A method for preparing chromium-based electrocatalyst using chromium-containing waste chips

Abstract

The present invention discloses a method for preparing a chromium-based electrocatalyst using chromium-containing waste chips, specifically: soaking the chromium-containing waste chips in deionized water, then pouring them into a homogenizer to crush them, then washing them with water and drying them; dissolving RuCl3 in deionized water and stirring to obtain a RuCl3 solution; then slowly adding the pretreated chromium-containing waste chips to the RuCl3 solution, and stirring the resulting mixture at room temperature; then recovering the product by centrifugation, washing it with water several times, and drying it; placing the RuCl3-loaded chromium-containing catalyst precursor in a tubular furnace for calcination, cooling it to room temperature, and collecting the resulting black product, which is a chromium-based electrocatalyst. The chromium-based electrocatalyst synthesized using chromium-containing waste chips in the present invention has excellent hydrogen evolution reaction performance; in addition, its preparation process is simple, which can effectively reduce the emission of chromium-containing waste and the pollution it causes to the environment.

Description

Technical Field

[0001] The invention belongs to the technical field of catalytic material preparation, and particularly relates to a method for preparing a chromium-based electrocatalyst by utilizing chromium-containing waste chips. Background Art

[0002] Currently, alkaline electrolyzers are the most mature and cost-effective hydrogen production technologies for water electrolysis, and commercial hydrogen production is typically carried out under alkaline conditions. Over the past few decades, researchers have focused on the preparation of novel electrocatalysts for the hydrogen evolution reaction (HER). To ensure efficient and continuous hydrogen evolution reaction (HER), catalysts must promote proton reduction with minimal overpotential to minimize additional energy consumption. Platinum is considered a benchmark catalyst for the HER due to its optimal binding to hydrogen, resulting in low overpotential, small Tafel slope, and high current density. However, in addition to its high cost and scarcity, Pt suffers from poor electrochemical stability, which is associated with leaching in corrosive electrolytes and irreversible aggregation of Pt nanoparticles, limiting its practical application. To replace Pt, efforts have been focused on developing catalysts based on earth-abundant elements for the HER, such as phosphates, carbides, oxides, and transition metal sulfides. However, these catalysts often suffer from low electrochemical activity and poor durability.

[0003] Metal doping is an effective way to improve catalyst performance by changing the electronic structure of the catalyst surface. By doping with metal elements, the conductivity of the catalyst can be enhanced, and additional active sites can be introduced to reduce the kinetic barrier of the HER reaction, thereby promoting the HER reaction. Recently, researchers have synthesized an endogenous oxide material (Cr) with excellent oxygen evolution reaction performance under acidic conditions. 0.6 Ru 0.4 O2), experimental results and DFT calculations indicate that Cr has a positive impact on OER performance. Dong et al. fabricated 4.4 wt% CoCrRu LDHs, demonstrating excellent OER electrocatalytic activity. DFT calculations revealed the importance of the synergistic effect between Cr, Ru, and Co in promoting OER activity. However, chromium and its compounds are known to be harmful to humans and the environment. Therefore, minimizing environmental harm while utilizing Cr is crucial.

[0004] Chromium (Cr) is widely used in numerous industries, including the leather industry, automotive interior design, chemical metallurgy, and aerospace. The chrome tanning process employed in the leather industry generates a significant portion of waste containing chromium, a rich source of chromium. Currently, researchers are primarily interested in extracting and utilizing collagen from chromium-containing leather waste. After industrial alkaline treatment converts chromium-containing leather waste into products such as industrial collagen, chromium remains in the chromium-containing soil. If chromium-containing sludge is discharged directly into the environment without treatment, it can seep through the soil into the ground, contaminating surface and groundwater sources and ultimately leading to chromium poisoning. However, there are few reports on the utilization of chromium resources in chromium-containing sludge generated from leather waste. Theoretically, converting the chromium in chromium-containing sludge into highly efficient catalysts is a reasonable approach to achieve high-value utilization of waste chromium resources, with minimal changes. This approach avoids the environmental risk of discarding new chromium-containing materials created through the "waste-to-treasure" concept. Summary of the Invention

[0005] The object of the present invention is to provide a method for preparing a chromium-based electrocatalyst using chromium-containing waste chips. The chromium-based electrocatalyst synthesized using chromium-containing waste chips has excellent hydrogen evolution reaction performance.

[0006] The technical solution adopted by the present invention is a method for preparing a chromium-based electrocatalyst using chromium-containing waste chips, which is specifically implemented according to the following steps:

[0007] Step 1: soaking the chromium-containing waste chips in deionized water, then pouring them into a homogenizer to crush them, and then washing them with water and drying them;

[0008] Step 2: dissolving RuCl3 in deionized water and stirring to obtain a RuCl3 solution; then slowly adding the chromium-containing waste chips pretreated in step 1 to the RuCl3 solution, and stirring the resulting mixture at room temperature; then recovering the product by centrifugation, washing it with water several times, and drying it;

[0009] Step 3: Place the RuCl3-loaded chromium-containing catalyst precursor in a tubular furnace for calcination. After cooling to room temperature, collect the resulting black product, which is the chromium-based electrocatalyst.

[0010] The present invention is also characterized in that:

[0011] In step 1, the mass ratio of chromium-containing waste chips to deionized water is 1:5-10; and the crushing time is 1-5 minutes.

[0012] In step 2, the mass concentration of the RuCl3 solution is 0.1-10 mg / mL.

[0013] In step 2, the drying temperature is 70° C. and the drying time is 6 h; the first stirring time is 5 min, and the second stirring time is 20 h.

[0014] In step 3, the calcination conditions are: heating to 500-900° C. at a rate of 5° C. / min under a nitrogen atmosphere and keeping the temperature for 3 h.

[0015] The beneficial effects of the present invention are:

[0016] (1) The present invention realizes the resource utilization of chromium in chromium-containing waste scraps produced in the leather making process;

[0017] (2) The chromium-based electrocatalyst synthesized from chromium-containing waste chips in the present invention has excellent hydrogen evolution reaction (HER) performance, providing a new idea for the preparation of high-performance and low-cost electrocatalysts;

[0018] (3) The preparation process of the present invention is simple and can effectively reduce the emission of chromium-containing waste and the pollution it causes to the environment;

[0019] (4) The chromium-based electrocatalyst synthesized from chromium-containing waste chips in the present invention has excellent HER performance under alkaline conditions and can be used in industrial water electrolysis to produce hydrogen. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 1 is a polarization curve diagram of chromium-based electrocatalysts prepared at different concentrations according to the present invention;

[0021] Figure 2 is a Tafel diagram of the chromium-based electrocatalyst of the present invention;

[0022] Figure 3 is the Nyquist plot of the chromium-based electrocatalyst of the present invention;

[0023] Figure 4 1 is a graph showing the cyclic stability test results of the chromium-based electrocatalyst of the present invention and a commercial platinum-carbon catalyst;

[0024] Figure 5 is the XRD pattern of the chromium-based electrocatalyst of the present invention;

[0025] Figure 6 This is a HAADF-STEM image of the chromium-based electrocatalyst of the present invention and the corresponding EDS surface scan image;

[0026] Figure 7 It is a transmission electron microscope image of the chromium-based electrocatalyst of the present invention. DETAILED DESCRIPTION

[0027] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0028] The present invention provides a method for preparing a chromium-based electrocatalyst using chromium-containing waste chips, which is specifically implemented according to the following steps:

[0029] Step 1, pretreatment of chromium-containing waste: soak the chromium-containing waste discarded from the factory in deionized water, then pour it into a homogenizer to crush it, and then wash it with water and dry it;

[0030] The mass ratio of chromium-containing waste chips to deionized water is 1:5-10;

[0031] Crushing time is 1-5min;

[0032] Step 2: dissolving anhydrous ruthenium trichloride (RuCl3) in deionized water and stirring for 5 minutes to obtain a RuCl3 solution; then slowly adding the chromium-containing waste chips pretreated in step 1 to the RuCl3 solution, and stirring the resulting mixture at room temperature for 20 hours; then recovering the product by centrifugation and washing it with water three times to remove the RuCl3 remaining on the surface of the chromium-containing waste chips; finally, placing the RuCl3-loaded chromium-containing catalyst precursor in an oven for drying;

[0033] The mass concentration of RuCl3 solution is 0.1-10 mg / mL; the drying temperature is 70°C and the drying time is 6 hours;

[0034] Step 3: Place the RuCl3-loaded chromium-containing catalyst precursor in a tube furnace for calcination. After cooling to room temperature, collect the resulting black product, which is the chromium-based electrocatalyst;

[0035] The calcination conditions were as follows: heating to 500-900°C at a rate of 5°C / min under nitrogen atmosphere and keeping the temperature for 3 h;

[0036] Chromium-containing scrap has a large specific surface area, which facilitates the adsorption of ruthenium atoms from the RuCl₃ solution. Furthermore, the numerous -COOH groups in the chromium-containing scrap structure form bonds with ruthenium atoms, reducing their aggregation into metal nanoparticles during high-temperature calcination and maximizing catalytic activity. Furthermore, experiments have demonstrated that the metallic chromium in the chromium-containing scrap also plays a synergistic role in promoting the catalyst.

[0037] Example 1

[0038] (1) Pretreatment of chromium-containing waste: Weigh 50 g of factory-discarded chromium-containing waste, add 500 mL of deionized water, pour it into a homogenizer and crush it for five minutes, then wash and dry it;

[0039] (2) 0.25 g of anhydrous ruthenium trichloride was dissolved in 250 mL of deionized water and stirred for 5 minutes. Then, 2 g of the treated chromium-containing waste chips in 1 was weighed and slowly added to the RuCl3 solution. The resulting mixture was stirred at room temperature for 20 hours.

[0040] (3) After impregnation, the product was recovered by centrifugation and washed three times with water to remove the RuCl3 remaining on the surface of the chromium-containing waste chips. Finally, the RuCl3-loaded chromium-containing catalyst precursor was placed in an oven and dried at 70°C for 6 hours.

[0041] (4) Finally, the RuCl3-loaded chromium-containing catalyst precursor was placed in a tube furnace and heated to 500°C at a heating rate of 5°C / min under a nitrogen atmosphere and maintained for 3 hours. After cooling to room temperature, the resulting black product was collected.

[0042] Example 2

[0043] (1) Pretreatment of chromium-containing waste: Weigh 50 g of factory-discarded chromium-containing waste, add 500 mL of deionized water, pour it into a homogenizer and crush it for five minutes, then wash and dry it;

[0044] (2) 0.5 g of anhydrous ruthenium trichloride was dissolved in 500 mL of deionized water and stirred for 5 minutes. Then, 2 g of the treated chromium-containing waste chips in (1) was weighed and slowly added to the RuCl3 solution. The resulting mixture was stirred at room temperature for 20 hours.

[0045] (3) After impregnation, the product was recovered by centrifugation and washed three times with water to remove the RuCl3 remaining on the surface of the chromium-containing waste chips. Finally, the RuCl3-loaded chromium-containing catalyst precursor was placed in an oven and dried at 70°C for 6 hours.

[0046] (4) Finally, the RuCl3-loaded chromium-containing catalyst precursor was placed in a tube furnace and heated to 800°C at a heating rate of 5°C / min under a nitrogen atmosphere and maintained for 3 hours. After cooling to room temperature, the resulting black product was collected.

[0047] Example 3

[0048] (1) Pretreatment of chromium-containing waste: Weigh 100 g of chromium-containing waste discarded from the factory, add 1 L of deionized water to it, pour it into a homogenizer and crush it for 5 minutes, then wash and dry it;

[0049] (2) 1 g of anhydrous ruthenium trichloride was dissolved in 1 L of deionized water and stirred for 5 minutes. Then, 2 g of the treated chromium-containing waste chips in (1) was weighed and slowly added to the RuCl3 solution. The resulting mixture was stirred at room temperature for 20 hours.

[0050] (3) After impregnation, the product was recovered by centrifugation and washed three times with water to remove the RuCl3 remaining on the surface of the chromium-containing waste chips. Finally, the RuCl3-loaded chromium-containing catalyst precursor was placed in an oven and dried at 70°C for 6 hours.

[0051] (4) Finally, the RuCl3-loaded chromium-containing catalyst precursor was placed in a tube furnace and heated to 900°C at a heating rate of 5°C / min under a nitrogen atmosphere and maintained for 3 hours. After cooling to room temperature, the resulting black product was collected.

[0052] Comparative Example

[0053] Weigh 50 g of chromium-containing waste chips discarded from the factory, add 500 mL of deionized water to it, pour it into a homogenizer and crush it for five minutes, wash it and dry it, then put it into a tube furnace and heat it to 500°C at a heating rate of 5°C / min under a nitrogen atmosphere, and maintain it for 3 hours. After cooling to room temperature, collect the resulting black product.

[0054] Figure 1 The polarization curves (LSV) of chromium-based electrocatalysts prepared at different concentrations are shown. Among the prepared electrocatalysts, the catalyst prepared by calcining waste leather scraps without RuCl3 loading in the control group has the lowest catalytic activity and almost no catalytic performance, which may be due to the lack of active materials, indicating that coupling chromium-containing waste scraps with metallic ruthenium atoms is essential for the catalyst to have good HER performance. The catalysts prepared by calcining waste leather scraps loaded with RuCl3 showed better catalytic performance than simple waste leather scraps. When the catalyst was prepared at a concentration of 0.1 mg / mL, they still showed poor HER activity with a relatively high overpotential at 10 mA / cm 2 The HER activity of the chromium-based electrocatalyst was 234 mV at 10 mA / cm2, which was attributed to the low content of ruthenium in the catalyst. 2 The overpotential at 100 mV is only 32 mV, which is almost comparable to that of commercial platinum-carbon catalysts. However, when the concentration of RuCl3 continues to increase to 100 mV, the HER performance decreases. This is because, on the one hand, a large number of metal particles agglomerate, resulting in a decrease in specific surface area. On the other hand, excessive loading of ruthenium metal leads to insufficient contact between the active material and the carbon-based material formed after calcination of chromium-containing waste, thereby reducing the electrical conductivity of the catalyst.

[0055] Figure 2The Tafel plots obtained from the LSV polarization curves for all catalysts are shown. Smaller Tafel slopes indicate stronger electron transfer capability for the same current density and a smaller overpotential requirement, indicating faster HER kinetics. The RuCl3 concentration of 1 mg / mL exhibited the smallest Tafel slope of only 71.1 mV / dec, further confirming its excellent HER activity. EIS analysis was further performed to evaluate the transport kinetics of the resulting chromium-based electrocatalysts. Figure 3 The Nyquist plot shows that when the concentration of RuCl3 is 1 mg / mL, the catalyst exhibits the smallest semicircle diameter, confirming the optimal charge transfer ability to promote the HER process. Figure 4 The cyclic stability test of chromium-based electrocatalyst and commercial platinum-carbon catalyst was shown. After 10,000 cyclic voltammetry (CV) tests, the chromium-based electrocatalyst exhibited a stable electrochemical performance at a current density of 10 mA / cm 2 When the overpotential of the chromium-based electrocatalyst was increased by only 13 mV from the initial 32 mV to 45 mV, it was superior to the commercial platinum-carbon catalyst.

[0056] The catalyst was characterized by XRD to further confirm the composition of the catalyst. Figure 5 It can be seen that the diffraction peaks in the figure clearly appear at several main peak positions at 24.5°, 33.6°, 36.2°, and 54.8°, corresponding to the (0 1 2), (1 0 4), (1 10), and (1 1 6) crystal planes, respectively, which match the data of PDF#82-1484 and appear to be Cr2O3. No information about the metallic ruthenium element was detected by XRD, which is due to the low concentration of ruthenium. Figure 7 Shown is a transmission electron microscope (TEM) image of a chromium-based electrocatalyst. From the TEM results, it can be seen that the catalyst has a jelly-like shape, is relatively regular, and is about 150 nanometers in size. Figure 6 This is the HAADF-STEM image of the chromium-based electrocatalyst and the corresponding EDS surface scan image, showing the presence of Ru element.

Claims

1. A method for preparing a chromium-based electrocatalyst using chromium-containing waste chips, characterized in that: Please follow the steps below to implement: Step 1: soaking the chromium-containing waste chips in deionized water, then pouring them into a homogenizer to crush them, and then washing them with water and drying them; The mass ratio of chromium-containing waste chips to deionized water is 1:5-10; the crushing time is 1-5 minutes; Step 2: dissolving RuCl3 in deionized water and stirring to obtain a RuCl3 solution; the mass concentration of the RuCl3 solution is 0.1-10 mg / mL; then slowly adding the chromium-containing waste chips pretreated in step 1 to the RuCl3 solution, and stirring the resulting mixture at room temperature; then recovering the product by centrifugation, washing it with water several times, and drying it; Step 3: Place the RuCl3-loaded chromium-containing catalyst precursor in a tubular furnace for calcination. After cooling to room temperature, collect the resulting black product, which is the chromium-based electrocatalyst.

2. The method for preparing a chromium-based electrocatalyst using chromium-containing waste chips according to claim 1, characterized in that: In the step 2, the drying temperature is 70° C. and the drying time is 6 h; the first stirring time is 5 min, and the second stirring time is 20 h.

3. The method for preparing a chromium-based electrocatalyst using chromium-containing waste chips according to claim 1, characterized in that: In step 3, the calcination conditions are: heating to 500-900° C. at a rate of 5° C. / min under a nitrogen atmosphere and keeping the temperature for 3 hours.

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