Preparation method of nickel-cobalt-based sulfide catalyst and application thereof in electrolysis of water

Abstract

The application is synthesis of nickel cobalt sulfide with foamed nickel as substrate, and relates to preparation method and application of oxygen evolution electrocatalyst. First, nickel cobalt organic framework precursor is synthesized on foamed nickel by solvothermal method with cobalt nitrate, nickel nitrate and adenine as raw materials, then sulfur element is doped by using high-temperature controllable heat treatment method under nitrogen atmosphere to synthesize a kind of efficient oxygen evolution electrocatalyst. When the catalyst is used for electrolysis of water in 1 M KOH solution, only 109 mV overpotential is needed to reach 10 mA / cm 2 The current density, and the Tafel slope is only 38.81 mV / dec, and the performance of the catalyst can still be maintained stable after long time use.

Description

Technical Field

[0001] This invention belongs to the field of electrocatalytic nanomaterials, specifically relating to a method for preparing a nickel-cobalt-based sulfurized oxygen evolution electrocatalyst and its application in the oxygen evolution reaction of water electrolysis. Background Technology

[0002] The increasingly serious environmental problems and the depletion of fossil fuels are constantly impacting people's production and lives, making the development of new energy materials an urgent research topic. Driven by the global demand for energy security and sustainable development technologies, finding efficient methods for producing clean energy and storing it safely has become a top priority. Water electrolysis is one of the most efficient ways to produce clean energy—hydrogen—but the oxygen evolution reaction (OER) at the anode limits the efficiency of water electrolysis. Therefore, highly active and stable electrocatalysts must be used to overcome kinetic barriers and promote the rapid and stable progress of the reaction.

[0003] Commercially available Ir / Ru-based OER catalysts have limited their industrial application due to their high cost. Therefore, developing transition metal-based catalysts to replace noble metal materials is a feasible and viable option. Currently, researchers have synthesized a large number of non-noble metal materials with high OER performance, such as spinel oxides, perovskites, and layered double hydroxides, with overpotentials generally above 200 mV. Sulfides, with their high conductivity and rich redox chemistry, and diverse structures, are expected to become ideal alternatives to noble metal catalysts. Developing novel sulfide materials for OER is of great significance. Electrocatalytic water splitting, as a sustainable green energy production process, is emerging as a promising alternative to hydrogen production, potentially addressing the energy crisis and increasingly serious environmental problems. Summary of the Invention

[0004] This invention provides a method for preparing a nickel-cobalt-based sulfide catalyst and its application in water electrolysis. Application studies show that this catalyst exhibits excellent oxygen evolution electrocatalytic activity and good chemical stability. This material is a nickel-cobalt-based sulfide composite material synthesized via a simple hydrothermal method and a high-temperature sulfidation method. The objective of this invention is achieved through the following technical solutions: First, cobalt nitrate, nickel nitrate, and adenine were weighed according to a specific feeding ratio and placed in a beaker containing a certain amount of deionized water. The mixture was ultrasonically dissolved at room temperature for 30 minutes. Then, the treated nickel foam and the ultrasonically dissolved solution were placed together in a reactor and reacted at 120℃ for 12 hours to obtain nickel foam supported on the nickel-cobalt precursor. Next, the nickel foam supported on the nickel-cobalt precursor was placed at the inlet of a tube furnace, and sulfur powder was weighed and placed at the inlet. The reaction was carried out at 350℃ for 2 hours to obtain a nickel-cobalt-based sulfide catalyst. This catalyst requires only 109 mV overpotential to reach 10 mA / cm² when electrolyzing water in 1 M KOH solution.2 The catalyst exhibits a high current density and a Tafel slope of only 38.81 mV / dec, and its performance remains stable even after 40 hours of use. These results suggest that the nickel-cobalt sulfide catalyst of this invention holds promise for use in the oxygen evolution reaction (OER) of electrocatalytic reactions.

[0005] The advantages of this invention are: The raw materials used in the preparation method of this invention are abundant and inexpensive, the process is simple and easy to operate, and the nickel-cobalt-based sulfide catalyst prepared according to the above method exhibits high-efficiency OER performance, indicating that the obtained nickel-cobalt sulfide catalyst is a highly efficient oxygen evolution reaction catalyst.

[0006] The essential features of this invention are: This invention utilizes a simple process route and mild reaction conditions to prepare a nickel-cobalt-based sulfide oxygen evolution catalyst. The method for preparing the nickel-cobalt-based sulfide precursor involves a reactant mass ratio of cobalt nitrate: nickel nitrate: adenine = 1:0.999:2.784. The solvent used in this method is deionized water, with 16.892 mL of water used per gram of adenine and 29.100 mL of water used per gram of the cobalt nitrate and nickel nitrate mixture. The reaction conditions are: a reaction temperature of 120℃ and a reaction time of 12 h. The synthesized nickel-cobalt-based sulfide oxygen evolution electrocatalyst exhibits excellent performance in the oxygen evolution reaction under electrocatalytic conditions. The nickel-cobalt-based sulfide oxygen evolution electrocatalyst of this invention requires only 109 mV overpotential to reach 10 mA / cm² in the electrolysis of water using 1 M KOH solution. 2 The current density. Attached Figure Description

[0007] Figure 1 This is the X-ray diffraction pattern of a nickel-cobalt-based sulfide catalyst; Figure 2 This is a scanning electron microscope image of a nickel-cobalt-based sulfide catalyst; Figure 3 This is a transmission electron microscope (TEM) image of a nickel-cobalt-based sulfide catalyst. Figure 4 This is an energy-dispersive X-ray spectroscopy image of a nickel-cobalt-based sulfide catalyst; Figure 5 This is a polarization curve of the oxygen evolution reaction of a nickel-cobalt-based sulfide catalyst; Figure 6 This is a Tafel slope diagram of the oxygen evolution reaction of nickel-cobalt-based sulfide catalysts; Figure 7 This is a graph showing the stability test of the oxygen evolution reaction of a nickel-cobalt-based sulfide catalyst. Implementation Example

[0008] Pretreatment of the substrate nickel foam (NF): 20mm × 35mm × 1.5mm nickel foam sheets were sequentially sonicated in 3M hydrochloric acid solution for 30 minutes, in a 1:1 acetone-ethanol mixture for 20 minutes, then sonicated in deionized water for 10 minutes, washed three times with deionized water, and finally rinsed at 60°C. o Clean nickel foam was obtained by drying in a vacuum oven for 6 hours. 0.2027g of adenine was placed in a beaker containing 12mL of deionized water and sonicated at room temperature for 10 minutes to obtain solution 1. 0.0727g of nickel nitrate hexahydrate and 0.0728g of cobalt nitrate hexahydrate were placed in a beaker containing 5mL of deionized water and sonicated at room temperature for 10 minutes to obtain a mixed solution 2 of nickel cobalt nitrate. At room temperature, under the action of ultrasound, the mixed solution 2 of nickel cobalt nitrate was added dropwise to solution 1 and sonicated for 30 minutes to obtain mixed solution 3. The prepared nickel foam and mixed solution 3 were transferred to a reactor. The reactor was heated in an oven at a starting temperature of 30°C and a heating rate of 6°C / min. When the temperature reached 120°C, a hydrothermal reaction was carried out at this temperature for 12 hours to obtain a nickel foam-supported metal-organic framework. The obtained nickel-foamed metal-organic framework was washed three times with deionized water at 60°C. o Dry nickel foam-loaded metallo-organic frameworks were obtained by drying in a vacuum oven at C for 6 hours. The dried nickel foam-supported metallo-organic framework obtained above was cut into blocks of 20mm×20mm×1.5mm and placed on the left side of a ceramic boat. 0.5g of sulfur powder was placed on the right side. The ceramic boat was placed in a tube furnace, and nitrogen gas was introduced from the right side for 20 minutes. The initial temperature was 30℃, and the heating rate was 3℃ / min. When the temperature reached 350℃, it was kept at this temperature for 2 hours to carry out a high-temperature sulfidation reaction to obtain a nickel-cobalt-based sulfide catalyst.

[0009] The present invention also provides a method for using the above-mentioned nickel-cobalt-based sulfide catalyst in the oxygen evolution reaction of water electrolysis.

[0010] The ability of nickel-cobalt-based sulfide catalysts to electrocatalyze water splitting and oxygen evolution was tested using a standard three-electrode system on an electrochemical workstation. The specific test method is as follows: Polarization curves (LSV) and cyclic voltammetry (CV) were performed using a CHI 760E electrochemical workstation in a 1M KOH solution. A carbon rod was used as the counter electrode, and Hg / HgO was used as the reference electrode. To eliminate interference, nitrogen gas was bubbled into the electrolyte for 30 minutes before each experiment to remove dissolved oxygen. The scan rate was set to 5 mV / s. -1 .

[0011] The Tafel curve is obtained by plotting the overpotential (η) against log(j), and the electrocatalytic oxygen evolution kinetics of the catalyst is evaluated by the Tafel slope.

[0012] According to the X-ray diffraction test method Figure 1 Analysis revealed that the nickel-cobalt-based sulfide catalyst obtained in this invention contains Co3S4, NiS, and Co, as shown in the scanning electron microscope image (…). Figure 2 The image shows that the catalyst is composed of numerous prisms, as indicated by energy-dispersive X-ray spectroscopy (EDX-mapping). Figure 3 The transmission electron microscope (TEM) showed that Ni, Co, and S were uniformly distributed. Figure 4 The results show that there are Co3S4(220) crystal planes, NiS(220) crystal planes, and Co(002) crystal planes.

[0013] Figure 5 The figure shows the linear sweep voltammetric polarization curve of the product obtained in the examples as a catalyst in 1 M KOH. The figure shows that the nickel-cobalt-based sulfide catalyst obtained in this invention has good electrocatalytic activity, and its catalytic water electrolysis requires only 109 mV overpotential to reach 10 mA / cm. 2 current density, Figure 6 The figure shows the Tafel slope of the product obtained in the examples. It indicates that the nickel-cobalt-based sulfide catalyst obtained in this invention has a low Tafel slope, with a Tafel slope of only 38.81 mV / dec. Figure 7 The product obtained in this invention is subjected to constant current density (10 mA / cm²). 2 The performance remained stable even after 40 hours of continuous testing.

Claims

1. A method for preparing a nickel-cobalt-based sulfide catalyst, characterized in that, 0.2027 g adenine was added to a beaker containing 12 mL of deionized water and sonicated at room temperature to obtain solution 1. 0.0727 g nickel nitrate hexahydrate and 0.0728 g cobalt nitrate hexahydrate were added to 5 mL of deionized water and sonicated at room temperature to obtain a mixed solution 2 of nickel-cobalt nitrate. At room temperature, under ultrasonic treatment, the mixed solution 2 of nickel-cobalt nitrate was added dropwise to solution 1 and sonicated for 30 minutes to obtain mixed solution 3. Then, the treated nickel foam and the sonicated mixed solution were placed together in a reactor and reacted at 120 °C for 12 h to obtain nickel foam supported on nickel-cobalt precursor. The nickel foam supported on nickel-cobalt precursor was then placed at the inlet of a tubular furnace, and sulfur powder was weighed and placed at the gas inlet. The reaction was carried out at 350 °C for 2 h to obtain a nickel-cobalt-based sulfide catalyst. The synthesized nickel-cobalt-based sulfide oxygen evolution electrocatalyst was applied to the oxygen evolution reaction under electrocatalytic conditions.

2. The method for preparing a nickel-cobalt-based sulfide catalyst as described in claim 1, characterized in that, Nickel-cobalt-based sulfide catalysts require only 109 mV overpotential to reach 10 mA / cm² when electrolyzing water in 1 M KOH solution. 2 The current density.

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