Preparation method of heavy p region metal modified transition metal coordination polymer and application thereof in electrolysis of seawater to produce hydrogen

Abstract

This invention discloses a heavy p Preparation methods of transition metal-modified transition metal coordination polymers and their application in seawater electrolysis for hydrogen production, in the fields of transition metals, heavy metals, and heavy metals. p In the presence of both metal and complexing agent, a one-step co-precipitation method was used to prepare heavy metals. p Transition metal coordination polymers modified with region metals. The heavy metals prepared in this invention... p Transition metal-modified polymers can be used to modify transition metal coordination polymers through heavy metal modification. p The strong Lewis acidity of the metal in the region repels chloride ions, inhibiting the chlorination side reaction, and can also pass through the heavy metal. p The polarization of the metal in the region activates the lattice oxygen oxidation mechanism, lowering the energy barrier for seawater oxidation reactions. p The anion exchange membrane seawater electrolyzer constructed using a transition metal coordination polymer modified with a metal zone as the anode exhibits both excellent reactivity and corrosion resistance, demonstrating significant application prospects in the field of direct seawater electrolysis. This invention utilizes low-cost raw materials, employs a simple preparation process, and is feasible and economical for large-scale production.

Description

Technical Field

[0002] This invention belongs to the field of seawater electrolysis hydrogen production catalyst technology, specifically relating to a method for preparing a heavy p-block metal-modified transition metal coordination polymer and its application in seawater electrolysis hydrogen production. Background Technology

[0004] Green hydrogen, as a zero-carbon energy carrier, is becoming a key driver of energy structure transformation. Water electrolysis is an important method for large-scale hydrogen production, but its anodic oxygen evolution reaction (OER) is a four-electron transfer process, characterized by slow kinetics and high overpotential, becoming a critical bottleneck restricting the efficiency and cost of water electrolysis for hydrogen production. Therefore, developing a highly efficient, inexpensive, and stable OER catalyst has become a key focus of current clean energy research. However, current mainstream water electrolysis hydrogen production technologies are highly dependent on freshwater resources, and the uneven distribution and increasing scarcity of global freshwater resources severely limit their large-scale application. Seawater accounts for 96.5% of the Earth's water resources and is virtually inexhaustible; therefore, direct seawater electrolysis for hydrogen production is considered one of the ideal ways to solve future energy crises and freshwater shortages.

[0005] Currently, researchers have developed various high-performance anode catalysts. Noble metal-based catalysts such as Ir, Ru, and Pt exhibit the best water electrolysis performance, but the low abundance of these precious metals on Earth and their high cost limit their large-scale industrial application. Meanwhile, the high concentration of chloride ions (Cl-) in seawater... - Approximately 0.5 M of chlorine can adsorb onto the surface of the anode catalyst, triggering competitive side reactions that produce chlorine or hypochlorite, leading to severe corrosion of the catalyst, electrode, and film. Therefore, suppressing chlorine evolution side reactions, improving oxygen evolution selectivity, and extending electrode lifespan remain significant challenges.

[0006] Inexpensive transition metal materials have become a focus of attention as catalysts due to their excellent electrochemical activity and good stability. However, single transition metal catalysts struggle to simultaneously achieve both high activity in seawater oxidation and selectivity in the chlorine evolution reaction. Therefore, this invention discloses a method for preparing a heavy p-block metal-modified transition metal coordination polymer for seawater electrolysis to produce hydrogen. The resulting heavy p-block metal-modified transition metal coordination polymer can both suppress chlorine oxidation side reactions by repelling chloride ions through the strong Lewis acidity of the heavy p-block metal and activate the lattice oxygen oxidation mechanism through the polarization effect of the heavy p-block metal, thereby lowering the energy barrier of the seawater oxidation reaction. It possesses both "active chlorine removal" and "low-barrier catalysis" functions.

[0007] Existing technology, patent document CN202511625262.1 discloses a method for preparing a cobalt-calcium coordination polymer and its application in photocatalytic hydrogen production. The cobalt-calcium coordination polymer has the chemical formula CoCa(2-sina)2, is monoclinic, and exhibits stable catalytic sites in its crystal structure during photocatalytic reactions, thus accelerating the reaction rate. In the presence of photosensitizers and sacrificial agents, this cobalt-calcium coordination polymer demonstrates good hydrogen production performance under visible light irradiation. Patent document CN201910250986.0 discloses a Cu(I) coordination polymer, its preparation method, and its application. The Cu(I) coordination polymer has the molecular formula {[Cu... I (H2PO4)(dpe)] 5( dpe) 0.5 (H2O)7} n ; dpe is 1,2-bis(4-pyridyl)ethylene; the Cu(I) coordination polymer is centered on monovalent Cu, with two dpe organic ligands and one H2PO4 surrounding each Cu. - This Cu(I) coordination polymer exhibits high photocatalytic activity, capable of decomposing water into hydrogen without the need for any photosensitizers or co-catalysts. Patent document CN202311167738.2 discloses the preparation of a nickel-based coordination polymer and its photocatalytic hydrogen production application. The nickel-based coordination polymer has the chemical formula [Ni5(L)3(μ3-O)3(H2O)3]·5H2O. The crystal contains a ring-shaped building block composed of 6 central clusters and 12 L ligands. Each building block has a ring of active catalytic sites distributed along its center, and this building block extends continuously along the c-axis, constructing a three-dimensional framework structure. In the photocatalytic reaction, the active sites of this structure are ideally exposed in the channels, which helps ensure the stable existence of the photoexcited intermediate, shortens the distance between the catalytic sites and the reaction substrate, and accelerates the reaction efficiency. In the presence of photosensitizers and sacrificial agents, this nickel-based coordination polymer exhibits good hydrogen production performance under visible light irradiation. While the technical solutions in the aforementioned three patent documents describe the photocatalytic hydrogen production applications of cobalt-based, copper-based, and nickel-based coordination polymers, they do not contain any information on heavy p-region metal-modified transition metal coordination polymers or the application of such coordination polymers in seawater electrolysis for hydrogen production. Furthermore, they lack any technical insights regarding the dual functions of "active chlorine removal" and "low-barrier catalysis," which involve using the strong Lewis acidity of heavy p-region metals to repel chloride ions, suppress chlorine oxidation side reactions, and activating the lattice oxygen oxidation mechanism through the polarization of heavy p-region metals to lower the energy barrier of seawater oxidation reactions. Additionally, they do not contain any information on solving the technical problems of high energy barriers and poor resistance to chloride ion corrosion in existing seawater oxidation catalysts. Summary of the Invention

[0009] This invention aims to solve the technical problems of high energy barriers and poor resistance to chloride ion corrosion in existing seawater electrolysis hydrogen production catalysts. It provides a method for preparing a heavy p-block metal-modified transition metal coordination polymer. Based on coordination chemistry and Lewis acid-base theory, this method constructs a coordination polymer that combines a transition metal center and a heavy p-block metal. Through the polarization effect and strong Lewis acidity of the heavy p-block metal, the oxidation activity of seawater and the inhibition of chlorine evolution are enhanced, achieving high-performance seawater electrolysis hydrogen production. The prepared heavy p-block metal-modified transition metal coordination polymer, as an anode, exhibits high catalytic activity and stability for seawater electrolysis hydrogen production and effectively suppresses the chlorine evolution side reaction, demonstrating good application potential.

[0010] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0011] A method for preparing a heavy p-block metal-modified transition metal coordination polymer, the specific preparation process being as follows: a transition metal salt and a heavy p-block metal salt are co-precipitated in one step under the action of a complexing agent to obtain a heavy p-block metal-modified transition metal coordination polymer; wherein the transition metal salt is one or more of cobalt nitrate, nickel chloride, or manganese chloride, the heavy p-block metal salt is one or more of bismuth chloride, tin chloride, or lead acetate, and the complexing agent is one or more of phytic acid, citric acid, chitosan, or ethylenediamine.

[0012] A method for preparing a heavy p-block metal-modified transition metal coordination polymer includes the following steps: uniformly dispersing a transition metal salt and a heavy p-block metal salt in a polar solvent, adding a complexing agent solution, and co-precipitating the polymer at 20-60°C. After the reaction is completed, the polymer is centrifuged, washed, and dried to obtain the heavy p-block metal-modified transition metal coordination polymer. This coordination polymer has a unique amorphous nanoparticle structure, possessing both a transition metal center and a heavy p-block metal. Through the polarization effect and strong Lewis acidity of the heavy p-block metal, it enhances the oxidation activity of seawater and inhibits chlorine evolution, thereby achieving high-performance seawater electrolysis for hydrogen production.

[0013] Further specifying, the polar solvent is one or more of water, methanol, ethanol, acetic acid, or N,N-dimethylformamide.

[0014] Further specified, the molar ratio of metal ions in the transition metal salt to metal ions in the p-block metal salt is 1:0.05 to 1:0.20.

[0015] Further specified, the molar concentration of the complexing agent in the complexing agent solution is 0.005–0.02 mol / L.

[0016] Further specified, the coprecipitation reaction temperature is room temperature, and the coprecipitation reaction time is 10~60 minutes.

[0017] The application of the heavy p-region metal-modified transition metal coordination polymer described in this invention as an anode in seawater electrolysis for hydrogen production, wherein the heavy p-region metal-modified transition metal coordination polymer effectively repels chloride ions and inhibits chlorination side reactions through the polarization effect of the heavy p-region metal and strong Lewis acidity, exhibiting excellent seawater oxidation selectivity, seawater oxidation activity and long-term stability.

[0018] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0019] 1. The heavy p-region metal-modified transition metal coordination polymer prepared by this invention for seawater electrolysis hydrogen production achieves confined adsorption and selective shielding of reaction substrates through the polarization effect of heavy p-region metals and the dual protection mechanism of strong Lewis acidity. This fundamentally solves the problems of mass transfer resistance caused by traditional solid protective layers or anion barrier layers and easy detachment under high current, effectively addressing the industry pain points of high salt corrosion, high energy consumption and high cost in seawater electrolysis.

[0020] 2. This invention employs a one-step co-precipitation method, enabling catalyst synthesis at room temperature, thus avoiding complex and demanding reaction conditions such as high temperature and high pressure. The raw materials are inexpensive and readily available, and the preparation process is time-saving, efficient, and easily scaled up, demonstrating promising prospects for industrial application.

[0021] 3. Compared with the traditional desalination-then-hydrogen production route, the present invention uses the prepared heavy p-region metal-modified transition metal coordination polymer as the anode, which can be directly used for alkaline seawater electrolysis to produce hydrogen, eliminating the seawater desalination pretreatment step, reducing the energy consumption per unit of hydrogen production by more than 20%, and achieving the goal of energy saving and cost reduction in seawater electrolysis hydrogen production.

[0022] The heavy p-block metal-modified transition metal coordination polymer for seawater electrolysis hydrogen production proposed in this invention effectively suppresses the chlorine evolution side reaction based on the unique polarization effect and strong Lewis acidity of heavy p-block metals, thus exhibiting excellent electrocatalytic seawater oxidation activity and long-term stability in alkaline seawater solutions. Attached Figure Description

[0024] Figure 1 The image shows a scanning electron microscope (SEM) image of the bismuth-doped cobalt phytate coordination polymer prepared in Example 1.

[0025] Figure 2 The image shows the X-ray diffraction pattern of the bismuth-doped cobalt phytate coordination polymer prepared in Example 1.

[0026] Figure 3 The image shows the energy dispersive X-ray spectrum of the bismuth-doped cobalt phytate coordination polymer prepared in Example 1.

[0027] Figure 4The energy dispersive X-ray spectrum of the lead-doped chitosan cobalt coordination polymer prepared in Example 2 is shown.

[0028] Figure 5 Linear sweep voltammetric curves of the bismuth-doped cobalt phytate, cobalt phytate, and bismuth phytate catalysts prepared in Example 1 and Comparative Examples 1-2.

[0029] Figure 6 Linear sweep voltammetric curves of the bismuth-doped cobalt phytate and cobalt phytate-based seawater hydrogen production device (Bi-CoPA || Pt / C) constructed in alkaline seawater solution prepared for Example 1 and Comparative Example 1, and constructed with cobalt phytate as the anode.

[0030] Figure 7 Chronopotential curves of a seawater hydrogen production device (Bi-CoPA||Pt / C) constructed using the bismuth-doped cobalt phytate catalyst prepared in Example 1 as the anode in alkaline seawater solution. Detailed Implementation

[0032] The following examples further illustrate the above-mentioned content of the present invention in detail. All technologies implemented based on the above-mentioned content of the present invention fall within the scope of the present invention.

[0033] Example 1

[0034] Bismuth-doped cobalt phytate coordination polymer (Bi-CoPA) prepared by a one-step co-precipitation method:

[0035] 0.9 mmol Co(NO3)2·6H2O and 0.1 mmol BiCl3 were dissolved in 30 mL of ethanol solution, and the mixture was stirred continuously for 10 minutes to obtain a clear solution. Then, 300 μL of phytic acid solution was slowly added dropwise to the above solution, and the reaction was continued with stirring for 30 minutes. The product was collected by centrifugation and washed several times with ethanol. The obtained solid was dried in an oven at 60 °C for 6 h to obtain a bismuth-doped cobalt phytate coordination polymer.

[0036] The scanning electron microscope image of the bismuth-doped cobalt phytate coordination polymer obtained in Example 1 is shown below. Figure 1 As shown, the morphology exhibits a uniform nanoparticle structure with an average particle size of 30 nm.

[0037] The X-ray diffraction pattern of the bismuth-doped cobalt phytate coordination polymer obtained in Example 1 is shown below. Figure 2 As shown, the structure exhibits an amorphous state.

[0038] The energy dispersive X-ray spectrum of the bismuth-doped cobalt phytate coordination polymer obtained in Example 1 is shown below. Figure 3 As shown, this demonstrates the successful doping of heavy p-region metallic bismuth.

[0039] Example 2

[0040] Preparation of lead-doped chitosan cobalt coordination polymer (Pb-CoPA) based on a one-step co-precipitation method:

[0041] Dissolve 0.05 g of chitosan in glacial acetic acid solution with a pH of 3-6, and stir continuously for 10 minutes to obtain a clear solution. Add 0.9 mmol Co(NO3)2·6H2O and 0.1 mmol Pb(CH3COO)2·3H2O to the above solution and continue stirring for 30 minutes. Collect the product by centrifugation and wash several times with ethanol. Filter the obtained product at 60 °C. o The lead-doped chitosan cobalt coordination polymer (Pb-CoPA) was obtained by drying in an oven at C for 6 h.

[0042] The energy dispersive X-ray spectrum of the lead-doped chitosan cobalt coordination polymer obtained in Example 2 is shown below. Figure 4 As shown, this demonstrates the successful doping of heavy p-region metallic lead.

[0043] Comparative Example 1

[0044] In this comparative example, 1 mmol of Co(NO3)2·6H2O was dissolved in 30 mL of ethanol solution, and the other steps were the same as in Example 1 to obtain the monometallic coordination polymer material CoPA.

[0045] Comparative Example 2

[0046] In this comparative example, 1 mmol of BiCl3 was dissolved in 30 mL of ethanol solution, and the other steps were the same as in Example 1 to obtain the monometallic coordination polymer material BiPA.

[0047] To demonstrate the beneficial effects of this invention, the bismuth-doped cobalt phytate coordination polymer Bi-CoPA prepared in Example 1 and the monometallic coordination polymers CoPA and BiPA prepared in Comparative Examples 1 and 2 were respectively drop-coated onto nickel foam to form a three-electrode system as the anode. Electrocatalytic performance was tested in an alkaline simulated seawater solution (1.0 M KOH + 0.5 M NaCl). Figure 5 The results show that the bismuth-doped cobalt phytate coordination polymer Bi-CoPA exhibits the lowest onset oxidation potential and the best seawater oxidation performance. Specifically, it reaches 100 mA cm⁻¹. −2 At that time, the bismuth-doped cobalt phytate coordination polymer Bi-CoPA requires an overpotential of only 326 mV, while the monometallic coordination polymers CoPA and BiPA require 393 mV and 476 mV, respectively.

[0048] To further demonstrate this, an anion exchange membrane seawater electrolyzer was constructed using the bismuth-doped cobalt phytate coordination polymer Bi-CoPA prepared in Example 1 and the monometallic coordination polymer material CoPA prepared in Comparative Example 1 as the anode. Electrocatalytic performance was tested in an alkaline seawater solution (1.0 M KOH + seawater). Figure 6-7 This indicates that Bi-CoPA possesses excellent seawater oxidation activity and stability.

[0049] The above embodiments describe the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are only illustrative of the principles of the present invention. Various changes and modifications can be made to the present invention without departing from the scope of the principles of the present invention, and all such changes and modifications fall within the protection scope of the present invention.

Claims

1. A method for preparing a heavy p-block metal-modified transition metal coordination polymer, characterized in that... The specific preparation process is as follows: a transition metal salt and a heavy p-block metal salt are co-precipitated in one step under the action of a complexing agent to obtain a heavy p-block metal-modified transition metal coordination polymer; the transition metal salt is one or more of cobalt nitrate, nickel chloride or manganese chloride, the heavy p-block metal salt is one or more of bismuth chloride, tin chloride or lead acetate, and the complexing agent is one or more of phytic acid, citric acid, chitosan or ethylenediamine.

2. The method for preparing the heavy p-region metal-modified transition metal coordination polymer according to claim 1, characterized in that... The specific preparation steps are as follows: the transition metal salt and the heavy p-block metal salt are uniformly dispersed in a polar solvent, a complexing agent solution is added, and a co-precipitation reaction is carried out at 20~60℃. After the reaction is completed, the heavy p-block metal-modified transition metal coordination polymer is obtained by centrifugation, washing, and drying. This coordination polymer has a unique amorphous nanoparticle structure, which combines the transition metal center and the heavy p-block metal. Through the polarization effect of the heavy p-block metal and the strong Lewis acidity, the oxidation activity of seawater and the inhibition of chlorine evolution are enhanced, thereby realizing high-performance electrolysis of seawater to produce hydrogen.

3. The method for preparing the heavy p-region metal-modified transition metal coordination polymer according to claim 2, characterized in that: The polar solvent is one or more of water, methanol, ethanol, acetic acid, or N,N-dimethylformamide.

4. The method for preparing the heavy p-region metal-modified transition metal coordination polymer according to claim 2, characterized in that: The molar ratio of metal ions in the transition metal salt to those in the p-block metal salt is 1:0.05 to 1:0.

20.

5. The method for preparing the heavy p-region metal-modified transition metal coordination polymer according to claim 2, characterized in that: The molar concentration of the complexing agent in the complexing agent solution is 0.005–0.02 mol / L.

6. The method for preparing the heavy p-region metal-modified transition metal coordination polymer according to claim 2, characterized in that: The coprecipitation reaction temperature is room temperature, and the coprecipitation reaction time is 10~60 minutes.

7. The application of the heavy p-region metal-modified transition metal coordination polymer prepared by the method according to any one of claims 1 to 5 as an anode in the electrolysis of seawater to produce hydrogen.

8. The application according to claim 7, characterized in that: The heavy p-region metal-modified transition metal coordination polymer effectively repels chloride ions and inhibits chlorination side reactions through the polarization effect and strong Lewis acidity of the heavy p-region metal, exhibiting excellent seawater oxidation selectivity, seawater oxidation activity, and long-term stability.

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