Metal monatomic catalyst as well as preparation method and application thereof

Abstract

The invention discloses a metal monatomic catalyst as well as a preparation method and application thereof, and belongs to the technical field of electro-catalysis. According to the invention, the perovskite strontium cobaltate oxide is doped with metal elements, and the perovskite strontium cobaltate oxide is subjected to hydrothermal treatment in a high-temperature and high-pressure environment so as to be converted into hydroxyl cobalt oxide; the doped metal elements are separated from crystal lattices of the perovskite strontium cobaltate oxide and are anchored on the surface of the formed layered hydroxyl cobalt oxide in a monodisperse manner, so that the monatomic catalyst is prepared; the problems that an existing monatomic catalyst is complex in process and high in cost, and metal monatomic spontaneously gathers are solved, the prepared metal monatomic catalyst has high dispersity and stability, accurate anchoring of the monatomic at a specific active site can be achieved, and the metal monatomic catalyst has wide application prospects in the field of electro-catalysis.

Description

Technical Field

[0001] The present invention specifically relates to a metal single-atom catalyst, a preparation method thereof and an application thereof, belonging to the field of electrocatalytic technology. Background Art

[0002] Transition metal hydroxides or oxyhydroxides have become important materials in electrochemical research due to their rich chemical composition, adjustable electronic structure and excellent catalytic performance. Especially in the fields of energy conversion and storage such as electrochemical oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), they show broad application prospects. In recent years, cobalt oxyhydroxide (CoOOH) has received extensive attention due to its rich reserves, low price and stable catalytic activity for oxygen evolution reaction, but its own oxygen evolution reaction activity still needs to be improved.

[0003] A single-atom catalyst is a catalyst in which isolated metal atoms are loaded on a substrate material. Due to its high exposure of active centers, it is expected to achieve an active center utilization rate of about 100%. Using cobalt oxyhydroxide as the substrate material of the single-atom catalyst and modifying isolated metal single atoms on its surface to prepare a single-atom catalyst is an effective means to improve the catalytic activity of the cobalt oxyhydroxide catalyst. Chinese Patent CN113546637A discloses a method for controllable doping of high-valence metals into cobalt oxyhydroxide and its preparation method and application. This method uses zeolitic imidazolate framework-67 containing a cobalt source as a template, and then introduces molybdate and tungstate into cobalt oxyhydroxide grown in situ on the template through a hydrothermal reaction. The prepared material has a regular and uniform cubic hollow framework structure, and the entire framework structure is composed of many two-dimensional layered hydroxides cross-linked with each other. Molybdenum and tungsten atoms are uniformly and controllably doped into the lattice of cobalt oxyhydroxide nanosheets. This material shows high catalytic activity in the electrocatalytic water splitting oxygen evolution reaction. Chinese Patent CN114045524A discloses an iridium single-atom catalyst. This patent uses linear voltammetry scanning method. Under the driving condition of negative voltage, the positive ion group IrCl in the electrolyte 3+ is selectively grown at the triple hollow sites with negatively charged surface oxygen to obtain a single-atom catalyst. This catalyst shows catalytic activity superior to that of commercial oxygen evolution reaction catalyst iridium oxide and has good stability. Chinese Patent CN115874221A provides a suspended noble metal single-atom catalyst, a preparation method thereof and an application thereof. This patent uniformly anchors and disperses noble metal single-atom active centers in a suspended form on the carrier cobalt oxyhydroxide nanosheets through liquid nitrogen treatment and light radiation treatment methods, not only realizing the maximum utilization of noble metals, but also optimizing the adsorption and desorption of intermediate products through the spatial interaction between noble metal single-atom active sites and cobalt oxyhydroxide nanosheet carriers, thereby promoting the oxygen evolution reaction.

[0004] It can be seen that in addition to traditional hydrothermal methods, precipitation methods, impregnation methods, etc., in order to solve the problems of poor uniformity of doped elements in cobalt oxyhydroxide and easy aggregation in existing single-atom catalysts, the prior art also uses means such as electrochemical voltammetry and photo-radiation treatment to enhance the strong interaction between metal single atoms and the support, so as to realize the preparation of single-atom catalysts of metal atom-modified cobalt oxyhydroxide. However, these methods generally face problems such as complex preparation schemes and high costs, which limit the large-scale preparation and application of single-atom catalysts. Therefore, developing a single-atom catalyst with both good performance and low process cost is still a problem that needs to be overcome urgently at present. Summary of the Invention

[0005] Aiming at the problems in the prior art, the present invention provides a metal single-atom catalyst, its preparation method and application. The present invention obtains a metal single-atom catalyst by subjecting strontium cobaltate perovskite oxide doped with the metal element corresponding to the metal single atom to hydrothermal treatment in a high-temperature and high-pressure environment. The present invention solves the problems of complex process, high cost and spontaneous aggregation of metal single atoms in existing single-atom catalysts. The prepared metal single-atom catalyst has high dispersion and high stability, and has broad application prospects in the field of electrocatalysis.

[0006] The technical solution of the present invention is as follows:

[0007] The present invention provides a preparation method of a metal single-atom catalyst, which obtains a metal single-atom catalyst by dispersing and heating strontium cobaltate perovskite oxide doped with the metal element corresponding to the metal single atom in water.

[0008] Preferably, the metal element corresponding to the metal single atom is one or more of Ir, Pt, Au, and Ru.

[0009] Preferably, the preparation method of the metal single-atom catalyst can be carried out according to the following steps:

[0010] S1. Weigh strontium nitrate, cobalt nitrate and the soluble salt of the metal element corresponding to the metal single atom, mix and dissolve them in deionized water to obtain a metal salt solution;

[0011] S2. Add citric acid (CA) and ethylenediaminetetraacetic acid (EDTA) to the metal salt solution, mix well, and use 25wt% ammonia water to adjust the pH value of the obtained solution to 7-8. Then, the solution is continuously stirred at 90 °C until a transparent sol is obtained; the sol is dried to a dry sol and ground into powder, and then the powder is heated to 750-850 °C at a rate of 5 °C / minute and annealed in an air atmosphere for 4-12 h to obtain strontium cobaltate perovskite oxide doped with the metal element corresponding to the metal single atom;

[0012] S3. Disperse the perovskite strontium cobalt oxide doped with the metal element corresponding to the metal single atom in deionized water, and then treat it in a reaction kettle at 150 - 200 °C for 0 - 12 h. The product is filtered by suction, washed, and dried to obtain the metal single atom catalyst.

[0013] Preferably, the soluble salt of the metal element corresponding to the metal single atom in step S1 can be IrCl 3 、H 2 PtCl 6 、AuCl 3 、RuCl 3 or one or more of them.

[0014] Preferably, the addition amount of strontium nitrate in step S1 is 0.15 - 0.2 mol, the addition amount of cobalt nitrate is 0.15 - 0.2 mol, and the addition amount of the soluble salt of the metal element is 0.01 - 0.05.

[0015] Preferably, in step S2, citric acid (CA) and ethylenediaminetetraacetic acid (EDTA) are added according to a molar ratio of 1:1:1.5 to the total amount of metal ions in the metal salt solution.

[0016] The present invention also provides a metal single atom catalyst prepared by the above - mentioned preparation method of the metal single atom catalyst. This metal single atom catalyst is composed of cobalt oxyhydroxide and metal single atoms monodispersed and anchored on the surface of cobalt oxyhydroxide.

[0017] The present invention prepares a catalyst with rich highly - exposed active sites through the structural reorganization between perovskite oxides doped with the metal element corresponding to the metal single atom and hydroxyoxides in a hydrothermal environment. The structural reorganization of perovskite oxides promotes the electron coupling and interfacial interaction between the metal single atoms detached from the lattice and the formed cobalt oxyhydroxide matrix, which makes the surface of the prepared single atom catalyst have a more excellent electronic structure, such as an optimized d - band center position and a regulated oxygen adsorption energy, and has potential high catalytic activity.

[0018] The metal single atom catalyst provided by the present invention can be applied to the electrocatalytic oxygen evolution reaction.

[0019] Different from the prior art, the present invention has the following beneficial effects:

[0020] 1. The present invention provides a novel method for preparing a metal single-atom catalyst, which utilizes the structure tolerance of perovskite oxides and their structural reorganization characteristics in a hydrothermal environment. By doping a metal element in strontium cobaltate perovskite oxide and subjecting the strontium cobaltate perovskite oxide to hydrothermal treatment in a high-temperature and high-pressure environment to convert it into cobalt oxyhydroxide, the doped metal element is detached from the lattice of the strontium cobaltate perovskite oxide and dispersed on the surface of the formed layered cobalt oxyhydroxide. The metal element doped in the strontium cobaltate perovskite oxide of the present invention can be one or any combination of Ir, Pt, Au, and Ru. Ir, Pt, Au, or Ru can be anchored on the surface of the cobalt oxyhydroxide in the form of single atoms, thereby realizing the preparation of the metal single-atom catalyst. The preparation method of this single-atom catalyst is simple and fast, solving the problems of complex steps and high costs in the previous processes, and having high economy and operability, being suitable for batch production.

[0021] 2. The method for preparing a metal single-atom catalyst provided by the present invention has good structural tunability. By regulating the type and concentration of the doped metal, various types and concentrations of metal single atoms can be anchored on the surface of the cobalt oxyhydroxide, having good applicability, and at the same time solving the problem that it is difficult to regulate the concentration of metal elements in the existing preparation process of single-atom catalysts.

[0022] 3. The metal single-atom catalyst prepared by the method for preparing a metal single-atom catalyst provided by the present invention benefits from the structural transformation from perovskite oxide to oxyhydroxide, having abundant highly exposed active sites. At the same time, the electron coupling and interfacial interaction between the single atoms and the cobalt oxyhydroxide matrix enable the metal single atoms to be anchored on the surface of the oxyhydroxide by forming strong interactions (such as metal-oxygen coordination bonds) with the active sites on the surface of the oxyhydroxide. Therefore, the single-atom catalyst prepared by the present invention has both potential high catalytic activity and high stability, and has broad practicality in multiple fields including the electrocatalysis field. Detailed Embodiments

[0023] The following further describes the present invention in conjunction with preferred embodiments. The provided embodiments are only for clarifying the present invention, rather than limiting the scope of the present invention.

[0024] The materials, reagents, etc. used in the following embodiments can be obtained from commercial channels without special instructions; the methods in the following embodiments are conventional methods without special instructions.

[0025] Example 1

[0026] This example provides a method for preparing a metal single-atom catalyst, including the following steps:

[0027] S1. Weigh 0.2 mol of strontium nitrate, 0.19 mol of cobalt nitrate, and 0.01 mol of IrCl3 , mix and dissolve it in 100 mL of deionized water to obtain a metal salt solution;

[0028] S2. Add citric acid (CA) and ethylenediaminetetraacetic acid (EDTA) to the metal salt solution according to a molar ratio of 1:1:1.5 to the total amount of metal ions in the metal salt solution, and mix well by magnetic stirring; use ammonia water (25 wt%) to adjust the pH value of the obtained solution to 7 - 8, then continuously stir the solution at 90 °C until a transparent sol is obtained; transfer the obtained sol to an alumina crucible, keep it at a temperature of 160 °C in a vacuum oven for 20 hours until a dry gel is formed; grind the obtained dry gel into powder, and heat it to 800 °C at a rate of 5 °C per minute in a box-type resistance furnace and then anneal it in an air atmosphere for 8 hours. Finally, grind the calcined powder in a mortar to prepare strontium cobaltate perovskite oxide doped with Ir element;

[0029] S3. Disperse the strontium cobaltate perovskite oxide doped with Ir element in deionized water, and then treat it in a reaction kettle at 150 °C for 1 h. The product is filtered, washed, and dried to obtain the metal single-atom catalyst.

[0030] The metal single-atom catalyst prepared by the above preparation method is an Ir metal single-atom catalyst, which is composed of cobalt oxyhydroxide and Ir single atoms monodispersed and anchored on the surface of cobalt oxyhydroxide.

[0031] Example 2

[0032] This example provides a preparation method of a metal single-atom catalyst, including the following steps:

[0033] S1. Weigh 0.15 mol of strontium nitrate, 0.15 mol of cobalt nitrate and 0.01 mol of H 2 PtCl 6 , mix and dissolve it in 100 mL of deionized water to obtain a metal salt solution;

[0034] S2. Add citric acid (CA) and ethylenediaminetetraacetic acid (EDTA) to the metal salt solution according to a molar ratio of 1:1:1.5 to the total amount of metal ions in the metal salt solution, and mix well by magnetic stirring; use ammonia water (25 wt%) to adjust the pH value of the obtained solution to 7 - 8, then continuously stir the solution at 90 °C until a transparent sol is obtained; transfer the obtained sol to an alumina crucible, keep it at a temperature of 180 °C in a vacuum oven for 24 hours until a dry gel is formed; grind the obtained dry gel into powder, and heat it to 850 °C at a rate of 5 °C per minute in a box-type resistance furnace and then anneal it in an air atmosphere for 12 hours. Finally, grind the calcined powder in a mortar to prepare strontium cobaltate perovskite oxide doped with Pt element;

[0035] S3. Disperse the perovskite strontium cobalt oxide doped with Pt element in deionized water, and then treat it in a reaction kettle at 200 °C for 12 h. The product is filtered by suction, washed, and dried to obtain the metal single-atom catalyst.

[0036] The metal single-atom catalyst prepared by the above preparation method is a Pt metal single-atom catalyst, which is composed of cobalt oxyhydroxide and Pt single atoms monodispersed and anchored on the surface of cobalt oxyhydroxide.

[0037] Example 3

[0038] This example provides a preparation method of a metal single-atom catalyst, including the following steps:

[0039] S1. Weigh 0.16 mol of strontium nitrate, 0.16 mol of cobalt nitrate, and 0.05 mol of AuCl 3 , mix and dissolve them in 100 mL of deionized water to obtain a metal salt solution;

[0040] S2. Add citric acid (CA) and ethylenediaminetetraacetic acid (EDTA) to the metal salt solution according to a molar ratio of 1:1:1.5 to the total amount of metal ions in the metal salt solution, and stir magnetically to mix evenly; use ammonia water (25 wt%) to adjust the pH value of the obtained solution to 7-8, and then continuously stir the solution at 90 °C until a transparent sol is obtained; transfer the obtained sol to an alumina crucible, keep it in a vacuum oven at 150 °C for 12 hours until a dry gel is formed; grind the obtained dry gel into powder, and heat it to 750 °C at a rate of 5 °C per minute in a box-type resistance furnace and anneal it in an air atmosphere for 4 hours. Finally, grind the calcined powder in a mortar to prepare the perovskite strontium cobalt oxide doped with Au element;

[0041] S3. Disperse the perovskite strontium cobalt oxide doped with Au element in deionized water, and then treat it in a reaction kettle at 160 °C for 6 h. The product is filtered by suction, washed, and dried to obtain the metal single-atom catalyst.

[0042] The metal single-atom catalyst prepared by the above preparation method is an Au metal single-atom catalyst, which is composed of cobalt oxyhydroxide and Au single atoms monodispersed and anchored on the surface of cobalt oxyhydroxide.

[0043] Example 4

[0044] This example provides a preparation method of a metal single-atom catalyst, including the following steps:

[0045] S1. Weigh 0.17 mol of strontium nitrate, 0.17 mol of cobalt nitrate, and 0.03 mol of RuCl 3, mix and dissolve them in deionized water to obtain a metal salt solution;

[0046] S2. Add citric acid (CA) and ethylenediaminetetraacetic acid (EDTA) to the metal salt solution according to a molar ratio of 1:1:1.5 to the total amount of metal ions in the metal salt solution, and mix well by magnetic stirring; use ammonia water (25 wt%) to adjust the pH value of the obtained solution to 7 - 8, then continuously stir the solution at 90 °C until a transparent sol is obtained; transfer the obtained sol to an alumina crucible, and keep it at 150 °C in a vacuum oven for 12 hours until a dry gel is formed; grind the obtained dry gel into powder, and heat it to 750 °C at a rate of 5 °C per minute in a box-type resistance furnace and then anneal it in an air atmosphere for 4 hours. Finally, grind the calcined powder in a mortar to prepare strontium cobaltate perovskite oxide doped with Ru element;

[0047] S3. Disperse the strontium cobaltate perovskite oxide doped with Ru element in deionized water, and then treat it in a reaction kettle at 160 °C for 12 h. The product is filtered, washed, and dried to obtain the metal single-atom catalyst.

[0048] The metal single-atom catalyst prepared by the above preparation method is a Ru metal single-atom catalyst, which is composed of cobalt oxyhydroxide and Ru single atoms monodispersed and anchored on the surface of cobalt oxyhydroxide.

[0049] Example 5

[0050] This example provides a preparation method of a metal single-atom catalyst, including the following steps:

[0051] S1. Weigh 0.2 mol of strontium nitrate, 0.2 mol of cobalt nitrate, 0.01 mol of IrCl 3 and 0.04 mol of RuCl 3 , mix and dissolve them in 100 mL of deionized water to obtain a metal salt solution;

[0052] S2. Add citric acid (CA) and ethylenediaminetetraacetic acid (EDTA) to the metal salt solution according to a molar ratio of 1:1:1.5 to the total amount of metal ions in the metal salt solution, and mix well by magnetic stirring; use ammonia water (25 wt%) to adjust the pH value of the obtained solution to 7 - 8, then continuously stir the solution at 90 °C until a transparent sol is obtained; transfer the obtained sol to an alumina crucible, and keep it at 160 °C in a vacuum oven for 14 hours until a dry gel is formed; grind the obtained dry gel into powder, and heat it to 800 °C at a rate of 5 °C per minute in a box-type resistance furnace and then anneal it in an air atmosphere for 8 hours. Finally, grind the calcined powder in a mortar to prepare strontium cobaltate perovskite oxide doped with Ir and Ru elements;

[0053] S3. Disperse the perovskite strontium cobalt oxide doped with Ir and Ru elements in deionized water, and then treat it in a reaction kettle at 200 °C for 1 h. The product is filtered, washed and dried to obtain the metal single-atom catalyst.

[0054] The metal single-atom catalyst prepared by the above preparation method is an Ir and Ru bimetallic single-atom catalyst, which is composed of cobalt oxyhydroxide and Ir single atoms and Ru single atoms monodispersed and anchored on the surface of cobalt oxyhydroxide.

[0055] Example 6

[0056] In this example, the Ir single-atom catalyst prepared by the preparation method of the metal single-atom catalyst described in Example 1 is applied to the electrocatalytic water splitting oxygen evolution reaction. The introduction of the Ir metal element is 5%. At 10 mA / cm 2 The overpotential is only 242 mV, indicating that the Ir single-atom catalyst has good electrocatalytic water oxygen evolution performance.

[0057] In addition, in the preparation methods of the metal single-atom catalysts described in the above Examples 1 to 5, by changing the types and dosages of the soluble salts of the metal elements corresponding to the metal single atoms used in step S1 (such as IrCl 3 , H 2 PtCl 6 , AuCl 3 , RuCl 3 etc.), the types and concentrations of the metal elements doped in the perovskite oxide can be regulated, and then the preparation of metal single-atom or multi-metal single-atom catalysts with different metal types and concentrations can be realized. The above examples of the present invention are only examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is impossible to list all the embodiments here. All obvious derivations from the technical solutions of the present invention belong to the scope of the present invention.

Claims

1. A method for preparing a metal single atom catalyst, characterized in that: The method is obtained by dispersing perovskite strontium cobalt oxide doped with a metal element corresponding to a metal single atom in water and heating the dispersed perovskite strontium cobalt oxide in water; the metal element corresponding to the metal single atom is one or more of Ir, Pt, Au and Ru.

2. The method for preparing a metal single atom catalyst according to claim 1, characterized in that: The steps include: S1. Weigh strontium nitrate, cobalt nitrate and a soluble salt of a metal element corresponding to a metal single atom, mix and dissolve them in deionized water to obtain a metal salt solution; S2, adding citric acid and ethylenediaminetetraacetic acid to the metal salt solution, mixing well, adjusting the pH value of the obtained solution to 7-8 with 25wt% ammonia water, and then continuously stirring the solution at 90°C until a transparent sol is obtained; drying the sol to a dry sol and grinding it into a powder, and then heating the powder to 750-850°C at 5°C / min, and annealing the powder in an air atmosphere for 4-12h to obtain a perovskite strontium cobalt oxide doped with a metal element corresponding to a metal single atom; S3. Dispersing the perovskite strontium cobalt oxide doped with the metal element corresponding to the metal single atom in deionized water, and then treating it in a reactor at 150-200° C. for 1-12 hours. The product is filtered, washed, and dried to obtain the metal single atom catalyst.

3. The method for preparing a metal single atom catalyst according to claim 2, characterized in that: The soluble salt of the metal element corresponding to the metal single atom in step S1 is one or more of IrCl3, H2PtCl6, AuCl3, and RuCl3.

4. The method for preparing a metal single atom catalyst according to claim 2, characterized in that: In step S1, the amount of strontium nitrate added is 0.15-0.2 mol, the amount of cobalt nitrate added is 0.15-0.2 mol, and the amount of soluble salt of the metal element corresponding to the metal single atom added is 0.01-0.

05.

5. The method for preparing a metal single atom catalyst according to claim 2, characterized in that: In step S2, citric acid and ethylenediaminetetraacetic acid are added in a molar ratio of 1:1:1.5 to the total amount of metal ions in the metal salt solution.

6. A metal single atom catalyst, characterized in that: The catalyst is prepared by the method for preparing the metal single atom catalyst according to claim 1.

7. The metal single atom catalyst according to claim 6, characterized in that The metal single atom catalyst consists of cobalt oxyhydroxide and metal single atoms monodispersed and anchored on the surface of cobalt oxyhydroxide.

8. Use the metal single atom catalyst prepared by the preparation method of the metal single atom catalyst according to any one of claims 1 to 5 or the metal single atom catalyst according to any one of claims 6 to 7 in an electrocatalytic oxygen evolution reaction.