Hydrogen production catalyst for electrolysis of various sewage and preparation method thereof

Abstract

The present application relates to electrolytic hydrogen production from various water sources and simultaneous metal recovery from wastewater, and discloses a sulfur-doped carbon-coated ultra-low iridium loading particle catalyst, wherein the iridium particles are uniformly sized and uniformly dispersed in sulfur-doped carbon nanosheets. The present application also provides a preparation method for the sulfur-doped carbon-coated ultra-low iridium loading particle catalyst, comprising the following steps: step 1, placing 12-18 mg of iridium chloride trihydrate, 0.8-1.2 g of L-methionine and 0.15-0.25 g of sulfur in a ball mill jar, collecting and drying after ball milling for 2 h, and then calcining under an inert atmosphere; step 2, immersing the above powder in CS2 liquid, stirring for 2 h, freeze-drying, and then calcining under an inert atmosphere. The sulfur-doped carbon-coated ultra-low iridium loading particle catalyst prepared by the present application has uniform particle size, all less than 3 nm, and is uniformly dispersed in sulfur-doped carbon nanosheets. Meanwhile, the iridium loading is only 9.81%, and the utilization rate of iridium elements is higher.

Description

Technical Field

[0001] The present invention relates to the technical field of hydrogen production by electrolyzing multiple water sources, and in particular to a catalyst for producing hydrogen by electrolyzing sewage and simultaneously recovering metals in the sewage, and a preparation method thereof. Background Art

[0002] Hydrogen production from water electrolysis is one of the effective paths to achieving a clean, low-carbon transition in the global energy structure. Currently, water electrolysis hydrogen production technologies primarily utilize alkaline electrolysis systems and proton exchange membrane electrolysis systems. Both of these technologies rely on high-purity freshwater as a water source. However, freshwater accounts for a small portion of Earth's water resources, and most of it is contaminated water that cannot be used directly, such as domestic and industrial wastewater. Directly electrolyzing contaminated water to produce hydrogen would reduce pressure on freshwater resources and alleviate the current energy and environmental crisis. However, contaminated water is filled with complex but high-concentration metal ions and organic matter. As electrolysis proceeds, electrode materials suffer severe corrosion. Therefore, developing efficient, corrosion-resistant electrode materials for hydrogen production from contaminated water electrolysis presents significant challenges.

[0003] In the process of electrolysis of contaminated water to produce hydrogen, the reduction effect of the cathode can reduce water to hydrogen. Due to the efficient reduction reaction, the pH of the catalyst surface area will change sharply, causing the metal ions to form insoluble precipitates. If a suitable catalyst can be developed to enable the cathode to carry out the above reaction efficiently and corrosion-resistantly, the metal ions in the electrolyte of contaminated water containing a large amount of metal ions can be directly recovered. In the treatment of contaminated water and industrial treatment and recycling of contaminated water, several flocculation and precipitation and several disinfection treatments are required, which requires huge costs. Therefore, the use of the cathode reduction effect of electrolysis of water to produce hydrogen and the regional increase of pH to produce hydrogen while precipitating and recovering metals has a high practical application value. However, this requires the cathode to be corrosion-resistant and highly stable.

[0004] Most catalysts that can meet the above requirements contain precious metal elements. Based on the need to reduce the cost of catalytic materials, when using precious metal elements as synthetic raw materials, it is necessary to ensure high performance while reducing the precious metal element loading in the catalyst, thereby improving the utilization efficiency of precious metal elements.

[0005] Therefore, developing a highly efficient, low-precious metal-loaded catalyst that can simultaneously electrolyze multiple water sources to produce hydrogen and recover metal ions from contaminated water is crucial for the efficient utilization of polluted water resources. However, this approach also presents significant challenges. Furthermore, it requires simple electrolysis equipment and catalytic materials capable of electrolyzing contaminated water at low potentials, high current densities, and high stability. Summary of the Invention

[0006] In order to solve the technical problems raised in the background technology, the present invention provides a catalyst for producing hydrogen by electrolyzing sewage and a preparation method thereof.

[0007] The present invention is implemented by the following technical solution: a sulfur-doped carbon-wrapped ultra-low iridium loading particle catalyst, wherein the iridium particles in the catalyst are uniform in size and evenly dispersed in the sulfur-doped carbon nanosheets.

[0008] The present invention also proposes a method for preparing a sulfur-doped carbon-coated ultra-low iridium loading particle catalyst, comprising the following steps:

[0009] Step 1: 12-18 mg of iridium chloride trihydrate, 0.8-1.2 g of L-methionine, and 0.15-0.25 g of sublimed sulfur are placed in a ball mill and milled for 2 hours. The pale yellow product is collected and dried in a vacuum drying oven at 60°C for 12 hours. The dried pale yellow powder is placed in a quartz boat, placed in a tube furnace, and calcined to obtain a black powder.

[0010] Step 2: Immerse the black powder in CS2 liquid, stir for 2 h, and then freeze-dry at -50°C for 12 h; the dried black powder is placed in a quartz boat and calcined in a tube furnace, and then cooled to obtain a catalyst.

[0011] Preferably, under the condition that the mass ratio of L-methionine, sublimed sulfur and iridium chloride trihydrate is 200:40:3, increasing the amount of the three can achieve large-scale synthesis.

[0012] Preferably, the calcination conditions in step 1 and step 2 are: in an Ar gas flow, the temperature is raised to 900° C. at programmed heating rates of 5° C. / min and 20° C. / min, respectively, and the mixture is calcined at a constant temperature for 60 min and 30 min.

[0013] The present invention proposes a method for preparing an electrode material. 5 mg of the catalyst prepared by the above method is weighed and then dispersed in 0.5 mL of a mixed solution containing anhydrous ethanol and naphthol in a volume ratio of 47:3. Ultrasonic dispersion is performed for 60 minutes to obtain a uniformly dispersed mixed solution. The obtained mixed solution is evenly dispersed and applied to an area of ​​0.5×0.5 cm 2 The carbon cloth is placed on the carbon cloth and the carbon cloth is dried.

[0014] The present invention provides an electrode material, which is prepared by adopting the preparation method of the electrode material.

[0015] This invention proposes an electrolytic system for hydrogen production from contaminated water. This system utilizes the aforementioned electrode materials as working electrodes, a Pt sheet as a counter electrode, and an Ag / AgCl electrode as a reference electrode to form a three-electrode system for testing hydrogen production from electrocatalytic water splitting. The wastewater used in this scheme includes, but is not limited to, domestic sewage, seawater, and chlor-alkali wastewater; recovered metals include, but are not limited to, magnesium, calcium, and iron.

[0016] Linear sweep voltammetry (LSV) was used to explore the electrocatalytic activity of the catalyst, and the constant potential method was used to test the change of current over time at a fixed potential to illustrate the stability of the catalyst.

[0017] The present invention proposes a method for producing hydrogen by electrolyzing contaminated water and recovering metals in the contaminated water. The above-mentioned electrode materials are used as working electrodes and counter electrodes to form a dual-electrode system. Solar panels are used to generate electricity, and an H-type electrolyzer is used to explore its hydrogen production and metal precipitation activity.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] The present invention uses an inexpensive, easily mass-produced method to prepare the catalyst. The method, which involves calcination and subsequent CS2 solution treatment to synthesize sulfur-doped carbon-encapsulated iridium particles, is simple and efficient to operate, enabling large-scale synthesis and promising broad application prospects in practical, large-scale industrial applications.

[0020] The sulfur-doped carbon-wrapped ultra-low iridium loading granular catalyst prepared by the present invention has uniform particle size, all less than 3nm, and is evenly dispersed on the sulfur-doped carbon nanosheets. At the same time, the iridium loading is only 9.81%, achieving more efficient utilization of the iridium element.

[0021] The sulfur-doped carbon-coated ultra-low iridium loading particle catalyst proposed in this invention can be used as a bifunctional electrocatalyst, showing excellent hydrogen evolution and metal recovery capabilities under contaminated water conditions. For the hydrogen evolution reaction, stability at high currents can be achieved, and the overpotential of a neutral buffer solution prepared with contaminated water as an electrolyte is 0.9 V. vs RHE, current density up to 1000 mA cm -2 At the same time, the pH in the cathode region changes dramatically, inducing metal ion deposition and thus recovering metals, achieving efficient resource recovery and maintaining a stable effect for hundreds of hours. The catalyst has high practical application value.

[0022] The solar hydrogen production device proposed in this invention uses solar panels to generate electricity, and a neutral buffer solution prepared from contaminated water serves as the electrolyte, achieving renewable energy generation, online electrolysis of contaminated water to produce hydrogen, and metal recovery. This device achieves efficient and stable catalytic cracking of contaminated water to produce hydrogen while simultaneously recovering metal ions, opening up a new path for efficient, low-cost, and large-scale hydrogen production and metal recovery. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is an optical photograph of a large-scale synthesis of sulfur-doped carbon-wrapped ultra-low iridium loading particle catalysts prepared by the present invention.

[0024] Figure 2It is the X-ray diffraction (XRD) pattern of the sulfur-doped carbon-wrapped ultra-low iridium loading particle catalyst prepared by the present invention.

[0025] Figure 3 This is a transmission electron microscope (TEM) photograph of the sulfur-doped carbon-wrapped ultra-low iridium loading particle catalyst prepared by the present invention.

[0026] Figure 4 X-ray photoelectron spectroscopy (XPS) diagram of the sulfur-doped carbon-wrapped ultra-low iridium loading particle catalyst prepared by the present invention.

[0027] Figure 5 This is a thermogravimetric analysis graph of the sulfur-doped carbon-wrapped ultra-low iridium loading particle catalyst prepared by the present invention.

[0028] Figure 6 It is a linear voltammetric sweep curve (LSV) diagram of the sulfur-doped carbon-wrapped ultra-low iridium loading particle catalyst prepared by the present invention in a contaminated water electrolyte.

[0029] Figure 7 The present invention is a curve showing the change in current density over time (it) of the sulfur-doped carbon-wrapped ultra-low iridium loading particle catalyst prepared in the present invention in a contaminated water electrolyte.

[0030] Figure 8 This is a schematic diagram illustrating metal ion deposition during wastewater electrolysis using the sulfur-doped carbon-coated ultra-low iridium loading granular catalyst prepared in the present invention. Figure a is an optical photograph of the cathode cell before the electrolysis experiment begins, Figure b is an optical photograph of the cathode cell during the electrolysis experiment, Figure c is an optical photograph of the cathode cell at the end of the electrolysis experiment, and Figure d is an optical photograph of the precipitated product obtained in the cathode cell after the electrolysis experiment.

[0031] Figure 9 This is the XPS graph of the precipitated product obtained in the cathode cell after the electrolysis experiment.

[0032] Figure 10 This is a schematic diagram of the actual operation of hydrogen evolution from wastewater under sunlight using the sulfur-doped carbon-wrapped ultra-low iridium loading granular catalyst prepared by the present invention. DETAILED DESCRIPTION

[0033] The present invention will be further described below in conjunction with the accompanying drawings and specific implementation methods. It should be noted that, in the event of any conflict, the various embodiments or technical features described below can be arbitrarily combined to form new embodiments.

[0034] Example 1

[0035] The chemical reagents used in this invention were all analytically pure L-methionine, iridium chloride trihydrate, sublimed sulfur, and CS2. The purity of the inert gas (argon) used in step 1 was 99.999%. All carbon cloths were purchased from Taiwan, China. All wastewater was sourced from Hefei, China.

[0036] Example 2

[0037] A method for preparing a sulfur-doped carbon-encapsulated ultra-low iridium loading granular catalyst comprises the following steps: 5 mg of iridium chloride trihydrate, 1 g of L-methionine, and 0.2 g of sublimed sulfur are placed in a ball mill and milled at 500 rpm for 2 hours. The pale yellow product is collected and dried in a 60°C vacuum drying oven for 12 hours. The dried pale yellow powder is placed in a quartz boat and placed in a tube furnace. The temperature is ramped at a rate of 5°C / min to 900°C in an Ar flow, and then calcined at this temperature for 60 minutes to obtain a black powder. The black powder is then immersed in CS2 liquid, stirred for 2 hours, and then frozen with liquid nitrogen and freeze-dried at -50°C for 12 hours. The resulting black powder is placed in a quartz boat and placed in a tube furnace. The temperature is ramped at a rate of 20°C / min to 900°C in an Ar flow, and then calcined at this temperature for 30 minutes to obtain a sulfur-doped carbon-encapsulated ultra-low iridium loading granular catalyst. Thermogravimetric testing determined that its iridium loading was only 9.81%.

[0038] Example 3

[0039] The present invention proposes an electrode prepared by using sulfur-doped carbon wrapped with ultra-low iridium loading particle catalyst. The preparation method thereof comprises the following steps: weighing 5 mg of the catalyst obtained in Example 1 above, dispersing it in 0.5 mL of a mixed solution containing anhydrous ethanol and naphthol in a volume ratio of 47:3, ultrasonically dispersing it for 60 minutes to obtain a uniformly dispersed mixed solution, and then uniformly dispersing it on an area of ​​0.5×0.5 cm 2 The carbon cloth coated with the catalyst was directly used as the working electrode after drying, and the Ag / AgCl electrode was used as the reference electrode, the Pt electrode was used as the counter electrode, and the sewage was used as the electrolyte.

[0040] Example 4

[0041] This solution uses the electrodes prepared in Example 2 as working electrodes, a Pt electrode as a counter electrode, and an Ag / AgCl electrode as a reference electrode to form a three-electrode system in an H-type electrolyzer. A neutral buffer solution prepared from sewage was used as the electrolyte for electrocatalytic sewage decomposition and hydrogen production testing. Linear sweep voltammetry (LSV) was used to investigate the electrocatalytic activity of the catalyst, and the constant potential method was used to investigate the change in current over time at a fixed potential to investigate the catalyst stability. Testing showed that the current density was as high as 1000 mA cm-2 It can be stable for 350 h, which shows the high efficiency and stability of the catalyst.

[0042] Electrocatalytic recovery of metals from wastewater: The constant potential method in Example 3 was used to test the change in current over time at a fixed potential. The white precipitate at the bottom of the electrolyte was collected, centrifuged and filtered, and dried in a vacuum drying oven at 60°C for 5 hours. After being ground into powder in a mortar, the main components were determined by XPS.

[0043] Example 5

[0044] This scheme proposes a method for electrolyzing wastewater to produce hydrogen and recovering metal ions in contaminated water. The electrodes prepared in Example 2 are used as working electrodes and counter electrodes to form a dual-electrode system. Solar panels are used to generate electricity as a power source, and a neutral buffer solution prepared from contaminated water is used as an electrolyte to achieve simultaneous electrolysis of contaminated water to produce hydrogen and recover metals.

[0045] like Figure 10 As shown, establishing a solar-powered wastewater electrolysis system for hydrogen production and metal recovery is undoubtedly the best way to promote the application of water splitting technology and wastewater treatment. Using commercial solar panels as the power system, during actual assembly, the electrolytic cell where the working electrode resides produced intense bubbles (inset). This demonstrates the excellent electrocatalytic performance of the device for hydrogen production from wastewater.

[0046] Result analysis:

[0047] like Figure 1 The optical photographs show that a large amount of catalyst can be obtained by increasing the raw materials of the sulfur-doped carbon-wrapped ultra-low iridium loading granular catalyst prepared by the present invention, indicating that the method for preparing the sulfur-doped carbon-wrapped ultra-low iridium loading granular catalyst of the present invention is simple and can be synthesized in large quantities.

[0048] like Figure 2 As shown, the catalyst was subjected to phase analysis using XRD, and the obtained diffraction peaks corresponded one-to-one with the metal iridium whose standard substance card number was JCPDS: 46-1044, indicating that the material synthesized by the present invention was metal iridium.

[0049] like Figure 3 As shown, according to the low-resolution TEM images, iridium nanoparticles are evenly dispersed on the two-dimensional graphitic carbon, and the average size is less than 3 nm.

[0050] like Figure 4 As shown, according to the full XPS spectrum, it can be known that the carbon-encapsulated iridium particles contain Ir, S, and C elements, indicating that the carbon material obtained in the present invention is a sulfur-doped and modified carbon material, that is, a sulfur-doped carbon-encapsulated iridium nanoparticle material is prepared.

[0051] like Figure 5As shown, according to thermogravimetric analysis, the iridium loading is only 9.81%, which is lower than the loading of common iridium catalysts on the market.

[0052] like Figure 6 As shown in the LSV test results, the sulfur-doped carbon-wrapped ultra-low iridium loading granular catalyst prepared by the present invention can produce hydrogen by electrolysis of sewage with a current density of 10 mA cm -2 The overpotential required is only 34 mV, which is lower than that of commercial Pt / C. In addition, the current density is as high as 1000 mA cm at an overpotential of 950 mV. -2 , which can achieve low voltage and high current hydrogen production effect.

[0053] like Figure 7 As shown in the curve of current density variation with time under constant potential, the catalyst can maintain a high current density (1000 mA cm) for hundreds of hours in the electrolysis of sewage test. -2） At the same time, by observing the metal precipitation in the cathode pool (as shown in Figure 8), it can be seen that precipitates are obviously precipitated from the catalyst. By XPS detection (as shown in Figure 9), the main 2+ ,Mg 2+ , Fe 3+ Elements (and trace amounts of other elements, mainly depending on the composition of metal ions in sewage) have high practical application value.

[0054] The above embodiments are only preferred embodiments of the present invention and cannot be used to limit the scope of protection of the present invention. Any non-substantial changes and replacements made by technicians in this field on the basis of the present invention fall within the scope of protection required by the present invention.

Claims

1. A method for preparing a sulfur-doped carbon-coated ultra-low iridium loading particle catalyst, wherein the iridium particles in the catalyst are uniform in size and evenly dispersed in sulfur-doped carbon nanosheets, characterized in that: The steps include: Step 1: 12-18 mg of iridium chloride trihydrate, 0.8-1.2 g of L-methionine, and 0.15-0.25 g of sublimed sulfur are placed in a ball mill and milled for 2 hours. The pale yellow product is collected and dried in a vacuum drying oven at 60° C. for 12 hours. The dried pale yellow powder is placed in a quartz boat, placed in a tube furnace, and calcined to obtain a black powder. Step 2: soaking the black powder in CS2 liquid, stirring for 2 hours, and then freeze-drying at -50°C for 12 hours; the dried black powder was placed in a quartz boat and calcined in a tube furnace, and then cooled to obtain a catalyst; The calcination conditions in step 1 and step 2 are as follows: in an Ar gas flow, the temperature is raised to 900° C. at programmed heating rates of 5° C. / min and 20° C. / min, respectively, and the temperature is kept constant for 60 min and 30 min, respectively.

2. The method for preparing a sulfur-doped carbon-coated ultra-low iridium loading granular catalyst according to claim 1, characterized in that: Under the condition that the mass ratio of L-methionine, sublimed sulfur and iridium chloride trihydrate is 200:40:3, large-scale synthesis can be achieved by increasing the dosage of the three.

3. A method for preparing an electrode material, characterized in that: Weigh 5 mg of the catalyst prepared by any method of claims 1-2, and then disperse it in 0.5 mL of a mixed solution containing anhydrous ethanol: naphthol in a volume ratio of 47:

3. Ultrasonic dispersion is performed for 60 minutes to obtain a uniformly dispersed mixed solution. The obtained mixed solution is evenly dispersed on a carbon cloth with an area of ​​0.5×0.5 cm2, and the carbon cloth is dried to obtain the product.

4. An electrode material, characterized in that Prepared by the method as claimed in claim 3.

5. An electrolysis system for electrocatalytic hydrogen production from multiple water sources, characterized in that: The electrode material according to claim 4 is used as a working electrode, a Pt sheet is used as a counter electrode, and an Ag / AgCl electrode is used as a reference electrode to form a three-electrode system to catalyze water decomposition to produce hydrogen and simultaneously realize metal recovery in wastewater.

6. The electrolysis system for electrocatalytic hydrogen production from multiple water sources according to claim 5, characterized in that: The water sources used include domestic sewage, chlor-alkali wastewater, seawater, and distilled water; the recovered metals include magnesium, calcium, and iron.

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