Difunctional electrocatalyst and preparation method thereof

Abstract

The invention provides a difunctional electrocatalyst and a preparation method thereof. The preparation method comprises the following steps: a) taking a foamed nickel base material as a cathode and a platinum sheet as an anode, and carrying out first electrodeposition in a first electrolyte to obtain a graded porous structure; the first electrolyte is prepared from NiCl2, NH4Cl and NaCl; b) taking the hierarchical porous structure obtained in the step a) as a cathode and a platinum sheet as an anode, performing secondary electrodeposition in a second electrolyte to form an alpha-Co (OH) 2-coated PN / NF electrode material, and cleaning and drying to obtain the difunctional electrocatalyst, and the second electrolyte is an electrolyte solution of Co (NO3) 2.6 H2O. Compared with the prior art, low-cost and high-efficiency production of the difunctional electrocatalyst is realized by optimizing the preparation process, and the prepared difunctional electrocatalyst shows excellent activity and robustness to HER and OER at the same time, and has wide application prospects.

Description

Technical Field

[0001] The present invention relates to the technical field of catalysts, and more specifically, to a bifunctional electrocatalyst and a preparation method thereof. Background Art

[0002] In the context of increasingly severe global energy and environmental issues, it is particularly important to find clean and efficient energy conversion and storage technologies. Water splitting as a sustainable hydrogen energy production method has received increasing attention because it can provide clean and efficient energy solutions.

[0003] However, existing water splitting technologies face a series of challenges, especially low reaction rates and high energy consumption. Currently, the most active catalysts for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) are still platinum group catalysts, but their large-scale applications are limited due to high costs and limited resources. The development of alternative efficient and economical electrocatalysts is the key to achieving large-scale application of electrolyzers. Transition metals, especially nickel and cobalt-based alloys or composites, exhibit good catalytic performance in water splitting. The cost-effectiveness and high activity of these materials make them strong candidates to replace traditional precious metal catalysts.

[0004] Chinese patent publication number CN116732566A discloses a NiCoO based on nickel foam. x A preparation method and application of a / NiCoP hydrogen evolution electrocatalyst, the preparation method comprising the following steps: (1) pretreatment of a nickel foam substrate: pretreatment of the nickel foam substrate to remove oil stains and an oxide layer on the surface of the nickel foam; (2) preparation of an electrodeposition solution: mixing cobalt chloride hexahydrate, nickel sulfate hexahydrate, ammonium chloride, sodium acetate, sodium hypophosphite and deionized water to obtain an electrodeposition solution; the mass volume ratio of the cobalt chloride hexahydrate, nickel sulfate hexahydrate, ammonium chloride, sodium acetate, sodium hypophosphite to deionized water is (0.357 g to 1. 071g): (0.300g~1.183g): (0.28g~0.5g): (0.492g~1.477g): (1.056g~2.112g): (50ml~70ml); preferably, when preparing the electrodeposition solution, the stirring speed is 60~80r / min, and the stirring time is 40~80min; the pretreated nickel foam substrate is placed in the electrodeposition solution for electrodeposition, and after the electrodeposition is completed, it is cleaned and dried to obtain NiCoO with nickel foam as the substrate. x / NiCoP hydrogen evolution electrocatalyst. However, this technical solution has the following disadvantages: (1) Poor catalyst activity and stability: The configuration of the electrodeposition solution in the above technical solution is relatively complex, requiring multiple chemical reagents and precise mass volume ratio control, which may increase the difficulty and complexity of the preparation process; at the same time, the electrodeposition method in the above technical solution cannot obtain an excellent microstructure; (2) Limited scope of application: The above technical solution may mainly focus on the hydrogen evolution reaction, but does not involve other types of electrocatalytic reactions, such as the oxygen evolution reaction, which limits the scope of application of the catalyst.

[0005] A Chinese patent with publication number CN107326392A discloses a method for preparing a hydrogen and oxygen evolution catalyst, comprising the following steps: (1) preparing a nickel foam substrate and pretreating the nickel foam substrate; (2) an in-situ growth method, preparing a NaOH solution, mixing the NaOH solution and nickel foam and placing them in a reactor for reaction, and after the reaction is completed, rinsing the nickel foam and drying it to obtain a Ni(OH)2 / nickel foam electrode; (3) an electrodeposition method, using KMnO4 as a manganese source, preparing an electrodeposition solution, an inert graphite electrode as an anode, and the nickel foam electrode prepared in step (2) as a cathode, applying a constant current for electrodeposition to prepare a MnO2-Ni(OH)2 / nickel foam electrode. However, this technical solution has the following disadvantages: (1) Limited large-scale preparation and scalability: The high-temperature in-situ growth process in the reactor is difficult to operate on a large scale and has a long preparation cycle, which limits scalability and large-scale production; (2) Catalyst structure and activity: This technical solution does not regulate the catalyst microstructure. Although a manganese source is introduced for modification, the number of active sites and specific surface area are poor. Summary of the invention

[0006] In view of this, the purpose of the present invention is to provide a bifunctional electrocatalyst and a preparation method thereof. On the one hand, the rapid two-step electrodeposition method is simpler and more economical, and a hierarchical porous structure is generated by a dynamic hydrogen bubble template method, thereby improving the activity and stability of the catalyst; on the other hand, the α-Co(OH)2@PN / NF electrocatalyst, due to its unique hierarchical porous structure, is beneficial to the diffusion of substances and reaction kinetics in the catalytic process, provides more active sites and a larger surface area, thereby enhancing the catalytic activity.

[0007] The present invention provides a method for preparing a bifunctional electrocatalyst, comprising the following steps:

[0008] a) using a nickel foam substrate as a cathode and a platinum sheet as an anode, and performing a first electrodeposition in a first electrolyte to obtain a hierarchical porous structure; the first electrolyte is composed of NiCl2, NH4Cl and NaCl;

[0009] b) using the hierarchical porous structure obtained in step a) as a cathode and the platinum sheet as an anode, performing a second electrodeposition in a second electrolyte to form an α-Co(OH)2@PN / NF electrode material, and obtaining a bifunctional electrocatalyst after washing and drying; the second electrolyte is an electrolyte solution of Co(NO3)2·6H2O.

[0010] Preferably, the nickel foam substrate in step a) is pretreated before use; the pretreatment process is specifically as follows:

[0011] The nickel foam substrate is ultrasonically cleaned in ethanol for 10 to 50 minutes to remove surface organic impurities, and then immersed in 1 wt% to 5 wt% dilute hydrochloric acid for 10 to 20 minutes to remove the oxide film to obtain a pretreated nickel foam substrate.

[0012] Preferably, in step a), the first electrolyte is an electrolyte solution consisting of 0.1M NiCl2, 1.0M NH4Cl and 1.0M NaCl.

[0013] Preferably, in step a), the pH value of the first electrolyte is 2-4.

[0014] Preferably, the first electrodeposition in step a) uses a dynamic hydrogen bubble template method, applying a current of 700 mA to 800 mA for 4 min to 6 min to construct a hierarchical porous structure.

[0015] Preferably, the hierarchical porous structure in step b) is cleaned and dried in an oven at 40° C. to 60° C. before use.

[0016] Preferably, in step b), the second electrolyte is a 50 mM Co(NO 3 ) 2 ·6H 2 O electrolyte solution.

[0017] Preferably, the second electrodeposition in step b) is performed by applying a current of 40 mA to 60 mA for 250 s to 350 s to achieve the growth of α-Co(OH)2 to form an α-Co(OH)2@PN / NF electrode material.

[0018] Preferably, the drying temperature in step b) is 40°C to 60°C.

[0019] The present invention also provides a bifunctional electrocatalyst, which is prepared by the preparation method described in the above technical solution.

[0020] The present invention provides a method for preparing a bifunctional electrocatalyst, comprising the following steps: a) using a nickel foam substrate as a cathode and a platinum sheet as an anode, and performing a first electrodeposition in a first electrolyte to obtain a hierarchical porous structure; the first electrolyte is composed of NiCl2, NH4Cl and NaCl; b) using the hierarchical porous structure obtained in step a) as a cathode and a platinum sheet as an anode, and performing a second electrodeposition in a second electrolyte to form an α-Co(OH)2@PN / NF electrode material, and after washing and drying, obtaining a bifunctional electrocatalyst; the second electrolyte is an electrolyte solution of Co(NO3)2·6H2O. Compared with the prior art, the present invention achieves low-cost and high-efficiency production of bifunctional electrocatalysts by optimizing the preparation process, and the prepared bifunctional electrocatalyst exhibits excellent activity and robustness for both HER and OER, and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a SEM image of the bifunctional electrocatalyst prepared in Example 1 of the present invention;

[0022] Figure 2 This is a characterization diagram of the binding energy of the bifunctional electrocatalyst prepared in Example 1 of the present invention;

[0023] Figure 3 The voltage-current density curve of the bifunctional electrocatalyst prepared in Example 1 of the present invention;

[0024] Figure 4 This is an overpotential characterization diagram of the bifunctional electrocatalyst prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0025] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0026] The present invention provides a method for preparing a bifunctional electrocatalyst, comprising the following steps:

[0027] a) using a nickel foam substrate as a cathode and a platinum sheet as an anode, and performing a first electrodeposition in a first electrolyte to obtain a hierarchical porous structure; the first electrolyte is composed of NiCl2, NH4Cl and NaCl;

[0028] b) using the hierarchical porous structure obtained in step a) as a cathode and the platinum sheet as an anode, performing a second electrodeposition in a second electrolyte to form an α-Co(OH)2@PN / NF electrode material, and obtaining a bifunctional electrocatalyst after washing and drying; the second electrolyte is an electrolyte solution of Co(NO3)2·6H2O.

[0029] The invention firstly uses a foamed nickel substrate as a cathode and a platinum sheet as an anode, and performs a first electrodeposition in a first electrolyte to obtain a hierarchical porous structure.

[0030] The present invention has no special restrictions on the sources of the nickel foam substrate and the platinum sheet, and commercially available products of nickel foam substrate materials and electrode platinum sheets well known to those skilled in the art can be used.

[0031] In the present invention, the thickness of the nickel foam (NF) substrate is preferably 1 mm to 2 mm, and is preferably cut into a size of 1 cm×1 cm; the platinum sheet is preferably cut into a size of 2 cm×2 cm.

[0032] In the present invention, the nickel foam substrate is preferably pretreated before use; the pretreatment process is preferably specifically as follows:

[0033] The nickel foam substrate is ultrasonically cleaned in ethanol for 10 to 50 minutes to remove organic impurities on the surface, and then immersed in 1 wt% to 5 wt% dilute hydrochloric acid for 10 to 20 minutes to remove the oxide film to obtain a pretreated nickel foam substrate;

[0034] More preferably:

[0035] The nickel foam substrate is ultrasonically cleaned in ethanol for 20 to 40 minutes to remove surface organic impurities, and then immersed in 2 wt% to 4 wt% dilute hydrochloric acid for 14 to 16 minutes to remove the oxide film to obtain a pretreated nickel foam substrate.

[0036] In the present invention, the first electrolyte is composed of NiCl2, NH4Cl and NaCl, preferably an electrolyte solution composed of 0.1MNiCl2, 1.0M NH4Cl and 1.0M NaCl. The present invention has no special restrictions on the sources of the NiCl2, NH4Cl and NaCl, and commercial products well known to those skilled in the art can be used. The present invention has no special restrictions on the preparation process of the first electrolyte, and the technical means for preparing the electrolyte well known to those skilled in the art can be used.

[0037] In the present invention, the pH value of the first electrolyte is preferably 2-4, more preferably 3.

[0038] In the present invention, the first electrodeposition preferably uses a dynamic hydrogen bubble template method, preferably applying a current of 700 mA to 800 mA for 4 min to 6 min to construct a hierarchical porous structure (PN / NF).

[0039] After obtaining the hierarchical porous structure, the present invention uses the obtained hierarchical porous structure as a cathode and a platinum sheet as an anode, performs a second electrodeposition in a second electrolyte to form an α-Co(OH)2@PN / NF electrode material, and obtains a bifunctional electrocatalyst after cleaning and drying.

[0040] In the present invention, the hierarchical porous structure is preferably cleaned and then dried in an oven at 40° C. to 60° C. before use.

[0041] In the present invention, the platinum sheet is the same as that in the above technical solution, and will not be described again.

[0042] In the present invention, the second electrolyte is an electrolyte solution of Co(NO3)2·6H2O, preferably an electrolyte solution of 50mM Co(NO3)2·6H2O. The present invention has no special restrictions on the source of the Co(NO3)2·6H2O, and commercial products well known to those skilled in the art can be used. The present invention has no special restrictions on the preparation process of the second electrolyte, and technical means for preparing the electrolyte well known to those skilled in the art can be used.

[0043] In the present invention, the second electrodeposition uses the prepared PN / NF as the cathode and the Pt sheet as the anode to electrodeposit α-Co(OH)2, immersing both the anode and cathode electrodes in the above-mentioned 50mM Co(NO3)2·6H2O electrolyte solution, and preferably applying a 40mA to 60mA current to the battery for 250s to 350s to achieve the growth of α-Co(OH)2 to form an α-Co(OH)2@PN / NF electrode material.

[0044] Finally, the present invention performs post-processing on the formed α-Co(OH)2@PN / NF electrode material: after cleaning and drying, a bifunctional electrocatalyst is obtained.

[0045] In the present invention, the drying temperature is preferably 40°C to 60°C, more preferably 50°C.

[0046] The preparation method provided by the present invention utilizes a fast and cost-effective two-step electrodeposition process to prepare an α-Co(OH)2@PN / NF electrocatalyst, and the preparation method is capable of preparing a bifunctional electrocatalyst with a hierarchical porous structure and nanosheet modification.

[0047] The structure and function of the bifunctional electrocatalyst provided by the present invention are as follows:

[0048] The α-Co(OH)2@PN / NF electrocatalyst exhibits excellent activity and robustness for HER and OER. Experimental results show that only 1.74 V is required to drive the water splitting process in 1 M KOH solution, and it can operate stably for more than 75 hours in 6 M KOH solution.

[0049] The bifunctional electrocatalyst provided by the present invention has a unique catalytic mechanism:

[0050] The self-supporting structure of nickel foam optimizes the electron transfer pathway, reduces the interference of the binder, and fully exposes the active centers; at the same time, the hierarchical porous structure constructed by the dynamic hydrogen bubble template method significantly increases the specific surface area of ​​the electrocatalyst; and the formation of the heterogeneous interface effectively reduces the potential energy of water adsorption and hydroxide adsorption, thereby promoting the water splitting reaction.

[0051] In summary, the bifunctional electrocatalyst provided by the present invention is obtained through the above-mentioned unique preparation method. Its high efficiency and stability in HER and OER reactions make it an important progress in sustainable energy solutions, and it has great application potential in the field of water splitting.

[0052] The present invention also provides a bifunctional electrocatalyst, which is prepared by the preparation method described in the above technical solution.

[0053] In order to solve the defects existing in the prior art, the present invention proposes a hierarchical porous structure nanosheet modified α-Co(OH)2@PN / NF bifunctional water splitting electrocatalyst, and introduces an economical, simple and fast preparation method; the preparation method is based on a rapid two-step electrodeposition method, has excellent HER and OER performance, and has good stability in a strong alkaline environment; in the first step, a hierarchical porous structure is electrodeposited on a three-dimensional porous nickel foam substrate (PN / NF) by a dynamic hydrogen bubble template method to obtain a high specific surface area; in the second step, the α-Co(OH)2 electrocatalyst is loaded onto the above-prepared PN / NF (α-Co(OH)2@PN / NF) by nitrate electrodeposition to form a heterogeneous interface structure. Compared with NiOOH or NiFe-LDH electrocatalysts prepared by traditional electro-oxidized nickel mesh, the present invention has the following outstanding advantages:

[0054] (1) Innovative porous structure design: The catalyst of the present invention has a hierarchical porous structure prepared by a dynamic hydrogen bubble template method, which provides a larger specific surface area and more active sites, which is crucial for improving catalytic efficiency.

[0055] (2) Introduction of heterogeneous interface structure: α-Co(OH)2 is loaded onto PN / NF through nitrate electrodeposition. The resulting heterogeneous interface structure can further enhance the electrocatalytic performance, which is difficult to achieve using traditional methods.

[0056] (3) High performance catalytic activity: α-Co(OH)2@PN / NF electrocatalyst exhibits excellent catalytic activity in hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), especially in a strong alkaline environment.

[0057] In summary, the present invention provides a bifunctional electrocatalyst and a preparation method thereof, which can improve the energy conversion efficiency of water electrolysis technology, reduce costs, reduce dependence on precious resources, and promote the sustainable development of clean energy.

[0058] The present invention provides a method for preparing a bifunctional electrocatalyst, comprising the following steps: a) using a nickel foam substrate as a cathode and a platinum sheet as an anode, and performing a first electrodeposition in a first electrolyte to obtain a hierarchical porous structure; the first electrolyte is composed of NiCl2, NH4Cl and NaCl; b) using the hierarchical porous structure obtained in step a) as a cathode and a platinum sheet as an anode, and performing a second electrodeposition in a second electrolyte to form an α-Co(OH)2@PN / NF electrode material, and after washing and drying, obtaining a bifunctional electrocatalyst; the second electrolyte is an electrolyte solution of Co(NO3)2·6H2O. Compared with the prior art, the present invention achieves low-cost and high-efficiency production of bifunctional electrocatalysts by optimizing the preparation process, and the prepared bifunctional electrocatalyst exhibits excellent activity and robustness for both HER and OER, and has broad application prospects.

[0059] To further illustrate the present invention, the following examples are used to provide a detailed description. The raw materials used in the following examples of the present invention are all commercially available; raw material preparation: 1.6 mm thick nickel foam (NF) substrate, nickel (II) chloride (NiCl2), cobalt (II) nitrate hexahydrate (Co(NO3)2·6H2O), sodium chloride (NaCl), and ammonium chloride (NH4Cl).

[0060] Example 1

[0061] (1) Substrate pretreatment: First, the 1.6 mm thick nickel foam substrate material was cut into 1 cm×1 cm sizes, and the cut nickel foam substrate material was ultrasonically cleaned in ethanol for half an hour to remove surface organic impurities, and then immersed in 3 wt % dilute hydrochloric acid for 15 minutes to remove the oxide film.

[0062] (2) Dynamic hydrogen bubble template electroplating: Prepare an electrolyte solution consisting of 0.1M NiCl2, 1.0M NH4Cl and 1.0M NaCl, and adjust the pH value to 3. Prepared nickel foam as cathode and platinum sheet as anode. Apply 750mA current for 5 minutes to prepare PN / NF. After washing, dry in a 50℃ oven for later use.

[0063] (3) Second step of electrodeposition: Prepare an electrolyte solution of 50 mM Co(NO3)2·6H2O. Apply 50 mA current for 300 seconds to obtain α-Co(OH)2@PN / NF, which is then washed and dried in an oven at 50°C to obtain a bifunctional electrocatalyst.

[0064] Electrochemical testing of electrocatalysts: The obtained catalysts were electrochemically tested using an electrochemical workstation in a standard three-electrode system. Each electrode was cut into 1×1 cm 2 The cross-sectional area of ​​the electrode was measured, and platinum sheet and mercury / mercury oxide electrode were used as counter electrode and reference electrode. Cyclic voltammetry (CV) and linear sweep voltammetry (LSV) techniques were used to evaluate the active area, prestability and hydrogen and oxygen evolution activities of the electrode.

[0065] Physical and Chemical Characterization of Electrocatalysts: Electrocatalysts were characterized using techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray electron spectroscopy (XPS), and transmission electron microscopy (TEM) to confirm their crystal structure, surface morphology, composition, and valence state.

[0066] Test results see Figures 1 to 4 The experimental results show that the present invention successfully prepared the hierarchical porous nanosheet-modified α-Co(OH)2@PN / NF bifunctional water splitting electrocatalyst through a fast and cost-effective two-step electrodeposition process, which showed excellent activity and robustness for both HER and OER. The electrochemical test showed that the electrocatalyst had a high activity at 0.1A·cm in 1M KOH solution. -2 Only 1.74 V is required to drive the entire water splitting process, and it is stable for more than 75 hours in 6MKOH solution.

[0067] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a bifunctional electrocatalyst, characterized in that: The following steps are involved: a) using a nickel foam substrate as a cathode and a platinum sheet as an anode, and performing a first electrodeposition in a first electrolyte to obtain a hierarchical porous structure; the first electrolyte is composed of NiCl2, NH4Cl and NaCl; b) using the hierarchical porous structure obtained in step a) as a cathode and the platinum sheet as an anode, performing a second electrodeposition in a second electrolyte to form an α-Co(OH)2@PN / NF electrode material, and obtaining a bifunctional electrocatalyst after washing and drying; the second electrolyte is an electrolyte solution of Co(NO3)2·6H2O.

2. The preparation method according to claim 1, characterized in that: The nickel foam substrate in step a) is pretreated before use; the pretreatment process is specifically as follows: The nickel foam substrate is ultrasonically cleaned in ethanol for 10 to 50 minutes to remove surface organic impurities, and then immersed in 1 wt% to 5 wt% dilute hydrochloric acid for 10 to 20 minutes to remove the oxide film to obtain a pretreated nickel foam substrate.

3. The preparation method according to claim 1, characterized in that: In step a), the first electrolyte is an electrolyte solution composed of 0.1M NiCl2, 1.0M NH4Cl and 1.0M NaCl.

4. The preparation method according to claim 1, characterized in that: In step a), the pH value of the first electrolyte is 2-4.

5. The preparation method according to claim 1, characterized in that: The first electrodeposition in step a) uses a dynamic hydrogen bubble template method, applying a current of 700 mA to 800 mA for 4 min to 6 min to construct a hierarchical porous structure.

6. The preparation method according to claim 1, characterized in that: The hierarchical porous structure in step b) is cleaned before use and then dried in an oven at 40° C. to 60° C.

7. The preparation method according to claim 1, characterized in that: In step b), the second electrolyte is a 50 mM Co(NO 3 ) 2 ·6H 2 O electrolyte solution.

8. The preparation method according to claim 1, characterized in that: The second electrodeposition in step b) is performed by applying a current of 40 mA to 60 mA for 250 s to 350 s to achieve the growth of α-Co(OH)2, thereby forming an α-Co(OH)2@PN / NF electrode material.

9. The preparation method according to claim 1, characterized in that: The drying temperature in step b) is 40°C to 60°C.

10. A bifunctional electrocatalyst, characterized in that: The preparation method is described in any one of claims 1 to 9.

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