Preparation and application of MnOx-modified NiCoP nanosheet array material

Abstract

The invention provides a MnOx modified NiCoP nanosheet array material and a preparation method of the MnOx modified NiCoP nanosheet array material. The invention provides a MnOx modified NiCoP nanosheet array material and a preparation method thereof, and the preparation method comprises the following steps: dissolving cobalt salt and 2-methylimidazole in deionized water, adding foamed nickel, and reacting at room temperature to obtain a Co-MOF precursor; then adding the precursor into a nickel source solution, and standing at room temperature to obtain NiCo-LDH; the preparation method comprises the following steps: placing anhydrous sodium hypophosphite and NiCo-LDH in an argon atmosphere together, and heating to obtain a NiCoP nanosheet array; and finally, the NiCoP nanosheet array is placed in a uniform solution containing a manganese source, and the MnOx modified NiCoP nanosheet array material is finally obtained through electro-deposition. The three-dimensional structure of the nanosheet array can fully expose active sites, and MnOx modification can improve the conductivity of the material and regulate and control the electronic structure, thereby improving the intrinsic activity of electrolyzed water. Practice shows that the material shows excellent overpotential and stability when being used as an electrolytic water electrode material.

Description

Technical Field

[0001] The present invention belongs to the cross-field of nano material preparation method and electrochemical application, and specifically relates to a MnO x Modified NiCoP nanosheet array material and preparation method thereof. Background Art

[0002] Hydrogen energy has attracted widespread attention as a promising clean energy source because it does not release carbon dioxide when used and has high energy density. Water electrolysis is an effective method to produce high-purity hydrogen through the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) at the cathode and anode, respectively. The development of cheap and efficient water electrolysis electrode materials is the key to improving the efficiency of water electrolysis.

[0003] Transition metal phosphide materials have relatively high activity for both HER and OER and have received increasing attention in recent years. However, their electrocatalytic activity and stability still need to be optimized to meet the requirements of industrial applications. Constructing micro-nanostructures to fully expose active sites is an effective way to improve electrocatalysis; modulating the electronic structure through composite metal oxides is one of the effective channels to further improve the efficiency of hydrogen production by water electrolysis. Summary of the invention

[0004] In order to solve the above technical problems, the present invention adopts a simple and low-cost preparation method to achieve a MnO x Preparation of modified NiCoP nanosheet array materials. First, using metal organic framework (Co-MOF) as a template, NiCoP nanosheet array materials were obtained by doping and phosphating nickel metal to fully expose active sites and improve electrocatalytic activity. x Modification can effectively improve the electron transfer efficiency of the material and thus improve the efficiency of hydrogen production by water electrolysis by regulating the electronic structure without affecting the original surface active sites of the material.

[0005] Therefore, MnO x The modified NiCoP nanosheet array material is widely used in the field of water electrolysis and is an ideal electrode material.

[0006] The present invention provides a MnO x The method for preparing the modified NiCoP nanosheet array material comprises the following steps:

[0007] (1) After dissolving cobalt salt and 2-methylimidazole in deionized water, adding the cleaned nickel foam, standing for reaction at room temperature for 4 hours, washing with distilled water and drying in a forced air drying oven to obtain a Co-MOF precursor;

[0008] (2) placing the Co-MOF precursor in 100 mL of nickel source aqueous solution for room temperature ion exchange reaction to obtain a porous NiCo-LDH nanosheet array;

[0009] (3) NiCo-LDH is placed in a porcelain boat, the surface of which is evenly covered with anhydrous sodium hypophosphite powder, and a NiCoP nanosheet array is obtained by a phosphating reaction in an argon atmosphere;

[0010] (4) dissolving manganese salt and sodium acetate in deionized water, and then immersing the NiCoP nanosheet array, platinum sheet and saturated calomel electrode prepared in step (3) into the above solution to assemble a three-electrode electrolytic cell, and obtaining MnO by electrodeposition. x Modified NiCoP nanosheet array material (abbreviated as MnO x / NiCoP).

[0011] In the step (1), the type of cobalt salt is not limited, including cobalt chloride, cobalt nitrate, cobalt acetate, etc., but cobalt nitrate hexahydrate is most preferred;

[0012] In the step (1), the molar ratio of cobalt nitrate hexahydrate to 2-methylimidazole is (1-3):(7-9), but the optimal ratio is 3:8;

[0013] In step (1), the volume of deionized water used is 50-100 mL, but most preferably 80 mL;

[0014] In the step (2), the type of nickel source is not limited, including nickel nitrate nonahydrate, nickel chloride hexahydrate, and nickel sulfate hexahydrate, but nickel nitrate nonahydrate is most preferred;

[0015] In the step (2), the ion exchange time at room temperature is 6-48 hours, but most preferably 24 hours;

[0016] In the step (3), the phosphating reaction temperature is 300-450°C, but most preferably 350°C;

[0017] In the step (3), the phosphating reaction time is 1-8 hours, but most preferably 3 hours;

[0018] In the step (4), the type of manganese source is not limited, including one or more of manganese chloride, manganese sulfate, manganese acetate, and manganese nitrate, but manganese sulfate is most preferred;

[0019] In the step (4), the electrodeposition current density is 0.1-5 mA / cm 2 , but most preferably 0.5 mA / cm 2 ;

[0020] In the step (4), the electrodeposition time is 30-180 seconds, but most preferably 80 seconds.

[0021] In summary, the present invention provides a MnO x The modified NiCoP nanosheet array material has the following beneficial effects:

[0022] (1) The raw material cost required to prepare NiCoP nanosheet arrays is low and the synthesis process is simple. Not only does the NiCoP material itself have good conductivity, but it also has rich redox reactions and strong electrochemical activity. Its hollow internal structure can well adapt to the volume expansion problem in the reaction. At the same time, the additionally abundant nanosheets on the surface provide more specific surface area and expose more active sites. NiCoP is treated with semiconductor material MnO x The modification can increase the redox reaction sites without affecting the morphology and active site state of the original electrode material. The interface effect can modulate the electronic structure, shorten the ion diffusion path, enhance the synergistic effect of different components, and further improve the electrolysis efficiency of the electrode material. Therefore, the material can be improved in many aspects such as overpotential reduction and stability.

[0023] (2) MnO prepared by the present invention x The modified NiCoP nanosheet array material exhibited low overpotential and excellent stability in electrochemical tests. -2 At a current density of 10 mA / cm2, the electrode material showed an overpotential of 93 mV for HER and 240 mV for OER. When the material was used as the cathode and anode to assemble a full water splitter, the overpotential was 240 mV for OER. 2 At a current density of , it showed a voltage of 1.59 V, and the voltage remained constant for 200 hours. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a scanning electron microscope image of the Co-MOF prepared in step (1) of Example 1 of the present invention;

[0025] Figure 2 This is a scanning electron microscope image of NiCo-LDH prepared in step (2) of Example 1 of the present invention;

[0026] Figure 3 This is a scanning electron microscope image of NiCoP prepared in step (3) of Example 1 of the present invention;

[0027] Figure 4 MnO prepared in step (4) of Example 1 of the present invention x / SEM image of NiCoP nanosheet array material;

[0028] Figure 5 MnO prepared in step (4) of Example 1 of the present invention x / Comparison of X-ray diffraction pattern of NiCoP nanosheet array material and standard card;

[0029] Figure 6 MnO prepared in step (4) of Example 1 of the present invention x Electrochemical performance of NiCoP nanosheet array material as electrode material in 1M KOH electrolyte solution. The left figure is the linear scanning voltammetry curve of HER at a scan rate of 2mV / s, and the right figure is the linear scanning voltammetry curve of HER at a scan rate of 10mA / cm 2 Chronoamperometry plots at current density;

[0030] Figure 7 MnO prepared in step (4) of Example 1 of the present invention x Electrochemical performance of NiCoP nanosheet array material as electrode material in 1M KOH electrolyte solution. The left figure is the linear scanning voltammetry curve of OER at a scan rate of 2mV / s, and the right figure is the linear scanning voltammetry curve of OER at a scan rate of 10mA / cm 2 Chronoamperometry plots at current density;

[0031] Figure 8 MnO prepared in step (4) of Example 1 of the present invention x Electrochemical performance of NiCoP nanosheet array materials as cathode and anode electrode materials in 1M KOH electrolyte solution. The left figure is the linear sweep voltammetry curve of the overall hydrolysis reaction at a scan rate of 2mV / s, and the right figure is the linear sweep voltammetry curve of the overall hydrolysis reaction at a scan rate of 10mA / cm 2 Chronoamperometry plots at different current densities. DETAILED DESCRIPTION

[0032] The preferred embodiments of the present invention are described in further detail below with reference to the accompanying drawings and examples.

[0033] Example 1

[0034] A MnO x The method for preparing the modified NiCoP nanosheet array material comprises the following steps:

[0035] (1) 0.582 g of cobalt nitrate hexahydrate and 1.313 g of 2-methylimidazole were dissolved in 80 mL of deionized water to obtain a reaction solution. The cleaned nickel foam was placed in the reaction solution, reacted at room temperature for 4 h, washed with distilled water, and then dried in a forced air drying oven to obtain a Co-MOF precursor, the scanning electron microscopy image of which is shown in FIG. Figure 1 As shown, the nanosheet morphology is smooth and has a certain thickness;

[0036] (2) The Co-MOF precursor was placed in 100 mL of an aqueous solution containing 0.291 g of nickel nitrate nonahydrate and allowed to stand at room temperature for 24 hours to obtain a nanosheet-modified NiCo-LDH nanosheet array, as shown in the scanning electron microscope image. Figure 2 As shown, the surface of the nanosheet is decorated with a large number of small nanosheet structures and the surface is rough;

[0037] (3) NiCo-LDH was placed in a porcelain boat and covered with 1.0 g of anhydrous sodium hypophosphite powder. The porcelain boat was then placed in a tube furnace and heated to 350°C at a heating rate of 4°C / min under an argon atmosphere. After reacting for 3 hours, a NiCoP nanosheet array was obtained. The scanning electron microscope image is shown in FIG. Figure 3 As shown, it presents a nanosheet-encapsulated nanosheet structure, and the nanosheet is slightly damaged;

[0038] (4) 15 mmol of anhydrous manganese sulfate and 30 mmol of sodium acetate were dissolved in 100 mL of deionized water, and then the NiCoP nanosheet array, platinum sheet and saturated calomel electrode prepared in step (3) were immersed in the above solution to assemble a three-electrode electrolytic cell. 2 MnO was obtained by electroplating at a current density of 80 s. x Modified NiCoP nanosheet array material (abbreviated as MnO x / NiCoP), the scanning electron microscope image of which is shown in Figure 4 As shown, a nanosheet-wrapped nanosheet structure is presented.

[0039] The MnO prepared in the above steps x / NiCoP X-ray diffraction pattern, such as Figure 4 As shown; most of the diffraction peaks belong to NiCoP (JCPDS No.71-2336) and some of the diffraction peaks belong to Ni 12 P 5 (JCPDS No.22-1190).

[0040] The MnO x / NiCoP was used as HER electrode material, and its electrochemical performance was tested in 1M KOH electrolyte solution. Figure 5 The left figure is the linear scanning voltammetry curve at a scan rate of 2mV / s, 10mA / cm 2 The overpotential is 93mV in the lower figure and 10mA / cm in the right figure. 2 Chronopotentiometry analysis at current density.

[0041] The MnO x / NiCoP was used as an OER electrode material, and its electrochemical performance was tested in 1M KOH electrolyte solution. Figure 6The left figure is the linear scanning voltammetry curve at a scan rate of 2mV / s, 10mA / cm 2 The overpotential is 240mV in the lower figure and 10mA / cm in the right figure. 2 Chronopotentiometry analysis at current density.

[0042] The above-prepared MnO x / NiCoP were used as cathode and anode to assemble water electrolysis devices, and their electrochemical performance was tested in 1M KOH electrolyte solution. Figure 7 The left figure is the linear scanning voltammetry curve at a scan rate of 2mV / s, and the right figure is the linear scanning voltammetry curve at a scan rate of 10mA / cm 2 Chronopotentiometry at current density. At 10 mA / cm 2 Under the condition of full hydrolysis, the decomposition voltage is 1.59V, and the voltage is constant after 200 hours of continuous testing.

[0043] Example 2

[0044] (1) 0.582 g of cobalt nitrate hexahydrate and 1.313 g of 2-methylimidazole were dissolved in 100 mL of deionized water to obtain a reaction solution, and the cleaned nickel foam was placed in the reaction solution, reacted at room temperature for 4 h, washed with distilled water, and then dried in a forced air drying oven to obtain a Co-MOF precursor;

[0045] (2) placing the Co-MOF precursor in 100 mL of an aqueous solution containing 0.291 g of nickel nitrate nonahydrate at room temperature for 12 hours to obtain a nanosheet-modified NiCo-LDH nanosheet array;

[0046] (3) NiCo-LDH was placed in a porcelain boat and the surface was covered with 1.0 g of anhydrous sodium hypophosphite powder; the porcelain boat was then placed in a tube furnace and heated to 300°C at a heating rate of 4°C / min under an argon atmosphere. After reacting for 2 hours, a NiCoP nanosheet array was obtained;

[0047] (4) 15 mmol of anhydrous manganese sulfate and 30 mmol of sodium acetate were dissolved in 100 mL of deionized water, and then the NiCoP nanosheet array, platinum sheet and saturated calomel electrode prepared in step (3) were immersed in the above solution to assemble a three-electrode electrolytic cell. 2 MnO was obtained by electroplating at a current density of 80 s. x Modified NiCoP nanosheet array material (abbreviated as MnO x / NiCoP).

[0048] The above-prepared MnO x / NiCoP was used as cathode and anode to assemble water electrolysis devices, and their electrochemical performance was tested in 1M KOH electrolyte solution.2 The full water decomposition voltage is 1.63V.

[0049] Example 3

[0050] (1) 0.582 g of cobalt nitrate hexahydrate and 1.313 g of 2-methylimidazole were dissolved in 100 mL of deionized water to obtain a reaction solution, and the cleaned nickel foam was placed in the reaction solution, reacted at room temperature for 4 h, washed with distilled water, and then dried in a forced air drying oven to obtain a Co-MOF precursor;

[0051] (2) placing the Co-MOF precursor in 100 mL of an aqueous solution containing 0.582 g of nickel nitrate nonahydrate at room temperature for 12 hours to obtain a nanosheet-modified NiCo-LDH nanosheet array;

[0052] (3) NiCo-LDH was placed in a porcelain boat and the surface was covered with 1.0 g of anhydrous sodium hypophosphite powder; the porcelain boat was then placed in a tube furnace and heated to 300°C at a heating rate of 4°C / min under an argon atmosphere. After reacting for 2 hours, a NiCoP nanosheet array was obtained;

[0053] (4) 15 mmol of anhydrous manganese sulfate and 30 mmol of sodium acetate were dissolved in 100 mL of deionized water, and then the NiCoP nanosheet array, platinum sheet and saturated calomel electrode prepared in step (3) were immersed in the above solution to assemble a three-electrode electrolytic cell. 2 MnO was obtained by electrodeposition at a current density of 80 s. x Modified NiCoP nanosheet array material (abbreviated as MnO x / NiCoP).

[0054] The above-prepared MnO x / NiCoP was used as cathode and anode to assemble water electrolysis devices, and their electrochemical performance was tested in 1M KOH electrolyte solution. 2 The full water decomposition voltage is 1.70V.

[0055] Example 4

[0056] (1) 0.582 g of cobalt nitrate hexahydrate and 1.313 g of 2-methylimidazole were dissolved in 100 mL of deionized water to obtain a reaction solution, and the cleaned nickel foam was placed in the reaction solution, reacted at room temperature for 6 h, washed with distilled water, and then dried in a forced air drying oven to obtain a Co-MOF precursor;

[0057] (2) placing the Co-MOF precursor in 100 mL of an aqueous solution containing 0.291 g of nickel nitrate nonahydrate at room temperature for 24 hours to obtain a nanosheet-modified NiCo-LDH nanosheet array;

[0058] (3) NiCo-LDH was placed in a porcelain boat, the surface of which was covered with 1.5 g of anhydrous sodium hypophosphite powder, and then the porcelain boat was placed in a tube furnace and heated to 300 °C at a heating rate of 4 °C / min under an argon atmosphere. After reacting for 4 hours, a NiCoP nanosheet array was obtained;

[0059] (4) 15 mmol of anhydrous manganese sulfate and 30 mmol of sodium acetate were dissolved in 100 mL of deionized water, and then the NiCoP nanosheet array, platinum sheet and saturated calomel electrode prepared in step (3) were immersed in the above solution to assemble a three-electrode electrolytic cell. 2 MnO was obtained by electroplating at a current density of 100 s. x Modified NiCoP nanosheet array material (abbreviated as MnO x / NiCoP).

[0060] The MnO x / NiCoP was used as cathode and anode to assemble water electrolysis devices, and their electrochemical performance was tested in 1M KOH electrolyte solution. 2 The full water decomposition voltage is 1.68V.

[0061] Example 5

[0062] (1) 0.582 g of cobalt nitrate hexahydrate and 1.313 g of 2-methylimidazole were dissolved in 100 mL of deionized water to obtain a reaction solution, and the cleaned nickel foam was placed in the reaction solution, reacted at room temperature for 6 h, washed with distilled water, and then dried in a forced air drying oven to obtain a Co-MOF precursor;

[0063] (2) placing the Co-MOF precursor in 100 mL of an aqueous solution containing 0.582 g of nickel nitrate nonahydrate at room temperature for 12 hours to obtain a nanosheet-modified NiCo-LDH nanosheet array;

[0064] (3) NiCo-LDH was placed in a porcelain boat and covered with 1.0 g of anhydrous sodium hypophosphite powder; the porcelain boat was then placed in a tube furnace and heated to 350°C at a heating rate of 4°C / min under an argon atmosphere; after reacting for 2 hours, a NiCoP nanosheet array was obtained;

[0065] (4) 30 mmol of anhydrous manganese sulfate and 30 mmol of sodium acetate were dissolved in 100 mL of deionized water, and then the NiCoP nanosheet array, platinum sheet and saturated calomel electrode prepared in step (3) were immersed in the above solution to assemble a three-electrode electrolytic cell. 2 MnO was obtained by electroplating at a current density of 1000 nm for 120 s.x Modified NiCoP nanosheet array material (abbreviated as MnO x / NiCoP).

[0066] The MnO x / NiCoP was used as cathode and anode to assemble water electrolysis devices, and their electrochemical performance was tested in 1M KOH electrolyte solution. 2 The full water decomposition voltage is 1.65V.

[0067] The embodiments described above are detailed descriptions of the technical solutions 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 that the present invention should enjoy.

Claims

1. A MnO x Modified NiCoP nanosheet array material and preparation method thereof, It is characterized in that The preparation method comprises the following steps: (1) 0.582 g of cobalt nitrate hexahydrate and 1.313 g of 2-methylimidazole were dissolved in 80 mL of deionized water to obtain a reaction solution, and the cleaned nickel foam was placed in the reaction solution, reacted at room temperature for 4 h, washed with distilled water, and then dried in a forced air drying oven to obtain a Co-MOF precursor; (2) placing the Co-MOF precursor in 100 mL of an aqueous solution containing 0.291 g of nickel nitrate nonahydrate at room temperature for 24 hours to obtain a NiCo-LDH nanosheet array; (3) NiCo-LDH was placed in a porcelain boat, and the surface was covered with 1.0 g of anhydrous sodium hypophosphite powder. The porcelain boat was then placed in a tube furnace and heated to 350°C at a heating rate of 4°C / min under an argon atmosphere. After reacting for 3 hours, a NiCoP nanosheet array was obtained. (4) 15 mmol of anhydrous manganese sulfate and 30 mmol of sodium acetate were dissolved in 100 mL of deionized water, and then the NiCoP nanosheet array, platinum sheet and saturated calomel electrode prepared in step (3) were immersed in the above solution to assemble a three-electrode electrolytic cell. 2 MnO was obtained by electrodeposition at a current density of 80 s. x Modified NiCoP nanosheet array materials.

2. MnO prepared by the preparation method according to claim 1 x Modified NiCoP nanosheet array material, Features The material consists of MnO x The modification was constructed on the surface of NiCoP nanosheet arrays.

3. MnO prepared by the preparation method according to claim 1 x Use of modified NiCoP nanosheet array materials as electrode materials for water electrolysis.

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