Pt-Ni alloy modified PBMPtNi catalyst, preparation method and application

Abstract

The invention discloses a Pt-Ni alloy modified PBMPtNi catalyst as well as a preparation method and application thereof, and belongs to the field of electro-catalysis. The preparation method of the Pt-Ni alloy modified PBMPtNi catalyst comprises the following steps: stirring and mixing praseodymium nitrate, barium nitrate, manganous nitrate tetrahydrate, platinum tetrachloride, nickel nitrate hexahydrate and water, and completely dissolving metal salt ions to obtain a metal salt ion solution; adding ethylenediaminetetraacetic acid and citric acid into the metal salt ion solution, and adjusting the pH value to 7 to obtain a mixed solution; heating and stirring the mixed solution into gel; the preparation method comprises the following steps: preparing a Pt-Ni alloy modified PBMPtNi catalyst, drying the gel, grinding into powder, calcining, grinding to obtain a PBMPtNi sample, and preparing the Pt-Ni alloy modified PBMPtNi catalyst from the PBMPtNi sample through a hydrogen reduction method, the catalyst improves the Pt utilization rate, reduces the cost, and can greatly improve the ammonia electrooxidation reaction activity.

Description

Technical Field

[0001] The invention belongs to the field of electrocatalysis, and in particular relates to a Pt-Ni alloy-modified PBMPtNi catalyst, a preparation method and an application thereof. Background Art

[0002] Environmental problems are becoming increasingly serious, and the growing ammonia emissions have caused large-scale environmental and human health problems. Industrial wastewater such as landfill leachate contains high concentrations of ammonia pollutants, which will cause ecological damage and eutrophication when discharged into natural water bodies. Traditional biological denitrification technology is completed through ammonification, nitrification, denitrification and assimilation. The process of traditional biological denitrification is mature and the denitrification effect is good. However, there are disadvantages such as long process flow, large land area, often need to add external carbon source, high energy consumption and high cost. Direct electrochemical ammonia oxidation reaction is simple to operate, no chlorine-containing reagents are added, and it is environmentally friendly. It is a very promising method. In addition to being used for wastewater treatment, direct electrochemical ammonia oxidation is also of great significance for direct ammonia fuel cells and ammonia electrochemical sensors. However, electrochemical ammonia oxidation is a process involving multiple reactants and multiple steps, so it is still a challenge to achieve efficient nitrogen-containing wastewater denitrification. Finding an efficient and low-cost catalyst is a necessary condition to overcome the slow ammonia oxidation reaction.

[0003] The electrochemical ammonia oxidation reaction (AOR) is a reaction that oxidizes NH3 to N2. Under alkaline conditions, the AOR is enhanced. AOR electrodes can be applied to ammonia electrolysis cells (AECs) by replacing the anode electrode in water electrolysis with an alkaline electrolyte. Precious metals generally have a strong affinity for NH3. Literature studies have shown that 5d metals (Pt, Ir) have steady-state activity for selective N2 generation. Pt has high catalytic activity and is considered to be the best AOR catalyst. Among non-precious metal catalysts, research has mainly focused on Ni and NiCu binary catalysts. Non-precious metal catalysts mainly include hydroxides, oxides, phosphides, and nitrates. In addition, a few studies have explored the application of non-precious metal catalysts in AEC or DAFC. Since the AOR performance of Pt-based catalysts is higher than that of non-precious metal catalysts, the development and modification of Pt-based catalyst materials has become an effective way to discover efficient AOR catalysts. Summary of the invention

[0004] In view of the deficiencies in the prior art, the purpose of the present invention is to provide a Pt-Ni alloy modified PBMPtNi catalyst, a preparation method and an application thereof, thereby solving the problems in the prior art.

[0005] The purpose of the present invention can be achieved by the following technical solutions: The preparation method of the Pt-Ni alloy modified PBMPtNi catalyst comprises the following steps: The praseodymium nitrate, barium nitrate, manganese nitrate tetrahydrate, platinum tetrachloride, nickel nitrate hexahydrate and water are stirred and mixed to completely dissolve the metal salt ions to obtain a metal salt ion solution; Adding ethylenediaminetetraacetic acid and citric acid to the metal salt ion solution and adjusting the pH to 7 to obtain a mixed solution; The mixed solution is heated and stirred into a gel; The gel was dried and ground into powder, and then calcined and ground to obtain the PBMPtNi sample, the molecular formula of which is: Pr 0.5 Ba 0.5 Mn 0.9 Pt 0.075 Ni 0.025 O 3-δ ; The PBMPtNi sample was reduced by hydrogen to prepare the Pt-Ni alloy modified PBMPtNi catalyst.

[0006] Furthermore, the molar ratio of praseodymium nitrate, barium nitrate, manganese nitrate tetrahydrate, platinum tetrachloride, and nickel nitrate hexahydrate is 1:1:1.8:0.15:0.05.

[0007] Furthermore, the molar ratio of ethylenediaminetetraacetic acid, citric acid and metal salt ions is 1:2:1.

[0008] Furthermore, ammonia water is used for pH adjustment.

[0009] Furthermore, the drying temperature is 250°C, the time is 5 hours, the calcination temperature is 1100°C, and the calcination time is 4 hours.

[0010] Furthermore, the hydrogen reduction method is: placing the PBMPtNi sample in a tubular furnace, introducing hydrogen and nitrogen, and reducing it at 800° C. for 4 hours.

[0011] The Pt-Ni alloy modified PBMPtNi catalyst is prepared by using the above-mentioned preparation method of the Pt-Ni alloy modified PBMPtNi catalyst.

[0012] Application of the above-mentioned Pt-Ni alloy modified PBMPtNi catalyst in ammonia oxidation reaction.

[0013] The above-mentioned Pt-Ni alloy modified PBMPtNi catalyst is used in the preparation of a direct ammonia electrolyzer.

[0014] A direct ammonia electrolyzer uses the above-mentioned Pt-Ni alloy-modified PBMPtNi catalyst as an electrode material.

[0015] Beneficial effects of the present invention: 1. The present invention proposes a simple, low-cost Pr 0.5 Ba 0.5 Mn 0.9 Pt 0.075 Ni 0.025 O 3-δ The invention discloses a method for preparing a catalyst; and a hydrogen reduction method is used to precipitate a Pt-Ni alloy from the surface of the catalyst to form a heterogeneous interface, thereby improving the utilization rate of Pt, reducing the cost, and greatly improving the activity of ammonia electrooxidation reaction.

[0016] 2. The Pt-Ni alloy-modified PBMPtNi catalyst prepared by the present invention can be used to assemble a direct ammonia electrolyzer driven by solar energy to degrade ammonia in boiling water, thereby obtaining a sustainable and environmentally friendly ammonia degradation device. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0018] Figure 1 is an X-ray diffraction (XRD) pattern of PBMPtNi prepared in Example 1; Figure 2 is an X-ray diffraction (XRD) pattern of the Pt-Ni alloy modified PBMPtNi prepared in Example 2; Figure 3 TEM image and element distribution diagram of Pt-Ni alloy modified PBMPtNi prepared in Example 2; Figure 4 are the electrochemical CV images of PBMPtNi, Pt-Ni alloy modified PBMPtNi and Pt / C; Figure 5 is the performance diagram of PBMPtNi, Pt-Ni alloy modified PBMPtNi and Pt / C full battery; Figure 6 This is a real picture of a solar-coupled ammonia electrolyzer assembled using the Pt-Ni alloy modified PBMPtNi prepared in Example 2 as the electrode material. DETAILED DESCRIPTION

[0019] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0020] Example 1 The preparation method of the PBMPtNi catalyst comprises the following steps: S1, at room temperature, in a beaker, add 2 mmol of analytical grade praseodymium nitrate, barium nitrate, manganese nitrate tetrahydrate, platinum tetrachloride, and nickel nitrate hexahydrate in a molar ratio of 1:1:1.8:0.15:0.05 to a beaker containing 150 mL of pure water, and stir for 40 min to completely dissolve the metal salt ions to obtain a metal salt ion solution; S2, adding ethylenediaminetetraacetic acid (EDTA) and citric acid to the metal salt ion solution, stirring for 3 hours, and adjusting the pH to 7 with ammonia water to obtain a mixed solution; wherein the molar ratio of EDTA, citric acid and the metal salt ions in the metal salt ion solution is 1:2:1; S3, placing the mixed solution on a magnetic stirrer, setting the hot plate to 80°C and stirring continuously until it becomes gel-like; S4, the gel was dried in a vacuum oven at 250°C for 5 h to obtain a black precursor; the black precursor was then ground into powder and calcined at 1100°C for 4 h, and finally fully ground to obtain a powdered PBMPtNi sample, whose molecular formula is Pr 0.5 Ba 0.5 Mn 0.9 Pt 0.075 Ni 0.025 O 3-δ .

[0021] Example 2 In this embodiment, the PBMPtNi catalyst in Example 1 is used to prepare a Pt-Ni alloy modified PBMPtNi catalyst, and the preparation process is as follows: The PBMPtNi sample obtained in Example 1 was placed in a corundum ark, the corundum ark was placed in a tube furnace, hydrogen and nitrogen (the volume ratio of hydrogen to nitrogen was 2:8) were introduced, the temperature was raised to 800°C at a rate of 2°C per minute, and the sample was reduced at 800°C for 4 hours (protected under 80% N2 throughout the process) to obtain a Pt-Ni alloy-modified PBMPtNi sample.

[0022] Example 3 In this example, the PBMPtNi sample prepared in Example 1 and the Pt-Ni alloy-modified PBMPtNi powder prepared in Example 2 were applied to a direct ammonia electrolyzer (DAEC) and ammonia oxidation (AOR) reaction under three electrodes, and related experimental tests were performed; 1. Determine the phase composition of the sample of Example 1 and the sample of Example 2, and the element distribution of the sample of Example 2; like Figure 1 As shown in the figure, the matrix of the PBMPtNi sample is PrBaMnO3-δ (PBMO). For the doping of PBMO perovskite oxide, most of them show lattice distortion of the perovskite cubic structure. 0.5 Ba 0.5 Mn 0.9 Pt 0.075 Ni 0.025 O 3-δ It is a mixed structure of cubic and hexagonal. From XRD, it can be seen that the PBMPtNi sample is a pure phase.

[0023] like Figure 2 As shown, under the condition of hydrogen as a reducing atmosphere, the prepared PBMPtNi (Pt-Ni alloy) is transformed from the original cubic and hexagonal mixed phase to a PBMPtNi containing a layered structure, and Pt-Ni alloy is precipitated. Figure 2 The areas marked at around 45° and 55° are the precipitated Pt-Ni alloy.

[0024] Figure 3 This is the element distribution diagram of the sample in Example 2. It can be seen that the Pr, Ba, and Mn elements are evenly distributed, and the Pt and Ni elements are precipitated from the surface in the form of particles and grow on the surface of the catalyst in the form of alloys.

[0025] 2. The ammonia oxidation (AOR) performance of the samples of Example 1 and Example 2 was tested under 0.1M KOH and 55M mNH 4 Cl. The test process is as follows: Electrochemical ammonia oxidation (AOR) tests were performed on an electrochemical workstation (AUT87986, Autolab BV, Metrohm, Switzerland) using a standard three-electrode system. The electrolyte used was 1 M KOH and 55 MmNH4Cl. A graphite rod electrode was used as the counter electrode, Ag / AgCl was used as the reference electrode, and Platinized Ti Fiber Paper was used as the substrate to prepare the working electrode. When preparing the working electrode, the catalyst powder (7 mg) and acetylene black (3 mg) were dissolved in anhydrous ethanol (300 ul) and Nafion (50 ul) solution, and ultrasonic treatment was performed for 1 h to uniformly disperse the catalyst slurry. Then, the catalyst slurry was dropped onto the Platinized TiFiber Paper substrate with a pipette, and the final catalyst loading was 0.25 mg cm-2. Cyclic voltammetry (CV) measurements were set at a scan rate of 5 mVs -1, and the obtained CV images were used to evaluate the AOR performance.

[0026] Test results: Figure 4 As shown, Figure 4 CV curves of the samples of Example 1 and Example 2 under 0.1M KOH and 55M mNH 4 Cl. Figure 4 It can be seen that the sample of Example 2 has the highest ammonia oxidation (AOR) current density, indicating that it has the highest activity for the AOR reaction.

[0027] 3. Performing a direct ammonia electrolyzer (DAEC) full cell test on the samples of Example 1 and Example 2; The results are as follows Figure 5 As shown; Figure 5 The current-voltage diagram of the full cell of the direct ammonia electrolyzer (DAEC) of the samples of Example 1 and Example 2. The samples of Example 1 and Example 2 were tested in full cells, and a symmetrical direct ammonia electrolyzer (the cathode and anode catalysts are the same, where the anode is the ammonia oxidation reaction (AOR) and the cathode is the hydrogen evolution reaction (HER)) was assembled. A voltage of 0-3V was applied to the electrolyzer, and the corresponding current was tested respectively. Figure 5 It can be seen that the sample of Example 1 (PBMPtNi modified with Pt-Ni alloy) is much higher than the PBMPtNi sample in terms of both starting potential and current density, and even much higher than the performance of Pt / C.

[0028] 4. Testing the performance of the sample of Example 2 (PBMPtNi modified with Pt-Ni alloy) applied to a solar-coupled ammonia electrolyzer; like Figure 6 The figure shows a real shot of a solar-coupled ammonia electrolyzer, in which the sample of Example 2 (PBMPtNi modified by Pt-Ni alloy) is used as the electrode material to assemble a solar-coupled ammonia electrolyzer, achieving green, efficient and sustainable ammonia degradation. Figure 6 It can be seen that the solar panels provide the ammonia electrolyzer with the voltage required for electrolysis to achieve ammonia degradation, providing a new model for using renewable energy to achieve ammonia degradation.

[0029] In the description of this specification, the description with reference to the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0030] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, and these changes and improvements all fall within the scope of the present invention to be protected.

Claims

1. A method for preparing a Pt-Ni alloy modified PBMPtNi catalyst, characterized in that: The following steps are involved: The praseodymium nitrate, barium nitrate, manganese nitrate tetrahydrate, platinum tetrachloride, nickel nitrate hexahydrate and water are stirred and mixed to completely dissolve the metal salt ions to obtain a metal salt ion solution; Adding ethylenediaminetetraacetic acid and citric acid to the metal salt ion solution and adjusting the pH to 7 to obtain a mixed solution; The mixed solution is heated and stirred into a gel; The gel was dried and ground into powder, and then calcined and ground to obtain the PBMPtNi sample, the molecular formula of which is: Pr 0.5 Ba 0.5 Mn 0.9 Pt 0.075 Ni 0.025 O 3-δ ; The PBMPtNi sample was reduced by hydrogen to prepare the Pt-Ni alloy modified PBMPtNi catalyst.

2. The method for preparing the Pt-Ni alloy modified PBMPtNi catalyst according to claim 1, characterized in that: The molar ratio of praseodymium nitrate, barium nitrate, manganese nitrate tetrahydrate, platinum tetrachloride, and nickel nitrate hexahydrate is 1:1:1.8:0.15:0.

05.

3. The method for preparing the Pt-Ni alloy modified PBMPtNi catalyst according to claim 1, characterized in that: The molar ratio of ethylenediaminetetraacetic acid, citric acid and metal salt ions is 1:2:

1.

4. The method for preparing the Pt-Ni alloy modified PBMPtNi catalyst according to claim 1, characterized in that: Ammonia was used to adjust the pH.

5. The method for preparing the Pt-Ni alloy modified PBMPtNi catalyst according to claim 1, characterized in that: The drying temperature is 250°C and the time is 5h, and the calcination temperature is 1100°C and the calcination time is 4h.

6. The method for preparing the Pt-Ni alloy modified PBMPtNi catalyst according to claim 1, characterized in that: The hydrogen reduction method is as follows: placing the PBMPtNi sample in a tube furnace, introducing hydrogen and nitrogen, and reducing it at 800° C. for 4 hours.

7. A Pt-Ni alloy modified PBMPtNi catalyst, characterized in that: The catalyst is prepared by the method for preparing a Pt-Ni alloy-modified PBMPtNi catalyst according to any one of claims 1 to 6.

8. Use of the Pt-Ni alloy modified PBMPtNi catalyst according to claim 7 in ammonia oxidation reaction.

9. Use of the Pt-Ni alloy modified PBMPtNi catalyst according to claim 7 in the preparation of a direct ammonia electrolyzer.

10. A direct ammonia electrolyzer, characterized in that: The Pt-Ni alloy modified PBMPtNi catalyst described in claim 7 is used as the electrode material.

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