Preparation and application of metalloporphyrin intercalated double-metal hydroxide material

Abstract

According to the preparation method, ZIF-67 is taken as a template, nickel nitrate and copper porphyrin are added at the same time, and the metalloporphyrin intercalated double-metal hydroxide material is successfully prepared through acid etching. The material is composed of copper porphyrin Cu-TCPP and hollow NiCo-LDH, and has a hollow porous structure and a large specific surface area. Benefited from the synergistic effect of Cu-TCPP and NiCo-LDH, only 204mv overpotential is needed when the material reaches the current density of 10mA. Cm <-2 >, the material is superior to transition metal-based OER electrocatalysts reported in most literatures, the performance is almost unchanged after a stable test for 12 hours, and the material has a relatively good application prospect.

Description

Technical Field

[0001] The invention belongs to the field of new material technology and electrocatalysis, and specifically relates to the preparation of a hollow hydrotalcite material with metal porphyrin intercalation and its application in oxygen evolution reaction by electrolysis of water. Background Art

[0002] With the rapid development of social economy, the extensive use of energy has brought many problems, including the destruction of the natural environment and potential energy crisis. In order to solve these problems, mankind has gradually begun to pay attention to the development and utilization of new energy. Hydrogen has attracted much attention as a green energy carrier. In large-scale hydrogen production technology, water electrolysis is considered to be the most feasible and promising method. However, as a key step restricting the production of hydrogen by water electrolysis, the oxygen evolution reaction (OER) on the anode is a four-electron process with slow reaction kinetics and usually requires higher energy to drive. At present, OER catalysts are mainly precious metal catalysts such as RuO2 and IrO2. However, they face problems such as limited reserves, high prices and general stability. Therefore, the design and development of abundant and inexpensive non-precious metal OER electrocatalysts has become a hot topic in this field.

[0003] Among various non-precious metal catalysts, transition metal-based layered double hydroxides (LDHs), also known as hydrotalcites, have attracted extensive attention from the scientific community due to their unique layered structure, tunable composition, and uniformly dispersed active sites. To date, a variety of hydrotalcite-based OER catalysts have been developed, such as NiFe-LDH, CoMn-LDH, ZnCo LDH, and NiAl-LDH, etc. However, the LDHs prepared by traditional methods have poor activity, conductivity, and stability. In order to overcome these shortcomings, researchers have taken many measures, such as combining with conductive materials such as carbon matrix (CN118127530A), carbon nanotubes (Nanomaterials 2022, 12 (6), 1015), reduced graphene (Energy. Adv., 2023, 2 (9): 1375-1380) or using it as a precursor for sulfurization (J. Energy Chem., 2022, 74: 376-386), phosphating (Inorg. Chem. Front., 2023, 10 (12): 3515-3524), etc. However, these methods are cumbersome or need to be carried out at high temperatures, which is not conducive to industrial promotion. Therefore, how to improve the electrocatalytic activity of LDH while ensuring the simplicity of the synthesis method is very challenging. Summary of the invention

[0004] In view of the shortcomings and deficiencies in the above-mentioned background technology, the present invention provides a hollow hydrotalcite material with metal porphyrin intercalation, a preparation method and application thereof. The material is composed of a hollow NiCo-LDH and a copper porphyrin Cu-TCPP with a threshold between the LDH layers, with a size between 0.5-1 μm, a polyhedral morphology, and a hollow porous structure. Through the synergistic effect of Cu-TCPP and NiCo-LDH, the material has excellent electrocatalytic activity and stability in OER.

[0005] The method for preparing the hollow hydrotalcite material with metal porphyrin intercalation provided by the present invention comprises the following steps:

[0006] (1) Synthesizing template ZIF-67 by hydrothermal method;

[0007] Cobalt nitrate and 2-methylimidazole are dissolved in equal amounts of methanol in a certain proportion, and then the latter solution is quickly poured into the former solution, stirred for 10-30 minutes, and then allowed to stand for 12-48 hours. Finally, centrifuged and dried to obtain an organic metal framework material ZIF-67, which serves as a template for subsequent synthesis.

[0008] (2) Hollow NiCo-LDH materials with Cu-TCPP intercalation were synthesized by template method.

[0009] ZIF-67 was added to ethanol, and then an ethanol solution containing nickel nitrate and tetrakis(4-carboxyphenyl)copperporphyrin (Cu-TCPP) was quickly poured in, stirred evenly, refluxed at 80-100°C for 0.5-1.5h, and finally centrifuged and dried to obtain the target product CT / HNCL.

[0010] The application of the hollow hydrotalcite material CT / HNCL intercalated with metal porphyrin prepared by the present invention in oxygen evolution reaction is tested in the following system:

[0011] On a Shanghai Chenhua electrochemical workstation (CHI 760E), a three-electrode system was constructed, i.e., a 4 mm diameter glassy carbon electrode was used as the working electrode, Hg / HgO was used as the reference electrode, and a graphite rod was used as the counter electrode, and the oxygen evolution reaction activity of the material was tested in a 1M KOH solution. All measured potential values ​​were converted to standard hydrogen potential according to the formula:

[0012]

[0013] Compared with the prior art, the advantages of the present invention are as follows:

[0014] 1. The hollow NiCo-LDH material with Cu-TCPP intercalation prepared by the present invention has fewer synthesis steps, low solvent toxicity, moderate reaction temperature, does not require too much energy and cost, and can be extended to the preparation of other hollow intercalation hydrotalcites.

[0015] 2. The hollow NiCo-LDH material with Cu-TCPP intercalation prepared by the present invention has a rich mesoporous structure and a large cavity, which is beneficial to full contact with the electrolyte and expose more active sites. The material also combines the advantages of Cu-TCPP and NiCo-LDH: the interlayer confinement of LDH inhibits the agglomeration and dissolution of Cu-TCPP, improves the utilization rate of active sites, and at the same time, in addition to being an active center itself, Cu-TCPP also plays a role as a conductive medium between layers, enhancing the conductivity of the material. Ultimately, under the synergistic effect of the two, the above material has high OER activity and stability.

[0016] 3. The hollow NiCo-LDH material with Cu-TCPP intercalation prepared by the present invention has excellent OER activity, which can reach 10 mA / cm at an ultra-low overpotential of 204 mV. 2 The current density is 2.33 W, and the performance remains almost unchanged after 1000 cycles and 12 h of stability testing, which is better than most transition metal-based OER catalysts. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 The present invention is a flow chart of the hollow hydrotalcite material with metal porphyrin intercalation prepared by the present invention.

[0018] Figure 2 (a, b) are SEM images of ZIF-67 prepared by the present invention; Figure 2 (c, d) are SEM images of HNCL prepared by the present invention; Figure 2 (e, f) are SEM images of 1-CT / HNCL prepared in the present invention.

[0019] Figure 3 It is the FT-IR graph of 1-CT / HNCL and HNCL prepared by the present invention.

[0020] Figure 4 It is the BET diagram of 1-CT / HNCL and HNCL prepared in the present invention.

[0021] Figure 5 (a), (b) and (c) are the LSV graph, Tafel graph and EIS graph of 1-CT / HNCL and HNCL prepared in the present invention, respectively; Figure 5 (d) is a stability curve diagram of 1-CT / HNCL prepared in the present invention.

[0022] Figure 6 It is the double-layer capacitance diagram of 1-CT / HNCL and HNCL prepared by the present invention. DETAILED DESCRIPTION

[0023] The following is a detailed description of the preparation method of the hollow hydrotalcite material with metal porphyrin intercalation of the present invention in combination with specific implementation methods and examples. The raw materials used in the examples are all conventional commercially available products. The main experimental reagents used are listed as follows: Co(NO3)2·6H2O(AR), 2-methylimidazole(AR), Ni(NO3)2·6H2O(AR), methanol(AR), ethanol(AR), anhydrous ethanol(AR), 5% Nafion solution(AR)

[0024] The present invention is described below by way of example, and the present invention includes but is not limited to the following embodiments:

[0025] Example 1

[0026] (1) Preparation of template ZIF-67: 1.164 g of Co(NO3)2·6H2O was dissolved in 100 ml of methanol. Similarly, 1.312 g of 2-methylimidazole was also dissolved in 100 ml of methanol. The latter solution was quickly poured into the former solution and stirred for 20 min. The mixture was allowed to stand at room temperature for 24 h. The mixture was then centrifuged three times with methanol and dried in an oven at 70°C for 12 h to obtain template ZIF-67.

[0027] (2) Preparation of metalloporphyrin intercalated hollow hydrotalcite (1-CT / HNCL): 0.8 g of Ni(NO3)2·6H2O and 1 mg of Cu-TCPP were dissolved in 40 ml of ethanol, and 0.16 g of ZIF-67 was dispersed in 60 ml of ethanol. The former mixed solution was then quickly poured into the stirred ZIF-67 and refluxed at 90°C for 1 h. The resulting precipitate was collected by ethanol centrifugation and recorded as 1-CT / HNCL after drying.

[0028] Example 2

[0029] Preparation of hollow hydrotalcite (HNCL): 0.8 g of Ni(NO3)2·6H2O and 0.16 g of ZIF-67 were dissolved in 40 ml and 60 ml of ethanol, respectively. The former solution was then quickly poured into the stirred ZIF-67 and refluxed for 1 h. Finally, the precipitate was centrifuged three times through ethanol to obtain a hollow NiCo-LDH material without porphyrin intercalation, recorded as HNCL.

[0030] Example 3

[0031] (1) The characterization test results of Example 1 and Example 2 are as follows:

[0032] Scanning Electron Microscopy (SEM): Figure 2 (a, b) are the template ZIF-67 prepared in Example 1, which has a smooth surface, sharp edges and regular shape. Figure 2(c, d) and (e, f) are HNCL and 1-CT / HNCL prepared in Example 1. It can be seen that the two retain the basic shape of the template to a large extent, but the surface is full of wrinkles formed by dense stacking of laminations, and from the damaged corner, it can be seen that the interior has changed from solid to hollow. The similar structural features of HNCL and 1-CT / HNCL mean that the introduction of Cu-TCPP does not destroy the formation of hydrotalcite.

[0033] Infrared spectroscopy (FT-IR): Figure 3 This is the FT-IR image of 1-CT / HNCL. The infrared characteristic peaks of 1-CT / HNCL are mainly HNCL, and the peaks at 1000cm -1 and 1686cm -1 The absorption peaks of N-Cu and carboxyl C=O belonging to CuTCPP appeared nearby, indicating that Cu-TCPP had successfully bound to the substrate HNCL. Further observation revealed that the interlayer water molecule peak of 1-CT / HNCL was weakened (1639cm -1 ) and interlayer ions NO3 - The peak part disappeared (1317cm -1 ) suggests that Cu-TCPP has successfully entered the interlamellar space of hydrotalcite and replaced some interlaminar species.

[0034] Specific surface area analysis (BET): Figure 4 The nitrogen adsorption-desorption isotherms and pore size distribution of HNCL and 1-CT / HNCL are shown. It can be seen that the isotherm characteristics of 1-CT / HNCL are similar to those of HNCL, but the pore size distribution is significantly different. The introduction of porphyrin forms a multi-level pore size distribution, and the specific surface area of ​​1-CT / HNCL (206.15 m 2 / g) is much larger than the precursor HNCL (130.93m 2 / g), which effectively improves the utilization of active sites.

[0035] (2) The OER test results of 1-CT / HNCL in Example 1 and Example 2 are as follows:

[0036] On a CHI 760E electrochemical workstation, the oxygen evolution reaction activity of the material was tested in 1M KOH solution by constructing a three-electrode system, i.e., a glassy carbon electrode (4 mm) as the working electrode, Hg / HgO as the reference electrode, and a graphite rod as the counter electrode. All measured potential values ​​were converted to standard hydrogen potential according to the formula:

[0037]

[0038] Overpotential is one of the important indicators for evaluating catalyst activity, which can be obtained by testing the linear sweep voltammetry (LSV) curve. The scan rate is set to 5mV / s and the voltage range is 0-0.9V. Figure 5 As shown in (a), 1-CT / HNCL reaches 10 mA / cm 2 The current density only needs 204mv.

[0039] The LSV curve was fitted, and the Tafel curve obtained further provided an understanding of the reaction kinetics of the material. Figure 5 As shown in (b), the Tafel slope of 1-CT / HNCL is smaller, which is 84.5 mV / dec.

[0040] The frequency of electrochemical impedance spectroscopy (EIS) was set from 1000000 Hz to 0.01 Hz, and the resistance data were fitted using ZView software. Figure 5 As shown in (c), the charge transfer resistance of 1-CT / HNCL is the smallest, which is 4.788Ω.

[0041] Long-term stability is one of the key parameters that determine the practical use capability of a material. The stability of 1-CT / HNCL is measured at 10 mA / cm 2 The results were evaluated by continuous testing for 43200s at a current density of Figure 5 As shown in (d), the potential of 1-CT / HNCL hardly changes, indicating that its performance is stable.

[0042] CV tests were performed at different scan rates (20, 40, 60, 80, 100 mV / s) in the non-Faraday region, and the double-layer capacitance (C dl ).Depend on Figure 6 It can be seen that 1-CT / HNCL has a large double-layer capacitance of 0.477mF / cm 2 .

[0043] The embodiments described above are detailed descriptions of the preparation method of the present invention, which should be understood as specific implementation measures of the present invention and are not used to summarize the present invention. Any modifications, supplements or similar replacements made within the scope of the principles of the present invention shall fall within the scope of protection of the present invention.

Claims

1. A hollow hydrotalcite material intercalated with metalloporphyrin, characterized in that: The material is prepared using zeolite imidazole framework-67 (ZIF-67) as a template and consists of a hollow nickel / cobalt double hydroxide (NiCo-LDH) and tetrakis(4-carboxyphenyl)copperporphyrin (Cu-TCPP) (labeled as CT / HNCL) limited between the LDH layers. It has a size between 0.5-1μm, exhibits a polyhedral morphology of stacked layers, and has a hollow porous structure.

2. The method for preparing a hollow hydrotalcite material with metal porphyrin intercalation according to claim 1, comprising the following steps: (1) Dissolving cobalt nitrate and 2-methylimidazole in an equal amount of methanol at a molar ratio of 1:4, then quickly pouring the 2-methylimidazole solution into the cobalt nitrate solution, stirring for 10-30 minutes, and then standing for 12-48 hours, and finally centrifuging and drying to obtain ZIF-67 as a template for subsequent synthesis; (2) The template ZIF-67, Ni(NO3)2·6H2O and Cu-TCPP are mixed and dissolved in ethanol in a certain proportion, stirred and refluxed at 80-100°C for 0.5-1.5h, and finally centrifuged and dried to obtain the target product CT / HNCL; wherein the mass ratio of ZIF-67 to Ni(NO3)2·6H2O is 1:(4-8), and the addition amount of Cu-TCPP is (0-10) mg per gram of ZIF-67.

3. A hollow hydrotalcite material with metal porphyrin intercalation prepared by the method according to claim 1 has excellent catalytic activity and stability in the application of water electrolysis oxygen evolution reaction (OER), that is, in a three-electrode test system with an electrolyte of 1M KOH solution, it reaches 10mA·cm -2 The current density required an overpotential between 200-220mv, and after 12h of stabilization testing, the performance remained almost unchanged.

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