TWI551348B - Preparation of pt/xc72 iron contained hydroxyapatite composites and the use thereof as catalysts - Google Patents

Description

Iron-containing hydroxyapatite (Pt/XCFeHAp) carrying reduced nano-platinum particles Preparation of composite materials and its application as a catalyst

This invention relates to a process for the preparation of a bifunctional carrier for the preparation of a coated nano-hydroxyapatite film having improved conductivity on XC72. More particularly, the present invention relates to a method for preparing a composite material of iron-containing hydroxyapatite (XCFeHAp) bearing reduced nano-gold particles, comprising surface-modified carbon black XC72 powder with phosphoric acid and calcium nitrate. The deposition of hydroxyapatite on XC72 is carried out to obtain an electric resistance-improved XCHAp powder, and platinum is reduced thereon to form a Pt/XCFeHAp catalyst via a platinum-containing compound solution containing a dispersing agent.

The earth's original natural fossil fuels are depleting, resulting in rising crude oil prices. Therefore, all countries in the world are committed to the development of new energy sources with low environmental pollution based on environmental and energy considerations. Therefore, they have low emission pollution, high conversion efficiency and stable safety. Fuel cells, such as the advantages of fuel cells, became the 21st century's high-profile new energy technology fuel cell. In 1839, British judge William Grove in a private amateur experiment, magical The principle of power generation of fuel cells was discovered, and a simple chemical experiment was used to illustrate the two-way reaction of electrolysis of water with hydrogen and oxygenation (JMLeger JMLeger et al., Phys . Chem 94 : 1021, 1990). It was not until more than one hundred years later that it was selected as an important power source in the US space program, and was officially applied to the spacecraft GEMINI V as the main power supply on board in 1965, and completed. Sailing mission. From the ensuing space operations, fuel cells began to take on the heavy responsibility and become an important power source for humans in space in the twentieth century. The principle of fuel cell power generation is to directly convert the chemical energy of fuel into electrical energy. Motors such as thermal power generation and nuclear power generation are simple in process and have high conversion efficiency. Moreover, its power generation process is almost zero pollution, low noise, and no harm to the environment and human health. It can be regarded as green energy (Carrette, L et al., Chemphyschem 1 : 162, 2000).

Fuel cells are mainly divided into the following types: (1) Proton-Exchange Membrane Fuel Cell (PEMFC), Direct Methanol Fuel Cell (DMFC), and Direct ethanol Fuel Cell (DEFC). : The working temperature is 20~100 °C, and the perfluorosulfonic acid membrane is the most electrolyte. (2) Phosphoric Acid Fuel Cell (PAFC): The working temperature is 100-200 ° C, and the electrolyte is phosphoric acid. (3) Alkaline Fuel Cell (AFC): The working temperature is 50-200 ° C, and the electrolyte is 30-75 wt% KOH solution. (4) Solid-Oxide Fuel Cell (SOFC): The working temperature is 900-1000 ° C, and cerium oxide or stabilized zirconia is used as the electrolyte. And (5) molten carbonate fuel cell Molten Carbonate Fuel Cell (MCFC): operating temperature is 650 ~ 700 ° C, the electrolyte is alkaline carbonate such as lithium carbonate or potassium carbonate. (Full Cell Hand Book (Fifth Edition), By EG&G Services Parsons, Inc. Science Applications International)

At the end of the twentieth century, PEMFC and DMFC became the focus of research and development. Because of its low operating temperature, it is a portable energy source with development power that can be applied to electronic products and automobiles (R. Manoharan, J. Prabhuram, J. Power source 96 : 220-225, 2001; Z. Liu et al, Langmuir 20 : 181-187, 2004). The electrode used in PEMFC and DEMFC is still platinum as the main active component. Now the commercial electrode catalyst uses carbon black as the support to make the added platinum have a higher dispersion to improve the utilization of platinum. Rate, which greatly increases the efficiency of the catalyst electrode. After more than one hundred years of development, the electrode material of fuel cells has not been found to be a more suitable alternative material than platinum, which is extremely rare in the catalyst for general chemical reactions. One of the reasons is that the electrode material is under working conditions. It is unstable and easy to be corroded. Another important reason is that the interaction between the potential of the electrocatalytic catalyst material and the current density is large, and it is obvious that the development and innovation of the electrode catalyst material is difficult. Basic platinum materials have not been replaced so far. Platinum increases its specific surface area at the nanometer scale, and makes the number of catalytic active centers (Active Center) higher than that of traditional platinum blocks. However, nanoparticles have the characteristics of easy aggregation, resulting in a large particle size of the catalytically active center, which affects the touch. Media efficiency. How to effectively control the dispersion and particle size and surface topography of nanoplatinum particles will be an important factor affecting the power generation efficiency of fuel cells (N. Toshima , T. Yonezawa, New J. Chem. 22 : 1179-1201, 1998).

Therefore, the selection of a suitable catalyst carrier is important for dispersing the nanoplatinum catalyst. The main function of the carrier is to support the catalyst and provide a transport channel for the electrons produced by the catalyst after the catalyst is catalyzed. Therefore, the high conductivity of the carrier is a necessary condition, and the carrier needs to be in an acid or alkali environment for a long time, so Corrosion resistance is also an important requirement for the carrier. At present, the general carrier is the main development direction of carbon materials. The carbon materials in commercial and research and development have the advantages of good conductivity and acid and alkali resistance, which will cause catalyst activity when high load (loading) catalyst is used. The central particle size is too large and the usage rate is low, and the synthesized nano platinum particles are agglomerated on the surface thereof. In addition, the spherical structure of carbon black and carbon black are also likely to be aggregated, resulting in aggregation. The nano platinum catalyst on the surface of carbon black is coated in the carbon cluster, which is the most important loss of battery efficiency; the use of high specific surface area carbon black (Cabot Vulcan XC-72 surface area ~250m ² /g) is the most important The disadvantage is that the surface area after loading platinum will be reduced to nearly 100m ² /g, and the high ratio of mesopores will cause the catalyst to be easily blocked in the micropores, greatly reducing the catalyst usage. Therefore, in order to improve the efficiency of the metal catalyst and still maintain the small particle size characteristics, it is necessary to seek a carrier surface area with superior performance.

The carbon nanotubes with excellent properties such as high specific surface area need to be modified before the preparation of the catalyst and the dispersion problem during coating is a difficult point. Poor distribution may cause waste of the catalyst, or it may be difficult after the modification. Conductive (see Liz Kalaugher "Functionalized nanotubes carry on conducting", 2006). Therefore, there is a need to develop a three-dimensional structural catalyst carrier that is not easily agglomerated, has a high specific surface area, and has nanopores, which is also the main research object of the present invention.

The bottlenecks encountered in the current development of DMFC are mainly three aspects: (1) insufficient methanol oxidation at the anode end; (2) methanol loss due to unnecessary breakthrough in the polymer proton exchange membrane, and at the cathode end. Forming a mixed potential, so that the efficiency of the battery is low; and (3) CO poisoning problem, Pt has high catalytic activity for methanol oxidation, can release electrons and protons at a low potential, but Pt is easily The intermediate product CO is tightly adsorbed on the surface, reducing the active area.

The mechanism of carbon monoxide (CO) poisoning affecting battery performance degradation is to poison the platinum in the anode catalyst layer. Carbon monoxide will form a stable bond with platinum, resulting in a reduction in the space available for hydrogen, so the use of hydrogen is reduced. It will directly affect the amount of electricity generated by the battery. The current solution is to add a second metal to form a binary catalyst to reduce CO adsorption (M. Peukert et al, J. Electrochem. Soc., 13 : 309, 1988), or not with CO. Catalyst for generating a reaction (Zhang, J., Datta, R., J. Electrochem. Soc. Vol. 149 : A1423-A1431, 2002). PtFe can increase the ORR reaction rate in fuel cells, but Fe-based catalysts are avoided as much as possible in PEMFC because Fe easily promotes the decomposition of Nafion films (A. Pozio et al., Electrochim . Acta 48 : 1543, 2003). Therefore, the present invention proposes to use iron-containing hydroxyapatite as a carrier to increase the ORR reaction rate in a fuel cell.

Hydroxyapatite microspheres are used not only as drug carriers in biomedical materials, but also as catalyst carriers for dental ceramics and fuel cells because of their good biocompatibility. When FeHAp is formed by ion exchange with divalent iron ions (Fe ⁺² ), the nano platinum particles are successfully reduced thereon and uniformly mixed with carbon black to obtain Pt/FeHAp/C, forming a dual-effect catalyst; Excellent electrochemical mass activity in methanol oxidation reaction, no carbon monoxide (CO) poisoning.

However, the calcium phosphate salt formed by calcium nitrate and phosphoric acid is a ceramic having a difference in electronic conductivity (7x10 ^-13 S/cm) and ionic conductivity (2x10 ^-7 S/cm) (JPGittings et al., Acta Biomaterialia 5 : 743-754, 2009). Previous studies by the inventors of the present invention have shown that the reduction of platinum to iron-containing hydroxyphosphite can not only provide effective electrochemically active surface area, but also effectively solve the phenomenon of carbon monoxide poisoning, but it is impeded by hydroxyl phosphatid electronic conductivity of the graphite of very poor (only 7x10 ^-13 S / cm), resulting in the cell when the polarization test, a very large number of additional XC72 was added so as to increase their conductivity, but added a lot of additional XC72 electrode thick through the resulting thick It will further lead to the failure of the waste fuel generated by the electrochemical test to be discharged as scheduled. In addition to causing water accumulation and affecting the overall performance of the membrane electrode assembly, it will also be tested between XC72 and iron-containing hydroxyapatite under long-term testing. Poor adhesion, and shedding affects the stability of long-term testing. Therefore, the present invention proposes a pretreatment step of depositing HAp on acetylene carbon black to increase its conductivity, first placing acetylene black in an oxygen-rich environment to change surface functional groups such as OH ^- to enhance hydroxyapatite The bond between the stone and the acetylene carbon black also enhances the conductivity of the hydroxyapatite (HAp) by this method.

According to previous studies, hydroxyapatite microspheres are used not only as drug carriers in biomedical materials, but also as catalyst carriers for dental ceramics and fuel cells because of good biocompatibility. When FeHAp is formed by ion exchange with divalent iron ions (Fe+2), the nano platinum particles are successfully reduced thereon and uniformly mixed with carbon black to obtain Pt/FeHAp/C, forming a dual-effect catalyst; Excellent electrochemical mass activity in methanol oxidation reaction, no carbon monoxide (CO) poisoning.

However, the calcium phosphate salt formed by calcium nitrate and phosphoric acid is a ceramic, and the electron conductivity of the hydroxyapatite is very poor (7x10 ^-13 S/cm), which causes the cell polarization test. A very large amount of XC72 needs to be added to increase its conductivity. However, the excessive addition of XC72 causes the electrode layer to be too thick, which further causes the waste fuel generated by the electrochemical test to fail to be discharged as scheduled. In addition to causing water accumulation and affecting the overall performance of the membrane electrode assembly, it will also affect the stability of the long-term test due to the poor adhesion between XC72 and iron-containing hydroxyapatite under long-term testing. Therefore, before the present invention attempts to deposit HAp onto acetylene carbon black to increase its conductivity, the acetylene black is first placed in an oxygen-rich environment to change surface functional groups such as OH ^- to enhance hydroxyapatite. Bonding with acetylene black also improves the conductivity of hydroxyapatite (HAp) by this method.

Based on the above object, the present invention finds that XC72 powder is passed through a strong oxidizing agent to modify the surface of carbon black to produce a functional group, and then phosphoric acid and calcium nitrate are added to carry out deposition reaction of hydroxyapatite on XC72 to obtain electric resistance improvement. The XCHAp powder is ion exchanged with divalent iron ions to form a mixture of acetylene black-iron-containing iron-hydrogen apatite composite (XCFeHAp), and then platinum solution is added by adding a hexachloroplatinic acid solution containing a CTABr dispersant. Forming Pt/XCFeHAp catalyst thereon, and then These catalysts were heat-treated at 100 ° C for 3 hours to obtain a composite material of iron-containing hydroxyapatite (XCFeHAp).

Accordingly, one aspect of the invention relates to a method for preparing a composite material of iron-containing hydroxyapatite (XCFeHAp) bearing reduced nano-gold, which mainly comprises XC72 hydroxyapatite (XCHAp) and a solution containing iron. Adding water to stir together to exchange part of calcium ions and iron ions; adding platinum precursor to exchange some iron ions with platinum ions; adding reducing agent and dispersing agent to reduce and disperse all platinum particles; and after reduction The powder was washed and collected to obtain Pt/XCFeHAp catalyst powder. The Pt/XCFeHAp catalyst prepared by the method of the present invention can be mixed with Nafion to form a Pt/XCFeHAp electrode catalyst.

The method according to the present invention comprises the steps of: surface modifying acetylene black (XC72) through a strong oxidizing agent to produce C=O and/or OH groups on the surface; and placing calcium nitrate and phosphoric acid at a concentration of 10 -15wt% H ₂ O ₂ surface modified XC72 solution, by chemical co-precipitation reaction of calcium nitrate with phosphoric acid, the surface of the acetylene carbon black is coated with a layer of XC72 hydroxyapatite (Ca ₁₀ (PO ₄ ) ₆ (OH) ₂ , HAp) nano-coating, called XCHAp; exchange of ferrous ions with calcium ions of XCHAp to form XC iron-containing hydroxyapatite (XCFeHAp); addition of platinum-containing compounds and iron ions Exchange to form platinum-containing iron hydroxyapatite (Pt/XCFeHAp); adding a reducing agent and a dispersing agent to completely reduce the remaining platinum ions to a platinum catalyst supported on XCFeHAp to form Pt/XCFeHAp; and after reduction The powder was washed and collected to obtain a Pt/XCFeHAp double-acting catalyst powder.

In some embodiments of the present invention, the method further comprises mixing the obtained Pt/XCFeHAp catalyst with Nafion to form a Pt/XCFeHAp electrode catalyst.

In some embodiments of the present invention, the chemical co-precipitation reaction of the calcium nitrate (CaNO ₃ ‧4H ₂ O) with phosphoric acid (H ₃ PO ₄ ) is obtained by adding different amounts of calcium nitrate and phosphoric acid. The carrier of XC72 to Hap weight ratio. In a specific embodiment of the present invention, the weight ratio of XC72 to HAp is 1:10~1:0.1.

In some embodiments of the invention, the calcium ion and iron ion exchange step is carried out at room temperature to 100 ° C, and the temperature holding time is from 10 minutes to 6 hours. In a specific embodiment of the present invention, the iron ion-containing solution used in the ion exchange step is an aqueous solution of NH ₂ Fe(SO ₄ ) _{2 having a} concentration of 0.39 to 3.9 mM.

In some embodiments of the present invention, the iron ion and platinum ion exchange step is carried out at room temperature to 100 ° C, and the temperature holding time is 5 minutes to 6 hours. In another specific embodiment of the present invention, the platinum ion reduction reaction temperature is a boiling temperature, and the temperature holding time is 10 minutes to 6 hours.

Another aspect of the invention pertains to a double effect modified catalyst for supporting platinum particles prepared according to the process of the invention having enhanced catalyst conductivity.

In one embodiment of the present invention, the double-effect improved catalyst is used to prepare a proton exchange membrane fuel cell (PEMFC) and a hydrogen oxidation reaction (HOR). In another embodiment of the present invention, the double effect modified catalyst is used to prepare a direct methanol fuel cell (DMFC).

FIG. 1 is a schematic flow chart of the process of the XCHAp carrier of the present invention.

2 is a schematic diagram showing the manufacturing process of the Pt/XCFeHAp and Pt/XCFeHAp/C catalysts of the present invention.

Figure 3 is a TEM and Live-FFT diagram of XCHAp and Pt/XCFeHAp of the present invention.

Figure 4 is a cyclic voltammogram of Pt/XCFeHAp and Pt/XCFeHAp/C of the present invention.

Figure 5 is a diagram showing the methanol oxidation reaction of Pt/XCFeHAp and Pt/C of the present invention.

Figure 6 is a Fourier transform map of Pt/XCFeHAp of the present invention.

Figure 7 is a 1000-cycle long-term stability test chart of the Pt/XCFeHAp of the present invention.

Figure 8 is a single electrode test chart of Pt/XCFeHAp of the present invention.

The invention is characterized in that after acetylene black (XC72) is surface-modified by a strong oxidizing agent (H ₂ O ₂ ), a surface of acetylene black is plated with a phosphorus oxyphosphate by chemical co-precipitation reaction of calcium nitrate and phosphoric acid. Gray stone (Ca ₁₀ (PO ₄ ) ₆ (OH) ₂ , HAp) nano-plating layer, thereby increasing the electronic conductivity of Ca ₁₀ (PO ₄ ) ₆ (OH) ₂ , Hap. The ferrous ions are then partially exchanged to form XC iron-containing hydroxyapatite (XCFeHAp) as a catalyst carrier. Then, a platinum ion-containing compound is exchanged to exchange a part of the iron ions in the XCFeHAp to form a platinum-containing iron hydroxyapatite (Pt/XCFeHAp), and the excess ferrous ion in the solution is further reduced to a part of platinum, and is stably formed with the carrier. The chemical bond, and then the addition of ethanol completely reduces the remaining platinum ions to a platinum catalyst, which is carried on XCFeHAp to form Pt/XCFeHAp. According to the method of the present invention, the Pt film which is the best among the sulfuric acid can be prepared to cohere to the surface of the hydroxyapatite with the (110) plane, so that the electrochemical active surface of the platinum is improved, and the electronic conduction is improved. Degree, as well as reducing the performance of platinum poisoned by CO.

The other features and advantages of the present invention are further exemplified and illustrated in the following examples, which are intended to be illustrative only and not to limit the scope of the invention.

Example 1: XC72 hydroxyapatite A layer of nano-sized hydroxyapatite was deposited on the surface-modified acetylene black by calcium co-precipitation from calcium nitrate and phosphoric acid.

In this embodiment, HAp is deposited on XC72 by coprecipitation, and the prepared XC hydroxyapatite (XCHAp) is prepared by ion exchange to prepare iron-containing hydroxyapatite (XCFeHAp) as reduced platinum. Carrier of the catalyst. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a flow chart showing the preparation of the XCHAp vector of the present invention. Powder XC72. The XC72 powder was mixed with a deionized aqueous solution containing 10% by weight of H ₂ O ₂ and stirred under ultrasonic vibration for one hour, and then NH ₄ OH was added dropwise to adjust the pH to 10.6-10.8. The XC72 powder was then thoroughly dispersed by magnetic stirring and further oxidized completely. After 20 hours, a starting reagent containing Ca(NO ₃ ) ₂ ‧4H ₂ O and H ₃ PO ₄ was added to the XC72 solution to obtain an acetylene black (XCHAp) on which HAp was deposited. Finally, the obtained XCHAp powder was washed with deionized water, suction-filtered 2-3 times, and dried at 55 ° C overnight.

A surface of acetylene black is coated with a layer of XC72 hydroxyapatite (Ca ₁₀ (PO ₄ ) ₆ (OH) ₂ , HAp) nano-coating of about 15 nm, called XCHAp, to increase Ca ₁₀ (PO ₄ ) _{6 .} (OH) ₂ , the electronic conductivity of Hap (see Table 1 below).

FIG. 2 exemplifies a manufacturing process and a device diagram of the Pt/FeXCHAp catalyst of the present invention. The hydroxyapatite obtained from XC (XCHAp) powder into 100ml H ₂ O was added 1.55g of the NH ₂ Fe (SO _{4) 2} powder was stirred and heated to 70 ℃, holding temperature for 20 minutes to ion exchange, The iron-containing hydroxyapatite (XCFeHAp) was obtained. Then, add 7.8ml of platinum ion-containing H ₂ PtCl ₆ solution, heat until the aqueous solution boils, keep the boiling temperature for nearly half an hour, and finally add 100ml of alcohol and heat to boil the solution for 3 hours to completely reduce Pt to XCFeHAp. on. After the reduction, the powder was washed with deionized water, collected and heated to catch water for 3 hours.

Possible chemical reactions

Co-precipitation reaction

10 Ca (NO _{3) 2.} 4 H ₂ O+6 H ₃ PO ₄ +20NH ₄ OH → Ca ₁₀ (PO ₄ ) ₆ (OH) ₂ +20 NH ₄ NO ₃ +22 H ₂ O

Ion exchange

Ca ₁₀ (PO ₄ ) ₆ OH ₂ +x Fe ²⁺ → Fe _x Ca _10-x (PO ₄ ) ₆ OH ₂ +xCa

Fe _x Ca _10-x (PO ₄ ) ₆ OH ₂ +yPt ²⁺ → Pt _y Fe _xy Ca _10-x (PO ₄ ) ₆ OH ₂ +yFe ²⁺

Oxidation reaction:

CH ₃ CH ₂ OH → CH ₃ CHO+4H ⁺ +4e ^- E ⁰ =0.32V

Reduction reaction:

PtCl ₆ ^2- +2e ^- → PtCl ₄ ^2- +2Cl ^-

PtCl ₄ ^2- +2e ^- → Pt ⁰ +4Cl ^-

Total response

CH ₃ CH ₂ OH+PtCl ₆ ^2- →Pt ⁰ +CH ₃ CHO+4H ⁺ +6Cl ^-

Example 2: Preparation of Pt/XCFeHAp/C electrode catalyst

As in Example 1, a layer of nano-sized hydroxyapatite was deposited from the surface-modified acetylene black by calcium nitrate and phosphoric acid using a chemical co-precipitation method. The prepared Pt/XCFeHAp catalyst powder was taken to 0.02 g, 0.4 ml of Nafion (Dupont) 5 wt% ethanol solution was added, and mixed with 0.05 ml of 95 wt% alcohol by ultrasonic wave for ten minutes to obtain a catalyst ink (catalyst). Ink). After forming the electrode catalyst, the carbon black powder was mixed with the weight ratio of the first two to 1:2 to form a Pt/XCFeHAp/C electrode catalyst.

The electrode active catalyst has an electrochemical active surface of 671 to 1150 cm ² /mg, and the platinum content of Pt/XCFeHAp is 6.4 to 10.4 wt%, and the Pt(1 1 0) increases the platinum catalyst. It is active and reduces the phenomenon that platinum is poisoned by carbon monoxide (CO).

Example 3: Preparation of a catalyst carrier having different weight ratios of acetylene carbon black to hydrogen apatite (XC72: HAp)

As in Example 1, a layer of nano-sized hydroxyapatite was deposited on the acetylene black having been surface-modified by a chemical co-precipitation method from calcium nitrate and phosphoric acid.

In this example, a carrier having a different weight ratio of XC72 to HAp was obtained by adding different amounts of calcium nitrate and phosphoric acid. In the surface treated acetylene black (XC72) and aqueous hydroxyapatite (HAp) solution, a solution having a weight ratio of 1:10, 1:3, 1:1 and 1:0.5 is obtained, and hydrogen is obtained. The oxyapatite is uniformly grown on acetylene black; it is ion exchanged with divalent iron ions to form a mixture of acetylene black-iron-containing hydroxyapatite composite (XCFeHAp); then a CTABr-containing dispersant is added. The hexachloroplatinic acid solution reduces platinum to the aforementioned XCFeHAp to form a catalyst such as Pt/XCFeHAp1:10, Pt/XCFeHAp1:101:3, Pt/XCFeHAp1:101:1 and Pt/XCFeHAp1:101:0.5, respectively. These catalysts were heat-treated at 100 ° C for 3 hours.

The characteristics of the obtained catalyst are X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM), field emission transmission electron microscope (FE-TEM Live-FFT), X -ray electron spectroscopy (XPS), inductively coupled plasma mass spectrometer (ICP-MS), Fourier transform infrared spectrometer (FTIR), membrane electrode assembly (MEA) and cyclic voltammetry (CV) were analyzed.

Figure 3 is a TEM and Live-FFT diagram of XCHAp and Pt/XCFeHAp of the present invention. The size of the dispersed platinum particles was calculated from the XRD equation to be 4.5 to 6.6 nm, and from TEM to be 2.64 to 4.42 nm.

The results of cyclic voltammetry in Figure 4 show that as the amount of acetylene black increases, the IR value decreases and becomes less pronounced, and the hydrogen adsorption peak ranges from -0.05V to -0.189V (vs. Ag/AgCl/saturated KCl). The electrochemically active surface area without additional carbon black is between 429.37-861.50 (cm ² /mg), and the electrochemical live surface area of the additional carbon black is increased to 670.91-1149.70 (cm ² /mg); The reaction diagram shows that Pt/XCFeHAp1:10 has the highest mass activity of 233 (A/g ^Pt ) and the lowest initial potential of 0.28 V, and no obvious reaction peak appears to show no toxicity reaction, indicating that the obtained catalyst can improve platinum The phenomenon of carbon monoxide (CO) poisoning.

Among the four catalysts with different weight ratios of XC72 to HAp prepared above, the MEA of Pt/XCFeHAp1:3 exhibited the highest current density and power density; and Pt/XCFeHAp1:10 There is the highest open circuit voltage (OCV), which is consistent with the lowest initial potential in MOR (Figure 5). In the 1000-cycle long-term stability test, the residual electrochemical active surface area of Pt/XCFeHAp1:1 was 96.53%, which was only 70.5% compared with the additional carbon black (Fig. 7).

Figure 8 is a single electrode test chart of Pt/XCFeHAp prepared by the present invention, wherein the current density and power density are 400 mA/cm ² /mg ^Pt and 35 mW/cm ² /mg ^Pt , respectively, which effectively solves the catalytic resistance and CO poisoning phenomenon. .

According to the above technical method, the invention obtains a new dual conductivity catalyst with improved electronic conductivity, which has the following advantages: 1. The invention improves the electronic conductivity of the carrier and the catalyst; 2. The invention utilizes hydrogen. Crystal structure characteristics of oxyapatite, the most electrochemically active Pt(110) surface is prepared for sulfuric acid The highest and lowest Tafel slope of the exchange current density in the solution; 3. The invention greatly reduces the platinum usage by 1/2 to 1/3 of the existing commercialization; 4. The invention greatly increases the rate of the cathodic redox reaction (ORR); The present invention inherits the situation in which the platinum is poisoned by CO. Therefore, it can be applied to a proton exchange membrane fuel cell (PEMFC), a direct methanol fuel cell (DMFC), a hydrogen evolution reaction (HER), and a hydrogen oxidation reaction (hydrogen oxidation). Reaction, HOR), the value of the use of cookware industry.

Claims (11)

A method for preparing a double-acting catalyst composite containing iron-hydrogen oxyapatite (Pt/XCFeHAp) carrying reduced nano-gold, comprising: (1) surface modification: acetylene black (XC72) is passed through a strong oxidant Surface modification to produce C=O and/or OH groups on the surface of the acetylene black; (2) Chemical co-precipitation reaction: adding calcium nitrate (CaNO ₃ .4H ₂ O) and phosphoric acid (H ₃ PO ₄ ) The surface of step (1) is modified with XC72 solution, and a surface of the acetylene carbon black is coated with a layer of hydroxyapatite (Ca ₁₀ (PO ₄ ) ₆ (OH) ₂ , HAp) nano-coating, called XCHAp; 3) ferrous ion exchange: the XC/hydroxyapatite powder of step (2) is placed in an aqueous solution containing ferrous ions, and the exchange of ferrous ions with the calcium ions of XCHAp is carried out at room temperature or under heating. Forming XC/iron-containing hydroxyapatite (XCFeHAp); (4) Platinum ion exchange: adding the platinum ion-containing compound to the XC/iron-containing hydroxyapatite solution in step (3) at room temperature or Exchange of platinum ions with iron ions under heating to form XC/hydroxyapatite (Pt/XCFeHAp) containing platinum and iron ions; (5) Platinum reduction: Pt/XCFeHAp solution added in step (4) Reducing agent and points The Pt/XCFeHAp powder is completely reduced to a platinum catalyst and supported on XCFeHAp to form Pt/XCFeHAp; and (6) the Pt/XCFeHAp powder after the reduction of the step (5) is washed and collected to obtain a Pt/XCFeHAp double-acting contact. Medium powder. The method of claim 1, further comprising mixing the obtained Pt/XCFeHAp catalyst with Nafion to form a Pt/XCFeHAp electrode catalyst. According to the method of claim 1, wherein the chemical co-precipitation reaction of the step (2) is carried out by adding different amounts of calcium nitrate and phosphoric acid to obtain a carrier having a different ratio of XC72 to Hap. The method of claim 1 or 2, wherein the weight ratio of the acetylene black XC72 to the HAp is from 1:10 to 1:0.1. The method of claim 1, wherein the strong oxidizing agent is hydrogen peroxide (H ₂ O ₂ ). According to the method of claim 1, wherein the calcium ion and ferrous ion exchange in the step (3) are carried out at room temperature to 100 ° C, and the holding time is from 10 minutes to 6 hours. The method according to claim 1 or 6, wherein the ferrous ion-containing solution in the step (3) is an aqueous solution of NH ₂ Fe(SO ₄ ) ₂ having a concentration of 0.39 to 3.9 mM. The method of claim 1, wherein the platinum ion-containing compound of the step (4) is hexachloroplatinic acid. The method according to claim 1 or 8, wherein the step of ion-exchange and platinum ion exchange in the step (4) is carried out at room temperature to 100 ° C, and the temperature holding time is 5 minutes to 6 hours. According to the method of claim 1, wherein the platinum ion reduction reaction temperature of the step (5) is a boiling temperature, and the temperature holding time is from 10 minutes to 6 hours. The method of claim 1 or 10, wherein the dispersing agent of the step (5) is CTABr.