Cl-Bi carbon dioxide reduction electrocatalyst, preparation method thereof and application of Cl-Bi carbon dioxide reduction electrocatalyst in preparation of formic acid through catalytic reduction of carbon dioxide

Abstract

The invention discloses a Cl-Bi carbon dioxide reduction electrocatalyst, a preparation method thereof and application of the Cl-Bi carbon dioxide reduction electrocatalyst in preparation of formic acid through catalytic reduction of carbon dioxide, and belongs to the technical field of electrocatalyst materials. The preparation method comprises the following steps: preparing a sodium chloride solution, adjusting the pH value with acid, adding Bi2O3, carrying out a stirring reaction, washing a reactant, and drying to obtain BiOCl; the preparation method comprises the following steps: dispersing BiOCl, carbon black and naphthol in ethanol, carrying out ultrasonic treatment to obtain ink, dripping the ink onto hydrophobic carbon paper, drying, and reducing under negative voltage to obtain the Cl-Bi carbon dioxide reduction electrocatalyst. The prepared Cl-Bi carbon dioxide reduction electrocatalyst is simple in preparation method, free of pollution, rich in raw material and low in price, and the Cl-Bi carbon dioxide reduction electrocatalyst has high formic acid production selectivity, high formic acid yield and excellent stability.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrocatalyst materials, and particularly relates to a Cl-Bi electrocatalyst for carbon dioxide reduction, a preparation method thereof, and an application thereof in catalytic reduction of carbon dioxide to formic acid. Background Art

[0002] Electrochemically reducing CO2 (CO2RR) to value-added fuels using distributed energy sources (such as solar energy, wind energy, tidal energy, etc.) is an effective strategy for reducing CO2 emissions, realizing CO2 resource utilization, and storing intermittent renewable energy. Due to the inertness of CO2 molecules and the diversity of products, efficient CO2RR still faces great challenges. Therefore, it is very necessary to develop efficient electrocatalysts to enhance the product selectivity of CO2RR and increase the product yield.

[0003] Developing efficient electrocatalysts for highly selective CO2RR has become a research hotspot. A series of products such as CO, methane, formate, methanol, ethylene, and alkanes with longer carbon chains can be produced through CO2RR. Among them, the production of CO, formate, and methane is one of the relatively easy reactions. In order to obtain products with high added value, Bi-based electrocatalysts have high selectivity for CO2RR to produce formic acid. However, due to the weak binding ability of Bi surface to H*, the available protonates on the Bi surface are insufficient, resulting in a low formic acid yield.

[0004] Acidic electroreduction CO2 to formic acid via interfacial modification of Bi nanoparticles at industrial-level current (Tian Dong et al., Nano Res., pp. 5818-5819) discloses an acidic electrochemical catalyst for reducing CO2 to formic acid by interfacial modification of Bi nanoparticles at industrial-level current density. However, the disclosed method for preparing the acidic electrochemical catalyst is relatively complex, and the selectivity for catalytic reduction of carbon dioxide to formic acid needs to be further improved.

[0005] Therefore, it is of great significance to develop a carbon dioxide reduction electrocatalyst with a simple preparation method and capable of preparing formic acid with high conversion rate and high selectivity. Summary of the Invention

[0006] Aiming at the problems of low formic acid production rate in the catalytic reduction of carbon dioxide by Bi-based electrocatalysts and the complex preparation process of modified Bi-based electrocatalysts, the present invention provides a Cl-Bi carbon dioxide reduction electrocatalyst, a preparation method thereof, and an application thereof in the catalytic reduction of carbon dioxide to prepare formic acid. The prepared electrocatalyst has high formic acid selectivity, high formic acid yield, excellent stability, and the method for preparing the Cl-Bi carbon dioxide reduction electrocatalyst is simple and easy to popularize and apply.

[0007] The present invention is realized through the following technical solutions: A preparation method of a Cl-Bi carbon dioxide reduction electrocatalyst, comprising the following steps: (1) Prepare a sodium chloride solution, adjust the pH value with an acid, add Bi2O3, stir and react, wash and dry the reactant to obtain BiOCl; (2) Disperse BiOCl, carbon black, and naphthol in ethanol, ultrasonically obtain an ink, drop the ink on a hydrophobic carbon paper, dry it, and place it in an electrolyte solution to be reduced under a negative voltage to obtain a Cl-Bi carbon dioxide reduction electrocatalyst.

[0008] Further, in step (1), the concentration of chloride ions in the sodium chloride solution is 2000-3000 mg•L -1 ; the pH value of the sodium chloride solution is adjusted to 1-3 with concentrated nitric acid.

[0009] Further, in step (1), the mass ratio of Bi2O3 to chloride ions is 2-3:5.

[0010] Further, in step (1), the stirring reaction time is 6-12 h, the stirring rate is 400-1000 r•min -1 , wash with water and ethanol, and dry at 60 °C.

[0011] Further, in step (2), the mass-volume ratio of BiOCl, carbon black, and naphthol is 1 mg:0.5 mg:5-10 μL.

[0012] Further, in step (2), the ultrasonic time is 10-30 min, the negative voltage reduction potential is -0.85 to -0.95 V vs. RHE, and the negative voltage reduction time is 0.5-1.5 h; the electrolyte solution in step (2) is an aqueous solution of 0.2-0.8 mol•L -1 of NaHCO3.

[0013] Further, the preparation method of Bi2O3 in step (1) is: 1) Dissolve cetyltrimethylammonium bromide in water to obtain a mixed solution A; 2) Dissolve bismuth nitrate in a dilute nitric acid solution to obtain a mixed solution B; 3) Add the mixed solution A to the mixed solution B, stir and react, and wash and dry the obtained product to obtain Bi2O3.

[0014] Furthermore, in step 3), the molar ratio of cetyltrimethylammonium bromide to bismuth nitrate is 0.7:1.

[0015] In the present invention, the Cl-Bi carbon dioxide reduction electrocatalyst prepared by the above preparation method.

[0016] In the present invention, the application of the Cl-Bi carbon dioxide reduction electrocatalyst in the catalytic reduction of carbon dioxide to prepare formic acid.

[0017] Beneficial effects The preparation method of the Cl-Bi carbon dioxide reduction electrocatalyst prepared in the present invention is simple, pollution-free, with rich raw materials and low price; the Cl-Bi carbon dioxide reduction electrocatalyst has high formic acid selectivity, high formic acid yield and excellent stability. Description of the drawings

[0018] Figure 1 It is the scanning electron microscope image of the Cl-Bi carbon dioxide reduction electrocatalyst in Example 1; Figure 2 It is the high-angle annular dark-field scanning transmission and elemental Mapping image of the Cl-Bi carbon dioxide reduction electrocatalyst in Example 1, (a) high-resolution transmission electron microscope image, (b) high-angle annular dark-field scanning transmission image, (c) Bi elemental Mapping image, (d) Cl elemental Mapping image; Figure 3 It is the XPS image of the Cl-Bi carbon dioxide reduction electrocatalyst in Example 1, (a) high-resolution XPS image of Cl 2p, (b) high-resolution XPS image of Bi 4f; Figure 4 It is the carbon dioxide reduction performance image of the Cl-Bi carbon dioxide reduction electrocatalyst in Examples 1-3, (a) Example 1, (b) Example 2, (c) Example 3; Figure 5 It is the stability test image of the electrocatalytic carbon dioxide reduction of the Cl-Bi carbon dioxide reduction electrocatalyst in Example 1 for continuous operation for 35 hours. Detailed implementation manners

[0019] In order to further understand the present invention, the preferred implementation manners of the present invention will be described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, rather than limiting the claims of the present invention.

[0020] Example 1 (1) Ultrasonically dissolve 0.35 mmol of cetyltrimethylammonium bromide (for 15 min) in 40 mL of water to obtain a mixed solution A; (2) Drop 0.5 mmol of Bi(NO3)3·5H2O into 5 mL of 0.4 M HNO3 to obtain a mixed solution B; (3) Add the mixed solution B to the mixed solution A, stir and react for 3 h, centrifuge to collect the obtained precipitate, wash it repeatedly with water and ethanol, and dry it at 60 °C overnight to obtain Bi2O3; (4) Mix NaCl and distilled water to obtain 20 mL of a sodium chloride solution containing 2300 mg L -1 chloride ions. Adjust the pH value to 1 with concentrated HNO3, add 100 mg of Bi2O3, and stir at 600 r min -1 at room temperature for 8 h. Centrifuge to collect the supernatant, wash it repeatedly with water and ethanol, and dry it at 60 °C overnight to obtain BiOCl; (5) Disperse 1 mg of BiOCl, 0.5 mg of carbon black, and 6 μL of naphthol in 250 mL of absolute ethanol to prepare an ink. Ultrasonicate for 15 min, and evenly drop the sonicated ink on one side of a hydrophobic carbon paper (size: 1.0 cm × 1.0 cm), and let it dry naturally overnight to be used as a working electrode. Then, form a three-electrode system with a counter electrode (carbon rod) and a reference electrode (silver-silver chloride). Place the above three electrodes in a 0.5 mol•L -1 aqueous sodium bicarbonate solution (pH = 7.4), and reduce it at -0.9 V vs. RHE for 1 h to obtain a Cl-Bi carbon dioxide reduction electrocatalyst.

[0021] Example 2 (1) Ultrasonically dissolve 0.35 mmol of cetyltrimethylammonium bromide (for 15 min) in 40 mL of water to obtain a mixed solution A; (2) Drop 0.5 mmol of Bi(NO3)3·5H2O into 5 mL of 0.4 M HNO3 to obtain a mixed solution B; (3) Add the mixed solution B to the mixed solution A, stir and react for 3 h, centrifuge to collect the obtained precipitate, wash it repeatedly with water and ethanol, and dry it at 60 °C overnight to obtain Bi2O3; (4) Mix NaCl and distilled water to obtain 20 mL of a sodium chloride solution containing 2600 mg L -1 chloride ions. Adjust the pH value to 1 with concentrated HNO3, add 100 mg of Bi2O3, and stir at 600 r min -1 at room temperature for 8 h. Centrifuge to collect the supernatant, wash it repeatedly with water and ethanol, and dry it at 60 °C overnight to obtain BiOCl; (5) Disperse 1 mg of BiOCl, 0.5 mg of carbon black, and 6 μL of naphthol in 250 mL of absolute ethanol to prepare an ink. Ultrasonic for 15 min, and evenly drop the ultrasonic ink on one side of a hydrophobic carbon paper (size: 1.0 cm × 1.0 cm), and let it dry naturally overnight to be used as a working electrode. Then, form a three-electrode system with a counter electrode (carbon rod) and a reference electrode (silver-silver chloride). Place the above three electrodes in an aqueous sodium bicarbonate solution (pH = 7.4) of 0.5 mol•L -1 After reduction at -0.9 V vs. RHE for 1 h, a Cl-Bi carbon dioxide reduction electrocatalyst is obtained.

[0022] Example 3 (1) Ultrasonic (15 min) and dissolve 0.35 mmol of cetyltrimethylammonium bromide in 40 mL of water to obtain a mixed solution A; (2) Drop 0.5 mmol of Bi(NO3)3·5H2O into 5 mL of 0.4 M HNO3 to obtain a mixed solution B; (3) Add the mixed solution B to the mixed solution A, stir and react for 3 h, centrifuge to collect the obtained precipitate, wash it repeatedly with water and ethanol, and dry it at 60 °C overnight to obtain Bi2O3; (4) Mix NaCl and distilled water to obtain 20 mL of a sodium chloride solution containing 2300 mg L -1 of chloride ions. Adjust the pH value to 1 with concentrated HNO3, add 100 mg of Bi2O3, and stir at 600 r min -1 at room temperature for 8 h. Centrifuge to collect the supernatant, wash it repeatedly with water and ethanol, and dry it at 60 °C overnight to obtain BiOCl; (5) Disperse 1 mg of BiOCl, 0.5 mg of carbon black, and 6 μL of naphthol in 250 mL of absolute ethanol to prepare an ink. Ultrasonic for 15 min, and evenly drop the ultrasonic ink on one side of a hydrophobic carbon paper (size: 1.0 cm × 1.0 cm), and let it dry naturally overnight to be used as a working electrode. Then, form a three-electrode system with a counter electrode (carbon rod) and a reference electrode (silver-silver chloride). Place the above three electrodes in an aqueous sodium bicarbonate solution (pH = 7.4) of 0.5 mol•L -1 After reduction at -0.85 V vs. RHE for 1 h, a Cl-Bi carbon dioxide reduction electrocatalyst is obtained.

[0023] Example 4 (1) Ultrasonic (15 min) and dissolve 0.35 mmol of cetyltrimethylammonium bromide in 40 mL of water to obtain a mixed solution A; (2) Add 0.5 mmol Bi(NO3)3·5H2O to 5 mL 0.4 M HNO3 to obtain mixed solution B. (3) Add mixed solution B to mixed solution A, stir and react for 3 h, collect the resulting precipitate by centrifugation, wash repeatedly with water and ethanol, and dry at 60 °C overnight to obtain Bi2O3; (4) Mix NaCl and distilled water to obtain 20 mL of 2300 mg L -1 The sodium chloride solution containing chloride ions was adjusted to pH 1 by concentrated HNO3, 100 mg Bi2O3 was added, and the mixture was heated at 600 r min at room temperature. -1 After stirring for 8 h, the supernatant was collected by centrifugation, washed repeatedly with water and ethanol, and dried at 60 °C overnight to obtain BiOCl; (5) 1 mg BiOCl, 0.5 mg carbon black, and 6 μL naphthol were dispersed in 250 mL anhydrous ethanol to prepare ink. The ink was ultrasonically treated for 15 min. The ultrasonic ink was evenly dropped on one side of a hydrophobic carbon paper (size: 1.0 cm × 1.0 cm). The paper was dried overnight and used as a working electrode. The ink was then used as a three-electrode system with a counter electrode (carbon rod) and a reference electrode (silver-silver chloride). The three electrodes were placed in a 0.5 mol•L -1 The Cl-Bi CO2 reduction electrocatalyst was obtained after reduction in an aqueous sodium bicarbonate solution (pH = 7.4) at -0.9 V vs. RHE for 1.5 h.

[0024] Performance Test: The scanning electron microscope image of the Cl-Bi carbon dioxide reduction electrocatalyst prepared in Example 1 is as follows: Figure 1 As shown, it can be seen that the Cl-Bi carbon dioxide reduction electrocatalyst prepared in Example 1 is a nanoflower morphology; the high-angle annular dark field scanning transmission and element mapping image of the Cl-Bi carbon dioxide reduction electrocatalyst prepared in Example 1 are as shown Figure 2 As shown, (a) is a high-resolution transmission electron microscope image, (b) is a high-angle annular dark field scanning transmission image, (c) and (d) are Bi and Cl element mapping images respectively; Figure 2 It can be seen that the lattice structure on the nanoflower corresponds to Bi. The Bi and Cl elements in the Cl-Bi carbon dioxide reduction electrocatalyst are evenly distributed on the nanoflower, which also confirms the successful doping of the Cl element.

[0025] The XPS graph of the Cl-Bi carbon dioxide reduction electrocatalyst in Example 1 is as follows: Figure 3 It can be seen that (a) is the Cl 2p high-resolution XPS graph, and (b) is the Bi 4f high-resolution XPS graph; Figure 3It can be seen that in the high-resolution XPS spectrum of Cl 2p, the peaks at 197.1 and 199.3 eV correspond to Cl 2p 2 / 3 and Cl 2p 1 / 3 in the Cl-Bi electrocatalyst for carbon dioxide reduction in Example 1 respectively; the peaks at 158.1 and 163.4 eV correspond to Bi 4f 7 / 2 and Bi 4f 5 / 2 in the Cl-Bi catalyst in Example 1 respectively.

[0026] The carbon dioxide reduction performance diagrams of the Cl-Bi electrocatalysts for carbon dioxide reduction prepared in Examples 1-3 are as shown in Figure 4 , corresponding to (a), (b) and (c) respectively; it can be seen from Figure 4 that the carbon dioxide reduction products of the Cl-Bi electrocatalysts for carbon dioxide reduction are all formic acid, carbon monoxide and hydrogen; at -0.95 V vs. RHE, the selectivity of the Cl-Bi electrocatalyst for carbon dioxide reduction prepared in Example 1 to formic acid products is as high as 96%, the selectivity of the Cl-Bi electrocatalyst for carbon dioxide reduction prepared in Example 2 to formic acid products reaches 91%, and the selectivity of the Cl-Bi electrocatalyst for carbon dioxide reduction prepared in Example 3 to formic acid products reaches 93%.

[0027] The stability test diagram of the Cl-Bi electrocatalyst for electrocatalytic carbon dioxide reduction running continuously for 35 hours is as shown in Figure 5 . It can be seen from Figure 5 that the Cl-Bi electrocatalyst for carbon dioxide reduction prepared in Example 1 still maintains stable performance after continuously electrocatalytic carbon dioxide reduction for 35 hours.

Claims

1. A preparation method of a Cl-Bi carbon dioxide reduction electrocatalyst, characterized in that, It includes the following steps: (1) Prepare a sodium chloride solution, adjust the pH value with an acid, add Bi2O3, stir and react, wash and dry the reactant to obtain BiOCl; (2) Disperse BiOCl, carbon black and naphthol in ethanol, obtain ink by ultrasonic treatment, drop the ink on a hydrophobic carbon paper, dry it, and place it in an electrolyte solution to be reduced under a negative voltage to obtain a Cl-Bi carbon dioxide reduction electrocatalyst.

2. The preparation method of the Cl-Bi carbon dioxide reduction electrocatalyst according to claim 1, characterized in that, In step (1), the concentration of chloride ions in the sodium chloride solution is 2000-3000 mg•L -1 ; the pH value of the sodium chloride solution is adjusted to 1-3 with concentrated nitric acid.

3. The preparation method of the Cl-Bi carbon dioxide reduction electrocatalyst according to claim 1, wherein, In step (1), the mass ratio of Bi2O3 to chloride ions is 2-3:

5.

4. The preparation method of the Cl-Bi carbon dioxide reduction electrocatalyst according to claim 1, characterized in that, The stirring reaction time in step (1) is 6 to 12 h, and the stirring rate is 400 to 1000 r•min -1 , washed with water and ethanol, and dried at 60 °C.

5. The preparation method of the Cl-Bi carbon dioxide reduction electrocatalyst according to claim 1, characterized in that, In step (2), the mass-volume ratio of BiOCl, carbon black and naphthol is 1 mg: 0.5 mg: 5-10 μL.

6. The preparation method of the Cl-Bi carbon dioxide reduction electrocatalyst according to claim 1, characterized in that, In step (2), the ultrasonic time is 10 - 30 min, the reduction potential of the negative voltage is -0.85 to -0.95 V vs. RHE, and the reduction time of the negative voltage is 0.5 - 1.5 h; the electrolyte solution described in step (2) is an aqueous solution of NaHCO3 with a concentration of 0.2 - 0.8 mol•L -1 -1.

7. The preparation method of the Cl-Bi carbon dioxide reduction electrocatalyst according to claim 1, characterized in that, The preparation method of Bi2O3 in step (1) is as follows: 1) Dissolve cetyltrimethylammonium bromide in water to obtain a mixed solution A; 2) Dissolve bismuth nitrate in a dilute nitric acid solution to obtain a mixed solution B; 3) Add the mixed solution A to the mixed solution B, stir and react, wash and dry the obtained product to obtain Bi2O3.

8. The preparation method of the Cl-Bi carbon dioxide reduction electrocatalyst according to claim 7, wherein, In step 3), the molar ratio of cetyltrimethylammonium bromide to bismuth nitrate is 0.7:

1.

9. A Cl-Bi carbon dioxide reduction electrocatalyst prepared by the preparation method according to any one of claims 1 to 8.

10. An application of the Cl-Bi carbon dioxide reduction electrocatalyst according to claim 9 in the catalytic reduction of carbon dioxide to prepare formic acid.

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