuel transfer test. The density of the transient current depends on the permeability, temperature, fuel concentration and the total number of electrons involved in the oxidation. The density of the transient current for 1 g-mole of methanol (at 80 ° C) is twice the density of the transition current for 1 g-mole of ethylene glycol and 0.25 g-mole of dimethyl oxalate. However, when the number of electrons is taken into account, and the fuel flow, expressed in terms of mole-s -1 · cm -2 (at 80 ° C and under diffusion control conditions), is normalized to 1 g-mole of fuel, it can be seen that the permeability (Flow) of ethylene glycol is one third of the methanol permeability (flow), while the permeability (flow) of dimethyl oxalate is almost the same as methanol.
| Table 1 Comparison of the use of different types of fuel | ||||||
| Number of electrons | Theoretical productivity [A · h / g] | Use at 0.4 V * [%] | Use at 0.2 V * [%] | |||
| Exp. | Corr. | Exp. | Corr. | |||
| Oxalic acid | 2 | 0.43 | 91 | |||
| Methanol | 6th | 5.03 | 79 | 81 | 82 | 85 |
| Ethylene glycol | 10 | 4.32 | 83 | 89 | 89 | 94 |
| Dimethyl oxalate | 14 | 3.18 | 64 | 67 | 93 | 95 |
| * Mean of at least two trials; Exp. - experimental values; Corr. - the corrected values, see the text. | ||||||
| table 2 Transition of various types of fuel | ||||
| 1. Fuel | Transfer test: | |||
| Pace. [FROM] | Conc. [G-mole] |
The density of the transient current [A / cm 2 ] | Fuel flow * [mole · s -1 · cm -2 ] 1 × 10 -8 | |
| Dimethyl oxalate | 60 | 0.10 | 0.009 | 6.7 |
| 60 | 0.25 | 0.025 | 7.4 | |
| 80 | 0.25 | 0.038 | eleven | |
| Ethylene glycol | 80 | 0.5 | 0.019 | 3.9 |
| 80 | 1/0 | 0.041 | 4.2 | |
| Methanol | 80 | 1.0 | 0.076 | 13 |
| * Normalized to 1 g-mole | ||||
Example 2 : Use of the fuel according to the invention in a Nafion-based fuel cell
The fuel cell housing was made of synthetic graphite plates purchased from Globetech Inc., in which the flow region was etched.
The anode was formed by the use of platinum-ruthenium paint, which was applied to a sheet of carbon fiber available for purchase from Toray paper , The catalyst bed consisted of 15% Teflon (DuPont), 15% Nafion q and 70% Pt-Ru nanopowder (50% carbon black Pt: Ru purchased from Johnson Matthey). Anode loading was 5 mg / cm 2 . The cathode used was purchased from ELAT E-TEK d and consisted of 4 mg Pt / cm 2 and 0.6 mg nafion / cm 2 . The anode and cathode were hot-pressed with the 117 Nafion membrane available from DuPont to form the membrane electrode assembly (EUM) as described in Example 1.
After cooling, the EUM was placed between the graphite plates, the flow regions were injected with polypropylene sealing and the element was assembled.
During operation, an aqueous solution of fuel selected from oxalic acid, dimethyl oxalate, ethylene glycol, glycerin in a concentration range of 0.1-0.5 gmole circulated past the anode (using a Masterflex L / S Cole-Parmer Instrument hose peristaltic pump Co.) with different flow rates from 4 to 15 ml / min.
Oxygen was introduced into the cathode compartment directly or through an aqueous bubbler under ambient pressure and at a flow rate of 7 to 40 ml / min. Elements functioned at a temperature of 60 ° C. We found that the polarization curves are similar to the polarization curves in Fig.
Example 3 : Organic fuel cell with a solid feedstock
2 illustrates an organic fuel cell with a solid feedstock having a plastic body 501, an anode 509, a cathode 511 and a polymeric solid electrolyte membrane 510. The membrane 510 was an MP membrane of the species described in WO 99/44245 consisting of 12% SiO 2 , 28% of polyvinylidene fluoride and 60% of voids (in which an acidic solution was introduced). The anode, cathode and EUM were prepared as in Example 1. Solid organic fuel was introduced through the fuel port 502 and sealed with a stopper 503. The fuel was dissolved in the tank and absorbed through a network of Hastelloy C-276 (Cabot) 507 in a porous carbon cloth 508. Dioxide Of the carbon formed in the anode compartment was removed through the exhaust nozzle 504. Since the liquid fuel can flow through the exhaust nozzle, the nozzle was covered with a thin hydrophobic porous layer 506. The hydrophobic layer is permeable to the gas only while the fuel solution remains in the reservoir. The cathode is open to air through a second network of Hastelloy 513. To prevent leakage of fuel from the cathode side, the EUM is sealed with a spacer 512. A second network 513 of hastalloy is also used as a coating for the entire assembly. 200 mg of dimethyl oxalate were dissolved in a fuel tank which contained a solution of 1 gmol of H 2 SO 4 . The fuel cell provided 30 mA at 0.35 V. The transient current density was 2 mA / cm 2 at room temperature.
CLAIM
1. Use of an organic compound selected from the group consisting of dimethyl oxalate, ethylene glycol, ethylene glycol ethers with oxalic, glyoxalic and formic acids, glyoxylic acid and its methyl esters, glyoxyalkaldehyde and polyethylene oxalate, as a fuel that undergoes conversion by more than 80 % In CO 2 in non-alkaline fuel cells.
2. The use according to claim 1, wherein said organic compound is selected from the group consisting of dimethyl oxalate, ethylene glycol, formic acid ester, ethylene oxalate and polyethylene oxalate, and mixtures thereof.
3. The use according to claim 1, wherein said organic compound is selected from the group consisting of ethylene glycol, dimethyl oxalate, and mixtures thereof.
4. The use according to claim 1, wherein said organic compound is selected from the group consisting of dimethyl oxalate, polyethylene oxalate and mixtures thereof.
5. Use according to any one of claims 1 to 4, wherein said organic compound is mixed with known fuel.
6. Use according to claim 5, wherein said known fuel is methanol.
7. The use according to any one of claims 1 to 6, wherein said fuel cell is a fuel cell with an acid electrolyte.
8. Use according to any one of claims 1 to 6, wherein said fuel cell has a proton-conducting membrane.
9. A direct oxidation fuel cell having an anode, a cathode, a proton-conducting membrane disposed between said anode and said cathode, means for storing or supplying organic fuel to the anode, and means for supplying oxygen to the cathode, wherein said organic fuel is selected from the group consisting of From dimethyl oxalate, ethylene glycol, ethylene glycol ether with oxalic, glyoxalic and formic acids, glyoxylic acid and its methyl esters, glyoxyalkaldehyde and polyethylene oxalate.
The direct oxidation fuel cell according to claim 9, wherein said fuel is selected from the group consisting of dimethyl oxalate, ethylene glycol, its oxalic ester and formic acid, ethylene oxalate, polyethylene oxalate, and mixtures thereof.
11. The direct oxidation fuel cell according to claim 10, wherein the fuel is selected from the group consisting of dimethyl oxalate, ethylene glycol, formic acid ester, ethylene oxalate, polyethylene oxalate, and mixtures thereof.
12. The direct oxidation fuel cell according to claim 11, wherein the fuel is selected from the group consisting of dimethyl oxalate, ethylene glycol and mixtures thereof.
13. The direct oxidation fuel cell according to any one of claims 9 to 12, wherein said fuel element is an element with a liquid feedstock.
14. The direct oxidation fuel cell according to claim 12, wherein the fuel is selected from the group consisting of polyethylene oxalate, dimethyl oxalate, and mixtures thereof.
15. The direct oxidation fuel cell according to any one of claims 9 or 14, having a thin hydrophobic porous matrix placed in an anode compartment or a fuel tank for the purpose of discharging therethrough CO 2 generated therethrough during operation of the fuel cell.
16. The direct oxidation fuel cell according to any one of claims 9 to 15, wherein said anode comprises a Pt: Ru catalyst.
17. A method of converting, in a fuel cell, more than 80% of a fuel into CO 2 , comprising the steps of
(I) providing a fuel cell having an anode, a cathode, a proton-conducting membrane disposed between said anode and said cathode, means for storing or supplying organic fuel to the anode, and means for supplying oxygen to the cathode,
(Ii) supplying fuel to said fuel cell, and
(Iii) the functioning of said fuel cell, characterized in that said fuel is selected from dimethyl oxalate, ethylene glycol, its oxalic acid esters, glyoxalic acid and formic acid, glyoxylic acid and its methyl esters, glyoxyalkaldehyde and polyethylene oxalate.
18. The method of claim 17, wherein said anode comprises a Pt: Ru catalyst.
19. The method of claim 17 or 18, wherein said fuel cell functions in step (iii) at a temperature of 60 ° C or higher.
20. The process of any of claims 17 to 19, wherein the cathode comprises an oxygen reduction catalyst and a fuel oxidation catalyst.
21. The method of claim 20, wherein said fuel oxidation catalyst is selected from the group consisting of Pt-Ru, Pt-Sn, Pt-Ru-Sn, Pt-Ag-Ru, Pt-Os and any combination thereof.
22. The process of any of claims 20 and 21, wherein the ratio between the fuel oxidation catalyst and the oxygen reduction catalyst is between 1% and 50% (weight percentage).
23. The method of claim 22, wherein said ratio is between 5% and 20% (weight percent).
24. The method of any of claims 17-23, wherein said organic compounds are selected from the group consisting of dimethyl oxalate, ethylene glycol, formic acid ester, ethylene oxalate and polyethylene oxalate, and mixtures thereof.
25. The process of any of claims 17-23, wherein said organic compounds are selected from the group consisting of ethylene glycol, dimethyl oxalate, and mixtures thereof.
26. The method of any of claims 17-23, wherein said organic compounds are selected from the group consisting of dimethyl oxalate, polyethylene oxalate, and mixtures thereof.
27. The method of any of claims 17-23, wherein said organic compounds are mixed with known fuel.
28. The method of claim 27, wherein said known fuel is methanol.
29. A direct oxidation fuel cell having a cathode comprising an oxygen reduction catalyst and a fuel oxidation catalyst.
30. The direct oxidation fuel cell of claim 29, wherein said fuel oxidation catalyst is selected from the group consisting of Pt-Ru, Pt-Sn, Pt-Ru-Sn, Pt-Ag-Ru, Pt-Os catalysts and any of them Combination.
31. The direct oxidation fuel cell of claim 30, wherein the ratio between the fuel oxidation catalyst and the oxygen reduction catalyst is between 1% and 50% (weight percentage).
32. The direct oxidation fuel cell according to claim 31, wherein said ratio is between 5% and 20% (weight percent).
33. The direct oxidation fuel cell according to any one of claims 29 to 32, wherein said fuel is a mixture as defined in claim 5 or 6.
34. A method for determining the concentration of fuel in a solution at a predetermined temperature, wherein the fuel is dimethyl oxalate, ethylene glycol, its esters of oxalic acid, glyoxalic acid and formic acid, glyoxylic acid and its methyl esters, glyoxyl aldehyde, polyethylene oxalate, comprising the following steps:
A) preparing calibration curves of the transient current as a function of the fuel concentration at said predetermined temperature in a given fuel cell,
B) measuring the transient current at said predetermined temperature in said fuel cell and determining the fuel concentration based on the transient current measured in step b) and the calibration curves prepared in step a).
35. A hybrid power source comprising at least one fuel cell according to any one of claims 9 to 16 or 29 to 33, a DC converter and a rechargeable battery.
print version
Date of publication 09.04.2007гг
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