Mo, mn co-doped ni-fe-l dh catalyst for electrocatalytic decomposition of water to produce oxygen and preparation method and application thereof

Abstract

The application discloses a Mo and Mn co-doped NiFe-LDH catalyst for electrocatalytic decomposition of water to produce oxygen, and a preparation method and application thereof, and belongs to the technical field of supported metal catalysts. The MoMn-NiFe LDH catalyst is obtained by a hydrothermal method. Performance testing shows that the MoMn-NiFe LDH catalyst can reach a current density of 100 mA cm ‑2 -5 mV overpotential, and long-time high-conversion performance results also show that the catalyst has excellent stability. The "metal-support interaction" is used to effectively regulate the oxygen evolution reaction performance, and the catalyst is a high-efficiency and stable electrocatalyst.

Description

Technical Field

[0001] This invention relates to the field of metal-supported catalyst technology, specifically to a Mo / Mn co-doped NiFe-LDH catalyst for electrocatalytic water splitting to produce oxygen, its preparation method, and its application. Background Technology

[0002] Electrochemical water splitting is one of the most promising methods for storing and utilizing renewable energy in the form of clean chemicals. For the energy-intensive and kinetically slow oxygen evolution reaction (OER), the use of efficient and economical catalysts is crucial. The development of this technology is based on the development and utilization of catalysts that can accelerate the OER reaction. Electrocatalysts can effectively reduce the complexity of water electrolysis equipment and are also key to achieving efficient electrochemical water splitting.

[0003] Supported noble metal catalysts primarily exert their catalytic activity by activating reactant molecules through elemental active metal sites on the support surface. Their catalytic activity is closely related to the atomic arrangement of the elemental active noble metal components on the support surface. Generally, when the loading of the noble metal component is constant, the better the dispersion of the active noble metal component, the more uniform the surface atomic arrangement, and the more abundant the number of exposed active sites, the stronger the catalytic reaction activity.

[0004] Utilizing metal-support interactions to achieve precise control and preparedness of supported metal catalysts has long been a crucial research area in industrial catalysis. Furthermore, given the current situation in my country where precious metals are expensive and scarce, developing new methods for highly dispersed supported precious metal catalysts can not only conserve precious metal resources but also significantly improve catalyst performance, facilitating greener and more efficient applications. Non-platinum precious metals have consistently been a research hotspot in electrochemical oxygen production. Among them, NiFe-LDH (nickel-iron layered double hydroxide) has gradually become a research focus due to its low cost, environmental friendliness, and excellent performance in alkaline OERs. However, it still suffers from poor conductivity, insufficient exposure of active sites, and poor stability. Summary of the Invention

[0005] To address the aforementioned shortcomings of existing technologies, the present invention aims to provide a Mo / Mn co-doped NiFe-LDH catalyst for electrocatalytic water splitting to produce oxygen, its preparation method, and its application. A Mo / Mn co-doped NiFe-LDH catalyst with a layered structure was synthesized. The oxygen evolution reaction performance was effectively regulated by the "metal-support interaction," and the active site Na was improved. 2+ The ratio of Fe nanoparticles was reduced, thereby enabling the regulation of catalytic performance.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A Mo / Mn co-doped NiFe-LDH catalyst for electrocatalytic water splitting is characterized in that: the catalyst is formed by supporting metallic Mo and Mn on a NiFe-LDH support, wherein the NiFe-LDH support is formed by supporting NiFe-LDH (NiFe layered double hydroxide) on a nickel foam (NF) substrate.

[0007] Furthermore, in this catalyst, the loading of Mo is 2.5-3.0 wt.% and the loading of Mn is 2.5-3.0 wt.%.

[0008] Furthermore, in this catalyst, the molar ratio of Mo, Mn, Ni and Fe is (0.7-2.1):(0.1-0.3):(0.9-1.1):(0.9-1.1).

[0009] Furthermore, the catalyst is formed by supporting metals Mo, Mn, Ni and Fe on a nickel foam framework to form MoMn-NiFeLDH. The MoMn-NiFe LDH on the nickel foam exhibits an ultrathin cross-linked nanosheet structure without aggregation; the Mo, Mn, Ni and Fe elements in the MoMn-NiFe LDH are uniformly distributed.

[0010] The method for preparing the Mo / Mn co-doped NiFe-LDH catalyst for electrocatalytic water splitting includes the following steps: (1) Pretreatment of nickel foam: The nickel foam was soaked in hydrochloric acid to remove the NiO layer, and then washed repeatedly with deionized water and ethanol alternately. (2) Dissolve nickel nitrate hexahydrate, ferric nitrate nonahydrate and urea in deionized water and stir magnetically until completely dissolved to obtain a mixture containing nickel and iron; (3) Manganese chloride tetrahydrate (MnCl2·4H2O) and ammonium molybdate tetrahydrate ((NH4)6Mo7O) 24 ·4H2O) was added to the mixture obtained in step (2), and stirred at room temperature until completely dissolved to obtain the catalyst precursor; (4) Add the pretreated nickel foam from step (1) to the catalyst precursor obtained in step (3) and place it in a hydrothermal box for hydrothermal treatment; after the hydrothermal treatment, the sample obtained is washed and dried to obtain the Mo, Mn co-doped NiFe-LDH catalyst for electrocatalytic water splitting.

[0011] Further, in step (1), the nickel foam has a sheet-like structure; the nickel foam is soaked in hydrochloric acid for 10-20 minutes with a hydrochloric acid concentration of 1 mol / L; and it is washed with deionized water and ethanol alternately 2-5 times.

[0012] Further, in step (2), the molar ratio of nickel nitrate hexahydrate, ferric nitrate nonahydrate, and urea is (0.9-1.1):(0.9-1.1):(4-6); the amount of nickel nitrate hexahydrate and ferric nitrate nonahydrate used is determined according to the required load.

[0013] Further, in step (3), the molar ratio of Mo, Mn, Ni and Fe elements in the catalyst precursor is (0.7-2.1):(0.1-0.3):(0.9-1.1):(0.9-1.1).

[0014] Further, in step (4), the temperature of the hydrothermal treatment is 100-140℃, the holding time is 6-12 hours, and the heating rate is 5-10℃ / min; the preferred treatment temperature is 115-125℃ and the holding time is 7-10 hours.

[0015] Further, in step (4), the washing and drying process is as follows: the obtained sample is washed repeatedly with deionized water and ethanol alternately, and the obtained sample is then transferred to an oven to dry.

[0016] The Mo / Mn co-doped NiFe-LDH catalyst used for electrocatalytic water splitting is applied to oxygen production from water electrocatalytic splitting.

[0017] The design mechanism of this invention is as follows: This invention provides a molybdenum- and manganese-doped nickel-iron layered double hydroxide catalyst with a layered structure, exhibiting excellent water splitting performance. Appropriate doping with Mo and Mn provides reaction sites for the adsorption and transformation of some lattice distortion intermediates in the material, thereby optimizing the charge distribution. Furthermore, the MoMn-NiFe LDH formed on nickel foam after doping exhibits an ultrathin cross-linked nanosheet structure, free from aggregation, and possesses a larger specific surface area, accelerating electrolyte penetration and significantly improving the catalyst's activity in alkaline media. Therefore, the Mo and Mn-doped NiFe-LDH catalyst can effectively enhance the oxygen evolution reaction performance through "metal-support interaction," making it a highly efficient and stable electrocatalyst. This technology provides a simple and economical strategy for the preparation of supported metal catalysts.

[0018] The present invention has the following advantages and beneficial effects: 1. This invention utilizes non-precious metal doped double-layer hydroxides to replace precious metals, significantly reducing catalyst costs.

[0019] 2. This invention utilizes the "metal-support interaction" to regulate the microstructure of the catalyst, thereby increasing the activity of Na+ sites. 2 +This reduces the aggregation of Fe nanoparticles, thereby enabling the regulation of catalytic performance and exhibiting highly efficient electrocatalytic activity. It provides a simple and economical strategy for the preparation of supported metal catalysts.

[0020] 3. Compared with previous methods for preparing non-precious metal-based catalysts, this invention prepares Mo and Mn-doped NiFe-LDH catalysts via a simple hydrothermal method, which is not only simple and low-cost, but also easy to promote and apply.

[0021] 4. Electrochemical performance testing confirmed that the Mo and Mn-doped NiFe-LDH catalyst prepared in this invention exhibits an overpotential of 226 mV and a Tafel slope of 21.17 mV when applied to the oxygen evolution reaction. -1 The potential remained stable over approximately 100,000 s of continuous operation, demonstrating excellent stability. This indicates that it possesses highly efficient electrocatalytic performance in the oxygen evolution reaction, making it an excellent electrocatalyst. Attached Figure Description

[0022] Figure 1 Scanning electron microscope images of the catalysts prepared in each example and comparative example; wherein: (a) is the Mo and Mn-doped NiFe LDH catalyst prepared in Example 1; (b) is the NiFe LDH catalyst prepared in Comparative Example 1; (c) is the Mo-doped NiFe LDH catalyst prepared in Comparative Example 2; and (d) is the Mn-doped NiFe LDH catalyst prepared in Comparative Example 3.

[0023] Figure 2 Scanning electron microscope images and elemental composition of the catalyst prepared in Example 1; Figure 3 XRD patterns of the catalysts prepared in each example and comparative example.

[0024] Figure 4 LSV curves of the catalysts prepared for the various examples and comparative examples for the electrochemical oxygen evolution reaction.

[0025] Figure 5 Tafel slope diagrams for the catalysts prepared in each embodiment and comparative example for the electrochemical oxygen evolution reaction.

[0026] Figure 6 The diagram shows the calculated Cdl values ​​for the catalysts prepared in each embodiment and comparative example for the electrochemical oxygen evolution reaction.

[0027] Figure 7 Stability graphs of the catalysts prepared for the various examples and comparative examples in the electrochemical oxygen evolution reaction. Detailed Implementation

[0028] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0029] In the following examples, the concentration of hydrochloric acid used was 1 mol / L. Example 1:

[0030] This embodiment describes the preparation of a Mo / Mn co-doped NiFe-LDH catalyst for electrocatalytic water splitting to produce oxygen. The specific process is as follows: 1. Pretreatment of nickel foam: Take two pieces of nickel foam with a size of 1cm×2cm×1mm, soak them in hydrochloric acid for about 15 minutes, then wash them three times alternately with deionized water and ethanol, and finally dry them in a 60℃ oven.

[0031] 2. Weigh 290.8 mg (0.001 mol) nickel nitrate hexahydrate, 404.1 mg ferric nitrate nonahydrate and 300.3 mg urea into a beaker, add 25 mL of deionized water, and stir magnetically until the mixture containing nickel and iron is completely dissolved. 3. Add 247.2 mg of ammonium molybdate tetrahydrate and 39.6 mg of manganese chloride tetrahydrate to the obtained mixture, and stir magnetically at room temperature until a homogeneous solution is obtained to obtain the catalyst precursor.

[0032] 4. Hydrothermal method: The pretreated nickel foam from step 1 and the catalyst precursor obtained in step 3 are placed together in a hydrothermal chamber for hydrothermal treatment. The hydrothermal treatment process is as follows: the temperature is raised to 120°C at a heating rate of 5°C / min and kept at a constant temperature for 8 hours. After cooling to room temperature, the Mo and Mn co-doped NiFe-LDH catalyst (denoted as MoMn-NiFe LDH) is obtained.

[0033] In the Mo and Mn co-doped NiFe LDH catalyst prepared in this embodiment, the Mo doping amount is about 2.7 wt.% and the Mn doping amount is about 2.7 wt.%.

[0034] Comparative Example 1: The difference from Example 1 is that step (3) is not performed, that is, ammonium molybdate tetrahydrate and manganese chloride tetrahydrate are not added; finally, the NiFe-LDH catalyst sample (denoted as NiFe LDH or NiFe-LDH) is obtained.

[0035] Transmission electron microscopy (TEM) image of the NiFe LDH catalyst prepared in Comparative Example 1 is shown below. Figure 1 As shown in (b).

[0036] Comparative Example 2: The difference from Example 1 is that manganese chloride tetrahydrate is not added in step (3); the final Mo-doped NiFe-LDH catalyst sample (denoted as Mo-NiFe LDH) is obtained.

[0037] Transmission electron microscopy (TEM) image of the MoNiFe LDH catalyst prepared in Comparative Example 2 is shown below. Figure 1 As shown in (c).

[0038] Comparative Example 3: The difference from Example 1 is that ammonium molybdate tetrahydrate is not added; the final Mn-doped NiFe-LDH catalyst sample (denoted as Mn-NiFe LDH) is obtained.

[0039] Transmission electron microscopy (TEM) image of the Mn-NiFe LDH catalyst prepared in Comparative Example 3 is shown below. Figure 1 As shown in (d).

[0040] The catalysts prepared in the above examples and comparative examples were characterized as follows: Scanning electron microscope image of the Mo, Mn co-doped NiFe LDH catalyst prepared in Example 1 is shown below. Figure 1 As shown in (a), it can be seen that the MoMnNiFe-LDH loaded on the nickel foam framework exhibits an ultrathin cross-linked nanosheet structure without any aggregation, which is different from the NiFe-LDH in Comparative Example 1. Figure 1 (b) Forming a contrast; Figure 1 (b) shows a scanning electron microscope image of NiFe-LDH in Comparative Example 1. The NiFe-LDH is uniformly distributed and has no obvious fluctuations. Figure 1 (c) and Figure 1 (d) shows scanning electron microscope images of Mo-doped NiFe-LDH and Mn-doped NiFe-LDH catalysts in Comparative Example 2, respectively. It can be seen that NiFe-LDH also has a distinctly uniformly distributed layered nanosheet structure after Mo or Mn doping.

[0041] Figure 2 The image shown is a scanning electron microscope image and elemental composition distribution of the Mo and Mn-doped NiFe LDH catalyst in Example 1. It can be seen that each element (Mo, Mn, Ni, Fe) is uniformly distributed in the catalyst.

[0042] Figure 3 The XRD patterns of the catalysts prepared in each embodiment and comparative example show that NiFe-LDH was successfully grown on nickel foam, exhibiting obvious three strong Ni peaks.

[0043] The catalysts prepared in Examples 1 and Comparative Examples 1-3 were applied to the electrochemical oxygen evolution reaction (OER): Electrochemical performance was tested in a three-electrode system (mercury oxide electrode, carbon rod electrode, and working electrode) and an alkaline electrolyte of 1 mol / L KOH within a voltage range of 0.2-0.9 V. The corresponding electrochemical performance results are as follows: Figure 4-7 As shown; specifically as follows: Figure 4The LSV plots for various catalysts used in the electrochemical oxygen evolution reaction (OER) are shown. The overpotential of the MoMn-NiFe LDH catalyst is only 208 mV at 50 mA and only 226 mV at 100 mA, indicating that the simultaneous doping of Mo and Mn elements accelerates the OER. The overpotential of the Mn-NiFe LDH catalyst at 100 mA is 282 mV, which is lower than that of the MoMn-NiFe LDH catalyst. The overpotential of the Mo-NiFeLDH catalyst at 100 mA is 312 mV, which is lower than that of the MoMn-NiFe LDH catalyst. The overpotential of the NiFe-LDH catalyst at 100 mA is 306 mV, which is lower than that of the MoMn-NiFe LDH catalyst.

[0044] Figure 5 The Tafel slope plots for various catalysts used in the electrochemical oxygen evolution reaction show that the Tafel slope for the MoMn-NiFe LDH catalyst is 21.17 mV dec. -1 The slope of the MoMn-NiFe LDH catalyst is significantly smaller than that of the NiFe-LDH catalyst and other control samples, indicating that the MoMn-NiFe LDH catalyst has the fastest reaction kinetics.

[0045] Figure 6 The calculated Cdl plots were plotted for each catalyst at open-circuit voltage as a function of scan rate. It can be seen that the Cdl value of the MoMn-NiFe LDH catalyst is 1.83, which is significantly higher than that of the NiFe-LDH catalyst and other control samples, indicating that the MoMn-NiFe LDH catalyst has the fastest reaction kinetics.

[0046] Figure 7 The stability diagrams of the various catalysts for the electrochemical oxygen evolution reaction show that the potentials of the Mo and Mn-doped NiFe LDH catalysts remained stable during continuous operation for approximately 100,000 s, demonstrating excellent stability.

[0047] The above description is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A Mo / Mn co-doped NiFe-LDH catalyst for electrocatalytic water splitting, characterized in that: The catalyst is formed by supporting metallic Mo and Mn on a NiFe-LDH support, which is formed by supporting NiFe layered double hydroxides on a nickel foam (NF) substrate.

2. The Mo / Mn co-doped NiFe-LDH catalyst for electrocatalytic water splitting according to claim 1, characterized in that: In this catalyst, the loading of Mo is 2.5-3.0 wt.% and the loading of Mn is 2.5-3.0 wt.%.

3. The Mo / Mn co-doped NiFe-LDH catalyst for electrocatalytic water splitting according to claim 1, characterized in that: In this catalyst, the molar ratio of Mo, Mn, Ni and Fe is (0.7-2.1):(0.1-0.3):(0.9-1.1):(0.9-1.1).

4. The Mo / Mn co-doped NiFe-LDH catalyst for electrocatalytic water splitting according to claim 1, characterized in that: The catalyst is formed by supporting metals Mo, Mn, Ni and Fe on a nickel foam framework to form MoMn-NiFe LDH. The MoMn-NiFe LDH on the nickel foam exhibits an ultrathin cross-linked nanosheet structure without aggregation; the Mo, Mn, Ni and Fe elements in the MoMn-NiFe LDH are uniformly distributed.

5. The method for preparing the Mo / Mn co-doped NiFe-LDH catalyst for electrocatalytic water splitting according to any one of claims 1-4, characterized in that: The method includes the following steps: (1) Pretreatment of nickel foam: The nickel foam was soaked in hydrochloric acid to remove the NiO layer, and then washed repeatedly with deionized water and ethanol alternately. (2) Dissolve nickel nitrate hexahydrate, ferric nitrate nonahydrate and urea in deionized water and stir magnetically until completely dissolved to obtain a mixture containing nickel and iron; (3) Manganese chloride tetrahydrate (MnCl2·4H2O) and ammonium molybdate tetrahydrate ((NH4)6Mo7O) 24 ·4H2O) was added to the mixture obtained in step (2), and stirred at room temperature until completely dissolved to obtain the catalyst precursor; (4) Add the pretreated nickel foam from step (1) to the catalyst precursor obtained in step (3) and place it in a hydrothermal box for hydrothermal treatment; after the hydrothermal treatment, the sample obtained is washed and dried to obtain the Mo, Mn co-doped NiFe-LDH catalyst for electrocatalytic water splitting.

6. The method for preparing the Mo / Mn co-doped NiFe-LDH catalyst for electrocatalytic water splitting according to claim 4, characterized in that: In step (1), the nickel foam has a sheet-like structure; the nickel foam is soaked in hydrochloric acid for 10-20 minutes with a hydrochloric acid concentration of 1 mol / L; and it is washed with deionized water and ethanol alternately 2-5 times.

7. The method for preparing the Mo / Mn co-doped NiFe-LDH catalyst for electrocatalytic water splitting according to claim 4, characterized in that: In step (2), the molar ratio of nickel nitrate hexahydrate, ferric nitrate nonahydrate, and urea is (0.9-1.1):(0.9-1.1):(4-6); the amount of nickel nitrate hexahydrate and ferric nitrate nonahydrate used is determined according to the required load.

8. The method for preparing the Mo / Mn co-doped NiFe-LDH catalyst for electrocatalytic water splitting according to claim 4, characterized in that: In step (3), the molar ratio of Mo, Mn, Ni and Fe elements in the catalyst precursor is (0.7-2.1):(0.1-0.3):(0.9-1.1):(0.9-1.1).

9. The method for preparing the Mo / Mn co-doped NiFe-LDH catalyst for electrocatalytic water splitting according to claim 4, characterized in that: In step (4), the temperature of the hydrothermal treatment is 100-140℃, the holding time is 6-12 hours, and the heating rate is 5-10℃ / min; in step (4), the washing and drying process is as follows: the obtained sample is washed repeatedly with deionized water and ethanol, and the obtained sample is then transferred to an oven for drying.

10. The application of the Mo / Mn co-doped NiFe-LDH catalyst for electrocatalytic water splitting according to claim 1, characterized in that: This catalyst is used for the electrocatalytic splitting of water to produce oxygen.

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