Supported catalyst, preparation method thereof and application

Abstract

The present invention provides a supported catalyst, a preparation method and application thereof. The preparation method of the supported catalyst comprises: step S1, allowing vanadate and a first ammonium salt to undergo precipitation reaction in a first solvent to obtain a first product system containing a support precursor; step S2, allowing a support precursor, a second ammonium salt, a noble metal compound, a chelating agent, and a first reducing agent to react in a second solvent to obtain a second product system containing a catalyst precursor; step S3, annealing the catalyst precursor and the second reducing agent in a protective gas to obtain a supported catalyst. The noble metal in the supported catalyst prepared by the method is not prone to migration and aggregation, and has better stability. In addition, the above preparation method requires less noble metal usage and has higher atomic utilization.

Description

Technical Field

[0001] The present invention relates to the technical field of catalyst preparation, and in particular, to a supported catalyst, a preparation method thereof, and an application thereof. Background Art

[0002] Currently, platinum-based catalysts (such as commercial Pt / C) are common electrocatalysts for oxygen reduction reactions. However, during the electrocatalytic oxygen reduction reaction (ORR), Pt particles are prone to aggregation, resulting in a reduced exposed area of Pt particles and a decreased utilization rate. Moreover, Pt / C has poor durability, a high price, and limited Pt reserves. Therefore, there is an urgent need to reduce the Pt usage while improving its durability and electrocatalytic activity.

[0003] Currently, methods for improving its durability include element doping and carrier structure confinement, etc. Among them, element doping includes nitrogen element doping, and the doping methods include in-situ synthesis method and post-treatment method. Among them, the former directly nitrides the carrier carbon with a nitrogen-rich substance as a precursor, while the latter first synthesizes a carbon material precursor and then modifies the surface of the carbon precursor with a nitrogen atom-containing reagent. Doping nitrogen elements can enhance the surface polarity of the carrier carbon material, improve the surface wettability, reduce the ion adsorption and desorption energy barrier, and modify the surface electronic structure of carbon atoms, thereby improving the adsorption performance of the carbon carrier and the durability of the catalyst. However, both of the above methods are to mix a noble metal ion solution and a precipitant to form a precipitate, and then impregnate and adsorb it on the surface of the nitrogen-doped carrier, and then perform steps such as filtration, washing, and drying. Finally, a platinum-based catalyst is obtained. The catalyst prepared by this method has a weak interaction force between the active metal particles and the carrier, which will cause the active metal particles to migrate and agglomerate. Moreover, the active metal particles are easily embedded into the pore structure of the carrier, and the active metal particles are wrapped, resulting in difficulty for the active metal particles to effectively contact the reactants during the catalytic reaction process, and the atomic utilization rate of the active metal particles at the phase interface is low. Based on the above analysis, the existing methods have problems such as a long preparation process, a large amount of noble metal used, high cost, and easy migration, aggregation, and poor durability of the noble metal in the prepared platinum-based catalyst.

[0004] Carbon materials have a large specific surface area, high porosity, good electrical conductivity, excellent chemical stability, and corrosion resistance, and have become one of the most commonly used carriers for supported catalysts. Metal-nitrogen-carbon (M-N-C) is a strong competitor for reducing or replacing noble metal Pt-based catalysts; the sp 2 hybrid structure of its active sites has delocalized π orbitals and exhibits good electrical conductivity. In addition, in the M-N-C structure, the N atom has a stronger electronegativity than the C atom, which can cause electrons to aggregate around the N atom, thereby reducing the electron cloud density near the C atom and promoting O 2The adsorption of molecules, thus accelerating the process of the oxygen reduction reaction (ORR). Non-precious metal oxides, nitrides, sulfides, selenides, phosphides, etc. have been studied to improve the reaction kinetics of ORR; among them, transition metal nitrides, by introducing nitrogen atoms, change the electron cloud state density of the d-band center of the parent metal, so that the electronic structure of transition metal nitrides is similar to that of precious metals (Pd and Pt), and have excellent electrocatalytic activity and durability. For example, vanadium nitride (VN) has electronic properties similar to Pt; however, the electrocatalytic performance of VN is restricted due to factors such as electronic configuration and insufficient exposure of active sites, resulting in restricted improvement of its electrocatalytic performance. In addition, the preparation methods of vanadium nitride (VN) can be specifically divided into physical methods and chemical methods. Among them, physical methods mainly include physical vapor deposition and pulsed laser deposition, because they require high-pressure or high-temperature devices; and it is not easy to control the morphology and structure of VN during the preparation reaction process. The chemical method is to use a vanadium-containing precursor to react with a nitrogen-containing substance under certain conditions to generate VN. Among them, the vanadium-containing precursor mainly includes vanadium oxides, sulfides, chlorides, and vanadates, etc., and the nitrogen-containing substances mainly include NH 3 , N 2 and nitrogen-containing organic compounds, etc. However, it is difficult to achieve the coordinated regulation of the VN structure and morphology by this process, and the prepared VN has serious agglomeration, small specific surface area, and low purity, which in turn leads to problems such as insufficient durability and poor activity of the catalyst with VN as the carrier.

[0005] Therefore, it is necessary to research and develop a supported catalyst with a simple preparation process flow, low cost, difficult migration and aggregation of precious metals, long-lasting durability, and high activity, which is of great significance for improving the activity and durability of the electrocatalyst for the oxygen reduction reaction at the cathode of hydrogen fuel cells. Summary of the Invention

[0006] The main object of the present invention is to provide a supported catalyst, a preparation method thereof and an application, so as to solve the problems of complex and lengthy preparation process of the supported catalyst in the prior art, large amount of precious metal used, easy migration and aggregation of precious metals in the prepared catalyst, poor durability and poor activity.

[0007] To achieve the above object, on the one hand, the present invention provides a preparation method of a supported catalyst, and the preparation method of the supported catalyst includes: Step S1, making a vanadate react with a first ammonium salt in a first solvent to obtain a first product system containing a carrier precursor; Step S2, making the carrier precursor, a second ammonium salt, a precious metal-containing compound, a chelating agent, and a first reducing agent react in a second solvent to obtain a second product system containing a catalyst precursor; Step S3, annealing the catalyst precursor and a second reducing agent in a protective gas to obtain the supported catalyst.

[0008] Further, the weight ratio of vanadate, the first ammonium salt and the first solvent is (1 - 30):(0.01 - 10):(100 - 1500).

[0009] Further, the vanadate is selected from one or more of the group consisting of sodium vanadate, potassium vanadate, calcium vanadate, sodium pyrovanadate, potassium pyrovanadate, calcium pyrovanadate, sodium metavanadate, potassium metavanadate and calcium metavanadate.

[0010] Further, the first ammonium salt is selected from one or more of the group consisting of ammonium chloride, ammonium sulfate, ammonium bisulfate, ammonium bicarbonate, ammonium carbonate, polydopamine, hexamethylenetetramine, melamine, ammonium polyacrylate and dopamine hydrochloride.

[0011] Further, the first solvent is a mixture of water and an organic solvent, and the organic solvent is selected from one or more of the group consisting of methanol, ethanol, propanol, ethylene glycol, isopropanol, polyacrylic acid, N,N-dimethylformamide, N,N-dimethylacetamide and diethylformamide; preferably, the first solvent is a mixture of water and an organic solvent with a volume ratio of (50 - 1000):(5 - 500).

[0012] Further, step S1 includes: step S1-1, mixing the vanadate-containing raw material with water to obtain a mixed system, adjusting the pH of the mixed system to 7.5 - 10.5 with an alkali solution to remove impurities, and obtaining a purified mother liquor containing vanadate; step S1-2, mixing the first ammonium salt with the first solvent to obtain an ammonium salt solution; step S1-3, mixing the purified mother liquor with the ammonium salt solution and performing a precipitation reaction to obtain a first product system.

[0013] Further, the alkali solution is selected from one or more of the group consisting of an aqueous NaOH solution, an aqueous Na 2 CO 3 solution, an aqueous NaHCO 3 solution, an aqueous KOH solution, an aqueous K 2 CO 3 solution, an aqueous KHCO 3 solution, and an aqueous sodium acetate solution, and preferably the mass concentration of the alkali solution is 5.0 - 100.0 g / L.

[0014] Further, in step S1-1, the temperature of the mixing is 10 - 95°C, the time is 5 - 180 min, preferably stirring is performed during the mixing process, and preferably the stirring speed is 300 - 500 rpm.

[0015] Further, the mass concentration of the ammonium salt solution is 5.0 - 100.0 g / L.

[0016] Further, in step S1-3, the ammonium salt solution is dropped into the purified mother liquor; preferably, the dropping rate is 1 - 30 mL / min.

[0017] Further, the volume ratio of the purified mother liquor to the ammonium salt solution is (2 - 5):1.

[0018] Further, the temperature of the precipitation reaction is 20 - 80 °C, and the time is 10 - 60 min.

[0019] Further, the above preparation method further includes: performing solid-liquid separation and drying on the first product system in sequence to obtain a carrier precursor.

[0020] Further, the solid-liquid separation is selected from centrifugal separation.

[0021] Further, the drying temperature is 50 - 90 °C, and the time is 6 - 24 h.

[0022] Further, the weight ratio of the carrier precursor to the noble metal-containing compound is (1 - 20):(0.1 - 10).

[0023] Further, the weight ratio of the noble metal-containing compound to the chelating agent is (0.1 - 10):(0.001 - 15).

[0024] Further, the molar ratio of the noble metal-containing compound to the first reducing agent is (0.001 - 0.1):(0.005 - 0.5).

[0025] Further, the noble metal-containing compound is a platinum salt compound, preferably one or more selected from the group consisting of chloroplatinic acid, chloroplatinate, [Pt(acac) 2 , platinum diamminedinitrite, and [Pt(CH 3 NH 2 ) 4 [PtCl 4 .

[0026] Further, the chelating agent is selected from one or more of the group consisting of thiourea, sulfite, phosphoric acid, oxalic acid, arsonic acid, polyacrylic acid, and polyvinyl alcohol.

[0027] Further, the first reducing agent is selected from one or more of the group consisting of elemental sulfur, ascorbic acid, sodium ascorbate, sodium citrate, formaldehyde, acetaldehyde, formic acid, acetic acid, hydrazine hydrate, metal borohydride salts, sulfites, ammonium chloride, and oleylamine.

[0028] Further, the second solvent is selected from water and / or ethylene glycol.

[0029] Further, step S2 includes: step S2-1, mixing a carrier precursor, a second ammonium salt, a noble metal-containing compound, a chelating agent and a third solvent to obtain a first mixed solution; step S2-2, mixing a first reducing agent, a dispersant and a fourth solvent to obtain a second mixed solution; step S2-3, mixing the first mixed solution and the second mixed solution and reacting them to obtain a second product system.

[0030] Further, the weight ratio of the carrier precursor, the noble metal-containing compound to the third solvent is (1-20):(0.1-10):(100-5000).

[0031] Further, the weight ratio of the carrier precursor to the second ammonium salt is (1-20):(0.001-15).

[0032] Further, the second ammonium salt is selected from one or more of the group consisting of ammonium chloride, ammonium sulfate, ammonium bisulfate, ammonium bicarbonate, ammonium carbonate, polydopamine, ethylenediaminetetraacetic acid, ethylenediamine, triethylenetetramine, triethanolamine, hexamethylenetetramine, melamine, ammonium polyacrylate and dopamine hydrochloride.

[0033] Further, the second ammonium salt has the same type as the first ammonium salt.

[0034] Further, the third solvent is selected from water and / or ethylene glycol.

[0035] Further, the fourth solvent is selected from one or more of the group consisting of water, methanol, ethanol, propanol, ethylene glycol, isopropanol, N,N-dimethylformamide, N,N-dimethylacetamide and diethylformamide.

[0036] Further, in step S2-1, the mixing temperature is 0-150°C and the time is 30-180 min.

[0037] Further, in step S2-2, the molar concentration of the first reducing agent in the second mixed solution is 0.01-10 mol / L.

[0038] Further, in step S2-3, the first mixed solution is dropped into the second mixed solution at a rate of 1-10 mL / min. Preferably, the mixing is carried out under stirring, and preferably the stirring speed is 300-500 rpm; preferably the reaction time is 10-60 min.

[0039] Further, a dispersant is also added in step S2-3.

[0040] Further, in the second mixed solution, the mass concentration of the dispersant is 1.0-5.0 g / L.

[0041] Further, the dispersant is selected from one or more of the group consisting of polyethylene glycol, polyvinyl alcohol, polyvinylpyrrolidone, methylcellulose, polyacrylic acid, sodium sulfosuccinate, sodium dodecyl sulfate, sodium citrate, and quaternary ammonium salts.

[0042] Further, the above preparation method further includes: sequentially performing solid-liquid separation and freeze-drying on the second product system to obtain a catalyst precursor.

[0043] Further, the solid-liquid separation is selected from centrifugal separation treatment.

[0044] Further, the temperature of the freeze-drying treatment is -10°C to -60°C, and the time is 6 to 24 h.

[0045] Further, the annealing treatment includes stepwise temperature increase treatment, including first-stage heat treatment, second-stage heat treatment, third-stage heat treatment, and fourth-stage heat treatment performed in sequence.

[0046] Further, the first-stage heat treatment includes: heating from 25°C to 300 - 350°C at a heating rate of 5 - 30°C / min and holding for 1 - 1.5 h; the second-stage heat treatment includes: continuing to heat to 600 - 650°C at a heating rate of 5 - 10°C / min and holding for 1 - 3 h; the third-stage heat treatment includes: continuing to heat to 800 - 900°C at a heating rate of 5 - 10°C / min and holding for 1 - 3 h; the fourth-stage heat treatment includes: continuing to heat to 1100 - 1200°C at a heating rate of 5 - 10°C / min and holding for 1 - 3 h.

[0047] Further, the protective gas includes one or more of the group consisting of argon, nitrogen, helium, and NH 3 in the composition.

[0048] Further, the second reducing agent is elemental carbon; more preferably, the weight ratio of the second reducing agent to the catalyst precursor is (0.1 - 0.5):1; preferably, the average particle size of the second reducing agent is 50 - 1000 nm.

[0049] Further, the annealing treatment is carried out in a tubular vacuum furnace, and the volume flow rate of the protective gas is 1 - 10 L / min.

[0050] Further, the preparation method further includes: grinding the thermally reduced product after the annealing treatment to obtain a supported catalyst.

[0051] To achieve the above object, another aspect of the present invention further provides a supported catalyst, which includes a carrier and a noble metal; the supported catalyst is prepared by using the above preparation method of the supported catalyst provided in this application.

[0052] Further, in the supported catalyst, the loading amount of the noble metal is 20-40 wt%.

[0053] Further, the pore volume of the supported catalyst is 0.01-10.0 cm 3 / g, the average pore diameter is 5-50 nm, and the specific surface area is 450-600 m 2 / g.

[0054] Another aspect of the present invention provides a hydrogen fuel cell, including a catalyst, and the catalyst includes the above-mentioned supported catalyst provided by this application.

[0055] Applying the technical solution of the present invention, compared with the traditional method of first preparing a vanadium nitride (VN) support and then impregnating it in a platinum salt compound solution for deposition reduction of elemental platinum particles loading, in this application, atomic platinum can be in-situ deposited on the surface of the support precursor during the reduction of the noble metal compound. This can not only improve the utilization rate of the active component (i.e., noble metal Pt) in the supported catalyst, but also improve the uniformity of the distribution of the noble metal on the support surface. Moreover, the noble metal in the supported catalyst prepared by this method is not prone to migration and aggregation, and can realize the regulation of the interaction between the noble metal and the support in the supported catalyst, making the interaction force between the noble metal and the support stronger, effectively anchoring the noble metal, and making the durability of the prepared supported catalyst better. In addition, the amount of noble metal required for the above preparation method in this application is less, and the atomic utilization rate is higher. Furthermore, compared with the traditional impregnation deposition reduction method, the above preparation method provided by this application can well retain the morphology while changing the composition structure of the supported catalyst, exposing more active sites.

[0056] During the annealing treatment of the catalyst precursor, the release of NH 3 gas can, on the one hand, form a porous structure, which can play the role of pore expansion and increasing the specific surface area of the support, so that the supported catalyst can expose more catalytic active sites. Applying it in a hydrogen fuel cell can significantly improve the transport of reactants and products during the cathode oxygen reduction reaction and strengthen mass transfer; on the other hand, under the action of the local micro-jet airflow in the capillary pores at the support interface, the interaction energy between noble metal particles is weakened, thus effectively inhibiting the aggregation and migration of noble metal particles.

[0057] In addition, the supported catalyst prepared by the phase separation method assisted by noble metal chelates has the following advantages: (1) Due to the good interaction between Pt and VN, the electronic structure at the adjustable coupling interface can be adjusted; (2) Reducing the particle size can provide more active sites; (3) The unique porous network of the VN support can not only improve the structural integrity and electrochemical durability, but also provide ultra-fast electron / ion transfer channels. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] The accompanying drawings forming a part of this application are used to provide a further understanding of the present invention. The schematic embodiments and descriptions thereof of the present invention are used to explain the present invention and do not unduly limit the present invention. In the drawings:

[0059] Figure 1 Shows the transmission electron microscope image (TEM image) of the supported catalyst prepared in Example 1;

[0060] Figure 2 Shows the transmission electron microscope image (TEM image) of the supported catalyst prepared in Example 1;

[0061] Figure 3 Shows the nitrogen adsorption - desorption isotherm of the supported catalyst prepared in Example 1;

[0062] Figure 4 Shows the pore size distribution diagram of the supported catalyst prepared in Example 1;

[0063] Figure 5 Shows the cyclic voltammetry curve (CV curve) of the supported catalyst prepared in Example 1;

[0064] Figure 6 Shows the linear sweep voltammetry curve (LSV curve) of the supported catalyst prepared in Example 1. Detailed Description of the Invention

[0065] It should be noted that, without conflict, the embodiments in this application and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the embodiments.

[0066] As described in the background art, the existing supported catalysts have problems such as complex preparation processes, large amounts of precious metals used, easy migration and aggregation of precious metals in the prepared catalysts, poor durability, and poor activity. To solve the above - mentioned technical problems, in the first aspect of this application, a preparation method of a supported catalyst is provided. The preparation method of the supported catalyst includes: Step S1, causing a vanadate and a first ammonium salt to undergo a precipitation reaction in a first solvent to obtain a first product system containing a carrier precursor; Step S2, causing the carrier precursor, a second ammonium salt, a precious metal - containing compound, a chelating agent, and a first reducing agent to react in a second solvent to obtain a second product system containing a catalyst precursor; Step S3, annealing the catalyst precursor and a second reducing agent in a protective gas to obtain a supported catalyst.

[0067] In Step S1, when the vanadate and the first ammonium salt undergo a precipitation reaction, ammonium metavanadate (NH 4 VO 3 ) is obtained. At the same time, the excess vanadate that does not participate in the precipitation reaction undergoes hydration to obtain [VO 2 (H2 O) 3 + , deprotonation generates VO(OH) 3 , obtaining a carrier precursor containing NH 4 VO 3 and a small amount of VO(OH) 3 . The following reactions occur during this process: . Since NH 4 VO 3 has very low solubility in water, the following metathesis reaction occurs: (1) ; (2) .

[0068] Step S2 uses a hydrometallurgical process to efficiently enrich platinum, forms a hardly ionizable precious metal precipitate compound through metathesis reaction and phase transformation, and impregnates and deposits on the surface of the carrier precursor to form a catalyst precursor. The following reactions occur during this process:

[0069] When the second ammonium salt is ammonium chloride and the precious metal compound is chloroplatinic acid: ;

[0070] When the chelating agent is oxalic acid, a phase transformation of the platinum salt (NH 4 ) 2 PtCl 6 occurs, generating ammonium chloroplatinate (NH 4 ) 2 PtCl 4 (ammonium chloroplatinate is highly soluble in water), that is, the following reaction occurs: ;

[0071] And the following reactions occur under the action of a weak reducing agent hydrogen peroxide and / or hydrazine hydrate:

[0072] ;

[0073] .

[0074] Moreover, introducing a chelating agent in step S2 can form a precious metal chelate with the precious metal, so that the precious metal is more uniformly dispersed under the steric hindrance of the chelating agent in the second solvent. That is, through the precious metal cation chelate effect, the concentration of precious metal ions can be regulated. Therefore, the growth rate of nanocrystalline nuclei slows down, enabling the nanosized Pt grains to be in-situ deposited with a smaller volume, thus enabling the reactions in the system to proceed more stably and improving the distribution uniformity of the precious metal in the carrier precursor.

[0075] In step S3, under a protective atmosphere, from NH 4 VO 3 ​The V and N atoms in it are in-situ transformed into small VN particles, while consuming the carbon in the noble metal chelate framework and the added second reducing agent (such as elemental carbon) to promote the reduction of elemental Pt. Since the atoms in the polymer act as dispersants and protectants, it is ensured that while phase separation occurs, the particles do not agglomerate and grow. At the same time, ammonium metavanadate undergoes thermal decomposition in step S3 to obtain vanadium pentoxide (V 2 O 5 ), and ammonia (NH 3 ), and at the same time, VO(OH) 3 dehydrates to form V 2 O 5 , V 2 O 5 is reduced by the second reducing agent to form vanadium nitride (VN), that is, the following reactions occur:

[0076] , , ;

[0077] Thus, a supported catalyst with vanadium nitride as the carrier and noble metal loaded is formed.

[0078] The following reactions occur in this process:

[0079] ;

[0080] .

[0081] Compared with the traditional deposition reduction method of first preparing a vanadium nitride (VN) carrier and then impregnating it in a platinum salt compound solution for elemental platinum loading, the present application can be deposited in-situ on the surface of the carrier precursor during the reduction of the noble metal compound. It can not only improve the utilization rate of the active component (i.e., noble metal Pt) in the supported catalyst, but also improve the distribution uniformity of the noble metal on the carrier surface. Moreover, the noble metal in the supported catalyst prepared by this method is not easy to migrate and aggregate, and the interaction between the noble metal and the carrier in the supported catalyst can be regulated, making the force between the noble metal and the carrier stronger, effectively anchoring the noble metal, and making the durability of the prepared supported catalyst better. Moreover, the amount of noble metal required for the above preparation method of the present application is less, and the atomic utilization rate is higher. In addition, compared with the traditional impregnation deposition reduction method, the above preparation method provided by the present application can well retain its morphology while changing the composition structure of the supported catalyst, exposing more active sites.

[0082] During the annealing treatment of the catalyst precursor, NH 3On the one hand, the release of gas can form a porous structure, which can play the role of expanding pores and increasing the specific surface area of the carrier, so that the supported catalyst can expose more catalytic active sites. Applying it in a hydrogen fuel cell can significantly improve the transport of reactants and products during the cathode oxygen reduction reaction and strengthen mass transfer. On the other hand, under the action of the local micro-jet airflow in the capillary pores at the carrier interface, the interaction energy between noble metal particles is weakened, so that the aggregation and migration of noble metal particles can be effectively inhibited.

[0083] In addition, the supported catalyst prepared by the phase separation method assisted by noble metal chelates has the following advantages: (1) Due to the good interaction between Pt and VN, the electronic structure at the adjustable coupling interface can be adjusted; (2) Reducing the particle size can provide more active sites; (3) The unique porous network of the VN carrier can not only improve the structural integrity and electrochemical durability, but also provide an ultra-fast electron / ion transfer channel.

[0084] In a preferred embodiment, the weight ratio of vanadate, the first ammonium salt to the first solvent is (1-30):(0.01-10):(100-1500). The weight ratio of vanadate, the first ammonium salt to the first solvent includes but is not limited to the above range. Limiting it within the above range is beneficial to improving the utilization rate of raw materials and the formation rate of ammonium metavanadate, thus facilitating the subsequent formation of the catalyst precursor.

[0085] To provide a source of vanadium element and reduce the introduction of impurity elements, preferably, the vanadate includes one or more of the group consisting of sodium vanadate, potassium vanadate, calcium vanadate, sodium pyrovanadate, potassium pyrovanadate, calcium pyrovanadate, sodium metavanadate, potassium metavanadate and calcium metavanadate.

[0086] To undergo a precipitation reaction with vanadate and facilitate the subsequent thermal decomposition reaction of the catalyst precursor to obtain V 2 O 5 Preferably, the first ammonium salt includes one or more of the group consisting of ammonium chloride, ammonium sulfate, ammonium bisulfate, ammonium bicarbonate, ammonium carbonate, polydopamine, hexamethylenetetramine, melamine, ammonium polyacrylate and dopamine hydrochloride.

[0087] In a preferred embodiment, the first solvent includes but is not limited to a mixture of water and organic solvents. The organic solvents include but are not limited to one or more of the group consisting of methanol, ethanol, propanol, ethylene glycol, isopropanol, polyacrylic acid, N,N-dimethylformamide, N,N-dimethylacetamide and diethylformamide. Compared with other types, using the above types of the first solvent is beneficial to improving the dispersibility of vanadate and ammonium salt, thus facilitating the precipitation reaction between the two.

[0088] To further improve the dispersibility of vanadate and ammonium salt, preferably, the first solvent is a mixture of water and an organic solvent with a volume ratio of (50 - 1000):(5 - 500).

[0089] In a preferred embodiment, step S1 includes: step S1-1, mixing the vanadate-containing raw material with water to obtain a mixed system, adjusting the pH of the mixed system to 7.5 - 10.5 with an alkali solution to remove impurities, and obtaining a purified mother liquor containing vanadate; step S1-2, mixing the first ammonium salt with the first solvent to obtain an ammonium salt solution; step S1-3, mixing the purified mother liquor with the ammonium salt solution and performing a precipitation reaction to obtain a first product system. Utilizing the difference in the solubility products of impurity elements, adjusting the pH value of the mixed system within the above range with an alkali solution is beneficial to realizing the purification and impurity removal of the vanadate-containing raw material, improving the purity of vanadate, and obtaining a purified mother liquor containing vanadate; mixing the purified mother liquor obtained after purification and impurity removal with the ammonium salt solution and performing a precipitation reaction is beneficial to improving the purity of the carrier precursor. Moreover, the carrier precursor prepared by the above method has water molecules adsorbed on its surface, which is beneficial to improving its wettability, facilitating subsequent processing and the loading of precious metals on the surface of the carrier, thus omitting the carrier pretreatment process, making the process more concise, efficient, with lower energy consumption and more significant cost advantages.

[0090] To further improve the removal rate of impurities and further reduce the impurity removal cost, preferably, the alkali solution includes but is not limited to one or more of the group consisting of NaOH aqueous solution, Na 2 CO 3 aqueous solution, NaHCO 3 aqueous solution, KOH aqueous solution, K 2 CO 3 aqueous solution, KHCO 3 aqueous solution, sodium acetate aqueous solution.

[0091] To further improve the removal rate of impurities, preferably, the mass concentration of the alkali solution is 5.0 - 100.0 g / L.

[0092] In a preferred embodiment, the temperature of mixing in step S1-1 is 10 - 95°C and the time is 5 - 180 min. The temperature and time of mixing in this step include but are not limited to the above range. Limiting them within the above range is beneficial to improving the solubility and dispersibility of the vanadate-containing raw material in the mixed system, thus facilitating subsequent processing.

[0093] To further improve the solubility and dispersibility of the vanadate-containing raw material in the mixed system, preferably, stirring is performed during the mixing in step S1-1, and the preferred stirring speed is 300 - 500 rpm.

[0094] In a preferred embodiment, the mass concentration of the ammonium salt solution is 5.0 - 100.0 g / L. The mass concentration of the ammonium salt solution includes but is not limited to the above range. Limiting it within the above range is beneficial to the raw material utilization rate of the ammonium salt, while improving the reaction efficiency of the precipitation reaction and the yield of the precipitation reaction product (including the carrier precursor containing NH 4 VO 3 and a small amount of VO(OH) 3 ).

[0095] To better control the precipitation reaction rate, preferably, in step S1-3, the ammonium salt solution is dropped into the purified mother liquor. To further control the precipitation reaction rate and make the formed NH 4 VO 3 structure more stable, preferably, the dropping rate is 1 - 30 mL / min.

[0096] In a preferred embodiment, the volume ratio of the purified mother liquor containing vanadate to the ammonium salt solution is (2 - 5):1. The volume ratio of the purified mother liquor containing vanadate to the ammonium salt solution includes but is not limited to the above range. Limiting it within the above range is beneficial to improving the yield of NH 4 VO 3 and facilitating the subsequent preparation of the catalyst precursor.

[0097] To make the precipitation reaction more complete, preferably, the temperature of the precipitation reaction is 20 - 80 °C and the time is 10 - 60 min.

[0098] In a preferred embodiment, the above preparation method provided by the present application further includes: performing solid-liquid separation and drying on the first product system in sequence to obtain the carrier precursor. Performing solid-liquid separation on the first product system is beneficial to separating the carrier precursor from the first solvent to obtain a solid-phase product, and drying the solid-phase product is beneficial to removing the residual solvent entrained in the solid-phase product, facilitating subsequent processing.

[0099] To improve the separation efficiency of the carrier precursor and the first solvent, preferably, the solid-liquid separation includes but is not limited to centrifugal separation.

[0100] To improve the removal rate of the residual solvent entrained in the solid-phase product, preferably, the drying temperature is 50 - 90 °C and the time is 6 - 24 h.

[0101] In a preferred embodiment, the weight ratio of the carrier precursor to the noble metal compound-containing is (1 - 20):(0.1 - 10). The weight ratio of the carrier precursor to the noble metal compound-containing includes but is not limited to the above range. Limiting it within the above range is beneficial to improving the noble metal utilization rate and at the same time beneficial to reducing the noble metal dosage.

[0102] In a preferred embodiment, the weight ratio of the noble metal compound to the chelating agent is (0.1 to 10):(0.001 to 15). The weight ratio of the noble metal compound to the chelating agent includes but is not limited to the above range. Limiting it within the above range is beneficial to improving the dispersibility of the noble metal compound, thereby improving the uniformity of the distribution of the noble metal in the catalyst precursor on the surface of the support precursor, and facilitating the subsequent inhibition of agglomeration and migration of the noble metal in the supported catalyst.

[0103] To improve the reaction efficiency, preferably, the molar ratio of the noble metal compound to the first reducing agent is (0.001 to 0.1):(0.005 to 0.5).

[0104] To improve the dispersibility of the noble metal compound in the second solvent, facilitate the formation of platinum metal single particles after the reaction so as to exert its catalytic effect, and at the same time, to improve the catalytic efficiency of the supported catalyst, preferably, the noble metal compound is a platinum salt compound, preferably chloroplatinic acid, chloroplatinate, [Pt(acac) 2 , platinum diamminedinitrite, and [Pt(CH 3 NH 2 ) 4 [PtCl 4 and one or more selected from the group consisting of.

[0105] In a preferred embodiment, the chelating agent includes but is not limited to one or more selected from the group consisting of thiourea, sulfite, phosphoric acid, oxalic acid, arsonic acid, polyacrylic acid, and polyvinyl alcohol. Compared with other types, using the above types of chelating agents is beneficial to improving the dispersibility of the noble metal compound in the second solvent, facilitating the formation of platinum metal single particles after the reaction, and thus exerting its catalytic effect.

[0106] In a preferred embodiment, the first reducing agent includes but is not limited to one or more selected from the group consisting of elemental sulfur, ascorbic acid, sodium ascorbate, sodium citrate, hydrogen peroxide, formaldehyde, acetaldehyde, formic acid, acetic acid, hydrazine hydrate, metal borohydride salts, sulfites, ammonium chloride, and oleylamine. Compared with other types, using the above types of the first reducing agent is beneficial to improving the reaction efficiency.

[0107] To improve the dispersibility of each material, preferably, the second solvent includes but is not limited to water and / or ethylene glycol.

[0108] In a preferred embodiment, step S2 includes: step S2-1, mixing a carrier precursor, a second ammonium salt, a noble metal-containing compound, a chelating agent and a third solvent to obtain a first mixed solution; step S2-2, mixing a first reducing agent, a dispersing agent and a fourth solvent to obtain a second mixed solution; step S2-3, mixing the first mixed solution and the second mixed solution and reacting to obtain a second product system. Using a mixed solution of water and / or ethylene glycol in the first mixed solution is beneficial to improving the wettability of the carrier precursor and is beneficial to improving the loading effect of noble metal particles. Moreover, using the above preparation process to prepare the second product system is beneficial to improving the dispersibility of each reaction raw material in the solvent, beneficial to improving the raw material utilization rate of each reaction raw material, and at the same time is also beneficial to the reaction proceeding more smoothly, thereby improving the yield of the catalyst precursor and the distribution uniformity of the noble metal in the catalyst precursor.

[0109] In order to make the amount of noble metal in the subsequent prepared supported catalyst more appropriate and improve the catalytic activity of the supported catalyst, preferably, the weight ratio of the carrier precursor, the noble metal-containing compound and the third solvent is (1-20):(0.1-10):(100-5000).

[0110] In order to improve the effect of phase transformation of the platinum salt and generate a noble metal chelate, preferably, the weight ratio of the carrier precursor to the second ammonium salt is (1-20):(0.001-15).

[0111] In order to improve the effect of phase transformation of the platinum salt and generate a noble metal chelate, preferably, the second ammonium salt includes one or more of the group consisting of ammonium chloride, ammonium sulfate, ammonium bisulfate, ammonium bicarbonate, ammonium carbonate, polydopamine, ethylenediaminetetraacetic acid, ethylenediamine, triethylenetetramine, triethanolamine, hexamethylenetetramine, melamine, ammonium polyacrylate and dopamine hydrochloride.

[0112] In a preferred embodiment, the second ammonium salt has the same type as the first ammonium salt.

[0113] In order to improve the dispersibility of each raw material in the third solvent, preferably, the third solvent includes but is not limited to water and / or ethylene glycol.

[0114] To improve the dispersibility of each raw material in the fourth solvent, preferably, the fourth solvent includes one or more selected from the group consisting of water, methanol, ethanol, propanol, ethylene glycol, isopropanol, N,N-dimethylformamide, N,N-dimethylacetamide, and diethylformamide. When the fourth solvent includes an organic solvent of the above type, the functional group of the organic solvent replaces the non-bridging hydroxyl groups on the surface of the carrier precursor, and plays a certain steric hindrance effect to inhibit the aggregation of the carrier precursor, and is beneficial to controlling the nucleation rate of the noble metal and the noble metal particle size; moreover, the organic solvent has a lower surface tension than water, which is convenient for subsequent annealing treatment.

[0115] In a preferred embodiment, in step S2-1, the temperature of the mixing is 0 to 150 °C, and the time is 30 to 180 min. The temperature and time of the mixing include but are not limited to the above ranges. Limiting them within the above ranges is beneficial to improving the dispersibility of the carrier precursor, the noble metal-containing compound, and the chelating agent in the second solvent, and is convenient for subsequent reactions.

[0116] In a preferred embodiment, in step S2-2, the molar concentration of the first reducing agent in the second mixed solution is 0.01 to 10 mol / L. The molar concentration of the first reducing agent includes but is not limited to the above range. Limiting it within the above range is beneficial to improving the reaction efficiency, thereby being beneficial to increasing the yield of zero-valent noble metal and being beneficial to improving the catalytic activity of the supported catalyst.

[0117] In a preferred embodiment, in step S2-3, the first mixed solution is dropped into the second mixed solution at a rate of 1 to 10 mL / min. Mixing the first mixed solution and the second mixed solution in the above manner is beneficial to improving the reaction efficiency, thereby being beneficial to increasing the yield of zero-valent noble metal.

[0118] To further improve the reaction efficiency and further increase the yield of zero-valent noble metal, preferably, the mixing in step S2-3 is carried out under stirring conditions, and the stirring speed is 300 to 500 rpm.

[0119] To further improve the reaction efficiency and further increase the yield of zero-valent noble metal, preferably, the reaction time is 10 to 60 min.

[0120] To further improve the dispersibility and compatibility of each raw material during the reaction, preferably, in the second mixed solution, the mass concentration of the dispersant is 1.0 to 5.0 g / L.

[0121] To further improve the dispersibility and compatibility of each raw material during the reaction, preferably, the dispersant includes one or more selected from the group consisting of polyethylene glycol, polyvinyl alcohol, polyvinylpyrrolidone, methylcellulose, polyacrylic acid, sodium sulfosuccinate, sodium dodecyl sulfate, sodium citrate, and quaternary ammonium salts.

[0122] In a preferred embodiment, the above preparation method provided by this application further includes: performing solid-liquid separation and freeze-drying treatment on the second product system in sequence to obtain a catalyst precursor. Performing solid-liquid separation on the second product system can separate the catalyst precursor from the second solvent, thereby obtaining a solid-phase product; performing freeze-drying treatment on the solid-phase product can remove the residual second solvent in the solid-phase product, and compared with other drying treatments, using the freeze-drying treatment method is beneficial to suppressing particle aggregation caused by capillary adsorption effect.

[0123] To improve the separation efficiency of the catalyst precursor from water and the fourth solvent, preferably, the solid-liquid separation includes but is not limited to centrifugal separation treatment.

[0124] To further improve the removal efficiency of the residual water and the fourth solvent in the solid-phase product, and at the same time further suppress particle aggregation, preferably, the temperature of the freeze-drying treatment is -10°C to -60°C, and the time is 6 to 24 h.

[0125] In a preferred embodiment, the annealing treatment includes stepwise temperature increase treatment, including first-stage heat treatment, second-stage heat treatment, third-stage heat treatment, and fourth-stage heat treatment performed in sequence. Compared with heat treatment under a single temperature condition, using stepwise temperature increase treatment is beneficial to improving the annealing treatment effect, beneficial to increasing the yield of VN, and beneficial to providing more active sites.

[0126] In a preferred embodiment, the first-stage heat treatment includes: heating from 25°C to 300 - 350°C at a heating rate of 5 - 30°C / min and holding for 1 - 1.5 h; the second-stage heat treatment includes: continuing to heat to 600 - 650°C at a heating rate of 5 - 10°C / min and holding for 1 - 3 h; the third-stage heat treatment includes: continuing to heat to 800 - 900°C at a heating rate of 5 - 10°C / min and holding for 1 - 3 h; the fourth-stage heat treatment includes: continuing to heat to 1100 - 1200°C at a heating rate of 5 - 10°C / min and holding for 1 - 3 h. During the first-stage heat treatment, the free water is heated and volatilized, and at the same time, the carrier precursor starts to thermally decompose. During the second-stage heat treatment, V 2 O 5 undergoes a pre-reaction, during which the ammonium salt undergoes sufficient thermal decomposition, and the NH released by the thermal decomposition 3It can be used as a reducing agent at high temperatures. Meanwhile, under the erosion and dilution effects of gases, it is beneficial to increase the specific surface area and porosity of the carrier. During the third-stage heat treatment process, the thermally decomposed platinum salt decomposes into elemental Pt. During the fourth-stage heat treatment process, the electronic structure between Pt and VN is adjusted, and the elemental Pt changes from a disordered structure to an ordered structure, thereby improving the electrocatalytic activity and durability of the supported catalyst.

[0127] In a preferred embodiment, the protective gas includes one or more of argon, nitrogen, helium, and NH 3 selected from the group consisting of.

[0128] In a preferred embodiment, the second reducing agent is elemental carbon. Elemental carbon can reduce V 2 O 5 to VN, thereby obtaining a VN carrier.

[0129] To improve the reduction efficiency in the annealing treatment and thus increase the yield of the VN carrier, preferably, the weight ratio of the second reducing agent to the catalyst precursor is (0.1 - 0.5):1.

[0130] To better exert the reduction effect of the second reducing agent and thus increase the yield of the VN carrier, preferably, the average particle size of the second reducing agent is 50 - 1000 nm.

[0131] In a preferred embodiment, the annealing treatment is carried out in a tubular vacuum furnace, and the volume flow rate of the protective gas is 1 - 10 L / min. The introduction rate of the protective gas includes but is not limited to the above range. Limiting it within the above range is beneficial to improving the annealing treatment effect, thereby being beneficial to improving the catalytic activity and stability of the supported catalyst.

[0132] In a preferred embodiment, the above preparation method provided by the present application further includes: grinding the thermally reduced product after the annealing treatment to obtain a supported catalyst. Compared with not grinding, the supported catalyst obtained after grinding has a more uniform particle size and is convenient for application in hydrogen fuel cells.

[0133] The second aspect of the present application provides a supported catalyst, which includes a carrier and a noble metal; the supported catalyst is prepared by using the above preparation method of the supported catalyst provided by the present application. In the supported catalyst provided by the present application, the noble metal is not prone to aggregation and migration, and has good stability.

[0134] To improve the catalytic activity of the supported catalyst, in a preferred embodiment, the loading amount of the noble metal in the supported catalyst is 20 - 40 wt%.

[0135] The supported catalyst provided by the present application has a relatively large specific surface area and can support more noble metals. In a preferred embodiment, the pore volume of the supported catalyst is 0.01 - 10.0 cm 3 / g, the average pore diameter is 5 - 50 nm, and the specific surface area is 450 - 600 m 2 / g.

[0136] The third aspect of the present application provides a hydrogen fuel cell, including a catalyst, and the catalyst includes the above-mentioned supported catalyst provided by the present application. The noble metals in the supported catalyst provided by the present application are not prone to migration and aggregation, and have good stability. Applying it to a hydrogen fuel cell can improve its service life.

[0137] The following further describes the present application in detail with specific embodiments, and these embodiments should not be construed as limiting the scope claimed by the present application.

[0138] Example 1

[0139] A preparation method of a supported catalyst includes:

[0140] (1) Mix 20 g of Na 3 VO 4 (CAS: 13721 - 39 - 6, reagent grade, purity 99%) with 200 mL of water to obtain a mixed system. Adjust the pH of the mixed system to 8.0 ± 0.5 with an aqueous solution of NaHCO 3 with a mass concentration of 50 g / L, stir at 30°C and 300 rpm for 30 min, and filter to remove trace impurities such as aluminum, iron, and calcium to obtain a purified mother liquor containing Na 3 VO 4 ;

[0141] (2) Mix 0.175 mol of ammonium chloride with a mixed solvent of 50 mL of water and 50 mL of ethanol, and stir at 300 rpm for 30 min to obtain an ammonium salt solution with a mass concentration of 93.6 g / L;

[0142] (3) Drop the above 100 mL of ammonium salt solution into 200 mL of the above purified mother liquor at a rate of 10 mL / min for precipitation reaction. The temperature of the precipitation reaction is 25°C and the time is 60 min. After the reaction is completed, a first product system containing the carrier precursor is obtained. After centrifugal separation and three washes with anhydrous ethanol in sequence, it is dried at 60°C for 12 h to obtain the carrier precursor;

[0143] (4) Mix 5.75 g of the above carrier precursor, 0.3 g of ammonium chloride, 0.42 g of chloroplatinic acid, 0.02 g of oxalic acid, 150 mL of water, and 50 mL of ethylene glycol at 10°C for 30 min to obtain a first mixed solution;

[0144] (5) Mix 1.76 g of ascorbic acid with 0.2 g of polyacrylic acid and 100 mL of water to obtain a 100 mL, 0.1 mol / L ascorbic acid solution (the second mixed solution).

[0145] (6) Under the stirring condition of 300 rpm, add 200 mL of the above-mentioned first mixed solution into 100 mL of the above-mentioned second mixed solution at a dropping rate of 10 mL / min and carry out the phase transformation metathesis reaction of the Pt salt. After reacting for 60 min, a second product system containing the catalyst precursor is obtained. After centrifugal separation and washing three times with absolute ethanol in sequence, it is freeze-dried at -50 °C for 12 h to obtain the catalyst precursor.

[0146] (7) Transfer the above-prepared catalyst precursor and carbon powder with an average particle size of 100 nm to a tubular vacuum furnace for annealing treatment. Introduce nitrogen, and the introduction rate of nitrogen is 1 L / min. Heat from 25 °C to 350 °C at a heating rate of 15 °C / min, hold for 1 h, continue to heat to 650 °C at a heating rate of 10 °C / min, hold for 1 h, continue to heat to 900 °C at a heating rate of 5 °C / min, hold for 1 h, continue to heat to 1200 °C at a heating rate of 5 °C / min, hold for 3 h, and then naturally cool to room temperature to obtain the supported catalyst. The carrier of this supported catalyst is VN, the active component is the noble metal Pt, and the loading amount of the noble metal is 20 wt%.

[0147] As Figure 1 and Figure 2 shown, the noble metal Pt particles in the supported catalyst prepared in Example 1 are evenly distributed, and the average particle size of the Pt particles is 3.5 nm.

[0148] As Figure 3 shown, when the relative pressure P / P 0 ≥ 0.45, the adsorption isotherm of the supported catalyst prepared in Example 1 has a hysteresis loop, conforms to the type IV isothermal curve type, and the hysteresis loop is of the H3 type, which is caused by the capillary condensation phenomenon in the mesopores. This indicates that the pores in the catalyst are mesopores and have good connectivity. Through BET model calculation, using the formulas and , the specific surface area of the catalyst is calculated to be 565.09 m 2 / g. Among them, P represents the pressure of the gas at the adsorption equilibrium, P 0 represents the saturated vapor pressure of the adsorbate at the experimental temperature, V represents the volume of the adsorbed gas, Vm represents the monolayer adsorption gas capacity, C represents a constant related to the adsorption heat and the heat of vaporization, N A represents Avogadro's constant, A M represents the cross-sectional area of the adsorbed gas, and V M represents the volume per gram molecule under standard conditions.

[0149] It can be seen from Figure 4 that the pore size distribution of the supported catalyst prepared in Example 1 is bimodal, with mesopores in the ranges of 4 - 5 nm and 5 - 50 nm respectively. Calculated by the BJH model, the pore volume and average pore diameter of the supported catalyst are 0.39 cm 3 / g and 14.21 nm respectively.

[0150] From Figure 5 it can be seen that the catalyst prepared in Example 1 and the commercial Pt / C catalyst exhibit similar hydrogen adsorption - desorption peaks and Pt oxidation - reduction peaks. Using the formula , the electrochemically active surface area ECSA = 108.09 m 2 / g of Example 1 is calculated. Among them, Q H in the above calculation formula represents the charge generated by hydrogen adsorption / desorption, and [Pt] represents the loading amount of platinum on the working electrode. From Figure 6 it can be seen that the half - wave potential E 1 / 2 of the above - mentioned supported catalyst prepared in Example 1 is 0.829 V, which is significantly higher than that of the commercial Pt / C catalyst (E 1 / 2 = 0.63 V), indicating that through annealing treatment, a high - specific - surface - area oxygen reduction reaction electrocatalyst Pt / VN more suitable for the oxygen reduction reaction is obtained.

[0151] Example 2

[0152] The difference from Example 1 is that in step (1), 20 g of the raw material containing Na 3 VO 4 (the same as in Example 1) is dissolved in 200 mL of water to obtain a mixed system. The pH of the mixed system is adjusted to 8.0 ± 0.5 with an aqueous solution of KHCO 3 with a mass concentration of 50 g / L, stirred at 30 °C and 300 rpm for 30 min, and filtered to remove trace impurities Fe, Ca, and Al to obtain a purified mother liquor containing Na 3 VO 4 ; in step (7), a mixed gas of nitrogen and ammonia is introduced into the tubular vacuum furnace, and the volume ratio of nitrogen to ammonia is 3:1. The remaining steps are the same as in Example 1.

[0153] Example 3

[0154] The difference from Example 1 is that ethylene glycol in step (4) is replaced with an equal amount of water.

[0155] Example 4

[0156] The difference from Example 1 is that the mixing temperature in step (1) is 10 °C and the time is 180 min.

[0157] Example 5

[0158] The difference from Example 1 is that: in step (1), the mixing temperature is 95 °C and the time is 5 min.

[0159] Example 6

[0160] The difference from Example 1 is that: in step (1), the mixing temperature is 10 °C.

[0161] Example 7

[0162] The difference from Example 1 is that no impurity removal is performed on Na 3 VO 4 That is, in step (1), the mixed system obtained by mixing 20 g of Na 3 VO 4 with 200 mL of water is used as the purification mother liquor for subsequent treatment steps.

[0163] Example 8

[0164] The difference from Example 1 is that: in step (2), the mass concentration of the ammonium salt solution is 5.0 g / L.

[0165] Example 9

[0166] The difference from Example 1 is that: in step (2), the mass concentration of the ammonium salt solution is 100.0 g / L.

[0167] Example 10

[0168] The difference from Example 1 is that: in step (2), the mass concentration of the ammonium salt solution is 1.0 g / L.

[0169] Example 11

[0170] The difference from Example 1 is that: in step (3), the dropping rate of the ammonium salt solution is 30 mL / min.

[0171] Example 12

[0172] The difference from Example 1 is that: in step (3), the dropping rate of the ammonium salt solution is 1 mL / min.

[0173] Example 13

[0174] The difference from Example 1 is that: in step (3), the dropping rate of the ammonium salt solution is 50 mL / min.

[0175] Example 14

[0176] The difference from Example 1 is that: in step (3), the temperature of the precipitation reaction is 20 °C.

[0177] Example 15

[0178] The difference from Example 1 is that in step (3), the temperature of the precipitation reaction is 80 °C and the time is 10 min.

[0179] Example 16

[0180] The difference from Example 1 is that in step (3), the time of the precipitation reaction is 90 min.

[0181] Example 17

[0182] The difference from Example 1 is that the molar concentration of the second mixed solution in step (5) is changed so that the molar ratio of chloroplatinic acid to the first reducing agent ascorbic acid in step (6) is 0.001:0.5.

[0183] Example 18

[0184] The difference from Example 1 is that the molar concentration of the second mixed solution in step (5) is changed so that the molar ratio of chloroplatinic acid to the first reducing agent ascorbic acid in step (6) is 0.1:0.005.

[0185] Example 19

[0186] The difference from Example 1 is that the molar concentration of the second mixed solution in step (5) is changed so that the molar ratio of chloroplatinic acid to the first reducing agent ascorbic acid in step (6) is 0.1:0.0025.

[0187] Example 20

[0188] The difference from Example 1 is that 0.85 g of sodium chloroplatinate is used to replace chloroplatinic acid in step (4) to obtain the first mixed solution.

[0189] Example 21

[0190] The difference from Example 1 is that 0.4 g of [Pt(acac) 2 is used to replace chloroplatinic acid in step (4) to obtain the first mixed solution.

[0191] Example 22

[0192] The difference from Example 1 is that 0.65 g of platinum diammine dinitrite is used to replace chloroplatinic acid in step (4) to obtain the first mixed solution.

[0193] Example 23

[0194] The difference from Example 1 is that the reaction time in step (6) is 10 min.

[0195] Example 24

[0196] The difference from Example 1 is that the reaction time in step (6) is 5 min.

[0197] Example 25

[0198] The difference from Example 1 is that in step (7), the temperature is raised from 25°C to 350°C at a heating rate of 5°C / min, held for 1 h, then continued to be heated to 650°C at a heating rate of 5°C / min, held for 1 h, then continued to be heated to 900°C at a heating rate of 5°C / min, held for 1 h, and then continued to be heated to 1200°C at a heating rate of 5°C / min, held for 3 h, and after naturally cooling to room temperature, a supported catalyst is obtained.

[0199] Example 26

[0200] The difference from Example 1 is that in step (7), the temperature is raised from 25°C to 350°C at a heating rate of 5°C / min, held for 1.5 h, then continued to be heated to 650°C at a heating rate of 5°C / min, held for 3 h, then continued to be heated to 900°C at a heating rate of 5°C / min, held for 3 h, and then continued to be heated to 1200°C at a heating rate of 5°C / min, held for 1 h, and after naturally cooling to room temperature, a supported catalyst is obtained.

[0201] Example 27

[0202] The difference from Example 1 is that in step (7), no staged heating treatment is carried out, the temperature is raised from 25°C to 1200°C at a heating rate of 5°C / min, held for 3 h, and after naturally cooling to room temperature, a supported catalyst is obtained.

[0203] Comparative Example 1

[0204] The difference from Example 1 is that Pt particles are supported on the VN support by the traditional impregnation-deposition reduction method.

[0205] Comparative Example 2

[0206] The difference from Example 1 is that a commercial Pt / C catalyst (Macklin P822267, platinum-carbon catalyst) is used, and the Pt loading in this catalyst is 20 wt%.

[0207] The specific surface areas of the supported catalysts prepared in all the above examples and comparative examples of the present application were tested by the nitrogen adsorption-desorption method, and the test results are shown in Table 1.

[0208] Table 1

[0209]

[0210] From the above description, it can be seen that the above examples of the present invention achieve the following technical effects:

[0211] The open and porous structure endows the supported catalyst prepared in this application with a large specific surface area and a rich pore structure, thereby exposing more active sites. This can not only effectively inhibit the aggregation, dissolution, and Ostwald ripening of nano-Pt particles, but also increase the loading amount of the active component. When applied in a hydrogen fuel cell, it can improve the transport and diffusion between the reactants, catalytic centers, and electrolytes, and enhance the utilization rate of the active metal atoms of the supported catalyst and the electrocatalytic reaction activity.

[0212] Compared with the traditional deposition reduction method in which vanadium nitride (VN) support is first prepared and then impregnated in a platinum salt compound solution for loading elemental platinum particles, in this application, it can be deposited in-situ on the surface of the support precursor during the reduction of the noble metal compound. This can not only improve the atomic utilization rate of the active component (i.e., noble metal Pt) in the supported catalyst, but also enhance the uniformity of the distribution of the noble metal on the support surface. Moreover, the noble metal in the supported catalyst prepared by this method is not prone to migration and aggregation, and can achieve the synergistic regulation of the interaction between the noble metal and the support in the supported catalyst, making the interaction force between the noble metal and the support stronger, effectively anchoring the noble metal, and making the prepared supported catalyst more stable. In addition, the amount of noble metal required for the above preparation method in this application is less, and the atomic utilization rate is higher. Furthermore, compared with the traditional impregnation deposition reduction method, the above preparation method provided in this application can well retain its morphology while changing the composition structure of the supported catalyst, exposing more active sites.

[0213] During the annealing treatment of the catalyst precursor, the release of NH 3 gas can, on the one hand, form a porous structure, playing the role of pore expansion and increasing the specific surface area of the support, so that the supported catalyst can expose more catalytic active sites. When applied in a hydrogen fuel cell, it can significantly improve the transport of reactants and products during the cathodic oxygen reduction reaction and strengthen mass transfer. On the other hand, under the action of the local microjet airflow in the capillary pores at the support interface, the interaction energy between noble metal particles is weakened, thus effectively inhibiting the aggregation and migration of noble metal particles.

[0214] In addition, the supported catalyst prepared by the phase separation method assisted by noble metal chelates has the following advantages: (1) Due to the good interaction between Pt and VN, the electronic structure at the adjustable coupling interface can be adjusted; (2) Reducing the particle size can provide more active sites; (3) The unique porous-network of the VN support can not only enhance the structural integrity and electrochemical durability, but also provide ultra-fast electron / ion transfer channels.

[0215] It should be noted that the terms "first", "second", etc. in the description and claims of this application are used to distinguish similar objects and do not necessarily describe a specific order or sequence. It should be understood that such terms can be interchanged under appropriate circumstances so that the embodiments of the present application described herein can be implemented in an order other than those described herein, for example.

[0216] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. 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 present invention.

Claims

1. A method for preparing a supported catalyst, characterized in that: The preparation method of the supported catalyst comprises: Step S1, allowing a vanadate and a first compound to undergo a precipitation reaction in a first solvent to obtain a first product system containing a carrier precursor; wherein the weight ratio of the vanadate, the first compound and the first solvent is (1-30): (0.01-10): (100-1500), the vanadate is selected from one or more of the group consisting of sodium vanadate, potassium vanadate, calcium vanadate, sodium pyrovanadate, potassium pyrovanadate, calcium pyrovanadate, sodium metavanadate, potassium metavanadate and calcium metavanadate, the first compound is selected from one or more of the group consisting of ammonium chloride, ammonium sulfate, ammonium bisulfate, ammonium bicarbonate, ammonium carbonate, polydopamine, hexamethylenetetramine, melamine, ammonium polyacrylate and dopamine hydrochloride, and the first solvent is a mixture of water and an organic solvent; Step S2, reacting the carrier precursor, the second compound, the noble metal compound, the chelating agent, and the first reducing agent in a second solvent to obtain a second product system containing a catalyst precursor; wherein the weight ratio of the carrier precursor to the noble metal compound is (1-20): (0.1-10), the weight ratio of the noble metal compound to the chelating agent is (0.1-10): (0.001-15), the molar ratio of the noble metal compound to the first reducing agent is (0.001-0.1): (0.005-0.5), and the second compound is selected from ammonium chloride, ammonium sulfate, ammonium bisulfate, ammonium bicarbonate , ammonium carbonate, polydopamine, ethylenediaminetetraacetic acid, ethylenediamine, triethylenetetramine, triethanolamine, hexamethylenetetramine, melamine, ammonium polyacrylate and dopamine hydrochloride, the noble metal-containing compound is a platinum compound, the chelating agent is selected from the group consisting of thiourea, sulfite, phosphoric acid, oxalic acid, arsenic acid, polyacrylic acid and polyvinyl alcohol, the first reducing agent is selected from the group consisting of elemental sulfur, ascorbic acid, sodium ascorbate, sodium citrate, formaldehyde, acetaldehyde, formic acid, acetic acid, hydrazine hydrate, borohydride metal salts, sulfites, ammonium chloride and oleylamine, and the second solvent is selected from water and / or ethylene glycol; Step S3, annealing the catalyst precursor and the second reducing agent in a protective gas to obtain the supported catalyst; wherein the second reducing agent is elemental carbon, and the annealing treatment includes staged heating treatment, including a first stage heat treatment, a second stage heat treatment, a third stage heat treatment and a fourth stage heat treatment performed in sequence; the first stage heat treatment includes: heating from 25°C to 300-350°C at a heating rate of 5-30°C / min, and keeping warm for 1-1.5h; the second stage heat treatment includes: continuing to heat up to 600-650°C at a heating rate of 5-10°C / min, and keeping warm for 1-3h; the third stage heat treatment includes: continuing to heat up to 800-900°C at a heating rate of 5-10°C / min, and keeping warm for 1-3h; the fourth stage heat treatment includes: continuing to heat up to 1100-1200°C at a heating rate of 5-10°C / min, and keeping warm for 1-3h.

2. The method for preparing a supported catalyst according to claim 1, wherein The organic solvent is selected from one or more of the group consisting of methanol, ethanol, propanol, ethylene glycol, isopropanol, polyacrylic acid, N,N-dimethylformamide, N,N-dimethylacetamide and diethylformamide.

3. The method for preparing a supported catalyst according to claim 2, wherein The first solvent is a mixture of water and an organic solvent in a volume ratio of (50-1000):(5-500).

4. The method for preparing a supported catalyst according to claim 1, characterized in that: The step S1 comprises: Step S1-1, mixing a vanadate-containing raw material with water to obtain a mixed system, and adjusting the pH of the mixed system to 7.5-10.5 with an alkali solution to remove impurities, thereby obtaining a purified mother liquor containing the vanadate; Step S1-2, mixing the first compound with the first solvent to obtain a first compound solution; Step S1-3, mixing the purified mother liquor with the first compound solution and performing the precipitation reaction to obtain the first product system.

5. The method for preparing a supported catalyst according to claim 4, characterized in that: The alkali solution is selected from one or more of the group consisting of NaOH aqueous solution, Na2CO3 aqueous solution, NaHCO3 aqueous solution, KOH aqueous solution, K2CO3 aqueous solution, KHCO3 aqueous solution, and sodium acetate aqueous solution; and / or the mass concentration of the alkali solution is 5.0 to 100.0 g / L.

6. The method for preparing a supported catalyst according to claim 4, characterized in that: The mixing temperature in step S1-1 is 10-95°C and the mixing time is 5-180 min; and / or stirring is performed during the mixing process and the stirring speed is 300-500 rpm.

7. The method for preparing a supported catalyst according to claim 4, characterized in that: The mass concentration of the first compound solution is 5.0 to 100.0 g / L.

8. The method for preparing a supported catalyst according to claim 4, characterized in that: In the step S1-3, the first compound solution is dripped into the purified mother solution at a dripping rate of 1 to 30 mL / min.

9. The method for preparing a supported catalyst according to claim 5 or 8, characterized in that: The volume ratio of the purified mother liquor to the first compound solution is (2-5):1; and / or the temperature of the precipitation reaction is 20-80°C and the time is 10-60 minutes.

10. The method for preparing a supported catalyst according to claim 1, characterized in that: The preparation method further comprises: sequentially performing solid-liquid separation and drying on the first product system to obtain the carrier precursor.

11. The method for preparing a supported catalyst according to claim 10, characterized in that: The solid-liquid separation is selected from centrifugal separation; and / or the drying temperature is 50 to 90° C. and the drying time is 6 to 24 hours.

12. The method for preparing a supported catalyst according to claim 1, characterized in that: The platinum compound is selected from one or more of the group consisting of chloroplatinic acid, chloroplatinate, [Pt(acac)2], diammine dinitrite platinum and [Pt(CH3NH2)4][PtCl4].

13. The method for preparing a supported catalyst according to claim 1, characterized in that: The step S2 comprises: Step S2-1, mixing the carrier precursor, the second compound, the noble metal-containing compound, the chelating agent and a third solvent to obtain a first mixed solution; Step S2-2, mixing the first reducing agent, dispersing agent and fourth solvent to obtain a second mixed solution; Step S2-3, mixing the first mixed liquid and the second mixed liquid and performing the reaction to obtain the second product system.

14. The method for preparing a supported catalyst according to claim 13, characterized in that: The weight ratio of the carrier precursor, the noble metal-containing compound and the third solvent is (1-20): (0.1-10): (100-5000); and / or, The weight ratio of the carrier precursor to the second compound is (1-20): (0.001-15); and / or, In the second mixed liquid, the mass concentration of the dispersant is 1.0 to 5.0 g / L.

15. The method for preparing a supported catalyst according to claim 13 or 14, characterized in that: The third solvent is selected from water and / or ethylene glycol; and / or, The fourth solvent is selected from one or more of the group consisting of water, methanol, ethanol, propanol, ethylene glycol, isopropanol, N,N-dimethylformamide, N,N-dimethylacetamide and diethylformamide; and / or, The dispersant is selected from one or more of the group consisting of polyethylene glycol, polyvinyl alcohol, polyvinyl pyrrolidone, methyl cellulose, polyacrylic acid, sodium sulfosuccinate, sodium lauryl sulfate, sodium citrate and quaternary ammonium salts.

16. The method for preparing a supported catalyst according to claim 15, characterized in that: The second compound is of the same type as the first compound.

17. The method for preparing a supported catalyst according to claim 13, characterized in that: In the step S2-1, the mixing temperature is 0 to 150° C. and the mixing time is 30 to 180 min; and / or, In the step S2-2, the molar concentration of the first reducing agent in the second mixed solution is 0.01 to 10 mol / L; and / or, In the step S2-3, the first mixed solution is dripped into the second mixed solution at a rate of 1 to 10 mL / min. The mixing is carried out under stirring conditions at a speed of 300 to 500 rpm. The reaction time is 10 to 60 min.

18. The method for preparing a supported catalyst according to claim 1, characterized in that: The preparation method further comprises: sequentially performing solid-liquid separation and freeze-drying treatment on the second product system to obtain the catalyst precursor.

19. The method for preparing a supported catalyst according to claim 18, characterized in that: The solid-liquid separation is selected from centrifugal separation; and / or the freeze-drying treatment is performed at a temperature of -10°C to -60°C for 6 to 24 hours.

20. The method for preparing a supported catalyst according to claim 1, characterized in that: The protective gas comprises one or more of the group consisting of argon, nitrogen, helium and NH3; and / or, The annealing treatment is carried out in a tubular vacuum furnace, and the volume flow rate of the protective gas is 1 to 10 L / min; and / or, The preparation method further comprises: grinding the thermal reduction product after the annealing treatment to obtain the supported catalyst.

21. The method for preparing a supported catalyst according to claim 1, characterized in that: The weight ratio of the second reducing agent to the catalyst precursor is (0.1-0.5):1; and / or the average particle size of the second reducing agent is 50-1000 nm.

22. A supported catalyst, characterized in that The supported catalyst comprises a carrier and a noble metal; the supported catalyst is prepared by the supported catalyst preparation method according to claim 1.

23. The supported catalyst according to claim 22, characterized in that In the supported catalyst, the loading amount of the noble metal is 20 to 40 wt %; The pore volume of the supported catalyst is 0.01 to 10.0 cm 3 / g, average pore size of 5-50nm, specific surface area of ​​450-600m 2 / g.

24. A hydrogen fuel cell comprising a catalyst, characterized in that: The catalyst comprises the supported catalyst according to claim 23.

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