PtTe-Co (OH) 2 core-shell catalyst as well as preparation method and application thereof

Abstract

The invention discloses a PtTe-Co (OH) 2 core-shell catalyst as well as a preparation method and application thereof, and belongs to the technical field of electrolyzed water catalysts. The morphology of the PtTe-coated Co (OH) 2 core-shell catalyst is in a sea cucumber-like shape, sea cucumber-like PtTe is used as a core, and amorphous Co (OH) 2 is used as a shell. The preparation method comprises the following steps: preparing sea cucumber-like PtTe by adopting a one-step wet chemical reduction method, and covering the surface of the PtTe with an amorphous Co (OH) 2 nano-sheet by adopting an in-situ growth method, so as to prepare the core-shell catalyst. The prepared PtTe-Co (OH) 2 core-shell catalyst has an excellent bifunctional characteristic, can drive an electrolyzed water reaction, and is simple in process, low in cost, safe in process, small in pollution and suitable for large-scale industrial production.

Description

Technical Field

[0001] The present invention belongs to the technical field of water electrolysis catalysts, and in particular relates to a PtTe@Co(OH)2 core-shell catalyst and a preparation method and application thereof. Background Art

[0002] As a clean, zero-carbon secondary energy source, hydrogen energy is of great strategic significance for improving the security of my country's energy system and achieving carbon neutrality. Hydrogen production by water electrolysis is one of the most promising hydrogen production technologies, among which alkaline water electrolysis occupies a dominant position in hydrogen production due to its mature technical route and low cost. Alkaline water electrolysis includes cathode hydrogen evolution reaction (HER) and anode oxygen evolution reaction (OER). The large overpotential of HER and OER seriously hinders the practical application of water electrolysis. At present, precious metal platinum and iridium / ruthenium oxides are the best HER and OER catalysts, respectively, but their high cost and low reserves restrict their large-scale use. Moreover, single-function HER / OER catalysts are not conducive to the simplification of equipment, and cross-contamination of different electrode materials during the electrolysis process will also reduce the catalytic performance. Therefore, the development of high-performance, low-cost new bifunctional catalysts for hydrogen production by water electrolysis is of great practical significance.

[0003] The core-shell structure can optimize the electronic and mass transport properties of a catalyst. By using highly active materials in the active shell, the overall activity of the catalyst can be enhanced, increasing the hydrogen generation rate. This structure can improve the thermal and chemical stability of the catalyst and reduce deactivation during the reaction. The protective effect of the outer layer can prevent partial oxidation of the active center or degradation caused by other reactions. In addition, the core-shell structure allows the reaction mechanism to be tuned through the combination of different materials. Different core and shell materials can combine different catalytic properties, thereby achieving higher product selectivity and efficiency. Therefore, due to their structural advantages, many core-shell catalysts have been developed and have practical application value in the field of electrochemistry.

[0004] However, core-shell catalysts that exhibit both electrocatalytic oxygen and hydrogen evolution are extremely rare. Most are based on precious metal alloy nanomaterials. Non-precious metal materials or those with ultra-low precious metal content still face several challenges in achieving bifunctional core-shell catalysts, including suboptimal stability, insufficient active site exposure, and structural collapse during cycling. Summary of the Invention

[0005] Purpose of the Invention: The present invention aims to address the shortcomings of the prior art by providing a PtTe@Co(OH)2 core-shell catalyst, its preparation method, and its application. Given the high intrinsic hydrogen evolution performance of PtTe and the excellent electrocatalytic oxygen evolution performance of Co(OH)2, as well as the strong interaction between the two components, the PtTe@Co(OH)2 core-shell catalyst prepared in the present invention exhibits excellent electrocatalytic hydrogen and oxygen evolution performance and can be used as a bifunctional electrocatalyst to drive overall water splitting.

[0006] Technical solution: The purpose of the present invention is achieved through the following technical solution:

[0007] The present invention provides a PtTe@Co(OH)2 core-shell catalyst. The catalyst has a sea cucumber-like morphology, with sea cucumber-like PtTe as the core and amorphous Co(OH)2 as the shell.

[0008] The PtTe core acts as the active center for the hydrogen evolution reaction, while the Co(OH)2 shell serves as the active center for the oxygen evolution reaction. The Co(OH)2 shell is a loose and porous nanosheet structure that promotes full penetration of the PtTe core into the electrolyte, thereby exposing more active sites. Furthermore, the unique core-shell structure and the strong interaction between PtTe and Co(OH)2 greatly enhance the electrochemical stability of the catalyst.

[0009] The present invention also provides a method for preparing the above-mentioned PtTe@Co(OH)2 core-shell catalyst, comprising the following steps:

[0010] (1) mixing a sea cucumber-like PtTe suspension with a concentration of 0.2-2 mg / mL and a Co(NO3)2 solution with a concentration of 1-5 mg / mL, and stirring to obtain a mixed solution;

[0011] (2) adding 0.5-5 mg / mL 2-methylimidazole solution to the mixture obtained in step (1) and stirring the mixture at room temperature for 2-5 h;

[0012] The reaction is carried out in air atmosphere during the whole process;

[0013] (3) The reaction product is collected by centrifugation, washed, and dried to obtain the PtTe@Co(OH)2 core-shell catalyst.

[0014] The present invention uses sea cucumber-like PtTe as a core and prepares the PtTe@Co(OH)2 core-shell catalyst by in-situ growing Co(OH)2 nanosheets.

[0015] Preferably, in step (1), the PtTe suspension is prepared by the following method:

[0016] K2TeO3, Pt(acac)2, ascorbic acid, and polyvinyl pyrrolidone are added to a mixed solvent of ethylene glycol and water, fully dissolved and mixed uniformly, and reacted at 150-200°C for 2-8 hours. The PtTe suspension is obtained through post-treatment.

[0017] The sea cucumber-like PtTe suspension of the present invention is prepared by the wet chemical reduction method.

[0018] Furthermore, the mass ratio of K2TeO3 and Pt(acac)2 is 1~5:0.5~1.

[0019] Furthermore, the mass ratio of Pt(acac)2 to ascorbic acid is 1-3:5-10.

[0020] Furthermore, the mass ratio of ascorbic acid to polyvinyl pyrrolidone is 1-5:3-10.

[0021] Furthermore, the volume ratio of ethylene glycol to water is 1-5:1-10.

[0022] Furthermore, the volume ratio of ethylene glycol to water is 1:1.

[0023] Preferably, in step (1), the mass ratio of PtTe to Co(NO3)2 is 1-5:2-10.

[0024] Preferably, the mass ratio of Co(NO3)2 to 2-methylimidazole is 1-5:2-20.

[0025] Preferably, in step (3), the drying method is vacuum drying, the drying temperature is 40-80° C., and the drying time is 12 to 48 hours.

[0026] The present invention also provides the use of the above-mentioned PtTe@Co(OH)2 core-shell catalyst in hydrogen evolution and oxygen evolution reactions by water electrolysis.

[0027] The present invention also provides the use of the above-mentioned PtTe@Co(OH)2 core-shell catalyst in overall water decomposition.

[0028] Beneficial effects:

[0029] (1) The present invention uses a one-step wet chemical reduction method to prepare sea cucumber-like PtTe, and then covers the surface of the PtTe with amorphous Co(OH)2 nanoflakes through in situ growth to prepare a core-shell catalyst. The prepared PtTe@Co(OH)2 core-shell catalyst has excellent bifunctional properties and can drive water electrolysis. It also features a simple process, low cost, safe process, and low pollution, making it suitable for large-scale industrial production.

[0030] (2) The PtTe@Co(OH)2 core-shell catalyst prepared by the present invention has excellent electrocatalytic hydrogen and oxygen evolution performance and can be used as a bifunctional electrocatalyst to drive total water splitting. It only requires ultra-low electrode potentials of 1.46 V and 1.58 V to achieve 10 mA cm -2 and 100mA cm -2 current density. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a transmission electron microscope photograph of the PtTe@Co(OH)2 core-shell catalyst prepared in Example 1 of the present invention; wherein, Figure 1 a is a transmission electron microscope photograph at a magnification of 100 nm; Figure 1 b is a transmission electron micrograph at a magnification of 50 nm.

[0032] Figure 2 This is the element surface scanning distribution diagram of the PtTe@Co(OH)2 core-shell catalyst prepared in Example 1 of the present invention.

[0033] Figure 3 Polarization curve diagram of the PtTe@Co(OH)2 core-shell catalyst prepared in Example 1 of the present invention as a bifunctional electrocatalyst for electrocatalytic water splitting.

[0034] Figure 4 Polarization curve diagram of the PtTe@Co(OH)2 core-shell catalyst prepared in Example 2 of the present invention as a bifunctional electrocatalyst for electrocatalytic water splitting.

[0035] Figure 5 Polarization curve diagram of the PtTe@Co(OH)2 core-shell catalyst prepared in Example 3 of the present invention as a bifunctional electrocatalyst for electrocatalytic water splitting.

[0036] Figure 6 The PtTe@Co(OH)2 core-shell catalyst prepared in Example 1 of the present invention has a high conductivity at 10 mA cm -2 The results of the chronopotentiometry test were performed under the following conditions. DETAILED DESCRIPTION

[0037] The technical solution of the present invention is described in detail below through specific embodiments, but the protection scope of the present invention is not limited to the embodiments.

[0038] Unless otherwise specified, the materials and reagents used in the following examples can be obtained from commercial sources. Unless otherwise specified, the experimental methods used in the following examples are conventional experimental methods.

[0039] Example 1 Preparation of PtTe@Co(OH)2 core-shell catalyst

[0040] 10.0 mg K2TeO3, 10.0 mg Pt(acac)2, 35.6 mg ascorbic acid, and 100 mg polyvinylpyrrolidone were added to a mixed solvent of 5 mL ethylene glycol and 5 mL deionized water, fully dissolved and mixed, and the reaction was continued at 180°C for 5 h. The obtained product was collected by centrifugation and washed with a mixed solution of ethanol / acetone (volume ratio 1:9) and vacuum dried at 60°C overnight to obtain a black PtTe solid powder.

[0041] 4 mg of PtTe solid powder was dispersed in 2 mL of deionized water to obtain a sea cucumber-like PtTe suspension. 20 mg of Co(NO₃)₂ was dispersed in 4 mL of deionized water to obtain a Co(NO₃)₂ solution. The PtTe suspension and Co(NO₃)₂ solution were stirred at room temperature for 2 hours. A 2-methylimidazole solution (50 mg of 2-methylimidazole dispersed in 10 mL of deionized water) was added. The solution mixture was stirred at room temperature for 4 hours. The entire synthesis process was carried out in an air atmosphere. The reaction product was collected by centrifugation, washed three times with water, and dried in vacuo at 60°C overnight to obtain the PtTe@Co(OH)₂ core-shell catalyst.

[0042] Figure 1 This is a transmission electron microscope photo of the PtTe@Co(OH)2 core-shell catalyst. Figure 1 a is a transmission electron microscope photograph at a magnification of 100 nm; Figure 1 b is a transmission electron microscope photo at a magnification of 50 nm. Figure 1 a and Figure 1 b It can be observed that the sea cucumber-like nanostructure outer layer surrounds the nanosheet structure.

[0043] Figure 2 This is a surface scan of the element distribution of the PtTe@Co(OH)2 core-shell catalyst. As can be seen, Pt and Te are distributed within the sea cucumber-like nanostructures, while Co and O are distributed within the outer nanosheet structure, confirming the synthesis of a core-shell catalyst.

[0044] The electrochemical performance test adopts the Shanghai Chenhua CHI 760e standard three-electrode system. The method for testing the water splitting electrocatalytic performance is as follows:

[0045] In 1M KOH solution, the reference electrode is Ag / AgCl, and PtTe@Co(OH)2 is loaded on the glassy carbon electrode as the anode and cathode electrodes with a loading of 0.01 mg / cm 2 , scan rate is 5mV s -1 , linear sweep voltammetry (LSV) test was performed to obtain the polarization curve of PtTe@Co(OH)2 core-shell catalyst for electrocatalytic water splitting, see Figure 3 .

[0046] Depend on Figure 3 It can be seen that only ultra-low electrode potentials of 1.46 V and 1.58 V are required to achieve 10 mA cm -2 and 100mA cm -2 current density.

[0047] Example 2

[0048] 10.0 mg K2TeO3, 2 mg Pt(acac)2, 10 mg ascorbic acid, and 100 mg polyvinylpyrrolidone were added to a mixed solvent of 5 mL ethylene glycol and 5 mL deionized water, fully dissolved and mixed, and the reaction was continued at 180°C for 5 h. The obtained product was collected by centrifugation and washed with a mixed solution of ethanol / acetone (volume ratio 1:9) and vacuum dried at 60°C overnight to obtain a black PtTe solid powder.

[0049] 1 mg of PtTe solid powder was dispersed in 2 mL of deionized water to obtain a sea cucumber-like PtTe suspension. 10 mg of Co(NO₃)₂ was dispersed in 4 mL of deionized water to obtain a Co(NO₃)₂ solution. The PtTe suspension and Co(NO₃)₂ solution were stirred at room temperature for 2 hours. A 20 mg solution of 2-methylimidazole (20 mg of 2-methylimidazole dispersed in 10 mL of deionized water) was added. The solution mixture was stirred at room temperature for 2 hours. The entire synthesis process was carried out in an air atmosphere. The reaction product was collected by centrifugation, washed three times with water, and dried in vacuo at 60°C overnight to obtain a PtTe@Co(OH)₂ core-shell catalyst.

[0050] The electrochemical performance test adopts the Shanghai Chenhua CHI 760e standard three-electrode system. The method for testing the water splitting electrocatalytic performance is as follows:

[0051] In 1M KOH solution, the reference electrode is Ag / AgCl, and PtTe@Co(OH)2 is loaded on the glassy carbon electrode as the anode and cathode electrodes with a loading of 0.01 mg / cm 2 , scan rate is 5mV s -1 , linear sweep voltammetry (LSV) test was performed to obtain the polarization curve of PtTe@Co(OH)2 core-shell catalyst for electrocatalytic water splitting, see Figure 4 .

[0052] like Figure 4 As shown, only ultra-low electrode potentials of 1.50 V and 1.63 V are required to achieve 10 mA cm -2 and 100mA cm -2 The current density is 10 mA cm -2The current density chronopotentiometry test was stable for 50 h.

[0053] Example 3

[0054] 10.0 mg of K2TeO3, 5 mg of Pt(acac)2, 25 mg of ascorbic acid, and 100 mg of polyvinylpyrrolidone were added to a mixture of 5 mL of ethylene glycol and 5 mL of deionized water, thoroughly dissolved and mixed, and the mixture was reacted at 180°C for 5 hours. The resulting product was collected by centrifugation, washed with a mixture of ethanol and acetone (1:9 by volume), and dried in vacuo at 60°C overnight to obtain a black PtTe solid powder.

[0055] 1 mg of PtTe solid powder was dispersed in 2 mL of deionized water to obtain a sea cucumber-like PtTe suspension. 4 mg of Co(NO₃)₂ was dispersed in 4 mL of deionized water to obtain a Co(NO₃)₂ solution. The PtTe suspension and Co(NO₃)₂ solution were stirred at room temperature for 2 hours. A 10 mg solution of 2-methylimidazole (10 mg of 2-methylimidazole dispersed in 10 mL of deionized water) was added. The solution mixture was stirred at room temperature for 2 hours. The entire synthesis process was carried out in an air atmosphere. The reaction product was collected by centrifugation, washed three times with water, and dried in vacuo at 60°C overnight to obtain the PtTe@Co(OH)₂ core-shell catalyst.

[0056] The electrochemical performance test adopts the Shanghai Chenhua CHI 760e standard three-electrode system. The method for testing the water splitting electrocatalytic performance is as follows:

[0057] In 1M KOH solution, the reference electrode is Ag / AgCl, and PtTe@Co(OH)2 is loaded on the glassy carbon electrode as the anode and cathode electrodes with a loading of 0.01 mg / cm 2 , scan rate is 5mV s -1 , linear sweep voltammetry (LSV) test was performed to obtain the polarization curve of PtTe@Co(OH)2 core-shell catalyst for electrocatalytic water splitting, see Figure 5 .

[0058] like Figure 5 As shown, only ultra-low electrode potentials of 1.505 V and 1.617 V are required to achieve 10 mA cm -2 and 100mAcm -2 The current density is 10 mA cm -2 The current density chronopotentiometry test was stable for 50 h.

[0059] Example 4 Electrochemical stability test

[0060] The electrochemical stability test uses the Shanghai Chenhua CHI 760e standard three-electrode system, and the method is as follows:

[0061] The PtTe@Co(OH)2 catalyst prepared in Example 1 was used in a 1 M KOH solution with an Ag / AgCl reference electrode and a current density of 10 mA cm -2 , the PtTe@Co(OH)2 catalyst was loaded on the glassy carbon electrode as the cathode and anode, and the chronopotentiometry test was performed. The test results are shown in Figure 6 .

[0062] like Figure 6 As shown in the chronopotentiometry test, the PtTe@Co(OH)2 catalyst can -2 It ran stably for 90 h under current density conditions without significant voltage changes, confirming its excellent electrochemical stability.

[0063] Comparative Example 1

[0064] 10 mg of Pt(NH₃)₄(NO₃)₂, 6.4 mg of K₂TeO₃, 35.6 mg of ascorbic acid (AA), 100 mg of PVP, 5 mL of ethylene glycol, and 5 mL of water were added to a 35 mL vial. After the vial was sealed, the mixture was ultrasonicated for approximately 1.5 hours. The resulting mixture was transferred to a hydrothermal autoclave, heated in an oven at 200°C for 5 hours, and then cooled to room temperature. The resulting product was washed with deionized water and ethanol and then dried to obtain the product.

[0065] The electrochemical stability test uses the Shanghai Chenhua CHI 760e standard three-electrode system, and the method is as follows:

[0066] In 1M KOH solution, the reference electrode is Ag / AgCl, and the prepared catalyst is loaded on a glassy carbon electrode as the anode, with a loading of 0.01 mg / cm 2 , scan rate is 5mV s -1 , linear sweep voltammetry (LSV) test was performed.

[0067] The catalyst prepared above reached 10 mA cm -2 The overpotential required for the current density is 560 mV.

[0068] In 1M KOH solution, the reference electrode is Ag / AgCl, and the prepared catalyst is loaded on a glassy carbon electrode as a cathode with a loading of 0.01 mg / cm 2 , scan rate is 5mV s -1 , linear sweep voltammetry (LSV) test was performed.

[0069] The catalyst prepared above reached 10 mA cm -2 The overpotential required for the current density is 98 mV.

[0070] Comparative Example 2

[0071] 0.232 g of Co(NO3)2 was dissolved in 8 mL of deionized water containing 4 mg of CTAB. The solution was then quickly poured into 56 mL of an aqueous solution containing 3.632 g of 2-methylimidazole and stirred continuously for 0.5 hours. The purple precipitate was then collected by centrifugation, washed six times with ethanol, and dried to obtain ZIF-67. Subsequently, 20 mg of ZIF-67 was uniformly dispersed in 20 mL of ethanol by ultrasonic treatment. 5 mL of water was then added, and the dispersion was placed in an oil bath at 85°C. The heating time was strictly controlled to 0.5 hours, 1 hour, and 1.5 hours. The products obtained were labeled Co(OH)2-0.5, Co(OH)2-1, and Co(OH)2-1.5, respectively.

[0072] The electrochemical stability test uses the Shanghai Chenhua CHI 760e standard three-electrode system, and the method is as follows:

[0073] In 1M KOH solution, the reference electrode is Ag / AgCl, and the prepared catalysts are loaded on the glassy carbon electrode as the anode, with a loading of 0.01 mg / cm 2 , scan rate is 5mV s -1 , linear sweep voltammetry (LSV) test was performed.

[0074] Co(OH)2-0.5 reaches 10 mA cm -2 The overpotential required for the current density is 355 mV; Co(OH)2-1 reaches 10 mA cm -2 The overpotential required for the current density is 332 mV; Co(OH)2-1.5 reaches 10 mA cm -2 The overpotential required for the current density is 368 mV.

[0075] In 1M KOH solution, the reference electrode is Ag / AgCl, and the prepared catalysts are loaded on glassy carbon electrodes as cathodes, with a loading of 0.01 mg / cm 2 , scan rate is 5mV s -1 , linear sweep voltammetry (LSV) test was performed.

[0076] Co(OH)2-0.5 reaches 10 mA cm -2 The overpotential required for the current density is 655 mV; Co(OH)2-1 reaches 10 mA cm -2The overpotential required for the current density is 672 mV; Co(OH)2-1.5 reaches 10 mA cm -2 The overpotential required for the current density is 568 mV.

[0077] As described above, although the present invention has been shown and described with reference to specific preferred embodiments, it should not be construed as limiting the present invention itself. Various changes may be made to it in form and detail without departing from the spirit and scope of the present invention as defined in the appended claims.

Claims

1. A PtTe@Co(OH)2 core-shell catalyst, characterized in that The catalyst has a sea cucumber-like morphology, with sea cucumber-like PtTe as the core and amorphous Co(OH)2 as the shell.

2. A method for preparing the PtTe@Co(OH)2 core-shell catalyst according to claim 1, characterized in that: The following steps are involved: (1) mixing a sea cucumber-like PtTe suspension with a concentration of 0.2-2 mg / mL and a Co(NO3)2 solution with a concentration of 1-5 mg / mL, and stirring to obtain a mixed solution; (2) adding 0.5-5 mg / mL 2-methylimidazole solution to the mixture obtained in step (1) and stirring the mixture at room temperature for 2-5 h; (3) The reaction product is collected by centrifugation, washed, and dried to obtain the PtTe@Co(OH)2 core-shell catalyst.

3. The preparation method according to claim 2, characterized in that In step (1), the PtTe suspension is prepared by the following method: K2TeO3, Pt(acac)2, ascorbic acid, and polyvinyl pyrrolidone are added to a mixed solvent of ethylene glycol and water, fully dissolved and mixed uniformly, and reacted at 150-200°C for 2-8 hours. The PtTe suspension is obtained through post-treatment.

4. The preparation method according to claim 3, characterized in that The mass ratio of K2TeO3 and Pt(acac)2 is 1~5:0.5~1.

5. The preparation method according to claim 3, characterized in that The mass ratio of Pt(acac)2 and ascorbic acid is 1-3:5-10.

6. The preparation method according to claim 3, characterized in that The mass ratio of ascorbic acid to polyvinyl pyrrolidone is 1-5:3-10.

7. The preparation method according to claim 3, characterized in that The volume ratio of ethylene glycol to water is 1-5:1-10.

8. The preparation method according to claim 2, characterized in that In step (1), the mass ratio of PtTe to Co(NO3)2 is 1-5:2-10.

9. The preparation method according to claim 2, characterized in that The mass ratio of Co(NO3)2 and 2-methylimidazole is 1-5:2-20.

10. Use of the PtTe@Co(OH)2 core-shell catalyst according to claim 1 in hydrogen and oxygen evolution reactions by water electrolysis.

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