Patent Application
20230335761
This application claims the priority benefit of Taiwan Application Serial No. 111113998, filed on Apr. 13, 2022. The entirety of the above-mentioned patent application is hereby incorporated by reference herein and made a part of this specification.
The disclosure relates to a phosphoric acid fuel cell technology, and particularly relates to a class of modified catalysts, a process for preparing the modified catalysts and implementation of the modified catalysts in phosphoric acid fuel cells, in which leakage of phosphoric acid can be reduced.
Fuel cells are currently one of the most popular energy solutions for the future. For example, phosphoric acid fuel cells have become a hot research topic in recent years due to their high efficiency and CO tolerance.
However, unlike polymer electrolyte membrane (PEM) fuel cells which use a solid-state ionomer membrane as an electrolyte, the phosphoric acid fuel cells use a phosphoric acid-doped porous medium as an electrolyte. Since the phosphoric acid is a liquid-state substance, leakage may occur during operation, and durability of the phosphoric acid fuel cells for long-term use may be reduced. Therefore, there is an urgent need for solutions to the aforementioned issue.
The disclosure provides the design of a class of modified catalysts of a phosphoric acid fuel cell, in which the modified catalysts can provide a proton conduction path while improving phosphoric acid adsorption capacity.
The disclosure further provides a phosphoric acid fuel cell in which electrolyte leakage can be reduced.
The disclosure also provides a process for preparing a class of modified catalysts of a phosphoric acid fuel cell, in which a modified catalyst having high phosphoric acid adsorption capacity can be prepared in a simple manner.
A modified catalyst of a phosphoric acid fuel cell according to the disclosure includes a particle of a metal-doped porous material and an amount of a phosphate-containing acid group or phosphate-containing acid groups. The particle of the metal-doped porous material is a particle of a porous carrier with metal microparticles and a plurality of hydroxyl groups on the surface of the porous carrier such that (i) the plurality of metal microparticles are attached to a first portion of the plurality of hydroxyl groups of the surface of the porous carrier and (ii) the phosphate-containing acid group or groups can be bonded to a second portion of the plurality of hydroxyl groups of the surface of the porous carrier to form the modified catalyst.
In one embodiment of the disclosure, the phosphate-containing acid group includes a phytic acid group, a phosphoric acid group or an inositol tetraphosphate group.
In one embodiment of the disclosure, the porous carrier includes activated carbon or carbon black.
In one embodiment of the disclosure, a material of the metal microparticles includes platinum, ruthenium, palladium, cobalt, iridium or nickel.
A phosphoric acid fuel cell according to the disclosure includes the modified catalyst as described above.
A process for preparing a modified catalyst of a phosphoric acid fuel cell according to the disclosure is described below. A substance that is a particle of a metal-doped porous material is provided as a catalyst. The particle is a particle of a porous carrier with metal microparticles and a plurality of hydroxyl groups on the surface of the porous carrier such that the plurality of metal microparticles are attached to a first portion of the plurality of hydroxyl groups of the surface of the porous carrier. The catalyst is then mixed with a phosphate-containing acid. Then, a second portion of the plurality of hydroxyl groups of the surface of the porous carrier is subjected to a chemical conjugation reaction with the phosphate-containing acid.
In another embodiment of the disclosure, the phosphate-containing acid includes phytic acid, phosphoric acid or inositol tetraphosphate.
In another embodiment of the disclosure, the catalyst includes a commercially available catalyst or a synthesized catalyst.
Based on the above, in the disclosure, the phosphate-containing acid group is bonded to the hydroxyl group of the surface of the catalyst through the chemical conjugation reaction. Since the phosphate-containing acid group has one or more phosphate groups, hydrophilicity of the catalyst layer for a fuel cell is improved and the effect of adsorbing phosphoric acid of the catalyst layer is enhanced as well. Also, the phosphate groups may serve as a proton conduction path.
Several exemplary embodiments accompanied with figures are described in detail below to further describe the disclosure in details.
Exemplary embodiments of the disclosure will be described below with reference to the drawings, but the disclosure may be embodied in various different forms and should not be construed as being limited to the embodiments described below. In the drawings, for the sake of clarity, each composition, particle and group are illustrated schematically rather than in accordance with their actual sizes. To facilitate the understanding, the same elements in the following description are marked with the same reference numerals.
Referring to
Referring to
Conventionally, in order to prevent or reduce phosphoric acid leakage in a phosphoric acid fuel cell, efforts have been made on the membrane materials of the phosphoric acid fuel cell, or a chemical substance has been mixed into the catalyst layer of the phosphoric acid fuel cell to enhance hydrophilicity. In contrast, in the present embodiment, a substance (that is, the phosphate-containing acid group 106) capable of conducting protons is directly bonded to a surface of the catalyst 300. Accordingly, a modified catalyst having high phosphoric acid adsorption capacity can be prepared in a simple manner.
The following describes experiments carried out for verifying the effects of the disclosure. However, the disclosure is not limited to the following description.
The materials included 200 mg of Pt/C (commercially available catalyst, model name: Vulcan® XC-72) and 8 ml of 50% phytic acid aqueous solution.
The above materials were mixed, uniformly stirred and dispersed, followed by subjecting the resultant to a heating reaction in an oven at 70° C. for two hours. After the reaction in the oven, the resultant product was processed by washing and centrifugation to remove excess phytic acid, and then dried at 85° C. to obtain a modified catalyst of the preparation example.
By X-ray photoelectron spectroscopy (XPS) analysis, it was determined that a surface of the modified catalyst prepared as described above contained 15.5 wt% of Phosphorus (P) and 9.59 wt% of Platinum (Pt).
By inductively coupled plasma (ICP) analysis, it was determined that the modified catalyst prepared as described above contained 5.49 wt% of P and 14.16 wt% of Pt.
The modified catalyst prepared as described above was used as both the anode catalyst and the cathode catalyst. The anode, the cathode and a polybenzimidazole (PBI) membrane were respectively immersed in phosphoric acid and then hot-pressed to obtain a membrane electrode assembly (MEA) which was then assembled into a phosphoric acid fuel cell.
A phosphoric acid fuel cell was fabricated in the same manner as in the experimental example except that the commercially available catalyst, Vulcan® XC-72, was directly used as both the anode catalyst and the cathode catalyst.
The following tests were conducted respectively on the fuel cells of the experimental example and the comparative example.
A long-term durability test was conducted on the fuel cells with the current density of the fuel cells being fixed at 0.2 A/cm2, the temperature being maintained at 160° C., and 200 sccm of hydrogen and oxygen being continuously fed. During the test, the gas (containing phosphoric acid vapor) generated respectively by the cathode and anode was passed into 10 ml of deionized water. The solution was replaced every 24 hours, and the collected solution was subjected to ICP-MS analysis to assess phosphoric acid leakage. The results are shown in Table 1 below and
As is clear from Table 1 and
A current density of the fuel cell was fixed at 0.2 A/cm2, the temperature was maintained at 160° C., and 200 sccm of hydrogen and oxygen were continuously fed in to conduct a long-term durability test, and a change in fuel cell load voltage with time was observed. The results are shown in
As is clear from
In summary, in the disclosure, a substance capable of conducting protons is directly conjugated to a catalyst. Accordingly, while proton conductivity of the catalyst is improved, the capacity in adsorbing phosphoric acid is enhanced for the catalyst as well. Thus, the leakage of phosphoric acid electrolyte in the fuel cell can be effectively reduced, thereby improving long-term performance and service life of the fuel cell.
It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the disclosed embodiments without departing from the scope or spirit of the disclosure. In view of the foregoing, it is intended that the disclosure cover modifications and variations of this disclosure provided they fall within the scope of the following claims and their equivalents.
| Number | Date | Country | Kind |
|---|---|---|---|
| 111113998 | Apr 2022 | TW | national |
