BINOCULAR PLATINUM(III) CATALYST CONTAINING A SULFATE OR HYDROGEN PHOSPHATE BRIDGE LIGAND SUPPORTED BY A CARBON-BASED MATERIAL FOR ELECTROCHEMICAL POWER SYSTEMS AND METHOD FOR PRODUCING THIS CATALYST

Abstract

The invention relates to carbon-supported platinum catalysts utilizing binuclear platinum(III) complexes containing sulfate [(NH4)2[Pt2(SO4)4(H2O)2] or hydrogen phosphate [(NH4)2[Pt2(HPO4)4(H2O)2] bridging ligands as a starting material supported by a carbon-based material, and to the process for producing these catalysts. The catalysts of the invention enhance the performance of proton exchange membrane fuel cells (PEMFCs). Furthermore, the binuclear platinum(III) catalyst containing sulfate or hydrogen phosphate bridging ligands supported by the carbon-based material described in the invention exhibits high catalytic activity and high corrosion resistance.

Description

[0001] BINUCLEAR PLATINUM(III) CATALYST CONTAINING SULFATE OR HYDROGEN PHOSPHATE BRIDGING LIGAND SUPPORTED BY CARBONBASED MATERIAL FOR ELECTROCHEMICAL POWER SYSTEMS AND METHOD OF PREPARATION OF THIS CATALYST

[0002] Technical Field

[0003] The invention relates to carbon-supported platinum catalysts using binuclear platinum(III) complexes containing sulfato [(NH4)2[Pt2(SO4)4(H2O)2] or hydrogen phosphato [(NH4)2[Pt2(HPO4)4(H2O)2] bridging ligands as starting material, supported by carbon-based material for electrochemical power systems, and the method of preparation of these catalysts. The catalysts of the invention increase the performance of proton-exchange membrane fuel cells (PEMFCs). In addition, the binuclear platinum(III) catalyst containing sulfate or hydrogen phosphate bridging ligands supported by the carbon-based material described in the invention has high catalytic activity and high corrosion resistance.

[0004] Background

[0005] Today, the need for energy is increasing unavoidably. Gasses released into the environment as a result of the use of fossil fuels, one of our most important energy sources, threaten our future by causing air pollution. In addition, interest in alternative energy sources to meet energy needs is increasing day by day, given the limited oil reserves and rising oil prices per gallon.

[0006] Fuel cells are of great interest in reliable, robust and environmentally friendly power generation methods in the state of the art due to their high efficiency and high-pressure characteristics as well as being environmentally friendly. Fuel cells convert fuel energy directly into electrical energy through electrochemical reactions. The fuel cells generate energy with externally supplied fuel (anode) and oxidizer (cathode). The most interesting of the fuel cells with many different types is the proton-exchange membrane fuel cells (PEMFCs) because they are highly efficient and modular. PEMFCs are a promising technology due to their ease of use, high power density and scalability and therefore they are an energy source on which intensive work is carried out.

[0007] In the state of the art, one of the most important parameters affecting the performance of PEMFCs is the choice of catalyst, and the most commonly used among these catalysts is platinum (Pt) because platinum shows a high catalytic activity in PEMFCs. Platinum catalysts cannot be used alone in PEMFCs. In order for platinum catalysts to be used in PEMFCs, they must be supported on an electrically conductive support material.

[0008] Support material helps to both distribute platinum compounds well and to increase PEMFCs performance by facilitating electron transfer. The materials to be used as a support material together with platinum catalysts in PEMFCs should be high conductivity, large surface area, chemically stable and mechanically resistant. Low-cost, mechanically flexible and porous, carbon black is a popular backing material for PEMFCs. Other carbon-based support materials such as graphene, carbon nanotube, multi-wall carbon nanotube, activated carbon, etc. are also used as support materials for platinum catalysts in PEMFCs.

[0009] In the state of the art, the most commonly used starting substance to prepare a carbon- supported platinum catalyst is platinum salts (Potassium Hexachloroplatinate (II) (B PtCk), etc.). In this structure, platinum ions are loaded with +2. At the end of the catalyst preparation process, platinum(II) is reduced to platinum(O) and homogenous distribution is expected on the carbon-supported surface. However, during this process, agglomeration problems of platinum metals are encountered and as a result of agglomeration, the active surface area of the catalyst decreases and as a result of all these, the catalytic performance of the catalyst is negatively affected. For this reason, it is necessary to develop a catalyst in which these problems are eliminated.

[0010] Brief Description and Objects of the Invention

[0011] The invention discloses carbon-supported platinum (Pt) catalysts using binuclear platinum(III) complexes containing sulfato [(NH4)2[Pt2(SO4)4(H2O)2] or hydrogen phosphato [(NH4)2[Pt2(HPO4)4(H2O)2] bridging ligands as starting materials, supported by carbon-based material for electrochemical power systems, and the method of preparation of these catalysts. The catalysts of the invention increase the performance of proton-exchange membrane fuel cells (PEMFCs). In addition, the binuclear platinum(III) catalyst containing sulfate or hydrogen phosphate bridging ligands supported by the carbon-based material described in the invention has high catalytic activity and high corrosion resistance.

[0012] The main object of the invention is to increase the performance of PEMFCs. Increasing the performance of PEMFCs is provided by new carb on- supported platinum catalysts that are the subject of the invention and use binuclear platinum(III) complexes containing sulfate or hydrogen phosphate bridging ligands as starting materials. With the use of carbon-supported platinum catalysts of the invention in PEMFCs, platinum metal agglomeration is prevented, and the active surface area is increased, and thus a significant increase in the performance of PEMFCs is achieved with the help of catalysts with high catalytic effect.

[0013] Another benefit of the invention is that the need for environmentally damaging resource uses such as fossil fuel and petroleum is reduced with the realization of more efficient energy production with environmentally friendly PEMFCs.

[0014] In the invention, a high-stability catalyst is provided for use in PEMFCs without the clumping problem. The fact that the new carbon-supported platinum catalysts using binuclear platinum(III) complexes containing sulfato or hydrogen phosphato bridging ligands as the starting material of the invention are a high stability catalyst that does not cause clumping problems is provided by the sulfato or hydrogen phosphato bridging ligands in the complexes.

[0015] Descriptions of the Drawings

[0016] Figure 1. Alternating voltammetry test results of Ptphosphato complex / support material

[0017] Figure 2. Ptsuifato complex / support material alternating voltammetry test results

[0018] Figure 3. Ptphosphato complex / support material TEM analysis test results

[0019] Figure 4. Ptsuifato complex / support material TEM analysis test results

[0020] Detailed Description of the Invention

[0021] The invention relates to carbon-backed platinum catalysts using binuclear platinum(III) complexes containing sulfato [(NH4)2[Pt2(SO4)4(H2O)2] or hydrogen phosphato [(NH4)2[Pt2(HPO4)4(H2O)2] bridging ligands as starting material, supported by carbon-based material for electrochemical power systems, and the method of preparation of these catalysts. The catalysts of the invention increase the performance of proton-exchange membrane fuel cells (PEMFCs). In addition, the binuclear platinum(III) catalyst containing sulfate or hydrogen phosphate bridging ligands supported by the carbon-based material described in the invention has high catalytic activity and high corrosion resistance.

[0022] The carbon-supported platinum (Pt) catalysts of the invention are obtained by supporting binuclear platinum(III) complexes containing sulfate or hydrogen phosphate bridging ligands on carbon-based material. Carbon-supported platinum catalysts subject to the invention adhere to the surface of the support material with the electrostatic interaction and / or hydrogen bonds between the sulfate or hydrogen phosphate bridging ligands in the structure of the platinum complexes and the carbon material and contain more platinum metal than the mononuclear platinum salts. In addition, platinum complexes in large molecular structures prevent the clumping of platinum metal on the support material and provide more homogeneous distribution and consequently the expansion of the active surface area during the preparation of catalysts. During this process, the two Pt+3ions in the structure of the complexes on the support material are rapidly reduced to Pt°, thus providing more active platinum formation on the surface. As a result, the performance of PEMFCs also increases.

[0023] The structure of the binuclear platinum(III) complexes containing sulfate or hydrogen phosphate bridging ligand used in the preparation of the carbon-supported platinum catalysts of the invention is shown in Formula 1 [(NH4)2[Pt2(SO4)4(H2O)2] and Formula 2 [(NH4)2[Pt2(HPO4)4(H2O)2];

[0024] Formula I Formula 2 A method of preparing carbon-supported platinum catalysts using binuclear platinum(III) complexes containing sulfato [(NH4)2[Pt2(SO4)4(H2O)2] or hydrogen phosphato [(NH4)2[Pt2(HPO4)4(H2O)2] bridging ligands as starting material, supported by carbon-based material, for use in fuel cells with proton exchange membrane (PEMFCs);

[0025] I. Preparation of binuclear platinum(III) complexes containing sulfato [(NH4)2[Pt2(SO4)4(H2O)2] or hydrogen phosphato [(NH4)2[Pt2(HPO4)4(H2O)2] bridging ligand,

[0026] II. Mixing 70-80 mg of carbon support material in a mixture of 30-40 ethylene glycol and 5-10 isopropyl alcohol for 1-2 hours using an ultrasonic mixer,

[0027] III. Adding a binuclear platinum(III) complex containing 80-83 mg sulfate or hydrogen phosphate bridging ligand prepared in 0.1 M 1-6 mL HC1O4 to the resulting mixture and continuing the ultrasonic mixing process for 5-10 minutes,

[0028] IV. Adjusting the pH of the mixture obtained with 0.1 M NaOH prepared in ethylene glycol after mixing to 10-12,

[0029] V. Putting the solution whose pH value is set to 10-12 in the 400-1000 W microwave reactor and performing the synthesis reaction for 40-180 s.

[0030] After the synthesis reaction above is completed, the pH of the mixture is reduced to 1-3 using 0.1 M HCIO4 solution and then the resulting mixture is washed with acetone and filtered. Afterward, it is washed overnight in an 80-100°C incubator.

[0031] The carbon-based materials mentioned in the preparation of the carbon-supported platinum catalysts of the invention are carbon-based structures such as carbon black, multi-wall and single-wall carbon nanotubes, graphene, or graphene oxide.

[0032] Supported with carbon-based material, binuclear platinum(III) complexes containing sulfato [(NH4)2[Pt2(SO4)4(H2O)2] or hydrogen phosphato [(NH4)2[Pt2(HPO4)4(H2O)2] bridging ligands were named as Ptsuifato compiex / support material and Ptphosphato compiex / support material, respectively.

[0033] The corrosion resistance of the catalysts of the invention was determined by performing at least 1000 scans with the alternating voltammetry method. The results showing the corrosion resistance of Ptphosphato compiex / support material and Ptsuifato compiex / support material catalysts are given in Figure 1 and Figure 2, respectively. Depending on the reaction time in the microwave reactor and the strength of the microwave, the active surface area losses of the Ptphosphato complex / support material and the Ptsuifato compiex / support material catalysts range from 6% to 68% and 37% to 64%, respectively, as clearly shown in Figure 1 and Figure 2. It is observed that 70-75% loss of active surface area occurs as a result of corrosion tests with commercial platinum / carbon (Pt / C) blackeners performed under the same conditions. When all these results are evaluated, it is clearly understood that the catalyst activities of the Ptphosphato complex / support material and Ptsuifato complex / support material complexes are quite high compared to the catalysts used in the electrochemical power systems in the state of the art.

[0034] Figure 3 and Figure 4 show the results of the TEM analysis of the carbon-supported catalyst complexes of the invention. When these results are examined, it is clearly seen that there is no flocculation on the support material and the platinum shows a homogeneous distribution on the carbon-based support material. In the PEMFC performance tests performed under the same conditions, an increase of approximately 25% was observed in the maximum power density values compared to the commercial catalyst with Ptphosphato complex / support material and Ptsuifato complex / support material catalysts. As a result, it is clear that the catalysts according to the invention perform better compared to commercially used PEMFC catalysts.

Claims

CLAIMS A catalyst for use in fuel cells with proton exchange membranes (PEMFCs), characterized in that it comprisesFormula 1 Formula 2 binuclear platinum (III) complexes containing sulfato [(NH4)2[Pt2(SO4)4(H2O)2] or hydrogen phosphato [(NH4)2[Pt2(HPO4)4(H2O)2] bridging ligand having Formula 1 or Formula 2 chemical structures supported by carbon-based support material.

2. A catalyst according to claim 1, is characterized in that said carbon-based support material is carbon black, multi-wall carbon nanotube, single-wall carbon nanotube, graphene, or graphene oxide.

3. A method of preparing carbon-backed platinum catalysts using binuclear platinum (III) complexes containing sulfato [(NH4)2[Pt2(SO4)4(H2O)2] or hydrogen phosphato [(NH4)2[Pt2(HPO4)4(H2O)2] bridging ligands as starting material, supported by carbon-based material, for use in proton exchange membrane fuel cells (PEMFCs), characterized in that it comprises the following:I. preparation of binuclear platinum(III) complexes containing sulfato [(NH4)2[Pt2(SO4)4(H2O)2] or hydrogen phosphato [(NH4)2[Pt2(HPO4)4(H2O)2] bridging ligand,II. mixing 70-80 mg of carbon support material in a mixture of 30-40 ethylene glycol and 5-10 isopropyl alcohol for 1-2 hours using an ultrasonic mixer,III. adding a binuclear platinum(III) complex containing 80-83 mg sulfate or hydrogen phosphate bridging ligand prepared in 0.1 M 1-6 mL HC1O4 to the resulting mixture and continuing the ultrasonic mixing process for 5-10 minutes,IV. adjusting the pH of the mixture obtained with 0.1 M NaOH prepared in ethylene glycol after mixing to 10-12,V. putting the solution whose pH value is set to 10-12 in the 400-1000 W microwave reactor and performing the synthesis reaction for 40-180 s. A method of preparing a catalyst according to claim 3, characterized in that said carbon-based support material is carbon black, multi-wall carbon nanotube, singlewall carbon nanotube, graphene, or graphene oxide.

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