Method for regulating characteristics of carbon-coated layer of ni-based heterostructure

Abstract

This invention discloses a method for controlling the properties of Ni-based heterostructure carbon coatings. The method involves using plasma electrodeposition to deposit Ni-containing... 2+ Fe 3+ / 2+ MoO4 2‑ Ionic salt compounds are used as the main salt component of the electrolyte. Organic solvents are selected as the carbon layer source. Resorcinol and formaldehyde are used to control carbon layer defects, sodium dodecyl sulfate is used to regulate carbon layer thickness, and butynediol is used to ensure the integrity and uniformity of the carbon layer coating. Plasma electrodeposition ensures that the carbon particle intermediates formed after the organic solvent decomposition are uniformly dispersed on the surface of the heterostructure without aggregation, resulting in a Ni-based@C heterostructure with controllable carbon coating thickness and defects. This invention can prepare carbon-coated metal / oxide heterojunctions, wherein the carbon layer is completely coated and of uniform thickness, with a higher proportion of carbon-oxygen defects in the carbon layer structure, achieving the goal of simultaneously improving catalyst activity and stability, and is applicable to the field of water electrolysis hydrogen production catalysts.

Description

Technical Field

[0001] This invention relates to the field of electrocatalytic materials technology, and more specifically, to a method for regulating the properties of Ni-based heterostructured carbon coatings. Background Technology

[0002] The high cost of precious metals such as Pt limits their practical application in catalysts. Using non-precious metals like Ni to prepare water electrolysis catalysts can significantly reduce costs. The construction of heterojunctions can significantly improve overall catalytic activity, with carbon coating effectively enhancing the catalytic stability of the heterojunction.

[0003] Metal / oxide heterojunctions constructed using plasma electrodeposition are prone to oxidation or reduction reactions during water electrolysis, leading to compositional / structural transformations and decreased activity. Therefore, coating the catalytic active sites with a carbon coating layer can effectively prevent structural failure during water electrolysis. Appropriate carbon layer thickness is crucial for ensuring both stability and effective catalytic activity of the protected active sites. Furthermore, increasing surface defects in the carbon layer enhances electron / proton transfer, further improving catalyst activity.

[0004] To address the issues of incomplete carbon coating, uneven carbon layer thickness, insufficient carbon defects leading to limited stability / activity improvement, and reduced activity due to some catalytically active materials remaining directly exposed in the electrolyte, we effectively avoided the problem of uneven coating caused by carbon layer aggregation by controlling the cracking, dispersion, and adsorption steps of the organic solvent to form the carbon layer. This resulted in uniform coating around the grains. The integrity and uniformity of the carbon layer coating are crucial for preventing structural failure of the material. Therefore, regulating the characteristics of the carbon layer plays a vital role in the preparation of highly efficient and stable catalysts. Summary of the Invention

[0005] The purpose of this invention is to provide a method for controlling the properties of carbon coating layers in Ni-based heterostructures. This method involves partially replacing aqueous solutions with a three-carbon chain alcohol-based organic solvent (glycerol) for plasma electrodeposition to form a carbon coating layer, thereby controlling the integrity and properties of the carbon coating. A complete and uniform carbon coating significantly improves the stability of the catalytically active material in Ni-based heterostructures, while simultaneously enhancing the catalytic activity of the catalyst. This is a simple, efficient, stable, and widely applicable method for improving the stability of transition metal catalysts.

[0006] The above-mentioned technical objective of the present invention is achieved through the following technical solution:

[0007] A method for controlling the properties of Ni-based heterostructure carbon coatings, wherein the method uses Ni-containing... 2+ Fe3+ / 2+ / MoO4 2- A solution of ionic salt compounds is used as the main solution. An organic solvent is selected as the carbon layer source. Sodium dodecyl sulfate ensures that the carbon intermediates formed by the plasma ionization and cracking of glycerol are uniformly dispersed on the surface of the active particles without agglomeration. Butynediol ensures that the C* intermediates dispersed on the surface of the active particles are interconnected and stacked on the surface of the active ions. Resorcinol and formaldehyde, through a condensation reaction, can regulate carbon layer defects and transform them into an amorphous form. This forms a complete, uniform, and stable carbon coating layer, improving carbon layer inhomogeneity and preventing incomplete coating of active materials, thereby improving catalytic stability. A ring-shaped conductive material is used as the anode to ensure uniform electric field strength during electrodeposition. This invention can prepare carbon-coated metal / oxide heterojunctions, wherein the carbon layer is completely coated and has a uniform thickness (2-4 nm), with a higher proportion of carbon-oxygen (CO, C=O) defects in the carbon layer structure, achieving the goal of simultaneously improving catalyst activity and stability, and is applicable to the field of water electrolysis hydrogen production catalysts.

[0008] A method for controlling the properties of a Ni-based heterostructure carbon coating, wherein the present invention is configured to: apply a DC power supply of 60-160V for plasma electrodeposition arc initiation. The deposition time is 0.5-5 min.

[0009] Furthermore, nickel salts, iron salts, and molybdates are used as the main sources of active particle phases, glycerol is used as the main source for forming a uniform carbon layer, and sodium dodecyl sulfate, butynediol, resorcinol, and formaldehyde are used to regulate the carbon layer structure and morphology, which are then mixed to form the electrolyte. Among them, sodium dodecyl sulfate and butynediol are mainly used to regulate the thickness and uniformity of the carbon layer, while resorcinol and formaldehyde are used to regulate carbon layer defects.

[0010] Furthermore, in the electrolyte, the concentration of nickel salt is 0.1-1.0 mol / L, the concentration of iron salt is 0.01-0.1 mol / L, and the concentration of molybdate is 0.02-0.05 mol / L.

[0011] Furthermore, the electrolyte also includes glycerol at a volume fraction of 10%-50%, sodium dodecyl sulfate at a concentration of 0.1-0.6 g / L, butynediol at a concentration of 0.5-5 g / L, resorcinol at a concentration of 0.5-5 g / L, and formaldehyde gas at room temperature, which is passed into 1-5 ml of deionized water to form a saturated solution.

[0012] Furthermore, the Ni-containing 2+ Fe 3+ / 2+ / MoO4 2- Salts of ions include commonly used inorganic salts such as sulfates, nitrates, sodium salts, and potassium salts.

[0013] Furthermore, the organic solvent includes organic compounds with single-carbon or multi-carbon chain structures.

[0014] Furthermore, the cathode is degreased with acetone and the conductive material surface is removed with dilute sulfuric acid.

[0015] The uniform carbon layer Ni-based heterojunction electrocatalyst of the present invention is prepared by the above method.

[0016] The carbon layer morphology of the present invention is amorphous.

[0017] In summary, the preparation method and the catalyst prepared in this invention have the following advantages and beneficial effects:

[0018] (1) This invention has excellent catalytic activity: 10 mA·cm -2 The overpotential for complete hydrolysis at current density is 247 mV.

[0019] (2) This invention exhibits excellent catalytic stability at a constant current of 10 mA·cm⁻¹. -2 The overpotential increase was 6mV after 12 hours of testing. Attached Figure Description

[0020] Figure 1 These are LSV curves of the total hydrolysis catalytic activity of Examples 1, 2, 3, Comparative Examples 1, 2, and 3 of the present invention;

[0021] Figure 2 These are transmission electron microscope (TEM) images of Comparative Example 1 of the present invention: a) low magnification, b) high magnification TEM images.

[0022] Figure 3 These are transmission electron microscope (TEM) images of Comparative Example 2 of the present invention: a) low magnification, b) high magnification TEM images.

[0023] Figure 4 These are transmission electron microscope (TEM) images of Comparative Example 3 of the present invention: a) low magnification, b) high magnification TEM images.

[0024] Figure 5 These are high-resolution TEM images and elemental distribution area scans of Embodiment 1 of the present invention, a, b) low magnification, c) high magnification and d) area scan elemental distribution;

[0025] Figure 6 Raman spectral characterization diagrams of Embodiment 1 and Comparative Example 3 of the present invention; Figure 7 These are the XPS spectra of Embodiment 1 and Comparative Example 3 of the present invention;

[0026] Figure 8 These are constant current stability test curves for Embodiment 1, Comparative Example 1, Comparative Example 2, and Comparative Example 3 of the present invention. Detailed Implementation

[0027] The present invention will be further described in detail below with reference to specific embodiments, but the implementation of the present invention is not limited thereto. For process parameters not specifically noted, conventional techniques can be referred to.

[0028] Example 1

[0029] A method for controlling the properties of Ni-based heterostructure carbon coatings includes the following steps:

[0030] (1) Conductive substrate pretreatment: The cathode is made of copper sheet (purity ≥99.9%) with a size of 10×50×1mm. It is ultrasonically cleaned in acetone and anhydrous ethanol for 10min respectively to remove oil stains, and then washed with deionized water to remove residues. It is then soaked in 0.1mol / L dilute sulfuric acid for 1min to remove surface oxide impurities.

[0031] (2) The plasma electrodeposition solution was prepared by mixing nickel sulfate, ferric sulfate, sodium molybdate, sodium dodecyl sulfate, butynediol, resorcinol, formaldehyde, glycerol, and water. The concentrations were: nickel sulfate 0.4 mol / L, ferric sulfate 0.02 mol / L, sodium molybdate 0.02 mol / L, glycerol 20% (volume fraction), sodium dodecyl sulfate 0.2 g / L, butynediol 1 g / L, resorcinol 1 g / L, and formaldehyde 2 ml of a saturated aqueous solution at room temperature. The voltage was 120 V, and the deposition time was 2 min.

[0032] (3) After preparation, the catalyst was washed with deionized water and dried in a drying oven at 40°C. A Ni-based heterojunction electrocatalyst with a uniform carbon-coated structure was obtained.

[0033] Example 2

[0034] A method for controlling the properties of Ni-based heterostructure carbon coatings includes the following steps:

[0035] (1) Conductive substrate pretreatment: The cathode is made of copper sheet (purity ≥99.9%) with a size of 10×50×1mm. It is ultrasonically cleaned in acetone and anhydrous ethanol for 10min respectively to remove oil stains, and then washed with deionized water to remove residues. It is then soaked in 0.1mol / L dilute sulfuric acid for 1min to remove surface oxide impurities.

[0036] (2) The plasma electrodeposition solution was prepared by mixing nickel sulfate, ferric sulfate, sodium molybdate, sodium dodecyl sulfate, butynediol, resorcinol, formaldehyde, glycerol, and water. The concentrations were: nickel sulfate 0.4 mol / L, ferric sulfate 0.02 mol / L, sodium molybdate 0.02 mol / L, glycerol 20% (volume fraction), sodium dodecyl sulfate 0.1 g / L, butynediol 1 g / L, resorcinol 1 g / L, and formaldehyde 2 ml of a saturated aqueous solution at room temperature. The voltage was 120 V, and the deposition time was 2 min.

[0037] (3) After preparation, the catalyst was washed with deionized water and dried in a drying oven at 40°C. A Ni-based heterojunction electrocatalyst with a uniform carbon-coated structure was obtained.

[0038] Example 3

[0039] A method for controlling the properties of Ni-based heterostructure carbon coatings includes the following steps:

[0040] (1) Conductive substrate pretreatment: The cathode is made of copper sheet (purity ≥99.9%) with a size of 10×50×1mm. It is ultrasonically cleaned in acetone and anhydrous ethanol for 10min respectively to remove oil stains, and then washed with deionized water to remove residues. It is then soaked in 0.1mol / L dilute sulfuric acid for 1min to remove surface oxide impurities.

[0041] (2) The plasma electrodeposition solution was prepared by mixing nickel sulfate, ferric sulfate, sodium molybdate, sodium dodecyl sulfate, butynediol, resorcinol, formaldehyde, glycerol, and water. The concentrations were: nickel sulfate 0.4 mol / L, ferric sulfate 0.02 mol / L, sodium molybdate 0.02 mol / L, glycerol 20% (volume fraction), sodium dodecyl sulfate 0.4 g / L, butynediol 1 g / L, resorcinol 1 g / L, and formaldehyde 2 ml of a saturated aqueous solution at room temperature. The voltage was 120 V, and the deposition time was 2 min.

[0042] (3) After preparation, the catalyst was washed with deionized water and dried in a drying oven at 40°C. A Ni-based heterojunction electrocatalyst with a uniform carbon-coated structure was obtained.

[0043] Comparative Example 1

[0044] A method for carbon-coated Ni-based heterostructures includes the following steps:

[0045] (1) Conductive substrate pretreatment: The cathode is made of copper sheet (purity ≥99.9%) with a size of 10×50×1mm. It is ultrasonically cleaned in acetone and anhydrous ethanol for 10min respectively to remove oil stains, and then washed with deionized water to remove residues. It is then soaked in 0.1mol / L dilute sulfuric acid for 1min to remove surface oxide impurities.

[0046] (2) The plasma electrodeposition solution was prepared by mixing nickel sulfate, ferric sulfate, sodium molybdate, sodium dodecyl sulfate, resorcinol, formaldehyde, glycerol, and water. The concentrations of nickel sulfate, ferric sulfate, sodium molybdate, and glycerol were 0.4 mol / L, 0.02 mol / L, and 20% (v / v). The concentrations of sodium dodecyl sulfate, resorcinol, and formaldehyde were 2 ml of a saturated aqueous solution at room temperature. The voltage was 120 V, and the deposition time was 2 min.

[0047] (3) After preparation, it is washed with deionized water and dried in a drying oven at 40°C. A Ni-based heterojunction electrocatalyst with a carbon-coated structure is obtained.

[0048] Comparative Example 2

[0049] A method for carbon-coated Ni-based heterostructures includes the following steps:

[0050] (1) Conductive substrate pretreatment: The cathode is made of copper sheet (purity ≥99.9%) with a size of 10×50×1mm. It is ultrasonically cleaned in acetone and anhydrous ethanol for 10min respectively to remove oil stains, and then washed with deionized water to remove residues. It is then soaked in 0.1mol / L dilute sulfuric acid for 1min to remove surface oxide impurities.

[0051] (2) The plasma electrodeposition solution was prepared by mixing nickel sulfate, ferric sulfate, sodium molybdate, butynediol, resorcinol, formaldehyde, glycerol, and water. The concentrations were: nickel sulfate 0.4 mol / L, ferric sulfate 0.02 mol / L, sodium molybdate 0.02 mol / L, butynediol 1 g / L, and glycerol 20% (volume fraction). The resorcinol concentration was 1 g / L, and the formaldehyde concentration was 2 ml of a saturated aqueous solution at room temperature. The voltage was 120 V, and the deposition time was 2 min.

[0052] (3) After preparation, it is washed with deionized water and dried in a drying oven at 40°C. A Ni-based heterojunction electrocatalyst with a carbon-coated structure is obtained.

[0053] Comparative Example 3

[0054] A method for carbon-coated Ni-based heterostructures includes the following steps:

[0055] (1) Conductive substrate pretreatment: The cathode is made of copper sheet (purity ≥99.9%) with a size of 10×50×1mm. It is ultrasonically cleaned in acetone and anhydrous ethanol for 10min respectively to remove oil stains, and then washed with deionized water to remove residues. It is then soaked in 0.1mol / L dilute sulfuric acid for 1min to remove surface oxide impurities.

[0056] (2) The plasma electrodeposition solution was formed by mixing nickel sulfate, ferric sulfate, sodium molybdate, butynediol, sodium dodecyl sulfate, glycerol, and water. The concentrations of nickel sulfate, ferric sulfate, sodium molybdate, sodium dodecyl sulfate, and glycerol were 0.4 mol / L, 0.02 mol / L, 0.02 mol / L, 0.2 g / L, 1 g / L, and 20% (v / v) of glycerol. The voltage was 120 V, and the deposition time was 2 min.

[0057] (3) After preparation, it is washed with deionized water and dried in a drying oven at 40°C. A Ni-based heterojunction electrocatalyst with a carbon-coated structure is obtained.

[0058] Catalyst microstructure and electrochemical catalytic activity characterization:

[0059] The prepared material was subjected to a full hydrolysis activity test, such as... Figure 1 The figure shows the total hydrolysis catalytic activity curves of Examples 1, 2, and 3, and Comparative Examples 1, 2, and 3. It can be seen that the examples effectively improve the catalytic activity. (10 mA·cm) -2 At the current density, the overpotentials of Comparative Example 1, Comparative Example 2, and Comparative Example 3 were 259mV, 280mV, and 336mV, respectively, while the overpotentials of Example 1, Example 2, and Example 3 were 247mV, 253mV, and 256mV, respectively.

[0060] To investigate the structural characteristics of the carbon layers, we performed high-resolution observations on Comparative Example 1, Comparative Example 2, Comparative Example 3, and Example 1, respectively. Figure 2 As shown, in Comparative Example 1, the active particles are surrounded by an amorphous structure with uneven thickness, fluctuating between 0-15 nm. The coating is incomplete, with some areas not fully coated, which is a result of carbon agglomeration. Figure 3 As shown, the carbon layer in Comparative Example 2 has very poor uniformity, with an outer layer of unevenly thick carbon, reaching a maximum thickness of 30 nm. This excessively thick carbon layer makes it difficult for the active material to effectively exert its catalytic effect. Figure 4 As shown, the carbon layer on the surface of Comparative Example 3 has obvious lattice stripes. The dense and ordered lattice stripes are difficult to ensure the transfer of H* during the catalytic process, which is not conducive to the overall catalytic process. Figure 5The high-resolution image of Example 1 shows a distinct coating structure that completely and uniformly covers the entire particle, with a thickness of approximately 3 nm. Compositional analysis reveals that Ni is primarily distributed within the core particle, while C is uniformly distributed across the entire surface, indicating the successful formation of the carbon coating structure.

[0061] Next, we will observe its phase composition and investigate the changes in the carbon layer structure. For example... Figure 6 The image shows the Raman spectra of Comparative Example 3 and Example 1, where the peak value at 1464 cm⁻¹ is [missing information]. -1 and 1577cm -1 The two peaks represent the sp of C defects (D bands) and C-C bonds, respectively. 2 The tensile vibration (G band) is correct. It can be seen that compared to Comparative Example 3, the D and G peaks of Example 1 are stronger, indicating that Example 1 forms more carbon, of which I... D / I G The larger ratio indicates that the carbon structure of Example 1 has more carbon defects.

[0062] To further investigate the chemical electronic states and bond structure characteristics of carbon, we performed X-ray photoelectron spectroscopy (XPS) analysis on Comparative Example 3 and Example 1. Figure 7 As shown, the proportion of CO and C=O bonds is higher in Example 1, indicating that the proportion of carbon defects formed in Example 1 is higher, which is consistent with the Raman spectroscopy analysis.

[0063] To investigate the effect of this coating structure change on catalytic stability, we conducted stability tests, such as... Figure 8 As shown, Example 1 and Comparative Examples 1, 2, and 3 were tested at 10 mA·cm⁻¹. -2 Under constant current density, the overpotential changes of both samples during the total hydrolysis catalysis were observed after 12 hours of constant current testing. It can be seen that the overpotentials of Comparative Examples 1, 2, and 3 increased by 15 mV, 10 mV, and 9 mV respectively during this process, while Example 1 only saw an increase of 6 mV. This indicates that the uniform coating of the carbon layer can effectively improve the catalytic stability of the catalyst. This is attributed to the cracking of the long-chain structure of glycerol under plasma electrodeposition, the uniform dispersion of cracked C around the active ions by sodium dodecyl sulfate, the promotion of C* particles to form a carbon coating around the active particles by butynediol, and the addition of resorcinol and formaldehyde to increase carbon structural defects, resulting in a uniform and suitable carbon layer.

[0064] The specific embodiments described herein are merely illustrative of the invention and are not intended to limit it. Those skilled in the art can make modifications to these embodiments without contributing any inventive step after reading this specification, but such modifications are protected by patent law as long as they fall within the scope of the claims of this invention.

Claims

1. A method for controlling the properties of a Ni-based heterostructure carbon coating, characterized in that: The method involves using a solution containing nickel compounds, iron compounds, and molybdate compounds as solutes to prepare a carbon-coated metal / oxide heterojunction all-water-splitting electrocatalyst via plasma electrodeposition. The concentration of nickel compounds in the solution used for plasma electrodeposition is 0.1-1.0 mol / L, the concentration of iron compounds is 0.01-0.1 mol / L, and the concentration of molybdate compounds is 0.02-0.05 mol / L. The deposition voltage is 60V-160V, and the deposition time is 0.5-5min. The solution also includes sodium dodecyl sulfate, butynediol, resorcinol, and formaldehyde. The concentration of sodium dodecyl sulfate is 0.1-0.6 g / L, the concentration of butynediol is 0.5-5 g / L, and the concentration of resorcinol is 0.5-5 g / L. Formaldehyde gas is introduced into 1-5 ml of deionized water at room temperature to form a saturated solution. An organic solvent that is miscible with water is used as the solvent to prepare the solution for plasma electrodeposition. The organic solvent is glycerol, with a volume fraction of 10%-50%. A ring-shaped conductive metal electrode is used as the anode, and a metal with good conductivity and a high melting point is selected as the catalyst support substrate for the cathode. The support substrate is selected from copper, iron, titanium, or tungsten.

2. The method for controlling the properties of Ni-based heterostructure carbon coatings according to claim 1, characterized in that: Before use, the conductive substrate is cleaned with organic solvents acetone and ethanol, and then soaked in 0.05-0.2 mol / L dilute sulfuric acid for 1-5 minutes to remove surface oil and oxide impurities.

3. The method for controlling the properties of Ni-based heterostructure carbon coatings according to claim 1, characterized in that: The method is specifically as follows: A catalyst for water electrolysis was prepared by using 0.1-1.0 mol / L of nickel compound, 0.01-0.1 mol / L of iron compound, 0.02-0.05 mol / L of molybdate compound, 0.1-0.6 g / L of sodium dodecyl sulfate, 0.5-5 g / L of butynediol, and 0.5-5 g / L of resorcinol, along with formaldehyde gas at room temperature, and passing them into 1-5 ml of deionized water to form a saturated solution. A voltage of 60V-160V was then applied to this solution using a DC power supply, and plasma electrodeposition was performed for 0.5-5 min.

4. The preparation method according to any one of claims 1-3 yields a Ni-based heterojunction electrocatalyst with a uniform carbon-coated structure.

5. The application of the method for regulating the characteristics of Ni-based heterostructure carbon coating layer according to claim 4 in the cathode and anode of the water electrolysis hydrogen production catalyst.

Images