Electrocatalytic water decomposition device with nickel hydroxide / amorphous black phosphorus electrode

Abstract

The invention discloses a nickel hydroxide / amorphous black phosphorus electrode electro-catalysis water decomposition device, and belongs to the technical field of electrochemistry. By constructing black phosphorus-based transition metal oxide interface electron transport engineering, an amorphous black phosphorus and beta-nickel hydroxide compounded efficient OER catalytic system is designed, and the preparation method has the advantages that the preparation method is simple and convenient, interface regulation and control are accurate and the like. Compared with a single beta-nickel hydroxide catalyst, the introduction of black phosphorus significantly enhances the electron transport capability and structural stability of the composite material, thereby enhancing the catalytic activity and stability. Compared with crystalline black phosphorus, the amorphous black phosphorus has higher carrier mobility, so that the interface charge transfer is further enhanced, the dynamic maintenance of active sites is promoted, and the continuous high efficiency of the reaction process is ensured. The electro-catalysis water decomposition device constructed by the invention can efficiently promote decomposition of water molecules under an illumination condition, and provides feasibility for constructing a solar-driven water decomposition system.

Description

TECHNICAL FIELD

[0001] The application relates to the field of electrochemistry, in particular to a nickel hydroxide / amorphous black phosphorus electrode electrocatalytic water splitting device. BACKGROUND

[0002] With the global energy structure transforming towards clean and low carbon, hydrogen energy has become an important energy type due to its high energy density and zero carbon emission. Among them, the electrocatalytic water splitting technology as the core path of green hydrogen production can realize the efficient conversion of electric energy to hydrogen energy. However, the overall efficiency of the technology is limited by the high overpotential and slow reaction kinetics of the anode oxygen evolution reaction (OER). Although the noble metal-based catalysts show excellent OER catalytic activity, their resource scarcity and high cost seriously limit large-scale application. Therefore, it has important scientific research value and commercialization potential to develop efficient, stable and economical non-noble metal-based OER electrocatalysts.

[0003] Among the many non-noble metal catalysts, transition metal-based materials are widely studied due to their high catalytic activity. Under the action of anode potential, such materials will undergo surface reconstruction to form high-valence metal oxides and act as active centers for OER. However, if the metal is excessively oxidized, it will affect the reaction stability of the catalyst. Studies have shown that the electron-proton transfer rate on the surface of the catalyst has an important influence on the metal oxidation process and its stability. When the electron-proton transfer process is relatively fast, the electrons lost during metal oxidation can be compensated by the electrons released by oxygen atoms during water oxidation, effectively inhibiting the risk of excessive oxidation of the metal; in this case, the metal oxidation and water oxidation processes are closely connected and almost simultaneous. On the contrary, if the electron-proton transfer kinetics at the active sites of the catalyst is slow, the metal will continue to lose electrons and be continuously oxidized, requiring higher voltage to restore electron balance, resulting in a clear platform region between the metal oxidation peak and the water oxidation reaction. Therefore, it is necessary to optimize the charge transfer behavior at the catalyst interface to improve the electron-proton transfer kinetics process, so as to narrow the potential interval between the metal oxidation peak and the water splitting reaction, thereby improving the stability of the overall catalytic system. SUMMARY

[0004] The present application aims to provide a nickel hydroxide / amorphous black phosphorus electrode electrocatalytic water splitting device to solve the above problems in the background art. The present application designs a nickel hydroxide / amorphous black phosphorus electrode material with high catalytic performance, which is prepared by loading the oxygen evolution reaction (OER) electrocatalyst of nickel hydroxide / amorphous black phosphorus on a carbon paper substrate. By effectively regulating the microstructure of the electrode and the interface electron transport engineering, the interface charge transfer rate is accelerated, the excessive oxidation and dissolution of the metal Ni are effectively inhibited, and the catalytic activity and stability of the electrode material are significantly improved compared with the unmodified electrocatalyst. The electrocatalytic water splitting device built in the present application can efficiently promote the decomposition of water molecules under light conditions, providing feasibility for constructing a solar-driven water splitting system.

[0005] To achieve the above-mentioned purpose, the present application provides the following technical scheme:

[0006] One of the technical schemes of the present application: a preparation method of a nickel hydroxide / amorphous black phosphorus electrode is provided, comprising the following steps:

[0007] 0.5 g red phosphorus powder is added to 75 mL ethylenediamine for intercalation reaction to obtain ethylenediamine intercalated crystalline black phosphorus;

[0008] The ethylenediamine intercalated crystalline black phosphorus is mixed with water for heating reaction to obtain amorphous black phosphorus;

[0009] The amorphous black phosphorus is mixed with β-nickel hydroxide powder in a dispersant to obtain a dispersion liquid, which is dried to obtain a nickel hydroxide / amorphous black phosphorus mixed powder;

[0010] The nickel hydroxide / amorphous black phosphorus mixed powder is loaded on an electrode substrate to obtain the nickel hydroxide / amorphous black phosphorus electrode.

[0011] Preferably, the amount ratio of the red phosphorus powder to ethylenediamine is 0.5 g:75 mL; the temperature of the intercalation reaction is 165 ℃, and the time is 24 h.

[0012] Preferably, the amount ratio of the ethylenediamine intercalated crystalline black phosphorus to water is 0.4 g:70 mL; the temperature of the heating reaction is 160 ℃, and the time is 24 h.

[0013] Preferably, the amount ratio of the amorphous black phosphorus, β-nickel hydroxide and dispersant is 5 mg:80 mg:10 mL; the dispersant is ethanol; and the drying treatment is vacuum drying at 50 ℃ for 12 h.

[0014] Preferably, the electrode substrate is carbon paper, and the loading amount of the nickel hydroxide / amorphous black phosphorus mixed powder on the electrode substrate is 1 mg cm -2 .

[0015] Preferably, the preparation method of the beta-nickel hydroxide powder comprises the following steps: dissolving 2 mmol of nickel nitrate into 40 mL of water, then adding 4 mL of oleylamine, 20 mL of ethanol, heating at 190 DEG C for 16 h, crushing, and obtaining the beta-nickel hydroxide powder.

[0016] The second technical scheme of the present application provides a nickel hydroxide / amorphous black phosphorus electrode obtained by the above preparation method.

[0017] The third technical scheme of the present application provides an application of the above nickel hydroxide / amorphous black phosphorus electrode in the field of electrocatalytic water splitting.

[0018] The fourth technical scheme of the present application provides a device for electrocatalytic water splitting, wherein the above nickel hydroxide / amorphous black phosphorus electrode is used as the electrode material of the device.

[0019] Preferably, a solar cell panel is connected to the device, and the light energy is converted into electrical energy by the solar cell panel to power the circuit of the device.

[0020] The beneficial technical effects of the present application are as follows:

[0021] The present application designs a high-efficiency OER catalytic system of amorphous black phosphorus and beta-nickel hydroxide composite by constructing a black phosphorus-based transition metal oxide interface electron transport project, which has the advantages of simple preparation method and precise interface regulation. Compared with a single beta-nickel hydroxide catalyst, the introduction of black phosphorus significantly enhances the electron transport capacity and structural stability of the composite material, thereby improving the catalytic activity and stability. Compared with crystalline black phosphorus, amorphous black phosphorus has higher carrier mobility, which further enhances the interface charge transfer and promotes the dynamic maintenance of active sites, ensuring the continuous efficiency of the reaction process.

[0022] The electrochemical test results show that the nickel hydroxide / amorphous black phosphorus electrode of the present application has a potential of only 332 mV at a current density of 10 mA·cm -2 The electrochemical stability (120 h) and high resistance to metal dissolution are excellent. The loading of amorphous black phosphorus shortens the distance between the metal oxidation peak and the OER starting potential, significantly accelerates the interface charge transfer rate, effectively inhibits the excessive oxidation and dissolution of Ni 3+ , improves the activity and stability of the catalyst, and ultimately improves the efficiency of the entire electrocatalytic water splitting device. The nickel hydroxide / amorphous black phosphorus electrode realizes a solar-hydrogen energy conversion efficiency (η STH), which is 89.8% higher than that of β-Ni(OH)2(3.42%) and has a nearly 100% Faraday efficiency. Therefore, the constructed black phosphorus-based composite catalytic system has high activity, high stability and excellent solar-hydrogen energy conversion characteristics, which is helpful to promote the application and development of high-efficiency OER catalytic system in the field of actual energy conversion. BRIEF DESCRIPTION OF DRAWINGS

[0023] In order to more clearly illustrate the technical solutions of the embodiments of the present application or the prior art, the drawings needed in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor on the basis of these drawings.

[0024] Figure 1 is the X-ray diffraction (XRD) spectrum of β-Ni(OH)2, ethylenediamine intercalated crystalline black phosphorus, amorphous black phosphorus, Ni(OH)2 / amorphous black phosphorus mixed powder in Example 1 and Ni(OH)2 / ethylenediamine intercalated crystalline black phosphorus mixed powder in Comparative Example 1;

[0025] Figure 2 is the transmission electron microscopy (TEM) image of (a) β-Ni(OH)2, (c) Ni(OH)2 / amorphous black phosphorus mixed powder in Example 1 and (b) Ni(OH)2 / ethylenediamine intercalated crystalline black phosphorus mixed powder in Comparative Example 1;

[0026] Figure 3 is the Raman spectrum of β-Ni(OH)2, Ni(OH)2 / amorphous black phosphorus mixed powder in Example 1 and Ni(OH)2 / ethylenediamine intercalated crystalline black phosphorus mixed powder in Comparative Example 1;

[0027] Figure 4 is the OER performance of Ni(OH)2 / amorphous black phosphorus electrode in Example 1, Ni(OH)2 / ethylenediamine intercalated crystalline black phosphorus electrode in Comparative Example 1 and β-Ni(OH)2 electrode in Comparative Example 2 in 1 M KOH electrolyte; wherein (a) is the linear sweep voltammetry (LSV) test curve, (b) is the overpotential when the current density is 10 mA cm-2, (c) is the Tafel slope, and (d) is the electrochemical stability when the current density is 10 mA cm-2. -2 -2

[0028] Figure 5 ​​The Ni concentration determined by inductively coupled plasma mass spectrometry (ICP-MS) after the nickel hydroxide / amorphous black phosphorus electrode in Example 1, the nickel hydroxide / ethylenediamine intercalated crystalline black phosphorus electrode in Comparative Example 1, and the β-nickel hydroxide electrode in Comparative Example 2 were reacted in 1 M KOH electrolyte for 2 h;

[0029] Figure 6 The LSV curves of the nickel hydroxide / amorphous black phosphorus electrode in Example 1, the nickel hydroxide / ethylenediamine intercalated crystalline black phosphorus electrode in Comparative Example 1, and the β-nickel hydroxide electrode in Comparative Example 2, and the potential difference from the oxidation peak to the OER starting potential thereof;

[0030] Figure 7 The Nyquist plots obtained by electrochemical impedance spectroscopy (EIS) test of the nickel hydroxide / amorphous black phosphorus electrode in Example 1, the nickel hydroxide / ethylenediamine intercalated crystalline black phosphorus electrode in Comparative Example 1, and the β-nickel hydroxide electrode under 1.2 V-1.7 V bias, and the corresponding phase angle change; wherein (a), (b), (c) are the Nyquist plots of the nickel hydroxide / ethylenediamine intercalated crystalline black phosphorus electrode, the β-nickel hydroxide electrode, and the nickel hydroxide / amorphous black phosphorus electrode, respectively, and (d) is the phase angle change;

[0031] Figure 8 is a structural schematic diagram of the photo-assisted electrocatalytic water splitting device of the present application;

[0032] Figure 9 is the current-voltage (J-V) characteristic curve of the photo-assisted electrocatalytic water splitting device prepared by using the nickel hydroxide / amorphous black phosphorus electrode in Example 1, the nickel hydroxide / ethylenediamine intercalated crystalline black phosphorus electrode in Comparative Example 1, and the β-nickel hydroxide electrode in Comparative Example 2.

[0033] Figure 10 is the H2 and O2 production curve diagram of the photo-assisted electrocatalytic water splitting device prepared by using the nickel hydroxide / amorphous black phosphorus electrode in Example 1 under 0 V bias. DETAILED DESCRIPTION

[0034] The detailed description set forth below is intended as a description of various example embodiments of the application and is not intended to represent the only embodiments in which the application can be practiced. It is also not intended to represent that the application cannot be practiced except as set forth in the following description and / or except as set forth in the claims below. It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting.

[0035] Also, for ranges of values, the disclosure herein also contemplates each and every value and sub-range within the range. For example, where a range of values is provided, it is intended to encompass each and every value and sub-range within the range. Further, where a range of values is provided, it is intended to encompass each and every value and sub-range within the range. These smaller ranges are merely examples of the larger range and are not intended to limit the scope of the disclosure to those ranges. The upper and lower limits of those smaller ranges can independently be included or excluded in the range.

[0036] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present application, preferred methods and materials are described. It is intended that the application not be limited to the specific methods and materials described herein.

[0037] With respect to the terms "comprising", "including", "containing", "having" and the like, these terms are used inclusively and are intended to mean that items can be added to those items already present.

[0038] The present application discloses a preparation method of a nickel hydroxide / amorphous black phosphorus electrode, comprising the following steps:

[0039] (1) Preparation of β-nickel hydroxide (β-Ni(OH)2) sample: first, 0.582 g (2.0 mmol) of nickel nitrate hexahydrate (Ni(NO3)2·6H2O) is dissolved in 40 mL of deionized water to form a clear green solution under magnetic stirring; 4 mL of oleylamine is quickly injected into the green solution, then 20 mL of ethanol is added, stirred for 30 min, and then the mixed solution is transferred to a polytetrafluoroethylene liner with a volume of 100 mL and placed in a corresponding stainless steel autoclave, heated to 190 ℃ and kept for 16 h; after the reaction is completed, it is naturally cooled to room temperature, and the obtained green sample is collected, washed with cyclohexane, distilled water and ethanol respectively, and then vacuum dried at 50 ℃ for 12 h to obtain β-nickel hydroxide;

[0040] (2) Preparation of ethylenediamine intercalated crystalline black phosphorus (eda-BP): ethylenediamine intercalated crystalline black phosphorus is prepared by a solvothermal method; first, 0.5 g of red phosphorus is ground into powder in a mortar, then it is added to 75 mL of ethylenediamine solution, stirred vigorously for 30 min, and then the mixture is transferred to a polytetrafluoroethylene liner with a volume of 100 mL and placed in a corresponding stainless steel autoclave; the stainless steel autoclave is placed in a constant temperature air drying oven, and the temperature is set to 165 ℃, heated for 24 h; after heating is completed, it is quickly cooled to room temperature using ice water, the precipitate product is collected, washed with water and ethanol alternately, and then dried under vacuum at 40 ℃ for 6 hours to obtain ethylenediamine intercalated crystalline black phosphorus;

[0041] (3) Preparation of amorphous black phosphorus: using a hydrothermal reaction method to remove ethylenediamine molecules between the interlayers of the ethylenediamine intercalated crystalline black phosphorus, destroy the intercalation structure and make the P-P bond twisted, thereby preparing amorphous black phosphorus; 0.4 g of the ethylenediamine intercalated crystalline black phosphorus and 70 mL of deionized water are added into a polytetrafluoroethylene liner with a volume of 100 mL, and the liner is placed in a corresponding stainless steel reaction kettle; the reaction kettle is placed in a constant temperature air oven, and the temperature is set to 160 ℃, and heated for 24 h; after the reaction is completed, the precipitate product is collected, washed with deionized water, and dried at 40 ℃ under vacuum for 12 h to obtain amorphous black phosphorus;

[0042] (4) Preparation of nickel hydroxide / amorphous black phosphorus: using an ultrasonic dispersion method to prepare nickel hydroxide / amorphous black phosphorus; first, the amorphous black phosphorus and the beta-nickel hydroxide are ground into powders in a mortar, 5 mg of amorphous black phosphorus powder and 80 mg of beta-nickel hydroxide powder are taken, and are dispersed into 10 mL of an ethanol solution, and the solution is placed in an ultrasonic cleaner for ultrasonic treatment to ensure the dispersion and combination of the nickel hydroxide and the amorphous black phosphorus, and a uniform dispersion liquid is obtained; the dispersion liquid is placed in a vacuum drying box and dried at 50 ℃ for 12 h, and after grinding, a dry nickel hydroxide / amorphous black phosphorus mixed powder is obtained;

[0043] (5) Preparation of a working electrode (beta-Ni(OH)2@a-BP): carbon paper (1.0 cm x 2.0 cm) is placed in anhydrous ethanol and cleaned under ultrasonic conditions for 10 min, and then the surface is washed with deionized water to remove surface oxides and contaminants, and is placed in a vacuum drying box at 60 ℃ for drying, to obtain pretreated carbon paper; 5 mg of the nickel hydroxide / amorphous black phosphorus mixed powder is dissolved in 600 μL of anhydrous ethanol, and then 5 μL of a Nafion binder is added, and a uniform catalyst slurry is obtained by stirring and ultrasonic treatment, and then 121 μL of the catalyst slurry is uniformly dropped onto a pretreated carbon paper with an area of 1 cm x 1 cm (catalyst loading: 1 mg cm -2 ), and the carbon paper is used as a catalyst carrier to obtain the nickel hydroxide / amorphous black phosphorus electrode.

[0044] The present application aims to destroy the layered lattice of eda-BP and make it amorphous, so as to obtain amorphous black phosphorus with rich defects and active sites.

[0045] Further, in steps (1)-(3): the washing condition is centrifugal washing at a speed of 9000-10000 rpm for 6-10 min.

[0046] Further, the frequency of the ultrasonic treatment in step (4) is 40-60 kHz, and the ultrasonic time is 8-12 min.

[0047] The application further discloses a nickel hydroxide / amorphous black phosphorus electrode prepared by the preparation method.

[0048] The application further discloses a device for electrocatalytic water decomposition to produce hydrogen, wherein the nickel hydroxide / amorphous black phosphorus electrode is used as an electrode material of the device.

[0049] Further, the device for electrocatalytic water decomposition to produce hydrogen comprises the following steps: taking the nickel hydroxide / amorphous black phosphorus electrode as an anode, taking a graphite rod as a cathode, taking 1 M KOH solution as an electrolyte, and taking a solar cell panel to provide external energy, so as to construct a light-assisted water decomposition system.

[0050] The solar cell panel can convert light energy of a light source into electric energy to power a circuit of the device, and a high-efficiency and stable photovoltaic-electrocatalytic coupling system is constructed; under light irradiation, the solar cell panel drives the electrocatalytic water decomposition device to realize synchronous hydrogen production and oxygen production.

[0051] The solar cell panel used in the following examples and comparative examples of the application is a single crystal silicon solar cell.

[0052] In the application, "room temperature" is 10-30 DEG C unless otherwise specified.

[0053] The raw materials used in the following examples and comparative examples of the application are all commercially available products.

[0054] Example 1

[0055] A nickel hydroxide / amorphous black phosphorus electrode and a preparation method of a light-assisted electrocatalytic water decomposition device prepared by using the electrode, and the steps are as follows:

[0056] 1. Preparing a nickel hydroxide / amorphous black phosphorus electrode:

[0057] (1) Preparation of a β-nickel hydroxide (β-Ni(OH)2) sample: β-nickel hydroxide was synthesized using a solvothermal method; first, 0.582 g (2.0 mmol) of nickel nitrate hexahydrate (Ni(NO3)2·6H2O) was dissolved in 40 mL of deionized water to form a clear green solution under magnetic stirring; 4 mL of oleylamine was quickly injected into the green solution, followed by the addition of 20 mL of ethanol, stirring for 30 min, and then the mixture solution was transferred to a polytetrafluoroethylene liner with a volume of 100 mL, which was placed in a corresponding stainless steel autoclave, heated to 190 °C, and maintained for 16 h; after the reaction was completed, it was naturally cooled to room temperature, and the green sample obtained was washed with cyclohexane, distilled water, and ethanol (centrifugal washing at a speed of 9000 rpm for 6 min), and then vacuum dried at 50 °C for 12 h to obtain β-nickel hydroxide;

[0058] (2) Preparation of ethylenediamine intercalated crystalline black phosphorus (eda-BP): ethylenediamine intercalated crystalline black phosphorus was prepared using a solvothermal method; first, 0.5 g of red phosphorus was ground into powder in a mortar, then it was added to a 75 mL ethylenediamine solution, and stirred vigorously for 30 min, and then the mixture was transferred to a polytetrafluoroethylene liner with a volume of 100 mL, which was placed in a corresponding stainless steel high-pressure reaction kettle; the stainless steel high-pressure reaction kettle was placed in a constant temperature air drying oven, and the temperature was set to 165 °C, and heated for 24 h; after the heating was completed, it was quickly cooled to room temperature using ice water, and the precipitate product was collected, washed with water and ethanol alternately (centrifugal washing at a speed of 9000 rpm for 6 min), and then dried under vacuum at 40 °C for 6 hours to obtain ethylenediamine intercalated crystalline black phosphorus;

[0059] (3) Preparation of amorphous black phosphorus (a-BP): amorphous black phosphorus was prepared by removing the ethylenediamine molecules between the layers of ethylenediamine intercalated crystalline black phosphorus using a hydrothermal reaction method, destroying the intercalation structure and causing the P-P bond to twist; first, 0.4 g of ethylenediamine intercalated crystalline black phosphorus and 70 mL of deionized water were added to a polytetrafluoroethylene liner with a volume of 100 mL, and the liner was placed in a corresponding stainless steel reaction kettle; the reaction kettle was placed in a constant temperature air oven, and the temperature was set to 160 °C, and heated for 24 h; after the reaction was completed, the precipitate product was collected, washed with deionized water (centrifugal washing at a speed of 9000 rpm for 6 min), and then dried under vacuum at 40 °C for 12 h to obtain amorphous black phosphorus;

[0060] (4) Preparation of nickel hydroxide / amorphous black phosphorus: The nickel hydroxide / amorphous black phosphorus was prepared by using ultrasonic dispersion method; first, the amorphous black phosphorus and β-nickel hydroxide were respectively placed in a mortar and ground into powder, 5 mg of amorphous black phosphorus powder and 80 mg of β-nickel hydroxide powder were taken and dispersed into 10 mL of ethanol solution, the solution was placed in an ultrasonic cleaner and ultrasonically treated at 40 kHz for 10 min to ensure the dispersion and combination of nickel hydroxide and amorphous black phosphorus, and a uniform dispersion liquid was obtained; the dispersion liquid was placed in a vacuum drying oven and dried at 50 °C for 12 h, and after grinding, the dried nickel hydroxide / amorphous black phosphorus mixed powder was obtained;

[0061] (5) Preparation of working electrode: carbon paper (1.0 cm x 2.0 cm) was placed in anhydrous ethanol and cleaned under ultrasonic conditions for 10 min, then the surface was washed with deionized water to remove surface oxides and contaminants, and was placed in a vacuum drying oven at 60 °C for drying to obtain pretreated carbon paper; 5 mg of nickel hydroxide / amorphous black phosphorus mixed powder was dissolved in 600 μL of anhydrous ethanol, then 5 μL of Nafion binder was added, and a uniform catalyst slurry was obtained by stirring and ultrasonic treatment, then 121 μL of the catalyst slurry was evenly dropped onto the pretreated carbon paper with an area of 1 cm x 1 cm (catalyst loading: 1 mg cm -2 ), and the carbon paper was used as a catalyst carrier, and after drying, a nickel hydroxide / amorphous black phosphorus electrode was obtained, which was denoted as β-Ni(OH)2@a-BP.

[0062] 2. Preparation of photo-assisted electrocatalytic water splitting device:

[0063] A commercial solar cell panel with an open-circuit voltage (Voc) of 2.2 V was selected, and the solar cell panel was connected to the electrocatalytic water splitting device to provide electrical energy to drive the water splitting reaction, and a photo-assisted water splitting system was constructed. A 150W xenon lamp with an AM1.5 filter was used as a constant light source to irradiate the solar cell panel to input energy.

[0064] A completely sealed H-shaped electrolytic cell with a gas pipe was used as the anode and cathode, respectively, wherein the anode used the nickel hydroxide / amorphous black phosphorus electrode described above, and the cathode used a graphite carbon rod electrode, and 1 M KOH solution was used as the electrolyte in the electrolytic cell. The photo-generated current was used to drive the water splitting reaction, thereby generating oxygen at the anode and hydrogen at the cathode. The volume of the generated gas was recorded using a drainage and gas collection method, and the curves of hydrogen and oxygen production over time were obtained.

[0065] Example 2 (adjusting the loading amount of nickel hydroxide / amorphous black phosphorus)

[0066] The difference from Example 1 is only that step (5) is modified as:

[0067] The carbon paper (1.0 cm × 2.0 cm) was placed in anhydrous ethanol and cleaned under ultrasonic conditions for 10 min, then the surface was rinsed with deionized water to remove surface oxides and contaminants, and placed in a vacuum drying oven at 60 °C for drying to obtain a pretreated carbon paper; 5 mg of nickel hydroxide / amorphous black phosphorus mixed powder was dissolved in 600 μL of anhydrous ethanol, then 5 μL of Nafion binder was added, and a uniform catalyst slurry was obtained by stirring and ultrasonic treatment, then 145.2 μL of the catalyst slurry was evenly dropped on the pretreated carbon paper with an area of 1 cm × 1 cm in 4 times (catalyst loading: 1.5 mg cm -2 ), and the carbon paper was used as a catalyst carrier to obtain a nickel hydroxide / amorphous black phosphorus electrode after drying.

[0068] Example 3 (adjusting the loading of nickel hydroxide / amorphous black phosphorus)

[0069] The difference from Example 1 is only that step (5) is modified as:

[0070] The carbon paper (1.0 cm × 2.0 cm) was placed in anhydrous ethanol and cleaned under ultrasonic conditions for 10 min, then the surface was rinsed with deionized water to remove surface oxides and contaminants, and placed in a vacuum drying oven at 60 °C for drying to obtain a pretreated carbon paper; 5 mg of nickel hydroxide / amorphous black phosphorus mixed powder was dissolved in 600 μL of anhydrous ethanol, then 5 μL of Nafion binder was added, and a uniform catalyst slurry was obtained by stirring and ultrasonic treatment, then 242 μL of the catalyst slurry was evenly dropped on the pretreated carbon paper with an area of 1 cm × 1 cm in 4 times (catalyst loading: 2 mg cm -2 ), and the carbon paper was used as a catalyst carrier to obtain a nickel hydroxide / amorphous black phosphorus electrode after drying.

[0071] Comparative Example 1

[0072] The difference from Example 1 is only that step (4) is modified as:

[0073] Preparation of nickel hydroxide / ethylenediamine intercalated crystalline black phosphorus: nickel hydroxide / amorphous black phosphorus was prepared using ultrasonic dispersion method; first, ethylenediamine intercalated crystalline black phosphorus and β-nickel hydroxide were respectively placed in a mortar and ground into powder, 5 mg of ethylenediamine intercalated crystalline black phosphorus powder and 80 mg of β-nickel hydroxide powder were taken and dispersed into 10 mL of ethanol solution, the solution was placed in an ultrasonic cleaner and ultrasonically treated at 40 kHz for 10 min to obtain a uniform dispersion; the dispersion was placed in a vacuum drying oven and dried at 50°C for 12 h, and after grinding, a dry nickel hydroxide / ethylenediamine intercalated crystalline black phosphorus mixed powder was obtained. The nickel hydroxide / ethylenediamine intercalated crystalline black phosphorus electrode prepared from this mixed powder is denoted as β-Ni(OH)2@eda-BP.

[0074] Comparative Example 2

[0075] The difference from Example 1 is only that the anode material in step (2) is changed from nickel hydroxide / amorphous black phosphorus electrode to an equal mass of β-nickel hydroxide electrode (denoted as β-Ni(OH)2). The preparation method of the nickel hydroxide electrode is as follows:

[0076] The carbon paper (1.0 cm x 2.0 cm) was placed in anhydrous ethanol and cleaned under ultrasonic conditions for 10 min, then the surface was washed with deionized water to remove surface oxides and contaminants, and placed in a vacuum drying oven at 60°C for drying to obtain pretreated carbon paper; 5 mg of β-nickel hydroxide of step (1) of Example 1 was ground into powder, dissolved in 600 μL of anhydrous ethanol, then 5 μL of Nafion binder was added, and a uniform catalyst slurry was obtained by stirring and ultrasonic treatment, then 121 μL of the catalyst slurry was evenly dropped onto a 1 cm x 1 cm area of pretreated carbon paper, and the carbon paper was used as a catalyst carrier, and after drying, a β-nickel hydroxide electrode was obtained.

[0077] Effect verification

[0078] Figure 1 is the XRD spectrum of the β-nickel hydroxide, ethylenediamine intercalated crystalline black phosphorus, amorphous black phosphorus, nickel hydroxide / amorphous black phosphorus mixed powder prepared in Example 1, and the nickel hydroxide / ethylenediamine intercalated crystalline black phosphorus mixed powder prepared in Comparative Example 1.

[0079] By comparing Figure 1It is found that the prepared β-nickel hydroxide sample has obvious diffraction peaks at 2θ angles of about 19.2°, 32.9°, 38.3° and 58.5°, which are consistent with the nickel hydroxide (Ni(OH)2) (JCPDS No. 14-0117) known in the standard database. After the β-nickel hydroxide is respectively compounded with the ethylenediamine intercalated crystalline black phosphorus and the amorphous black phosphorus, the obtained nickel hydroxide / ethylenediamine intercalated crystalline black phosphorus has, in addition to the characteristic diffraction peaks of the nickel hydroxide / amorphous black phosphorus, weak diffraction peaks at 10.3° and 17.7°, which may be caused by the low loading amount of the ethylenediamine intercalated crystalline black phosphorus. Since the amorphous black phosphorus is an amorphous material, the diffraction peak position of the nickel hydroxide / amorphous black phosphorus sample does not change significantly compared with the β-nickel hydroxide matrix.

[0080] Figure 2 The transmission electron microscopy (TEM) images of (a) the β-nickel hydroxide prepared in Example 1, (c) the nickel hydroxide / amorphous black phosphorus mixed powder and (b) the nickel hydroxide / ethylenediamine intercalated crystalline black phosphorus mixed powder prepared in Comparative Example 1.

[0081] It can be seen from the TEM image of the β-nickel hydroxide that it has a hexagonal sheet structure with a size of about 100 nm. The TEM images of the nickel hydroxide / ethylenediamine intercalated crystalline black phosphorus mixed powder and the nickel hydroxide / amorphous black phosphorus mixed powder show that the morphology of the β-nickel hydroxide nanosheet after compounding remains basically unchanged, and the hexagonal sheet structure is still clearly visible, and the β-nickel hydroxide is in close contact with the ethylenediamine intercalated crystalline black phosphorus or the amorphous black phosphorus, indicating that there is a certain interfacial interaction between them.

[0082] Figure 3 The Raman spectra of the β-nickel hydroxide prepared in Example 1, the nickel hydroxide / amorphous black phosphorus mixed powder and the nickel hydroxide / ethylenediamine intercalated crystalline black phosphorus mixed powder prepared in Comparative Example 1.

[0083] The Raman spectra of the nickel hydroxide / amorphous black phosphorus, the nickel hydroxide / ethylenediamine intercalated crystalline black phosphorus and the β-nickel hydroxide show characteristic peaks at 3580 cm -1 , which correspond to the nickel hydroxide. In addition, the β-nickel hydroxide has characteristic peaks at 320 and 440 cm -1 , which correspond to the Ni(OH)2, but the nickel hydroxide / amorphous black phosphorus and the nickel hydroxide / ethylenediamine intercalated crystalline black phosphorus are difficult to be observed due to the superposition of the characteristic peaks of the black phosphorus. The nickel hydroxide / amorphous black phosphorus and the nickel hydroxide / ethylenediamine intercalated crystalline black phosphorus have characteristic peaks at 362 and 466 cm -1 , which correspond to the black phosphorus A 1g and A 2gPhosphorene phonon vibration modes, are typical characteristic peaks of black phosphorus material. The appearance of these characteristic peaks indicates that the nickel hydroxide / amorphous black phosphorus intercalated crystalline black phosphorus and nickel hydroxide / ethylenediamine intercalated crystalline black phosphorus retain the inherent structural characteristics of black phosphorus, indicating that the structure of black phosphorus is not destroyed during the synthesis process.

[0084] The working electrode materials prepared in each example and the comparative example were subjected to electrochemical performance testing by the following method: a CHI 660E electrochemical workstation of Shanghai Chenhua Company was used for electrochemical performance testing, and the test system was a standard three-electrode system; wherein the working electrode was the product of step (5) of each example and the comparative example, the reference electrode was a silver / silver chloride (Ag / AgCl) electrode, and the counter electrode was a graphite rod electrode; the electrochemical test used 1 M potassium hydroxide (KOH) solution as the electrolyte, and the LSV test was carried out at a scan rate of 5 mV s -1 -2.0 V, the OER polarization curve of the electrode material was obtained, the overpotential of the catalyst was determined by the polarization curve, and the Tafel slope and other electrocatalytic properties were calculated; in the impedance mode, the in-situ electrochemical impedance spectrum (EIS) was tested, and the Nyquist plot and the corresponding phase angle change were obtained; the stability of the electrode material was observed by measuring the change of current on the electrode with time by chronocoulometry.

[0085] Figure 4 is the OER performance of the nickel hydroxide / amorphous black phosphorus electrode in Example 1, the nickel hydroxide / ethylenediamine intercalated crystalline black phosphorus electrode in Comparative Example 1, and the β-nickel hydroxide electrode in Comparative Example 2 in 1 M KOH electrolyte; wherein (a) is the LSV test curve at a scan rate of 5 mV s -1 -2.0 V, (b) is the overpotential at a current density of 10 mA cm -2 -2.0 V, (c) is the Tafel slope, and (d) is the electrochemical stability at a current density of 10 mA cm -2 -2.0 V.

[0086] As can be seen from Figure 4 , all three samples have a metal oxidation peak before starting the OER reaction, and through the OER activity, it can be found that the catalytic performance of the nickel hydroxide / ethylenediamine intercalated crystalline black phosphorus and the nickel hydroxide / amorphous black phosphorus is greatly improved compared with the β-nickel hydroxide, and the nickel hydroxide / amorphous black phosphorus can reach a larger current density under the same voltage; at a current density of 10 mA cm -2The overpotential of the nickel hydroxide / amorphous black phosphorus is only 332 mV, which is 72 mV lower than that of the beta-nickel hydroxide, and the overpotential of the nickel hydroxide / ethylenediamine intercalated crystalline black phosphorus is also improved compared with the beta-nickel hydroxide, and is reduced to 364 mV; the Tafel slope of the nickel hydroxide / amorphous black phosphorus is 145.0 mV·dec -1 , which is lower than that of the nickel hydroxide / ethylenediamine intercalated crystalline black phosphorus (158.1 mV·dec -1 ), and is much lower than that of the beta-nickel hydroxide (213.4 mV·dec -1 ), indicating that the catalytic reaction kinetics of the nickel hydroxide / amorphous black phosphorus is more rapid; the electrochemical stability of the catalyst at a current density of 10 mA cm -2 was tested for 120 h using an amperometric chronometry method, and the stability of the nickel hydroxide / ethylenediamine intercalated crystalline black phosphorus is improved compared with the beta-nickel hydroxide, but since the intrinsic stability of the ethylenediamine intercalated crystalline black phosphorus is poorer than that of the amorphous black phosphorus, it is easy to cause hydrolysis in the OER reaction, resulting in a large fluctuation in the stability test process.

[0087] Figure 5 The Ni concentration measured by ICP-MS after the nickel hydroxide / amorphous black phosphorus electrode in Example 1, the nickel hydroxide / ethylenediamine intercalated crystalline black phosphorus electrode in Comparative Example 1, and the beta-nickel hydroxide electrode in Comparative Example 2 were reacted in 1 M KOH electrolyte for 2 h.

[0088] It can be seen from Figure 5 that the Ni element concentration in the electrolyte after the reaction of the nickel hydroxide / amorphous black phosphorus is only 0.35 mg L -1 , which is lower than that of the nickel hydroxide / ethylenediamine intercalated crystalline black phosphorus (0.71 mg L -1 ), and is much lower than that of the beta-nickel hydroxide (1.05 mg L -1 ). The results of the nickel hydroxide / amorphous black phosphorus prove that the catalyst has good anti-dissolution ability and exhibits high stability. The results show that the compounding of the black phosphorus material can inhibit the excessive oxidation of nickel to a certain extent.

[0089] Figure 6 The LSV curves and the potential difference between the oxidation peak and the OER starting potential of the nickel hydroxide / amorphous black phosphorus electrode in Example 1, the nickel hydroxide / ethylenediamine intercalated crystalline black phosphorus electrode in Comparative Example 1, and the beta-nickel hydroxide electrode in Comparative Example 2.

[0090] It can be seen from the observation of the LSV curve that the composite black phosphorus material effectively reduces the reaction overpotential of the β-nickel hydroxide, and the high electron transmission rate of the black phosphorus advances the progress of the water decomposition reaction. At the same time, by comparing the oxidation peaks of the three materials, it can be seen that the potential and current density (oxidation peak area) of the metal oxidation peak in the LSV curve of the ethylenediamine intercalated crystalline black phosphorus sample are larger than those of the amorphous black phosphorus sample, indicating that the β-nickel hydroxide in these samples is more intense in the process of preliminary electrochemical reconstruction, and more active substances are generated on the surface of the catalyst electrode, and the sufficient coverage of the active substances can also ensure that the structure inside the electrode is not excessively oxidized to cause nickel (Ni) loss. In addition, by comparing the potential difference from the oxidation peak to the OER starting potential of the three catalysts, it can be found that the nickel hydroxide / amorphous black phosphorus has the smallest potential difference (128 mV), which is 58% shorter than that of the β-nickel hydroxide, and the smaller potential difference provides electrons to the metal in time, effectively preventing the occurrence of excessive oxidation.

[0091] Figure 7 Nyquist diagram and the corresponding phase angle change obtained by electrochemical impedance spectroscopy (EIS) test of the nickel hydroxide / amorphous black phosphorus electrode in Example 1, the nickel hydroxide / ethylenediamine intercalated crystalline black phosphorus electrode in Comparative Example 1, and the β-nickel hydroxide electrode in Comparative Example 2 under a bias of 1.2 V-1.7 V; wherein (a), (b), and (c) are the Nyquist diagrams of the nickel hydroxide / ethylenediamine intercalated crystalline black phosphorus electrode, the β-nickel hydroxide electrode, and the nickel hydroxide / amorphous black phosphorus electrode, respectively, and (d) is the phase angle change.

[0092] From the above results, it can be seen that the nickel hydroxide / amorphous black phosphorus electrode has the best catalytic effect on the OER process, and the nickel hydroxide / ethylenediamine intercalated crystalline black phosphorus electrode is better than the β-nickel hydroxide electrode. Figure 7It can be seen that in the Bode plots at different potentials, the peaks appearing in the low frequency region and the high frequency region are respectively attributed to the electron transfer between the interface of the electrolyte and the working electrode, and the transfer of electrons inside the electrode. In the low frequency region, all three electrodes have a large phase difference at low voltage, which means that there is a large resistance in the three electrodes before the OER starts. As the voltage increases, the characteristic peak moves to the medium frequency region, indicating that the transfer of electrons between the electrode and the electrolyte has begun. Both the nickel hydroxide / ethylenediamine intercalated crystalline black phosphorus and the nickel hydroxide / amorphous black phosphorus show a large negative phase angle in the medium frequency region, indicating that both samples have good reaction kinetics. The β-nickel hydroxide electrode sample has a large phase angle in the high frequency region and the low frequency region, indicating that there is a large resistance in the electrode and the interface between the electrode and the electrolyte. By observing the phase angle, it can be found that the phase angle of the nickel hydroxide / amorphous black phosphorus changes smoothly at different potentials, and the phase angle changes little, indicating that the interface capacitance effect is stable and the charge transfer process is efficient. Through the impedance analysis of the samples at different voltages, it can be seen that the addition of amorphous black phosphorus and ethylenediamine intercalated crystalline black phosphorus accelerates the charge transfer in the reaction process and effectively improves the reaction kinetics of β-nickel hydroxide in the OER process.

[0093] Figure 8 It is a structural schematic diagram of the light-assisted electrocatalytic water splitting device of the application.

[0094] By Figure 8 It can be seen that the light-assisted electrocatalytic water splitting device of the application is composed of a constant light source, a solar cell panel, an electrochemical workstation and a three-electrode electrolytic cell. The constant light source is used to provide stable light conditions to simulate the intensity of sunlight; the solar cell panel generates a photovoltaic potential difference under light to provide a driving voltage for the electrochemical reaction; the electrochemical workstation is used to control and detect the current, voltage and other electrochemical parameters in the reaction system; the electrolytic cell is provided with an anode, a cathode and a reference electrode, wherein the anode uses a nickel hydroxide / amorphous black phosphorus electrode, and a graphite carbon rod is used as the cathode to realize the catalytic conversion of the target reaction. Through the direct coupling of the solar panel-electrocatalytic system, the electrochemical reaction can be driven without external bias, realizing efficient conversion of light energy to chemical energy.

[0095] Figure 9 It is a current-voltage (J-V) characteristic curve of the light-assisted electrocatalytic water splitting device prepared by using the nickel hydroxide / amorphous black phosphorus electrode in Example 1, the nickel hydroxide / ethylenediamine intercalated crystalline black phosphorus electrode in Comparative Example 1 and the β-nickel hydroxide electrode in Comparative Example 2.

[0096] Figure 9is the J-V characteristic curve of the electrode material prepared by each embodiment and comparative example after connecting with the solar cell under two electrode conditions. Using solar cell-electrocatalytic coupling, the nickel hydroxide / amorphous black phosphorus electrode realizes 5.28 mA cm -2 (J op ) at zero bias, thereby generating the corresponding solar energy to η STH 6.49%. Compared with the η STH (3.42%) of β-nickel hydroxide, it is significantly improved by 89.8%.

[0097] Figure 10 is the H2 and O2 production curve of the light-assisted electrocatalytic water splitting device prepared by using the nickel hydroxide / amorphous black phosphorus electrode in embodiment 1 under 0 V bias.

[0098] Figure 10 In the embodiment, the durability test of the nickel hydroxide / amorphous black phosphorus is carried out under the condition of 0 V applied bias, 15 ℃ temperature and 1 M KOH electrolyte by using the photovoltaic-electrocatalytic system. The volume of generated gas is recorded by using the drainage gas collection method, and the comprehensive analysis of the hydrogen and oxygen production with time change shows that, in the process of electrolysis under light for 5 hours, the volume of generated gas basically maintains the ratio of hydrogen to oxygen as 2:1, and the faradic efficiency is close to 100%.

[0099] The above-described embodiments only describe the preferred modes of the present application, and do not limit the scope of the present application. Without departing from the design spirit of the present application, various modifications and improvements of the technical solutions of the present application made by those skilled in the art shall fall within the protection scope determined by the claims of the present application.

Claims

1. A method for preparing a nickel hydroxide / amorphous black phosphorus electrode, characterized in that, Includes the following steps: Red phosphorus powder was added to ethylenediamine, and an intercalation reaction was carried out to obtain crystalline black phosphorus intercalated with ethylenediamine. The crystalline black phosphorus intercalated with ethylenediamine was mixed with water and heated to obtain amorphous black phosphorus. The amorphous black phosphorus was mixed with β-nickel hydroxide powder in a dispersant to obtain a dispersion, which was then dried to obtain a nickel hydroxide / amorphous black phosphorus mixed powder. The nickel hydroxide / amorphous black phosphorus mixed powder is loaded onto an electrode substrate to obtain the nickel hydroxide / amorphous black phosphorus electrode.

2. The preparation method according to claim 1, characterized in that, The ratio of red phosphorus powder to ethylenediamine is 0.5 g:75 mL; the intercalation reaction temperature is 165 °C and the time is 24 h.

3. The preparation method according to claim 1, characterized in that, The ratio of crystalline black phosphorus to water used in the ethylenediamine intercalation is 0.4 g:70 mL; the heating reaction temperature is 160 °C and the time is 24 h.

4. The preparation method according to claim 1, characterized in that, The ratio of amorphous black phosphorus, β-nickel hydroxide, and dispersant is 5 mg:80 mg:10 mL; the dispersant is ethanol; the drying process is vacuum drying at 50 °C for 12 h.

5. The preparation method according to claim 1, characterized in that, The electrode substrate is carbon paper, and the loading amount of the nickel hydroxide / amorphous black phosphorus mixed powder on the electrode substrate is 1 mg cm⁻¹. -2 .

6. The preparation method according to claim 1, characterized in that, The preparation method of the β-nickel hydroxide powder includes the following steps: dissolving 2 mmol of nickel nitrate in 40 mL of water, then adding 4 mL of oleylamine and 20 mL of ethanol, heating at 190 °C for 16 h, and pulverizing to obtain the β-nickel hydroxide powder.

7. A nickel hydroxide / amorphous black phosphorus electrode prepared by the method according to any one of claims 1-6.

8. The application of the nickel hydroxide / amorphous black phosphorus electrode as described in claim 7 in the field of electrocatalytic water splitting.

9. An apparatus for electrocatalytic water splitting, characterized in that, The nickel hydroxide / amorphous black phosphorus electrode as described in claim 7 is used as the electrode material of the device.

10. The apparatus according to claim 9, characterized in that, The device is equipped with a solar panel, which converts light energy into electrical energy to power the device's circuitry.

Images