阅读说明：本技术 一种高效晶界催化剂的制备方法及其质子交换膜电解槽应用 (Preparation method of efficient grain boundary catalyst and application of efficient grain boundary catalyst in proton exchange membrane electrolytic cell ) 是由 张兴旺 郝少云 雷乐成 于 2020-12-31 设计创作，主要内容包括：本发明公开了一种高效晶界催化剂的制备方法及其质子交换膜电解槽应用。该方法利用快速升温和快速降温的方法,制备了具有富含众多晶界的催化剂。通过控制升温速率、降温速率,以及加入金属离子种类,可以有效制备不同金属组分的晶界催化剂。所制备的催化剂可以作为电催化析氧催化剂或作为质子交换膜电解槽阳极催化剂应用于电分解水。以制备的Ta-(0.1)Tm-(0.1)Ir-(0.8)O-(2-δ)(2-δ是为了各个元素在化合物中电荷平衡)为例,其在酸性环境下具有优异的析氧性能(η-(10)＝198mV)和稳定性(+10mA·cm～(–2)密度下可以稳定500小时),作为质子交换膜电解槽的阳极催化剂,在负载量仅为0.2mg cm～(–2),反应温度为50℃条件下,达到1.5A·cm～(–2)的偏压仅为1.868V。并且,在1.5A·cm～(–2)条件下可以稳定运行500小时。(The invention discloses a preparation method of a high-efficiency grain boundary catalyst and application of the high-efficiency grain boundary catalyst to a proton exchange membrane electrolytic cell. The method utilizes a method of rapid temperature rise and rapid temperature drop to prepare the catalyst rich in a plurality of crystal boundaries. By controlling the heating rate and the cooling rate and adding the metal ion species, the grain boundary catalyst with different metal components can be effectively prepared. The prepared catalyst can be used as an electrocatalytic oxygen evolution catalyst or a proton exchange membrane electrolytic cell anode catalyst to be applied to the electric decomposition of water. To prepared Ta 0.1 Tm 0.1 Ir 0.8 O 2‑δ (2-. delta. is for charge balance of each element in the compound) as an example, it has excellent oxygen evolution property (. eta.) in an acidic environment 10 198mV) and stability (+10mA · cm) –2 Stable for 500 hours at density) as anode catalyst of proton exchange membrane electrolyzer, and the loading is only 0.2mg cm –2 The reaction temperature reaches 1.5A cm under the condition of 50 DEG C –2 Is only 1.868V. And, at 1.5A · cm –2 The operation can be stably carried out for 500 hours under the condition.)

1. The preparation method of the high-efficiency grain boundary catalyst is characterized by comprising the following steps of:

1) dispersing a surfactant in the solution uniformly, and dispersing metal salt in the solution with the surfactant to obtain a metal precursor solution;

2) evaporating the metal precursor solution to dryness to obtain a reaction metal precursor;

3) feeding the metal precursor into a high-temperature area heated to the required temperature; after the reaction time is reached, the reactant is directly contacted with a cooling substance for rapid cooling, and the multi-metal catalyst with numerous crystal boundaries is obtained.

2. The method for preparing the high-efficiency grain boundary catalyst according to claim 1, wherein the metal salt is one or more of halide salt, nitrate, acetate and sulfate of metal; the metal in the metal salt is selected from one or more metal salts in different metal types, and the addition amount of the metal salt is 0.05-50 times of the addition amount of the surfactant.

3. The method for preparing a high efficiency grain boundary catalyst as claimed in claim 1 or 2, wherein the metal in the metal salt is selected from iridium, ruthenium, platinum, palladium, gold, cobalt, nickel, iron, tantalum, rare earth elements.

4. The method for preparing a high efficiency grain boundary catalyst as claimed in claim 1, wherein the surfactant is a carboxyl-based or sugar-based surfactant.

5. The method for preparing a high efficiency grain boundary catalyst according to claim 1, wherein in the step 3), the reaction process of the metal precursor in the high temperature region is performed under a certain atmosphere, and the certain atmosphere is hydrogen, air, methane, oxygen, nitrogen, argon, ammonia or a mixture of two or more of the above gases which react under the high temperature region.

6. The method for preparing the high-efficiency grain boundary catalyst according to claim 1, wherein the temperature reducing substance is a solvent which does not react with the reactant, ice water, liquid nitrogen or ice blocks.

7. The method for preparing a high efficiency grain boundary catalyst as claimed in claim 1, wherein the high temperature region is a region with a temperature greater than 300 ℃, and the rapid cooling means that the high temperature catalyst directly contacts with a temperature reducing substance.

8. A high efficiency grain boundary catalyst prepared by the method of any one of claims 1 to 7.

9. Use of a high efficiency grain boundary catalyst prepared by the method of any one of claims 1 to 7 as an electrocatalytic oxygen production catalyst.

10. The use of claim 9, wherein the high efficiency grain boundary catalyst is used as an anode catalyst in a proton exchange membrane electrolyzer.

Technical Field

The invention relates to the technical field of electrochemical water electrolysis, in particular to a preparation method of a multi-metal catalyst rich in crystal boundary and application of the multi-metal catalyst in high-efficiency proton exchange membrane electrolytic cell water electrolysis.

Background

The use of potential technologies for the storage and transportation of renewable energy sources is very important for fuel production using solar or wind energy. Compared with the traditional alkaline electrolytic cell, the hydrogen production by electrolyzing water in acid electrolyte through a Proton Exchange Membrane (PEM) electrolytic cell can realize higher current density due to lower resistance loss and higher product selective permeability. The efficiency of electrolytic water splitting is mainly determined by Oxygen Evolution Reaction (OER), which is a 4 electron transfer process involving multiple oxygen intermediates, thus resulting in higher overpotentials. Reducing the use of precious metal catalysts would make PEM electrolyzed water technology more competitive in the commercial hydrogen production market, where IrO_xIs the only known practical and industrial anode electrocatalyst. However, IrO in PEM electrolyzers is currently commercially available_xThe mass activity of the anode catalyst is low and cannot meet the requirements of high performance and high stability at commercial current density.

Research over decades has shown that OER activity can be predicted by the free energy (Δ GO) of the catalyst active site and the oxygen intermediates OH to O, which is closely related to the electronic structure of the iridium active site. The surface modification engineering can effectively enhance the activity of the nano-catalyst by adjusting M-O (M represents metal) bonds, because the catalytic performance is closely related to the strain condition of the surface of the catalyst. However, under highly oxidative and strongly corrosive acidic environments, disordered nanostructured catalysts are easily dissolved or oxidized during oxygen evolution reactions, resulting in a dramatic decrease in catalyst activity. Generally, generating a catalyst having fine Grain Boundaries (GB) by the movement of stacking faults may improve the catalytic activity of the catalyst, because the grain boundaries of the catalyst surface may flexibly regulate strain to optimize the catalytic effect. In addition, the crystal boundary enables the catalyst to have good reversible recovery capability, and the fracture of an M-O bond is avoided, so that the catalyst is endowed with good stability. Furthermore, the incorporation of heteroatoms into IrO_xFor example: multi-metal oxides and perovskite oxides have been considered as one of the effective strategies to modulate the electronic structure of the active site and enhance the activity of oxygen evolution reactions. Up to now, the passing through blockThe preparation of the multi-crystal-boundary multi-element Ir-based catalyst with high activity and stability by a rapid temperature rise and rapid temperature drop method is not reported.

Disclosure of Invention

The invention aims to solve the problem of providing a method for preparing a catalyst rich in a plurality of grain boundaries, realizing the regulation and control of components and surface structures of a multi-metal catalyst, and synthesizing ternary Ta with the grain boundaries_0.1Tm_0.1Ir_0.8O_2-δThe nano-particle catalyst improves the electro-catalytic oxygen evolution performance, realizes the application as an anode catalyst in water electrolysis of a proton exchange membrane electrolytic cell, and provides a good idea and a good method for preparing other multi-metal nano-catalysts with surface structures.

In order to achieve the purpose, the invention mainly adopts the following technical scheme,

the invention firstly provides a preparation method of a high-efficiency grain boundary catalyst, which comprises the following steps:

1) dispersing a surfactant in the solution uniformly, and dispersing metal salt in the solution with the surfactant to obtain a metal precursor solution;

2) evaporating the metal precursor solution to dryness to obtain a reaction metal precursor;

3) feeding the metal precursor into a high-temperature area heated to the required temperature; after the reaction time is reached, the reactant is directly contacted with a cooling substance for rapid cooling, and the multi-metal catalyst with numerous crystal boundaries is obtained.

As a preferable scheme of the invention, the metal salt is one or more of halide salt, nitrate, acetate and sulfate of metal; the metal in the metal salt is selected from one or more metal salts in different metal types, and the addition amount of the metal salt is 0.05-50 times of the addition amount of the surfactant.

In a preferred embodiment of the present invention, the metal in the metal salt is selected from iridium, ruthenium, platinum, palladium, gold, cobalt, nickel, iron, tantalum, and rare earth elements.

In a preferred embodiment of the present invention, the surfactant is a carboxyl-based or sugar-based surfactant.

In a preferred embodiment of the present invention, the surfactant is one or more selected from polyacrylic acid, citric acid, tannic acid, glucose, maltose, sucrose, fructose, porphyrin and tetraphenylporphyrin.

As a preferable embodiment of the present invention, in the step 3), the reaction process of the metal precursor in the high temperature region is performed under a certain atmosphere, where the certain atmosphere is hydrogen, air, methane, oxygen, nitrogen, argon, ammonia, or a mixture of two or more of the above gases that reacts under the condition of the high temperature region.

In a preferred embodiment of the present invention, the temperature-lowering substance is a solvent that does not react with the reactant, ice water, liquid nitrogen, or ice. The temperature reducing substance is used for realizing rapid cooling of the reactants; typically, but not by way of limitation, for example: the temperature of the reactant is reduced to room temperature or below within 1min, 3min or 5min after the reactant contacts with the cooling substance.

As a preferable scheme of the invention, the high-temperature area is an area with the temperature of more than 300 ℃, and the rapid cooling means that the high-temperature catalyst is directly contacted with a temperature-reducing substance.

The invention also provides the high-efficiency grain boundary catalyst prepared by the method.

The invention further provides an application of the high-efficiency grain boundary catalyst prepared by the method as an electro-catalytic oxygen production catalyst.

The invention further provides an application of the high-efficiency grain boundary catalyst prepared by the method as an anode catalyst.

As a preferable scheme of the invention, the high-efficiency grain boundary catalyst is used as an anode catalyst and applied to a proton exchange membrane electrolytic cell.

Compared with the prior art, the invention has the following advantages:

1. the synthesis process is simple, and the catalyst is prepared by quickly heating and quickly cooling the prepared precursor, so that the process flow is simplified.

2. The synthesis method can effectively regulate and control the defects of crystal boundary, dislocation and the like on the surface of the catalyst. By controlling the reaction temperature and the cooling temperature, the grain boundary catalyst with different contents can be generated.

3. The synthesis method can regulate and control the components. By controlling the types of metal ions in the reaction solution, the multi-metal catalyst with different components can be generated, and the types of the multi-metal catalyst are expanded.

4. The prepared electrode has excellent acidic oxygen evolution performance (eta)₁₀198 mV). Meanwhile, the material is in the range of +10mA cm^-2The operation can be stably carried out for 500h under the condition.

4. The prepared electrode can be used as an anode catalyst in a proton exchange membrane electrolytic cell. Performing water electrolysis reaction in proton exchange membrane electrolyzer at 50 deg.C and +1.50A cm^-2Is only 1.868V.

Drawings

FIG. 1-1 is the experimental result of comparative example 1;

FIGS. 1-2 are the results of the experiment of example 1 (catalyst with grain boundaries);

FIGS. 1-3 are graphs of a theoretical study of nucleation for rapid temperature ramp-up and ramp-down simulated in example 1;

FIGS. 1-4 are graphs of the morphology and elemental distribution of grain boundaries obtained by scanning electron microscopy under rapid temperature ramp-up and ramp-down conditions;

FIG. 2 is an analysis of the grain boundary Ta by X-ray photoelectron spectroscopy_0.1Tm_0.1Ir_0.8O_2-δThe valence of each element of the catalyst;

FIG. 3-1 is the grain boundary Ta in example 3_0.1Tm_0.1Ir_0.8O_2-δThe catalyst is applied to a polarization curve of oxygen evolution reaction;

FIG. 3-2 is the grain boundary Ta in example 3_0.1Tm_0.1Ir_0.8O_2-δThe stability curve of the catalyst applied to the oxygen evolution reaction;

FIGS. 3 to 3 are grain boundary Ta in example 3_0.1Tm_0.1Ir_0.8O_2-δAn active area test pattern of the catalyst;

FIG. 4-1 grain boundary Ta_0.1Tm_0.1Ir_0.8O_2-δ，Ta_0.1Ir_0.9O_2-δ，Tm_0.1Ir_0.9O_2-δ，IrO_2-δElectrochemical polarization curve in proton exchange membrane electrolyzer.

FIG. 4-2 grain boundary Ta_0.1Tm_0.1Ir_0.8O_2-δElectrochemical stability curves in proton exchange membrane cells.

FIG. 5 is a schematic diagram of a proton exchange membrane electrolyzer.

FIG. 6 is a view showing the grain boundary Ta obtained by scanning electron microscopy_0.1Tm_0.1Ir_0.8O_2-δThe morphology and element distribution diagram of the catalyst after the proton exchange membrane reaction.

Detailed Description

Comparative example 1

0.05mmol of citric acid was dissolved in 20mL of ethanol and 10mL of H with sonication₂O, for 60 minutes. While stirring in an ice bath, 1mmol of IrCl was added₃Added to ethanol containing citric acid to prevent hydrolysis of the precursor. After stirring for 2 hours, dropwise adding an ammonia water solution into the reaction solution within 1 hour, and adjusting the pH value to 6-8. After stirring for 6 hours, the reaction solution was transferred to a lyophilizer to dry or evaporated to dryness by heating. And after the precursor is dried, putting the precursor into a treated dry pot. Then, the dry pot containing the precursor is directly placed into a furnace, the atmosphere is air, the heating rate is 10 ℃/min, and the target temperature is 450 ℃. After reacting for 2 hours at 450 ℃, cooling to room temperature at a cooling rate of 10 ℃/min to obtain a catalyst (figure 1-1) without grain boundary, and figure 1-1(A) is a crystal boundary-free IrO_2-δA TEM image of (B); (B) grain boundary-free IrO_2-δThe TEM high resolution of (1); (C) grain boundary-free IrO_2-δTEM atomic phase resolution of (a); (D) grain boundary-free IrO_2-δMapping graph of (1).

Example 1

0.05mmol of citric acid was dissolved in 20mL of ethanol and 10mL of H with sonication₂O, for 60 minutes. While stirring in an ice bath, 1mmol of IrCl was added₃Added to ethanol containing citric acid to prevent hydrolysis of the precursor. After stirring for 2 hours, dropwise adding an ammonia water solution into the reaction solution within 1 hour, and adjusting the pH value to 6-8. After stirring for 6 hours, the reaction solution was transferredTransferring to a freeze drier for drying or heating for evaporating. And after the precursor is dried, putting the precursor into a treated dry pot. Then, the dry pot containing the precursor is directly placed into a furnace heated to 450 ℃, the heating rate of the precursor is 450 ℃/s, and the atmosphere is air. After reacting for 2 hours, directly contacting the catalyst with 450 ℃ with ice water to obtain the catalyst with grain boundary (figure 1-2), and figure 1-2(A) grain boundary IrO_2-δA TEM image of (B); (B) locally enlarged grain boundary IrO_2-δA TEM image of (B); (C) grain boundary IrO_2-δThe TEM high resolution of (1); (D) grain boundary IrO_2-δElement distribution mapping graph of (1).

Example 2

Referring to the catalyst preparation method of comparative example 1, a dry pot containing the precursor was directly placed in a furnace heated to 450 ℃ in an atmosphere of air. After reacting for 0.5-2 hours, the catalyst with 450 ℃ is contacted with ice water to obtain the catalyst with grain boundaries (figure 1-2). The remaining reaction conditions were the same as in example 1. IrO prepared under different reaction conditions can be obtained as shown in FIG. 1-1 and FIG. 1-2_2-δThe topography of (1). As can be seen from fig. 1-3, under the reaction conditions of rapid temperature rise and rapid temperature decrease, a catalyst rich in grain boundaries can be obtained, and the faster the temperature rise, the faster the temperature decrease, the more the grain boundaries, and the rapid temperature rise in fig. 1-3(a) form a grain boundary catalyst mechanism diagram; (B) the slow temperature rise forms a mechanism diagram of the non-grain boundary catalyst.

Example 3

With reference to the method described in example 2, the grain boundary Ta was prepared by a rapid temperature raising and lowering method_0.1Tm_0.1Ir_0.8O_2-δA catalyst. The method comprises the following steps: ultrasonic dissolution of 0.05mmol of citric acid in 20mL of ethanol and 10mL of H₂O, for 60 minutes. While stirring in an ice bath, 0.8mmol of IrCl was added₃0.1mmol of TaCl₃Tm (NO) of 0.1mmol₃)₃Simultaneously to ethanol containing citric acid to prevent hydrolysis of the precursor. After stirring for 2 hours, dropwise adding an ammonia water solution into the reaction solution within 1 hour, and adjusting the pH value to 6-8. After stirring for 6 hours, the reaction solution was transferred to a lyophilizer to dry or evaporated to dryness by heating. Wait for forerunnerAfter drying the body, the precursor was placed in a treated dry pan. Then, the dry pot containing the precursor is directly placed into a furnace heated to 450 ℃, the heating rate of the precursor is 450 ℃/s, and the atmosphere is air. After reacting for 2 hours, directly contacting a catalyst at 450 ℃ with ice water to obtain Ta with a crystal boundary_0.1Tm_0.1Ir_0.8O_2-δA catalyst.

FIGS. 1 to 4 are graphs of the morphology and the distribution of elements of the grain boundary obtained by scanning electron microscopy under the conditions of rapid temperature rise and temperature decrease. FIG. 1-4(A) grain boundary Ta_0.1Tm_0.1Ir_0.8O_2-δA TEM image of (B); (B) locally enlarged grain boundary Ta_0.1Tm_0.1Ir_0.8O_2-δA TEM image of (B); (C) grain boundary Ta_0.1Tm_0.1Ir_0.8O_2-δThe TEM high resolution map and the corresponding fourier transform map of (a); (D) ta of stacking faults_0.1Tm_0.1Ir_0.8O_2-δThe TEM high resolution map and the corresponding fourier transform map of (a); (E) grain boundary Ta_0.1Tm_0.1Ir_0.8O_2-δElement distribution map of (c). As can be seen from the figure, the resulting material has a grain boundary structure, and each element is uniformly distributed in the nanoparticle structure. FIG. 2 is an analysis of the grain boundary Ta by X-ray photoelectron spectroscopy_0.1Tm_0.1Ir_0.8O_2-δThe valence of each element of the catalyst. The prepared catalyst is dripped on an electrode to carry out electrochemical activity area, oxygen evolution test and stability research. FIG. 2(A) grain boundary Ta_0.1Tm_0.1Ir_0.8O_2-δ，Ta_0.1Ir_0.9O_2-δ，Tm_0.1Ir_0.9O_2-δ，IrO_2-δIr 4f X ray photoelectron spectroscopy; (B) grain boundary Ta_0.1Tm_0.1Ir_0.8O_2-δAnd Ta_0.1Ir_0.9O_2-δTa 4f X ray photoelectron spectroscopy; (C) grain boundary Ta_0.1Tm_0.1Ir_0.8O_2-δAnd Tm_0.1Ir_0.9O_2-δTm 4d X ray photoelectron spectroscopy; (D) grain boundary Ta_0.1Tm_0.1Ir_0.8O_2-δ，Ta_0.1Ir_0.9O_2-δ，Tm_0.1Ir_0.9O_2-δ，IrO_2-δO1s X-ray photoelectron spectroscopy. FIG. 3-1 shows that the material is +10mA cm^-2Under the condition of density, the overpotential of oxygen evolution is 198mV respectively. FIG. 3-2 shows that the material is +10mA cm^-2The stability of oxygen evolution under density conditions was 500 hours. FIGS. 3-3 show the grain boundary Ta_0.1Tm_0.1Ir_0.8O_2-δThe catalyst has a high active area.

Example 4

The grain boundary Ta prepared in example 3_0.1Tm_0.1Ir_0.8O_2-δCatalyst as anode catalyst at 0.5M H₂SO₄Stability tests were performed in solution using a two-electrode system. As shown in FIG. 4-1, the material was found to be 1.5A. cm^-2The voltage under the density condition is only 1.868V. Meanwhile, as can be seen from FIG. 4-2, it is 1.5A. cm^-2And a steady operation at 50 ℃ for 500 hours. FIG. 5 is a schematic diagram of water electrolysis in a proton exchange membrane electrolyzer.

Example 5

The grain boundary Ta prepared in example 3_0.1Tm_0.1Ir_0.8O_2-δCatalyst as anode catalyst at 0.5M H₂SO₄After the performance of the electrolyzed water in the solution is tested by adopting a double-electrode system, the analysis is carried out by a scanning electron microscope. FIG. 6(A) grain boundary Ta_0.1Tm_0.1Ir_0.8O_2-δTEM images after proton exchange membrane cell reaction; (B) grain boundary Ta_0.1Tm_0.1Ir_0.8O_2-δTEM high resolution TEM images after proton exchange membrane cell reaction; (C) grain boundary Ta_0.1Tm_0.1Ir_0.8O_2-δA TEM high-resolution local enlarged view after the reaction in the proton exchange membrane electrolytic cell; (D) grain boundary Ta_0.1Tm_0.1Ir_0.8O_2-δElemental profile after reaction in proton exchange membrane electrolyzer. As can be seen from FIG. 6, the material is 1.5A. cm^-2Under the condition of density, after the catalyst is stably operated for 500 hours, the catalyst still has a grain boundary structure, which shows that the grain boundary structure promotes the stable operation of the catalyst. Moreover, the distribution of each element is still uniform compared with that before reaction.