Efficient and stable platinum-based intermetallic nitride catalyst prepared based on nitridation strategy as well as preparation method and application of efficient and stable platinum-based intermetallic nitride catalyst

Abstract

The invention discloses an efficient and stable platinum-based intermetallic nitride catalyst prepared on the basis of a nitridation strategy as well as a preparation method and application of the efficient and stable platinum-based intermetallic nitride catalyst. The intermetallic nitride is Pt0. 8M0. 2CoN metal M which is selected from one of Ti, Al, V, Cr, Ga, Mn, Fe, In, Co, Ni and Cu or a combination of the Ti, the Al, the V, the Cr, the Ga, the Mn, the Fe, the In, the Co, the Ni and the Cu. The specific synthesis method comprises the following steps: A) ultrasonically dispersing ZIF-8 derived mesoporous carbon and metal salt in a solvent, and removing the solvent to obtain dry powder; b) performing low-temperature annealing on the dry powder to obtain a multi-carbon-supported alloy nano material; and C) performing high-temperature annealing on the carbon-loaded alloy material to obtain the carbon-loaded intermetallic nitride nano material. The prepared intermetallic nitride material loaded on the ZIF-8 derived mesoporous carbon carrier has an intermetallic ordered structure, is small in size, has high platinum utilization rate, and shows good oxygen reduction reaction activity and stability.

Description

Technical Field

[0001] The present invention relates to the technical field of new energy materials, and particularly relates to a highly efficient and stable platinum-based intermetallic nitride catalyst prepared by a nitridation strategy, a preparation method thereof, and an application thereof. Background Art

[0002] As a clean and renewable energy source, hydrogen energy is regarded as the most potential alternative to traditional fossil fuels in the future. Proton exchange membrane fuel cell technology (PEMFC) is considered to be the core technology to promote the development of the hydrogen energy field due to its high energy conversion efficiency, low environmental pollution and many other advantages. Among them, the oxygen reduction reaction (ORR) at the cathode is one of the key reactions of proton exchange membrane fuel cells. For a long time, platinum (Pt) has been considered the main catalyst for ORR. However, the high cost of pure platinum and its limitations in catalytic performance have become the key factors restricting its wide application.

[0003] When a transition metal M is incorporated into Pt in a certain proportion and annealed at high temperature, an intermetallic compound with long-range atomic order can be formed. This ordered structure can regulate the electronic structure and geometric structure of the catalyst, thereby improving the catalyst performance and effectively reducing the Pt content. However, in the harsh working environment of PEMFC, the transition metal M is easily dissolved out, resulting in the collapse of the catalyst structure, the attenuation of the catalyst activity, and further affecting the overall performance and stability of PEMFC. In recent years, doping light element N into alloys or intermetallic compounds has been an important research direction. The light element N can form strong d-p hybrid bonds with the transition metal M, greatly improving the anti-dissolution property of the transition metal, so that the original morphology and structure of the catalyst are maintained during the reaction process, showing high performance in PEMFC.

[0004] However, the synthesis of intermetallic nitrides faces severe challenges. Generally, the synthesis of intermetallic nitrides needs to be achieved by high-temperature annealing in an ammonia atmosphere. This often involves the phase separation between transition metal nitrides and platinum alloys and the problem of particle sintering, resulting in the activity and stability of the catalyst not meeting expectations. The literature (High-Performance Nitrogen-Doped Intermetallic PtNi Catalyst for the Oxygen Reduction Reaction, ACS Catalysis 2020, 10, 10637-10645, Xueru Zhao) discloses a method for preparing intermetallic nitride PtNiN by one-step reduction in an ammonia atmosphere, but the average particle size of the synthesized PtNiN is relatively large (~4.7 nm), and the utilization rate of Pt is not high.

[0005] Therefore, designing a strategy for synthesizing homogeneous metal nitrides has become an urgent problem to be solved in the development process of metal nitrides. Summary of the Invention

[0006] To solve the above problems, the purpose of the present invention is to provide a preparation method of a highly efficient and stable platinum-based metal nitride catalyst prepared based on a nitridation strategy and its application in the oxygen reduction reaction. The metal nitride provided by the present invention exhibits excellent ORR activity and stability as a catalyst for the oxygen reduction reaction (ORR).

[0007] The present invention provides a highly efficient and stable platinum-based metal nitride catalyst prepared based on a nitridation strategy. The metal nitride catalyst is composed of a ZIF-8-derived mesoporous carbon support and metal nitride nanoparticles loaded on the surface of the carbon support; the metal nitride is Pt 0.8 M 0.2 CoN, and the metal M is selected from one or a combination of Ti, Al, V, Cr, Ga, Mn, Fe, In, Co, Ni, and Cu.

[0008] Preferably, the average particle size of the metal nitride nanoparticles is <3 nm, and the loading rate of the metal nitride nanoparticles is 15-25 wt% of the total mass of the mesoporous carbon support and the metal nitride nanoparticles.

[0009] The present invention also provides a preparation method of a highly efficient and stable platinum-based metal nitride catalyst prepared based on a nitridation strategy, including the following steps:

[0010] (1) Ultrasonically disperse the ZIF-8-derived mesoporous carbon support, platinum salt, cobalt salt, and third non-noble metal salt in a solvent, and obtain a dry powder after removing the solvent;

[0011] (2) Perform low-temperature annealing on the dry powder in a hydrogen-argon mixed gas atmosphere to obtain carbon-supported alloy nanoparticles;

[0012] (3) Perform high-temperature annealing on the carbon-supported alloy nanoparticles in an ammonia atmosphere to obtain a carbon-supported metal nitride nanomaterial, that is, the highly efficient and stable platinum-based metal nitride catalyst.

[0013] Preferably, the platinum salt in step (1) is H 2 PtCl 4 ·6H 2 O.

[0014] Preferably, the cobalt salt in step (1) is Co(NO 3 ) 2 ·6H 2 O or CoCl2 ·6H 2 O。

[0015] Preferably, the third non-noble metal salt in step (1) is one or a combination of hydrochlorides, sulfates, nitrates and their hydrates of Ti, Al, V, Cr, Ga, Mn, Fe, In, Co, Ni and Cu. The third non-noble metal salt includes, but is not limited to, TiCl 3 , Co(NO 3 ) 2 ·6H 2 O, Fe(NO 3 ) 3 ·9H 2 O, Cu(NO 3 ) 2 ·3H 2 O, MnCl 2 .

[0016] Preferably, the solvent in step (1) is ultrapure water.

[0017] Preferably, the method for removing the solvent in step (1) is freeze-drying.

[0018] Preferably, the method for low-temperature annealing in step (2) is: heating the dried powder after removing the solvent to 350 - 450 °C at a heating rate of 5 - 10 °C / min in an atmosphere of hydrogen-argon mixture, holding for 2 - 3 hours, and cooling to room temperature to obtain carbon-supported alloy nanoparticles.

[0019] Preferably, the volume ratio of hydrogen to argon in the hydrogen-argon mixture is (5 - 10):(95 - 90).

[0020] Preferably, the method for high-temperature annealing in step (3) is: heating the carbon-supported alloy nanoparticles to 650 - 750 °C at a heating rate of 5 - 10 °C / min in an atmosphere of ammonia, holding for 6 - 9 hours, and cooling to room temperature to obtain a metal nitride nanomaterial supported on a ZIF-8-derived mesoporous carbon support.

[0021] The present invention also provides an application of a platinum-based metal nitride supported on a ZIF-8-derived mesoporous carbon support prepared by the above method as a catalyst in an oxygen reduction reaction.

[0022] The present invention inhibits the sintering of nanoparticles through a ZIF-8-derived mesoporous carbon support with a high specific surface area and a two-step heat treatment method. First, low-temperature annealing in a hydrogen-argon atmosphere promotes the alloying process to form nanoparticles with small particle sizes. Subsequently, long-term high-temperature annealing in an ammonia atmosphere promotes the ordering process, transforming into intermetallic nitride nanoparticles with an ordered structure. The nanoparticles of this catalyst are uniformly distributed, and the average particle size is less than 3 nm, with a high platinum utilization rate, demonstrating good oxygen reduction reaction activity.

[0023] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0024] (1) The platinum-based intermetallic nitride material supported on a ZIF-8-derived mesoporous carbon support prepared by the present invention based on a nitridation strategy and its application as an oxygen reduction reaction catalyst have not been reported. Moreover, the synthesis method is simple and has high repeatability, which is an excellent intermetallic nitride synthesis strategy.

[0025] (2) The present invention uses a two-step heat treatment method to synthesize intermetallic nitrides. First, different metal elements are reduced and form nanoparticles with small particle sizes at a relatively low temperature of 350-450 °C in an atmosphere of a hydrogen-argon mixture. Then, at a relatively high temperature of 650-700 °C in an ammonia atmosphere, the doping of light element nitrogen and the phase transformation from disordered to ordered are realized, reducing the generation of separated phases and the agglomeration of particles.

[0026] (3) The platinum-based intermetallic nitride supported on a ZIF-8-derived mesoporous carbon support prepared by the present invention based on a nitridation strategy still maintains a small particle size and uniform distribution after heat treatment, improving the utilization rate of precious metals in the catalyst.

[0027] (4) The platinum-based intermetallic nitride supported on a ZIF-8-derived mesoporous carbon support prepared by the present invention based on a nitridation strategy has an ordered structure and uniform element distribution compared with ordinary alloys, and can provide uniformly distributed active sites and better electrocatalytic activity and stability. Description of the Drawings

[0028] The present invention will be further described below with reference to the drawings and embodiments.

[0029] Figure 1 XRD patterns of the Pt 0.8 Ti 0.2 CoN, Pt 0.8 Fe 0.2 CoN and Pt 0.8 Co 1.2 N intermetallic nitride catalysts obtained in Examples 1-3.

[0030] Figure 2 The Pt obtained in Example 10.8 Ti 0.2 TEM and particle size distribution diagrams of CoN intermetallic nitride catalysts.

[0031] Figure 3 Pt obtained in Example 1 0.8 Ti 0.2 CV cyclic voltammograms and LSV linear polarization curves of CoN intermetallic nitride catalysts before and after 20,000 cycles of stability testing. Among them, Figure 3 Figure a in [reference] is the CV cyclic voltammogram, and Figure b is the LSV linear polarization curve.

[0032] Figure 4 Pt obtained in Example 2 0.8 Fe 0.2 TEM and particle size distribution diagrams of CoN intermetallic nitride catalysts.

[0033] Figure 5 Pt obtained in Example 2 0.8 Fe 0.2 CV cyclic voltammograms and LSV linear polarization curves of CoN intermetallic nitride catalysts before and after 20,000 cycles of stability testing. Among them, Figure 5 Figure a in [reference] is the CV cyclic voltammogram, and Figure b is the LSV linear polarization curve.

[0034] Figure 6 Pt obtained in Example 3 0.8 Co 1.2 TEM and particle size distribution diagrams of N intermetallic nitride catalysts.

[0035] Figure 7 Pt obtained in Example 3 0.8 Co 1.2 CV cyclic voltammograms and LSV linear polarization curves of N intermetallic nitride catalysts before and after 20,000 cycles of stability testing. Among them, Figure 7 Figure a in [reference] is the CV cyclic voltammogram, and Figure b is the LSV linear polarization curve.

[0036] Figure 8 Pt obtained in Comparative Example 1 0.8 Fe 0.2 XRD patterns of Co intermetallic compound catalysts.

[0037] Figure 9 Pt obtained in Comparative Example 1 0.8 Fe 0.2 TEM and particle size distribution diagrams of Co intermetallic compound catalysts.

[0038] Figure 10The Pt obtained in Comparative Example 1 0.8 Fe 0.2 CV cyclic voltammograms and LSV linear polarization curves of the Pt 0.8 Fe 0.2 Co intermetallic compound catalyst before and after 20,000 cycles of stability test. Among them, Figure 10 Figure a in Figure 10 is the CV cyclic voltammogram, and Figure b is the LSV linear polarization curve. Specific embodiments

[0039] The present invention provides an efficient and stable platinum-based intermetallic nitride catalyst prepared by a nitridation strategy. The intermetallic nitride catalyst is composed of a ZIF-8-derived mesoporous carbon support and intermetallic nitride nanoparticles loaded on the surface of the carbon support. It has an intermetallic ordered structure, small size, and abundant surface active sites.

[0040] The ZIF-8-derived mesoporous carbon used in the present invention provides a large specific surface area, increases the distance between nanoparticles, inhibits the agglomeration phenomenon during particle preparation and reaction, realizes the preparation of small-sized intermetallic nitrides and a highly active and stable surface, and the average particle size of the prepared nanoparticles is less than 3 nm.

[0041] The intermetallic nitride nanomaterial in the present invention is Pt 0.8 M 0.2 CoN intermetallic nitride. The metal element M can be any one of Ti, Al, V, Cr, Ga, Mn, Fe, In, Co, Ni, and Cu or a combination thereof. 0.8 M 0.2 The present application provides a preparation method of an efficient and stable platinum-based intermetallic nitride catalyst prepared by a nitridation strategy, including the following steps:

[0042] (1) Ultrasonically disperse the ZIF-8-derived mesoporous carbon support, platinum salt, cobalt salt, and third non-noble metal salt in a solvent, and obtain a dry powder after removing the solvent;

[0043] (2) Anneal the dry powder at a low temperature in a hydrogen-argon mixed gas atmosphere to obtain carbon-supported alloy nanoparticles;

[0044] (3) Anneal the carbon-supported alloy nanoparticles at a high temperature in an ammonia atmosphere to obtain carbon-supported intermetallic nitride nanomaterials.

[0045] (3) Anneal the carbon-supported alloy nanoparticles at a high temperature in an ammonia atmosphere to obtain carbon-supported intermetallic nitride nanomaterials.

[0046] The platinum salt is preferably H 2 PtCl 4 ·6H 2 2 PtCl 4 ·6H 2O, the cobalt salt and the third non-noble metal salt are one or a combination of hydrochlorides, sulfates, nitrates and their hydrates of Ti, Al, V, Cr, Ga, Mn, Fe, In, Co, Ni and Cu. Some metal salts are listed in the embodiments of the present invention, specifically TiCl 3 , Co(NO 3 ) 2 ·6H 2 O, Fe(NO 3 ) 3 ·9H 2 O, Cu(NO 3 ) 2 ·3H 2 O or MnCl 2 .

[0047] The atomic feeding ratio of Pt, M and Co in the present invention is 0.75:0.25:1 to 0.85:0.15:1, where (Pt + M):Co = 1. The loading rate of the intermetallic nitride is 15-25 wt% of the total mass of the mesoporous carbon support and the intermetallic nitride particles.

[0048] The mesoporous carbon in the present invention is a ZIF-8-derived mesoporous carbon support.

[0049] The solvent in the present invention is preferably ultrapure water.

[0050] There is no special limitation on the method for removing the solvent in the present invention, and freeze-drying method is preferred.

[0051] The method for low-temperature annealing in the present invention is as follows: the dried powder after removing the solvent is heated to 350-450 °C at a heating rate of 5-10 °C / min in an atmosphere of hydrogen-argon mixed gas, kept warm for 2-3 hours, and then cooled to room temperature to obtain carbon-supported alloy nanoparticles. Preferably, the volume ratio of hydrogen to argon in the hydrogen-argon mixed gas is (5-10):(95-90).

[0052] The method for high-temperature annealing in the present invention is as follows: the carbon-supported alloy nanoparticles are heated to 650-750 °C at a heating rate of 5-10 °C / min in an atmosphere of ammonia gas, kept warm for 6-9 hours, and then cooled to room temperature to obtain a ZIF-8-derived mesoporous carbon support-supported intermetallic nitride nanomaterial.

[0053] In the steps of the present invention, during the low-temperature annealing process in an atmosphere of hydrogen-argon mixed gas, metal ions are gradually reduced and small-sized alloy particles are formed. Subsequently, during the high-temperature annealing process in an atmosphere of ammonia gas, the alloy particles gradually combine with nitrogen elements to form intermetallic nitrides and promote the formation of an ordered arrangement inside, forming Pt 0.8 M 0.2 CoN intermetallic nitride.

[0054] The present invention also provides Pt supported on a ZIF-8-derived mesoporous carbon support prepared by the above synthesis method 0.8 Ti 0.2 CoN, Pt 0.8 Fe 0.2 CoN and Pt 0.8 Co 1.2 Application of CoN intermetallic nitride as a catalyst in the oxygen reduction reaction

[0055] The synthesis method provided by the present invention is simple, and the raw materials can be obtained through a wide range of channels, which is conducive to large-scale preparation and has universality

[0056] For the convenience of understanding the method, principle and effect of the present invention, the present invention will be further elaborated below through specific examples. These examples are only the preferred embodiments of the present invention and do not limit the present invention

[0057] Example 1 Carbon-supported Pt 0.8 Ti 0.2 Preparation of CoN intermetallic nitride nanomaterials

[0058] a. Take 80 mg of mesoporous carbon support, and a certain amount of H 2 PtCl 4 ·6H 2 O, Co(NO 3 ) 2 ·6H 2 O and TiCl 3 (The total metal loading of Pt, Ti and Co is 15 wt%) are placed in a 20 ml beaker, 3 ml of deionized water is added, and ultrasonic treatment is carried out for 2 h. After removing the solvent by freeze-drying, a uniformly mixed black powder precursor is obtained

[0059] b. Transfer the precursor obtained in step (a) to a tubular furnace, introduce a H 2 / Ar mixed gas with a hydrogen volume fraction of 10%, heat it to 450 °C at a rate of 5 °C / min, and keep it warm for 3 h. After cooling to room temperature, carbon-supported Pt 0.8 Ti 0.2 Co alloy nanoparticles are obtained

[0060] c. Introduce ammonia gas into the tubular furnace, heat it to 750 °C at a rate of 10 °C / min, keep it warm for 9 h, and after cooling to room temperature, carbon-supported Pt 0.8 Ti 0.2 CoN intermetallic nitride nanomaterials are obtained

[0061] Using a MiniFlex600 X-ray diffractometer from Rigaku Corporation of Japan, under the conditions of a test voltage of 35 kV and a current of 30 mA, the Pt obtained in Example 1 was tested0.8 Ti 0.2 Perform phase characterization on CoN intermetallic nitrides. The results are as Figure 1 Pt in 0.8 Ti 0.2 The curve of the CoN sample shows that the obtained catalyst exhibits superlattice diffraction peaks of the intermetallic ordered phase, indicating the successful preparation of the ordered phase of Pt 0.8 Ti 0.2 Perform morphological characterization on the Pt 0.8 Ti 0.2 CoN intermetallic nitrides obtained in Example 1 using a Talos F200X transmission electron microscope at a voltage of 200 kV. The results are as Figure 2 shown. The obtained catalyst particles are evenly distributed with a size of about 2.85 nm, indicating the successful preparation of Pt 0.8 Ti 0.2 CoN intermetallic nitride catalyst with evenly distributed and small-sized particles.

[0062] Perform electrochemical tests on the Pt 0.8 Ti 0.2 CoN intermetallic nitride catalyst obtained in Example 1. The test process is as follows:

[0063] 1. Perform CV tests from 0.05 V to 1.2 V (vs RHE) in a 0.1 M HClO 2 electrolyte saturated with N 4 at a scan rate of 50 mV s -1 .

[0064] 2. Perform CV tests from 0.05 V to 1.1 V (vs RHE) in a 0.1 M HClO 2 electrolyte saturated with O 4 at a scan rate of 10 mV s -1 .

[0065] 3. Perform CV tests from 0.6 V to 1.0 V (vs RHE) in a 0.1 M HClO 2 electrolyte saturated with O 4 to complete the stability test at a scan rate of 100 mV s -1 , with a scan cycle rate of 20,000 cycles.

[0066] The test results are as Figure 3 shown. The CV results show that there is almost no change in the hydrogen desorption region from 0.05 V to 0.4 V (vs RHE) before and after the stability test. The LSV results show that the catalyst has excellent activity before the stability test, and the half-wave potential hardly changes after the stability test. It is proved that Pt0.8 Ti 0.2 The CoN intermetallic nitride exhibits excellent ORR activity and stability.

[0067] Example 2: Pt supported on carbon 0.8 Fe 0.2 Preparation of CoN intermetallic nitride nanomaterials

[0068] a. Take 80 mg of the mesoporous carbon support and mix it with a certain amount of H 2 PtCl 4 ·6H 2 O, CoCl 2 ·6H 2 O, and Fe(NO 3 ) 3 ·9H 2 O (the total metal loading of Pt, Fe, and Co is 20 wt%). Place them in a 20 ml beaker, add 3 ml of deionized water, and sonicate for 2 h. After removing the solvent by freeze-drying, a uniformly mixed black powder precursor is obtained.

[0069] b. Transfer the precursor obtained in step (a) to a tube furnace, and introduce a H 2 / Ar mixture with a hydrogen volume fraction of 8%. Heat it to 350 °C at a rate of 5 °C / min and hold for 2 h. After cooling to room temperature, the Pt 0.8 Fe 0.2 Co alloy material supported on carbon is obtained.

[0070] c. Introduce ammonia gas into the tube furnace, heat it to 700 °C at a rate of 5 °C / min, and hold for 6 h. After cooling to room temperature, the Pt 0.8 Fe 0.2 CoN intermetallic nitride nanomaterials supported on carbon are obtained.

[0071] Perform phase characterization on the Pt 0.8 Fe 0.2 CoN intermetallic nitride obtained in Example 2. The results are as shown by the Pt Figure 1 in the Pt 0.8 Fe 0.2 CoN sample curve. The obtained catalyst exhibits superlattice diffraction peaks of the intermetallic ordered phase, indicating the successful preparation of the ordered-phase Pt 0.8 Fe 0.2 CoN intermetallic nitride. Perform morphology characterization on the Pt 0.8 Fe 0.2 CoN intermetallic nitride obtained in Example 2. The results are as shown in Figure 4 . The obtained catalyst particles are uniformly distributed with a size of about 2.80 nm, indicating the successful preparation of Pt 0.8 Fe 0.2CoN intermetallic nitride catalyst.

[0072] For the Pt obtained in Example 2 0.8 Fe 0.2 CoN intermetallic nitride catalyst, electrochemical tests were carried out. The test results are as Figure 5 shown. The CV results show that there is almost no change in the hydrogen desorption region from 0.05 V to 0.4 V (vs RHE) before and after the stability test. The LSV results show that the catalyst has excellent activity before the stability test, and the half-wave potential only decreases by 2 mV after the stability test. It is proved that Pt 0.8 Fe 0.2 CoN intermetallic nitride exhibits excellent ORR activity and stability.

[0073] Preparation of carbon-supported Pt 0.8 Co 1.2 N intermetallic nitride nanomaterials

[0074] a. Take 80 mg of mesoporous carbon support, and mix it with a certain amount of H 2 PtCl 4 ·6H 2 O and Co(NO 3 ) 2 ·6H 2 O (the total metal loading of Pt and Co is 25 wt%). Place them in a 20 ml beaker, add 3 ml of deionized water, sonicate for 2 h, and obtain a uniformly mixed black powder precursor after removing the solvent by freeze-drying.

[0075] b. Transfer the precursor obtained in step (a) to a tubular furnace, introduce a 5% (volume fraction) H 2 / Ar mixed gas, heat it to 400 °C at a rate of 10 °C / min, and keep it at this temperature for 3 h. After cooling to room temperature, obtain carbon-supported Pt 0.8 Co 1.2 alloy material.

[0076] c. Introduce ammonia gas into the tubular furnace, heat it to 650 °C at a rate of 10 °C / min, and keep it at this temperature for 6 h. After cooling to room temperature, obtain carbon-supported Pt 0.8 Co 1.2 N intermetallic nitride nanomaterials.

[0077] For the Pt 0.8 Co 1.2 N intermetallic nitride material obtained in Example 3, phase characterization was carried out. The results are as Figure 1 shown by the Pt 0.8 Co 1.2 N sample curve. The obtained catalyst exhibits superlattice diffraction peaks of the intermetallic ordered phase, indicating that an ordered-phase Pt 0.8 Co1.2 N metal nitride. For the Pt obtained in Example 3 0.8 Co 1.2 N metal nitride was characterized morphologically. The results are as Figure 6 shown. The obtained catalyst particles are evenly distributed with a size of about 2.73 nm, indicating that a Pt 0.8 Co 1.2 N metal nitride catalyst with evenly distributed and small-sized particles was successfully prepared.

[0078] The obtained Pt 0.8 Co 1.2 N metal nitride catalyst was subjected to electrochemical tests. The test results are as Figure 7 shown. The CV results show that there are minor changes in the hydrogen desorption region from 0.05 V to 0.4 V (vs RHE) before and after the stability test. The LSV results show that the catalyst has excellent activity before the stability test, and the half-wave potential drops by 8 mV after the stability test.

[0079] Comparative Example 1: Preparation of carbon-supported Pt 0.8 Fe 0.2 Co intermetallic compound nanomaterials

[0080] a. Take 80 mg of mesoporous carbon support and mix it with a certain amount of H 2 PtCl 4 ·6H 2 O, CoCl 2 ·6H 2 O, and Fe(NO 3 ) 3 ·9H 2 O (the total metal loading of Pt, Fe, and Co is 20 wt%). Place them in a 20 ml beaker, add 3 ml of deionized water, and sonicate for 2 h. After removing the solvent by freeze-drying, a uniformly mixed black powder precursor is obtained.

[0081] b. Transfer the precursor obtained in step (a) to a tubular furnace, introduce an 8% (by volume) H 2 / Ar mixed gas, and heat it to 900 °C at a rate of 10 °C / min and hold for 2 h. After cooling to room temperature, a carbon-supported Pt 0.8 Fe 0.2 Co intermetallic compound material is obtained.

[0082] The obtained Pt 0.8 Fe 0.2 Co intermetallic compound material in Comparative Example 1 was characterized by phase. The results are as Figure 8 in Pt 0.8 Fe 0.2As shown by the Co sample curve, the obtained catalyst exhibits superlattice diffraction peaks of the intermetallic ordered phase, indicating the successful preparation of the ordered-phase Pt 0.8 Fe 0.2 intermetallic compound. The Pt 0.8 Fe 0.2 intermetallic compound obtained in Comparative Example 1 was characterized morphologically. The results are as Figure 9 shown, and the obtained catalyst has a size of about 6.22 nm.

[0083] The obtained Pt 0.8 Fe 0.2 intermetallic compound catalyst was subjected to electrochemical testing. The test results are as Figure 10 shown. The CV results show that there are minor changes in the hydrogen desorption region from 0.05 V to 0.4 V (vs RHE) before and after the stability test. The LSV results show that the catalyst has excellent activity before the stability test, and the half-wave potential drops by 18 mV after the stability test.

[0084] Compared with the Pt 0.8 Ti 0.2 CoN in Example 1, the Pt 0.8 Fe 0.2 CoN in Example 2, and the Pt 0.8 Co 1.2 N intermetallic nitrides in Example 3, although the Pt 0.8 Fe 0.2 intermetallic compound in Comparative Example 1 also has an atomic ordered structure between metals, its stability is significantly reduced. This fully reflects the atomic anti-dissolution effect generated by strong d-p hybridization after introducing metal-nitrogen bonds in the intermetallic nitrides, thereby improving the stability of the catalyst. In addition, the stability order of the intermetallic nitrides in the examples is: Pt 0.8 Ti 0.2 CoN in Example 1 is superior to Pt 0.8 Fe 0.2 CoN in Example 2 is superior to Pt 0.8 Co 1.2 N in Example 3. This is due to the different bonding strengths of the introduced M-N bonds (Ti-N > Fe-N > Co-N), which reflects the significant improvement in the stability of the catalyst by introducing strong M-N bonds.

[0085] The above embodiments of the present invention are only examples for clearly illustrating the present invention, and are not limitations on the implementation manners of the present invention. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is impossible to list all the implementation manners here. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the claims of the present invention.

Claims

1. A method for preparing an efficient and stable platinum-based intermetallic nitride catalyst based on a nitridation strategy, characterized in that: The following steps are involved: (1) ultrasonically dispersing a ZIF-8-derived mesoporous carbon support, a platinum salt, a cobalt salt, and a third non-precious metal salt in a solvent, and removing the solvent to obtain a dry powder; (2) annealing the dried powder at low temperature in a hydrogen-argon mixed gas atmosphere to obtain carbon-supported alloy nanoparticles; (3) annealing the carbon-supported alloy nanoparticles at high temperature in an ammonia atmosphere to obtain carbon-supported intermetallic nitride nanomaterials, that is, the highly efficient and stable platinum-based intermetallic nitride catalyst.

2. The preparation method according to claim 1, characterized in that: The platinum salt in step (1) is H2PtCl4·6H2O.

3. The preparation method according to claim 1, characterized in that: The cobalt salt in step (1) is Co(NO3)2·6H2O or CoCl2·6H2O.

4. The preparation method according to claim 1, characterized in that: The third non-precious metal salt in step (1) is one or a combination of hydrochlorides, sulfates, nitrates and hydrates thereof of Ti, Al, V, Cr, Ga, Mn, Fe, In, Co, Ni and Cu.

5. The preparation method according to claim 1, characterized in that: The solvent in step (1) is ultrapure water.

6. The preparation method according to claim 1, characterized in that: The method of low-temperature annealing in step (2) is as follows: the dry powder after the solvent is removed is placed in an atmosphere of a hydrogen-argon mixed gas, wherein the volume ratio of hydrogen to argon in the hydrogen-argon mixed gas is (5-10): (95-90), and the temperature is raised to 350-450° C. at a heating rate of 5-10° C. / min, and the mixture is kept at this temperature for 2-3 hours, and then cooled to room temperature to obtain carbon-supported alloy nanoparticles.

7. The preparation method according to claim 1, characterized in that: The high temperature annealing method of step (3) is as follows: the carbon-supported alloy nanoparticles are heated to 650-750°C at a heating rate of 5-10°C / min in an ammonia atmosphere, kept warm for 6-9 hours, and cooled to room temperature to obtain the ZIF-8-derived mesoporous carbon carrier-supported intermetallic nitride nanomaterial.

8. A highly efficient and stable platinum-based intermetallic nitride catalyst prepared by the preparation method according to any one of claims 1 to 7.

9. The highly efficient and stable platinum-based intermetallic nitride catalyst according to claim 8, characterized in that: The intermetallic nitride catalyst is composed of a ZIF-8 derived mesoporous carbon carrier and intermetallic nitride nanoparticles loaded on the surface of the carbon carrier; the intermetallic nitride is Pt 0.8 M 0.2 CoN, metal M is selected from one or a combination of Ti, Al, V, Cr, Ga, Mn, Fe, In, Co, Ni and Cu; the average particle size of the intermetallic nitride nanoparticles is less than 3 nm, and the loading rate of the intermetallic nitride nanoparticles is 15-25wt% of the total mass of the mesoporous carbon support and the intermetallic nitride nanoparticles.

10. Use of the efficient and stable platinum-based intermetallic nitride catalyst according to claim 8 or 9 in oxygen reduction reaction.

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