Sponge nickel/octa-sulfide nine-nickel composite material and preparation method and application thereof
Technical Field
The invention relates toThe technical field of electrocatalyst materials, in particular to sponge nickel/octa-nickel sulfide (Ni)9S8) Composite materials, methods of making the same and their use as electrocatalysts.
Background
The current energy crisis is becoming more serious, and the development of renewable hydrogen energy sources is the subject of the world at present. The hydrogen comes from water, and the water molecules are driven to be degraded into the hydrogen by electric energy, so that the hydrogen is an effective strategy for environmental protection. In order to reduce the use of electrical energy, advanced electrocatalysts need to be designed to reduce the overpotential. Currently, the noble metal platinum and its alloys exhibit very good catalytic properties. However, their development is hampered by the high price and low natural abundance of noble metal catalysts and by their poor cycle stability. Therefore, there is a need to develop advanced non-noble metal electrocatalysts to replace noble metals. The sponge nickel/octa-sulfur nonanickel composite material has rich active sites and sulfur vacancies and high conductivity, thereby showing good electrocatalytic performance, and not only having relatively low overpotential but also having high stability.
The sponge nickel coated by graphene is used as a substrate, and nine nickel octasulfide (Ni) is loaded and grown on the substrate9S8) The nanowire array can effectively improve the electron conduction rate and the specific surface area of the nickel nonasulfide, thereby improving the electrochemical performance of the nickel nonasulfide. The sponge nickel/octa-nickel sulfide composite material can be used as an electrocatalyst with high efficiency for hydrogen evolution.
Disclosure of Invention
The invention aims to provide sponge nickel/nonanickel octasulfide (Ni) aiming at the problem that the development of the noble metal catalysts is hindered by high price, low natural abundance and poor cycling stability of the prior noble metal catalysts9S8) The sponge nickel/octasulfide nonanickel electrode material has low over potential, low Tafel slope and high safety and stability.
Sponge nickel/octa-nickel sulfide (Ni)9S8) The preparation method of the composite material comprises the following steps:
(1) taking nickel acetate as a nickel source and hydrazine hydrate as a reducing agent to carry out hydrothermal reaction to obtain a sponge nickel scaffold;
(2) and (2) putting the sponge nickel support prepared in the step (1) into a tubular furnace, continuously introducing a mixed gas of argon and hydrogen, taking ethanol as a carbon source, and reacting by a one-step CVD (chemical vapor deposition) method to obtain the graphene-coated sponge nickel.
(3) And (3) taking the graphene-coated sponge nickel prepared in the step (2) as a nickel source and thiourea as a sulfur source, and obtaining the sponge nickel/octasulfide nonanickel composite material by a hydrothermal method.
According to the invention, a sponge nickel support coated by graphene is prepared by a hydrothermal method and a CVD method, and the sponge nickel support is used as a carrier to prepare the octa-sulfide nonanickel nanowire array electrode material by the hydrothermal method. The material has a large specific surface area, and the nickel sponge is loaded with the octa-sulfide nine-nickel nanowire array, so that the contact area of electrolyte and a motor can be increased, a larger and more effective active reaction area is provided, meanwhile, the electron conduction rate is accelerated, and the electrochemical performance is improved.
The following are preferred technical schemes of the invention:
the step (1) specifically comprises the following steps:
dissolving nickel acetate in deionized water, adding hydrazine hydrate, and carrying out hydrothermal reaction to obtain a sponge nickel scaffold;
the dosage ratio of the nickel acetate, the deionized water and the hydrazine hydrate is 1.24-1.28 g: 60-80 mL: 5-7 mL.
The conditions of the hydrothermal reaction are as follows: the hydrothermal reaction temperature is 150 ℃ and 220 ℃, and the hydrothermal reaction time is maintained for 5-16 h.
In step (2), the flow rates of argon and hydrogen are respectively 140 sccm and 180sccm and 10-20 sccm.
The reaction conditions of the one-step CVD (chemical vapor deposition) method are as follows: heating the reaction to 600-900 ℃, keeping the temperature for 8-20min, then opening a switch of the bubbler, introducing an ethanol carbon source, and finishing the reaction after 8-20 min.
The step (3) specifically comprises the following steps:
and (3) dissolving thiourea and polyvinylpyrrolidone (PVP) in deionized water to form a mixed solution, transferring the mixed solution to a reaction kettle, adding the graphene-coated sponge nickel prepared in the step (2), and performing hydrothermal reaction to obtain the sponge nickel/octa-nickel sulfide composite material.
The usage ratio of thiourea, polyvinylpyrrolidone (PVP) and deionized water is 0.2-0.6 g: 0.3-0.6 g: 40-80 mL, most preferably 0.4 g: 0.5 g: 60 mL.
The reaction kettle is a polytetrafluoroethylene high-pressure kettle;
carrying out hydrothermal reaction for 6-20h at 150-230 ℃. Further preferably, the hydrothermal reaction is carried out at 160 ℃ to 200 ℃ for 10 to 20 hours.
The sponge nickel/octa-sulfur nonanickel composite material (namely sponge nickel/Ni) prepared by the invention9S8Material) has low overpotential, good electronic conductivity and high safety and stability, Ni9S8The nanowires have an average diameter of about 10-100 nm. The sponge nickel/Ni9S8The material is used as a new nickel sulfide composite material. Particularly as electrocatalyst materials (i.e., hydrogen-producing electrocatalysts).
Compared with the prior art, the invention has the following advantages:
the method prepares the sponge nickel substrate coated by the graphene by a hydrothermal method and a chemical vapor deposition method, and then prepares the sponge nickel/Ni by a simple hydrothermal method9S8And (4) obtaining a target product. The preparation method is simple and convenient, and is easy to control.
Sponge nickel/Ni prepared by the invention9S8Electrode material with large specific surface area and Ni loaded on sponge nickel9S8The nanowire array can increase the contact area of electrolyte and an electrode, provide a larger and more effective active reaction area, accelerate the electron conduction rate and improve the electrochemical performance. The invention overcomes the defects of stability and reaction kinetics, thereby realizing that a certain hydrogen yield can be obtained by adopting low overpotential.
Sponge nickel/Ni of the invention9S8The composite material has larger specific surface area, and Ni is loaded on the bacterial cellulose9S8The nanowire array can increase the contact area of electrolyte and a motor, provide a larger and more effective active reaction area,meanwhile, the electron conduction rate is accelerated, and the electrochemical performance is improved. Preparation of sponge Nickel/Ni by hydrothermal method and CVD method9S8An electrode material. Sponge nickel/Ni of the invention9S8The material has high cycle stability, low overpotential and low Tafel slope, and has great application prospect in the field of hydrogen energy electro-catalysts.
Sponge nickel/Ni of the invention9S8The material has the characteristics of long cycle life and low overpotential, and has wide application prospect in the fields of mobile communication, electric automobiles, solar power generation, aerospace and the like.
Drawings
FIG. 1 shows the sponge Ni/Ni obtained in example 19S8XRD pattern of the target product.
FIG. 2 shows the sponge Ni/Ni obtained in example 29S8Scanning electron micrograph of target product, FIG. 2 (a) is sponge nickel/Ni prepared in example 2 at high resolution of 500nm9S8Scanning electron micrograph of target product, FIG. 2 (b) is sponge nickel/Ni prepared in example 2 at low resolution of 2 μm9S8Scanning electron microscope images of the target product.
FIG. 3 shows the sponge Ni/Ni obtained in example 39S8Transmission electron microscopy images of the target product.
Detailed Description
The present invention will be described in detail with reference to examples, but the present invention is not limited thereto.
Example 1
1.243g of nickel acetate was dissolved in 69mL of deionized water, stirred to a clear solution, 6mL of hydrazine hydrate was slowly added, and stirring was continued to a clear solution. Transferring the solution into the inner liner of a hydrothermal reaction kettle, installing a stainless steel shell, screwing the stainless steel shell, and placing the stainless steel shell in an oven at 150 ℃ for reaction for 7 hours. After the reaction is finished, after the reaction kettle is cooled to room temperature, the sponge nickel growing in the lining is taken out. The dried sponge nickel sample was placed in a quartz boat and then placed in the middle of the CVD tube furnace while the bubbler was charged with an appropriate ethanol solution as the carbon source for the reaction. And introducing argon into the tubular furnace, evacuating, continuously introducing a mixed gas of argon (160sccm) and hydrogen (20sccm), heating the furnace to 850 ℃ within 40min, keeping the temperature for 15min, opening a switch of a bubbler, introducing an ethanol carbon source, and reacting for 15 min. And after the tubular furnace is cooled to the room temperature, taking out the tubular furnace to obtain the sponge nickel sample coated with the graphene. 0.4g of thiourea and 0.5g of polyvinylpyrrolidone (PVP) were dissolved in 60mL of deionized water to form a mixed solution, which was then transferred to the inner liner of a reaction vessel, the prepared SNG sample was added, and the reaction vessel was covered with a stainless steel outer shell and placed in an oven to react at 180 ℃ for 14 hours. And taking out the sample after the reaction kettle is cooled to room temperature, and washing with deionized water and absolute ethyl alcohol and drying in an oven to obtain the nickel sponge sulfide sample.
Sponge Nickel/Ni prepared in example 19S8Target product (abbreviated as Ni)9S8@ SNG) is shown in figure 1.
Example 2
1.343g of nickel acetate was dissolved in 69mL of deionized water, stirred until a clear solution was obtained, then 7mL of hydrazine hydrate was slowly added, and stirring was continued until a clear solution was obtained. Transferring the solution into the inner liner of a hydrothermal reaction kettle, installing a stainless steel shell, screwing down, and placing in an oven at 180 ℃ for reaction for 9 hours. After the reaction is finished, after the reaction kettle is cooled to the room temperature of 25 ℃, the sponge nickel growing in the lining is taken out. The dried sponge nickel sample was placed in a quartz boat and then placed in the middle of the CVD tube furnace while the bubbler was charged with an appropriate ethanol solution as the carbon source for the reaction. And introducing argon into the tubular furnace, evacuating, continuously introducing a mixed gas of argon (165sccm) and hydrogen (15sccm), heating the furnace to 950 ℃ within 40min, preserving the temperature for 20min, opening a switch of a bubbler, introducing an ethanol carbon source, and reacting for 20 min. And after the tubular furnace is cooled to the room temperature of 25 ℃, taking out the tubular furnace to obtain the sponge nickel sample coated with the graphene. 0.4g of thiourea and 0.5g of polyvinylpyrrolidone (PVP) were dissolved in 60mL of deionized water to form a mixed solution, which was then transferred to the inner liner of a reaction vessel, the prepared SNG sample was added, and the reaction vessel was covered with a stainless steel shell and placed in an oven to react at 190 ℃ for 18 hours. And taking out the sample after the reaction kettle is cooled to room temperature of 25 ℃, and obtaining the nickel sponge sulfide sample after the sample is washed by deionized water and absolute ethyl alcohol and dried by an oven.
Sponge Nickel/Ni prepared in example 29S8The scanning electron micrograph of the target product is shown in FIG. 2, and the target product has a large specific surface area, and Ni is loaded on the sponge nickel9S8Nanowire arrays, Ni9S8The nanowire arrays have an average diameter of about 10-100 nm.
Example 3
1.343g of nickel acetate was dissolved in 69mL of deionized water, stirred until a clear solution was obtained, then 7mL of hydrazine hydrate was slowly added, and stirring was continued until a clear solution was obtained. Transferring the solution into the inner liner of a hydrothermal reaction kettle, installing a stainless steel shell, screwing the stainless steel shell, and placing the stainless steel shell in a 185 ℃ oven for reaction for 6 hours. After the reaction is finished, after the reaction kettle is cooled to the room temperature of 25 ℃, the sponge nickel growing in the lining is taken out. The dried sponge nickel sample was placed in a quartz boat and then placed in the middle of the CVD tube furnace while the bubbler was charged with an appropriate ethanol solution as the carbon source for the reaction. And introducing argon into the tubular furnace, evacuating, continuously introducing a mixed gas of argon (155sccm) and hydrogen (25sccm), heating the furnace to 950 ℃ within 40min, preserving the temperature for 20min, opening a switch of a bubbler, introducing an ethanol carbon source, and reacting for 20 min. And after the tubular furnace is cooled to the room temperature of 25 ℃, taking out the tubular furnace to obtain the sponge nickel sample coated with the graphene. 0.4g of thiourea and 0.5g of polyvinylpyrrolidone (PVP) were dissolved in 60mL of deionized water to form a mixed solution, which was then transferred to the inner liner of a reaction vessel, the prepared SNG sample was added, and the reaction vessel was covered with a stainless steel outer shell and placed in an oven to react at 200 ℃ for 14 hours. And taking out the sample after the reaction kettle is cooled to room temperature of 25 ℃, and obtaining the nickel sponge sulfide sample after the sample is washed by deionized water and absolute ethyl alcohol and dried by an oven.
Sponge Nickel/Ni prepared in example 39S8The transmission electron micrograph of the target product is shown in FIG. 3.
Performance testing
Sponge Nickel/Ni prepared as described in examples 1-3 above9S8The material is used as a working electrode, the carbon rod is used as a counter electrode, the calomel electrode is used as a reference electrode, and 1M KOH solution is respectively used as the counter electrodeElectrocatalytic performance tests were performed and all voltages were converted to reversible hydrogen potentials. The cell performance was tested separately in the electrochemical workstation. The test voltage range is 0 to-1.6V, and the sponge nickel/Ni is measured in the environment of 25 +/-1 DEG C9S8LSV curve and electrochemical stability of the material.
The performance test results are as follows:
sponge Nickel/Ni of examples 1, 2 and 39S8The material was at 10mA cm-2At current density of (2), sponge nickel/Ni9S8The material showed the most excellent hydrogen evolution activity, with the minimum overpotential (120mV,118mV and 140mV), and without any significant increase in voltage for 30 hours, even at high current density (50mA cm)-2) And still good cycle stability.
This is the sponge nickel/Ni prepared in accordance with the invention9S8Electrode material with large specific surface area and Ni loaded on sponge nickel9S8The nanowire array can increase the contact area of electrolyte and an electrode, provide a larger and more effective active reaction area, accelerate the electron conduction rate and improve the electrochemical performance. Thus, the sponge of the invention is nickel/Ni9S8The material has the characteristics of long cycle life and low overpotential, and has wide application prospect in the fields of mobile communication, electric automobiles, solar power generation, aerospace and the like.