A two-dimensional Ni x Co 4-x Preparation method of N / NC ultrathin nanosheet honeycomb assembly array

Abstract

This invention discloses a two-dimensional Ni x Co 4‑x A method for preparing N / NC ultrathin nanosheet honeycomb assembly arrays involves first mixing NiCl2·6H2O, CoCl2·6H2O, and urea in any molar ratio to form a supramolecular solvent at a specific temperature. A certain amount of the synthesized supramolecular solvent is coated onto carbon cloth, and the carbon is arranged in a muffle furnace and calcined at 350–750°C under an inert atmosphere. The furnace is then cooled to room temperature to obtain the electrode material. The preparation method described in this invention is simple to operate, has low production cost, and can be mass-produced. The obtained Ni... x Co 4‑x N / NC ultrathin nanosheet arrays exhibited excellent hydrogen evolution performance in both general pH ranges and natural seawater.

Description

Technical Field

[0001] This invention belongs to the field of electrocatalytic materials and their preparation technology, specifically relating to a two-dimensional Ni x Co 4-x The method for creating an N / NC ultrathin nanosheet honeycomb assembly array, specifically, involves designing a two-dimensional N-doped carbon and a two-dimensional Ni... x Co 4-x A self-supporting electrode material consisting of a honeycomb-shaped ultrathin nanosheet array assembled from N ultrathin nanosheets. Background Technology

[0002] Hydrogen energy, as a clean and renewable energy source, is not only an important industrial raw material but can also replace increasingly depleted fossil fuels to alleviate environmental pollution and global warming. Electrocatalytic water splitting is considered one of the cleanest methods for hydrogen production. To realize the industrial application of hydrogen production, it is necessary to develop efficient electrocatalysts to reduce the overpotential of the reaction, accelerate reaction kinetics, and improve the efficiency of the hydrogen evolution reaction (HER). However, the HER performance of most reported electrocatalysts is limited to a very narrow pH range, which poses a significant challenge to practical applications under operating conditions within a general pH range. Furthermore, seawater accounts for 96.5% of the Earth's water resources. Hydrogen production through seawater electrolysis is crucial for alleviating the global freshwater shortage. This hydrogen production process can also be combined with the chlor-alkali industry for greater economic benefits. However, due to the complex composition of natural seawater, problems such as low conductivity, easy corrosion, and ion poisoning commonly exist during catalyst use, which increases the difficulty of designing efficient and stable electrocatalysts. Therefore, there is an urgent need to develop efficient electrocatalysts with high activity and stability in a general pH range and in natural seawater.

[0003] Transition metal compounds, especially sulfides, phosphides, carbides, and nitrides, have attracted widespread attention due to their abundant reserves, low cost, and excellent electronic properties. Among them, transition metal nitrides exhibit metal-like characteristics when nitrogen atoms are incorporated into the interstitial spaces of the metal lattice and covalently bonded to metal atoms, thus possessing better conductivity and stability. Furthermore, the formation of metal-nitrogen bonds at the d-band density of states provides electron-donating properties to metal nitrides, which is beneficial for transition metal nitrides (TMNs) to exhibit higher electrocatalytic activity in the HER process. Combining metal nitrides with nitrogen-doped carbon (NC) materials can increase the conductivity of the catalyst and prevent corrosion during catalysis. However, currently only a few studies have reported on the synthesis of metal nitride-composite nitrogen-doped carbon materials, and the preparation methods are relatively complex.

[0004] Supramolecular solvents, as a type of green solvent, have been applied in many fields such as electrochemistry, chemical engineering, energy, and materials due to their advantages such as tunable viscosity, low volatility, and wide electrochemical window. In materials synthesis, supramolecular solvents, due to their high viscosity and ionic strength, can be used as structure-directing agents to synthesize soft templates for materials with special morphologies and properties. Therefore, using supramolecular solvents as solvents and precursors holds promise for the simple and large-scale synthesis of high-performance metal nitride composite nitrogen-doped carbon materials. Summary of the Invention

[0005] In view of the shortcomings of the existing technology, the purpose of this invention is to provide a two-dimensional Ni x Co 4-x A method for synthesizing N / NC ultrathin nanosheet honeycomb assemblies is presented, characterized by a simple and mild preparation process, low cost, industrial-scale production capability, and environmental friendliness. The resulting Ni... x Co 4-x N / NC ultrathin nanosheet arrays not only exhibit excellent HER performance within a general pH range, but can also be efficiently and stably applied to the decomposition of natural seawater to produce hydrogen.

[0006] To achieve the above objectives, the present invention provides a two-dimensional Ni x Co 4-x A method for preparing an N / NC ultrathin nanosheet honeycomb assembly array, characterized in that the Ni x Co 4-x N / NC ultrathin nanosheets are made of Ni x Co 4-x The nanosheets are in-situ grown from N-doped carbon (NC) and composited with two-dimensional N-doped carbon, and grown on the surface of carbon fibers in carbon cloth to form a honeycomb-like assembly array structure of ultrathin nanosheets. This honeycomb assembly array is used as an electrode material and exhibits excellent hydrogen production efficiency in water splitting across the entire pH range. It also shows high efficiency and stable activity when applied to the decomposition of natural seawater to produce hydrogen. The preparation method specifically includes the following steps:

[0007] 1) Mix NiCl2·6H2O crystals and CoCl2·6H2O crystals according to Ni x Co 4-x The molar ratio of NiCl2·6H2O and CoCl2·6H2O is mixed, x = 0 to 1, and then the mixed crystals of NiCl2·6H2O and CoCl2·6H2O are mixed with urea at a molar ratio of 1:10 to 1:100, and heated at 35 to 95°C to form a supramolecular solvent.

[0008] 2) Coat the surface of carbon cloth with 10-2000 μL of the above-mentioned supramolecular solvent and place it in a covered boat. Place the boat in a muffle furnace and heat it to 350-750℃ at a heating rate of 1-20℃ / min under a nitrogen inert atmosphere. Hold the temperature at this temperature for 0.5-6 h. After cooling, wash the obtained sample three times with ethanol and deionized water, and dry it to obtain two-dimensional Ni. x Co 4-x N / NC ultrathin nanosheet honeycomb assembly array electrode material.

[0009] The preparation method described in this invention is simple to operate, the precursor can form a supramolecular liquid-like substance, the preparation cost is low, and it is easy to industrialize. The resulting two-dimensional Ni x Co 4-x N / NC ultrathin nanosheet honeycomb assembly arrays are uniformly grown on the surface of carbon cloth. Attached Figure Description

[0010] Figure 1 These are SEM images of the two-dimensional ultrathin nanosheet honeycomb assembly array prepared in Example 1 of this invention at different magnifications.

[0011] Figure 2 The elemental distribution diagram of the two-dimensional ultrathin nanosheet honeycomb assembly array prepared in Example 1 of this invention;

[0012] Figure 3 TEM (a) and HRTEM (b) images of the two-dimensional ultrathin nanosheet honeycomb assembly array prepared in Example 1 of the present invention;

[0013] Figure 4 The AFM spectrum of the two-dimensional ultrathin nanosheet honeycomb assembly array ultrathin nanosheets prepared in Example 1 of this invention;

[0014] Figure 5 Two-dimensional Ni prepared in Example 1 of this invention 2.4 Co 1.6 XRD patterns of N / NC ultrathin nanosheet honeycomb assembly arrays;

[0015] Figure 6 Two-dimensional Ni prepared in Example 1 of this invention 2.4 Co 1.6 Raman spectra of N / NC ultrathin nanosheet honeycomb assembly arrays;

[0016] Figure 7 Two-dimensional Ni prepared in Example 1 of this invention 2.4 Co 1.6 HER polarization curves of N / NC ultrathin nanosheet honeycomb assembly arrays at acidic pH;

[0017] Figure 8Two-dimensional Ni prepared in Example 1 of this invention 2.4 Co 1.6 HER polarization curves of N / NC ultrathin nanosheet honeycomb assembly arrays at alkaline pH;

[0018] Figure 9 Two-dimensional Ni prepared in Example 1 of this invention 2.4 Co 1.6 HER polarization curves of N / NC ultrathin nanosheet honeycomb assembly array at neutral pH;

[0019] Figure 10 Two-dimensional Ni prepared in Example 1 of this invention 2.4 Co 1.6 HER polarization curves of N / NC ultrathin nanosheet honeycomb assembly array in natural seawater;

[0020] Figure 11 Two-dimensional Ni prepared in Example 1 of this invention 2.4 Co 1.6 HER stability experiment of N / NC ultrathin nanosheet honeycomb assembly array at acidic pH;

[0021] Figure 12 Two-dimensional Ni prepared in Example 1 of this invention 2.4 Co 1.6 HER stability experiment of N / NC ultrathin nanosheet honeycomb assembly array at alkaline pH;

[0022] Figure 13 Two-dimensional Ni prepared in Example 1 of this invention 2.4 Co 1.6 HER stability experiment of N / NC ultrathin nanosheet honeycomb assembly array at neutral pH;

[0023] Figure 14 Two-dimensional Ni prepared in Example 1 of this invention 2.4 Co 1.6 HER stability experiment of N / NC ultrathin nanosheet honeycomb assembly array in natural seawater; Detailed Implementation

[0024] The present invention will be described below through specific embodiments and comparative examples, but the present invention is not limited thereto.

[0025] Unless otherwise specified, the experimental methods used in the following examples are conventional methods; unless otherwise specified, the reagents and materials used in the following examples are commercially available.

[0026] Example 1:

[0027] Accurately weigh NiCl2·6H2O, CoCl2·6H2O, and urea in a molar ratio of 3:2:70, and form a supramolecular solvent in a 60℃ oil bath; take a certain amount of the supramolecular solvent and coat it onto a working area of ​​1*1cm. -2 The material was placed on carbon cloth, then placed in a covered boat, transferred to a muffle furnace, and heated to 650°C at a rate of 5°C / min in an N2 atmosphere. The temperature was held for 4 hours, and then cooled with the furnace to obtain two-dimensional Ni. 2.4 Co 1.6 N / NC ultrathin nanosheet honeycomb assembly array.

[0028] Example 2:

[0029] Accurately weigh NiCl2·6H2O, CoCl2·6H2O, and urea in a molar ratio of 3:2:70, and form a supramolecular solvent in a 60℃ oil bath; take a certain amount of the supramolecular solvent and coat it onto a working area of ​​1*1cm. -2 The material was placed on carbon cloth, then placed in a covered boat, transferred to a muffle furnace, and heated to 550°C at a rate of 5°C / min in an N2 atmosphere. The temperature was held for 4 hours, and then cooled with the furnace to obtain two-dimensional Ni. 2.4 Co 1.6 N / NC ultrathin nanosheet honeycomb assembly array.

[0030] Example 3:

[0031] Accurately weigh NiCl2·6H2O, CoCl2·6H2O, and urea in a molar ratio of 3:2:70, and form a supramolecular solvent in a 60℃ oil bath; take a certain amount of the supramolecular solvent and coat it onto a working area of ​​1*1cm. -2 The material was placed on carbon cloth, then placed in a covered boat, transferred to a muffle furnace, and heated to 650℃ at a rate of 5℃ / min in an N2 atmosphere. The temperature was held for 6 hours, and then cooled with the furnace to obtain two-dimensional Ni. 2.4 Co 1.6 N / NC ultrathin nanosheet honeycomb assembly array.

[0032] Example 4:

[0033] Accurately weigh NiCl2·6H2O, CoCl2·6H2O, and urea in a molar ratio of 2:3:70, and form a supramolecular solvent in a 60℃ oil bath; take a certain amount of the supramolecular solvent and coat it onto a working area of ​​1*1cm. -2 The material was placed on carbon cloth, then placed in a covered boat, transferred to a muffle furnace, and heated to 650°C at a rate of 5°C / min in an N2 atmosphere. The temperature was held for 4 hours, and then cooled with the furnace to obtain two-dimensional Ni. 2.4 Co 1.6 N / NC ultrathin nanosheet honeycomb assembly array.

[0034] Example 5:

[0035] Accurately weigh NiCl2·6H2O, CoCl2·6H2O, and urea in a molar ratio of 1:4:70, and form a supramolecular solvent in a 60℃ oil bath; take a certain amount of the supramolecular solvent and coat it onto a working area of ​​1*1cm. -2 The material was placed on carbon cloth, then placed in a covered boat, transferred to a muffle furnace, and heated to 650°C at a rate of 5°C / min in an N2 atmosphere. The temperature was held for 4 hours, and then cooled with the furnace to obtain two-dimensional Ni. 2.4 Co 1.6 N / NC ultrathin nanosheet honeycomb assembly array.

[0036] Example 6:

[0037] Accurately weigh NiCl2·6H2O, CoCl2·6H2O, and urea in a molar ratio of 4:1:70, and form a supramolecular solvent in a 60℃ oil bath; take a certain amount of the supramolecular solvent and coat it onto a working area of ​​1*1cm. -2 The material was placed on carbon cloth, then placed in a covered boat, transferred to a muffle furnace, and heated to 650°C at a rate of 5°C / min in an N2 atmosphere. The temperature was held for 4 hours, and then cooled with the furnace to obtain two-dimensional Ni. 2.4 Co 1.6 N / NC ultrathin nanosheet honeycomb assembly array.

[0038] Comparative Example 1:

[0039] Accurately weigh NiCl₂·6H₂O and CoCl₂·6H₂O in a molar ratio of 3:2 and physically mix them. Place the mixture in an ark and then transfer it to the center of a tube furnace. Subsequently, place 2.0 g of urea upstream of the tube furnace. Under a nitrogen flow, the temperature is increased to 650 °C at 5 °C / min, held for 4 h, and then cooled with the furnace to obtain Ni. 2.4 Co 1.6 Ni catalyst. Subsequently, 20 mg of the catalyst was dispersed in 0.5 mL of deionized water, 0.45 mL of ethanol, and 50 μL of Nafion solution (5 wt.%), forming a homogeneous mixture under ultrasonic assistance. Then, 180 μL of the mixture was pipetted onto the surface of carbon cloth and dried at room temperature to obtain Ni. 2.4 Co 1.6 N electrode.

[0040] The morphology and structure of the product obtained in Example 1 were characterized, and its electrochemical hydrogen production performance was tested.

[0041] Figure 1 Two-dimensional Ni prepared according to Example 1 of the present invention 2.4 Co 1.6SEM images of the N / NC ultrathin nanosheet honeycomb assembly array at different magnifications show that the prepared material is an ultrathin nanosheet array that is uniformly grown on the carbon fiber surface of the carbon cloth.

[0042] Figure 2 Two-dimensional Ni prepared according to Example 1 of the present invention 2.4 Co 1.6 The elemental distribution diagram of the N / NC ultrathin nanosheet honeycomb assembly array shows that Ni, Co, N, and C elements are uniformly distributed on the carbon cloth.

[0043] Figure 3 Two-dimensional Ni prepared in Example 1 of this invention 2.4 Co 1.6 TEM (a) and HRTEM (b) images of an array of N / NC ultrathin nanosheet honeycomb assemblies; from Figure 3 The TEM image in image a shows that the prepared material is an ultrathin nanosheet structure; from Figure 3 The HRTEM image in b shows that the lattice fringes of the ultrathin nanosheets are clear and aligned with Ni. 2.4 Co 1.6 The uniformity of the lattice fringes of N indicates that Ni 2.4 Co 1.6 N crystallizes well.

[0044] Figure 4 Two-dimensional Ni prepared according to Example 1 of the present invention 2.4 Co 1.6 AFM images and spectra of N / NC ultrathin nanosheet honeycomb assembly array ultrathin nanosheets. As can be seen from the images, the thickness of a single ultrathin nanosheet material is approximately 1.5 nm.

[0045] Figure 5 Two-dimensional Ni prepared according to Example 1 of the present invention 2.4 Co 1.6 The XRD pattern of the N / NC ultrathin nanosheet honeycomb assembly array shows that the XRD diffraction peaks of the sample can all be attributed to no.PDF#15-0806, which is consistent with Ni. 2.4 Co 1.6 Consistent with the N-structure;

[0046] Figure 6 Two-dimensional Ni prepared according to Example 1 of the present invention 2.4 Co 1.6 The Raman spectrum of the N / NC ultrathin nanosheet honeycomb assembly array, with the presence of D and G peaks in the figure, combined with the elemental mapping results, further proves that the ultrathin nanosheet honeycomb assembly array material contains nitrogen-doped C.

[0047] Figure 7 Ni, an embodiment of the present invention 2.4 Co 1.6 The hydrogen evolution performance of the N / NC ultrathin nanosheet honeycomb assembly array and Comparative Example 1 in 0.5M H2SO4 electrolyte solution is significantly lower than that of Comparative Example 1, and the hydrogen production performance is superior to that of Comparative Example 1.

[0048] Figure 8 Ni, an embodiment of the present invention 2.4 Co 1.6 The hydrogen evolution performance of the N / NC ultrathin nanosheet honeycomb assembly array and Comparative Example 1 in 1.0M KOH electrolyte solution is shown to be that the overpotential of the hydrogen evolution performance is lower than that of Comparative Example 1, and the hydrogen evolution performance is better than that of Comparative Example 1.

[0049] Figure 9 Ni, an embodiment of the present invention 2.4 Co 1.6 The hydrogen evolution performance of the N / NC ultrathin nanosheet honeycomb assembly array and Comparative Example 1 in 1.0M PBS neutral electrolyte solution was compared. The overpotential of the hydrogen evolution performance of the N / NC ultrathin nanosheet honeycomb assembly array was lower than that of Comparative Example 1, and the hydrogen production performance was better than that of Comparative Example 1.

[0050] Figure 10 Ni prepared in Example 1 of this invention 2.4 Co 1.6 The HER curves of the synthesized Ni / NC ultrathin nanosheet array and comparative example 1 in natural seawater are shown in the figure. 2.4 Co 1.6 N / NC ultrathin nanosheet arrays have low overpotential in natural seawater, thus exhibiting excellent hydrogen evolution performance;

[0051] Figure 11 Ni prepared in Example 1 of this invention 2.4 Co 1.6 The hydrogen evolution stability test of the N / NC ultrathin nanosheet honeycomb assembly array in 0.5MH2SO4 electrolyte solution showed good hydrogen evolution stability.

[0052] Figure 12 Ni preparation in Example 1 of the present invention 2.4 Co 1.6 The hydrogen evolution stability test of the N / NC ultrathin nanosheet honeycomb assembly array in 1.0 MKOH electrolyte solution showed good hydrogen evolution stability.

[0053] Figure 13 Ni preparation in Example 1 of the present invention 2.4 Co 1.6The hydrogen evolution stability test of the N / NC ultrathin nanosheet honeycomb assembly array in 1.0M PBS neutral electrolyte solution showed very good hydrogen evolution stability.

[0054] Figure 14 Ni prepared in Example 1 of this invention 2.4 Co 1.6 The hydrogen evolution stability test of the N / NC ultrathin nanosheet array in natural seawater is shown in the figure. 2.4 Co 1.6 N / NC ultrathin nanosheet arrays exhibit excellent hydrogen evolution stability in natural seawater;

[0055] Ni prepared in the embodiments of the present invention 2.4 Co 1.6 N / NC ultrathin nanosheet honeycomb assembly arrays were used to construct an electrocatalytic reduction system to enhance the removal effect of nitrate nitrogen in wastewater by traditional electrocatalytic reduction. It has a higher removal rate of nitrate nitrogen in wastewater, and the mass catalytic activity of nitrate nitrogen can be increased by 2.8 times compared with the traditional electrode electrocatalytic reduction system within a reaction time of 3 hours.

[0056] Ni prepared in the embodiments of the present invention 2.4 Co 1.6 N / NC ultrathin nanosheet honeycomb assembly array is used for electrocatalytic reduction dechlorination to treat chlorinated organic wastewater. It can reduce chlorinated organics on the electrode surface and remove chlorine atoms, thereby achieving the purpose of removing pollutants. This technology also has the advantages of fast reaction speed, low secondary pollution, mild reaction conditions and low equipment cost.

[0057] Table 1 shows the Ni prepared according to the present invention. x Co 4-x The ICP-OES elemental analysis results of the N / NC ultrathin nanosheet array can be seen from the table. x Co 4-x The theoretical and actual molar ratios of Ni and Co elements in the N / NC ultrathin nanosheet array are consistent with the detection results, and the Ni prepared in Example 1... x Co 4-x In N / NC, the Ni:Co ratio is 2.4:1.6.

[0058] Table 1. Ni prepared according to the present invention x Co 4-x ICP-OES results of N / NC ultrathin nanosheet arrays

[0059]

[0060] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any other changes, substitutions, simplifications, etc. made without departing from the principle and process of the present invention are equivalent substitutions and should be included within the protection scope of the present invention.

Claims

1. A two-dimensional Ni 2.4 Co 1.6 The method for preparing N / NC ultrathin nanosheet honeycomb assembly array is characterized by, The Ni 2.4 Co 1.6 N / NC ultrathin nanosheets are made of Ni 2.4 Co 1.6 The composite material is formed by in-situ growth of N-doped carbon (NC) nanosheets and two-dimensional N-doped carbon fibers on the surface of carbon cloth, creating a honeycomb-like assembly array structure of ultrathin nanosheets. This honeycomb assembly array is used as an electrode material, exhibiting excellent hydrogen production efficiency across the entire pH range. It also demonstrates high efficiency and stable activity in the decomposition of natural seawater to produce hydrogen. Furthermore, it is used for the electrocatalytic reduction of nitrate nitrogen in wastewater and achieves high removal rates in the electrocatalytic reduction dechlorination of chlorinated organic wastewater. The preparation method is low-cost, the precursor can form a supramolecular liquid-like structure, the process is simple, and it is easily industrialized. Includes the following steps: Accurately weigh NiCl2·6H2O, CoCl2·6H2O, and urea in a molar ratio of 3:2:70, and form a supramolecular solvent in a 60℃ oil bath; take a certain amount of the supramolecular solvent and coat it onto a working area of ​​1*1cm. -2 The material was placed on carbon cloth, then placed in a covered boat, transferred to a muffle furnace, and heated to 650°C at a rate of 5°C / min in an N2 atmosphere. The temperature was held for 4 hours, and then cooled with the furnace to obtain two-dimensional Ni. 2.4 Co 1.6 N / NC ultrathin nanosheet honeycomb assembly array.

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