Carbon paper loaded BiF 3 Preparation method and application of electrocatalytic CO 2

Abstract

The present invention belongs to the technical field of nanocomposite materials, and relates to a preparation method of carbon paper supported BiF3, which includes dispersing a fluorine source in DMF, adding a bismuth source and ultrasonically dispersing them evenly, transferring to a high-temperature reaction kettle, and carrying out solvothermal reaction at 160-180 °C for 2-4 h; the obtained product is filtered, washed, and vacuum dried at 60 °C to obtain BiF3 nanoparticles; the prepared BiF3 nanoparticles are evenly dispersed in a mixed solution of deionized water, ethanol and 5 wt% Nafion 117, dropped onto the surface of the washed carbon paper, and after drying, carbon paper supported bismuth trifluoride is obtained, and it is applied to electrocatalytic carbon dioxide. The present invention effectively controls the particle size of BiF3 by fluorine doping, while making the active sites uniform, improving the electron transfer efficiency, and regulating the electronic structure of Bi, thereby improving the performance of the electrocatalyst for reducing CO2 to formate (root); the preparation method is easy to control, the raw material cost is low, and the target product is easy to obtain, and it has good electrocatalytic reduction activity of CO2 to formate (root).

Description

Technical Field

[0001] The present invention belongs to the technical field of nanocomposite materials, and relates to a carbon-supported electrocatalyst, and in particular to a carbon paper-supported BiF 3 Preparation method and application of electrocatalytic CO 2 . Background Art

[0002] The current economic society has led to the large-scale use of fossil fuel energy during the Industrial Revolution, accompanied by energy crises and human-induced climate change, such as global warming and ocean acidification. From the 19th to the 21st century, the atmospheric CO 2 The concentration has increased by 1.5 times, and the rapid emission of carbon dioxide has caused immeasurable damage to the global ecosystem. 2 Emission or conversion of CO 2 For high value-added products, ultimately achieving carbon neutrality has become a key task in scientific research.

[0003] At present, electrocatalytic carbon dioxide reduction has the advantages of simple equipment, mild conditions and low cost. 2 It is a stable linear molecule with high bond energy and is not easy to break. The reduction process is usually accompanied by hydrogen evolution reaction in aqueous solution. The slow kinetics and complex multi-step reaction process make electrocatalytic CO 2 The efficiency, selectivity and stability of reduction need to be further improved, and the preparation of low-cost and high-performance electrocatalysts is of great significance.

[0004] Formic acid is a widely used chemical product. It can be directly used as a chemical fuel for formic acid fuel cells. It is also a good hydrogen storage material and an ideal target product. Bismuth-based materials have the advantages of low cost and low toxicity, and are effective in reducing CO 2 The reaction intermediates in the formic acid production pathway have suitable adsorption energy. The use of non-metallic modification can effectively reduce the hydrogen evolution effect and improve the electrocatalytic performance, change the electronic structure, increase the active sites, and increase the electrochemical active area. It is expected to become an excellent formic acid production electrocatalyst through modification. Summary of the invention

[0005] In view of the above-mentioned deficiencies in the prior art, the present invention aims to provide a carbon paper loaded BiF 3 Preparation method.

[0006] Technical Solution

[0007] A carbon paper loaded BiF 3 The preparation method comprises the following steps:

[0008] (1) dispersing a fluorine source in DMF, adding a bismuth source and ultrasonically dispersing the mixture uniformly, transferring the mixture to a high temperature reactor, and subjecting the mixture to a solvent thermal reaction at 160 to 180° C. for 2 to 4 hours, preferably at 160° C. for 4 hours, wherein the molar volume ratio of the fluorine source, the bismuth source, and DMF is 3 to 5 mmoL: 1 to 1.6 mmoL: 50 to 150 mL, preferably 3 mol: 1 mol: 50 mL;

[0009] (2) The obtained product was filtered, washed, and dried under vacuum at 60°C to obtain BiF 3 Nanoparticles;

[0010] (3) The prepared BiF 3 The nanoparticles are uniformly dispersed in a mixed solution of deionized water, ethanol and 5wt% Nafion 117, and then added dropwise to the surface of the cleaned carbon paper. After drying, the carbon paper loaded with bismuth trifluoride is obtained, wherein the BiF 3 The mass volume ratio of nanoparticles to deionized water, ethanol and 5 wt% Nafion 117 is 10 mg: 0.7 mL: 0.25 mL: 0.05 mL.

[0011] In the preferred disclosed examples of the present invention, the fluorine source in step (1) is ammonium bifluoride, ammonium fluoride, sodium fluoride, potassium fluoride, etc., preferably ammonium bifluoride, and the bismuth source is bismuth chloride, bismuth nitrate, etc., preferably bismuth nitrate.

[0012] In a preferred disclosed example of the present invention, the power of the ultrasonic mixing in step (1) is 500-600 W, and the time of the ultrasonic mixing is 20-60 min.

[0013] In the preferred disclosed embodiment of the present invention, the BiF prepared in step (2) 3 The particle size of nanoparticles is 50 to 100 nm.

[0014] In a preferred embodiment of the present invention, the cleaned carbon paper in step (3) is cleaned by ultrasonic cleaning with acetone and water in sequence.

[0015] Another object of the present invention is to disclose the prepared carbon paper loaded with bismuth trifluoride for application in electrocatalysis of carbon dioxide.

[0016] The electrocatalytic carbon dioxide application comprises the following steps: using platinum as a counter electrode and an Ag / AgCl electrode as a reference electrode, and the prepared BiF-loaded 3 The carbon paper was used as the working electrode, potassium bicarbonate solution was used as the electrolyte, and the reduction reaction was carried out under the condition of saturating the electrolyte with carbon dioxide.

[0017] The catalyst loading is 0.10-0.30 mg / cm 2 , preferably 0.28 mg / cm 2 .

[0018] The concentration of the potassium bicarbonate solution is 0.1-0.5 mol / L, preferably 0.5 mol / L.

[0019] The flow rate of the carbon dioxide is 10-20 sccm, preferably 20 sccm.

[0020] The parameters of the reduction reaction include: temperature of 25° C., pressure of 1 atm, reduction potential of -0.8 to -1.3 V, relative to the reversible hydrogen electrode, the voltage range of the linear sweep voltammetry (LSV) curve is -0.8 to -1.3 V, and the sweep rate is 10 mV / s.

[0021] In the synthesis process, the present invention can effectively control the BiF 3 The particle size is small, and uniform active sites are obtained. Carbon paper is used as the loading substrate, and the catalyst particles are evenly dropped on it, which effectively improves the electron transfer, improves the electron transfer efficiency, regulates the electronic structure of Bi and optimizes the material's CO 2 adsorption and activation, thereby improving the electrocatalyst reduction of CO 2 The prepared catalyst for electrocatalytic carbon dioxide reduction reaction still has high selectivity at high current density.

[0022] Unless otherwise specified, the raw materials used in the present invention are commercially available.

[0023] Beneficial Effects

[0024] The present invention provides a carbon-supported BiF 3 Particle electrocatalyst and preparation method thereof for electrocatalytic reduction of CO 2 Produce formic acid (radical), effectively control BiF by fluorine doping 3 The particle size and uniform active sites can also improve the electron transfer efficiency and regulate the electronic structure of Bi, thereby improving the electrocatalyst reduction of CO 2 The preparation method of the present invention is easy to control, uses low raw material cost, and is easy to obtain the target product. The obtained carbon dioxide reduction electrocatalyst has good electrocatalytic reduction of CO 2 Formic acid producing activity. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 . Example 1 Preparation of BiF 3 X-ray diffraction pattern of nanocatalyst;

[0026] Figure 2 . Example 1 Preparation of BiF 3 SEM image of nanocatalyst;

[0027] Figure 3 Example 2 BiF prepared 3 SEM image of nanocatalyst;

[0028] Figure 4 Example 2 BiF prepared 3 High-resolution transmission TEM image of nanocatalyst;

[0029] Figure 5 Example 3 Preparation of BiF 3 High-resolution transmission TEM image of nanocatalyst;

[0030] Figure 6 . BiF prepared in Examples 1-3 3 Faradaic efficiency diagram of the electrocatalytic reduction of carbon dioxide to carbon monoxide over nanocatalysts. DETAILED DESCRIPTION

[0031] The present invention is described in detail below in conjunction with the embodiments so that those skilled in the art can better understand the present invention, but the present invention is not limited to the following embodiments.

[0032] Example 1

[0033] Weigh 0.11 g of ammonium bifluoride and dissolve it in 50 ml of DMF. Stir and ultrasonicate the solution until it becomes clear. Take 0.97 g of Bi(NO 3 ) 3 ·5H 2 O was dispersed in the above solution to obtain a suspension; then ultrasonicated for 30 minutes. The obtained suspension was transferred to a 100 mL reactor and reacted at 160°C for 4 hours. After cooling to room temperature, the obtained product was centrifuged, washed, and dried to obtain a powder.

[0034] Example 2

[0035] Weigh 0.11 g of ammonium bifluoride and dissolve it in 50 ml of DMF. Stir and ultrasonicate the solution until it becomes clear. Take 1.94 g of Bi(NO 3 ) 3 ·5H 2 O was dispersed in the above solution to obtain a suspension; then ultrasonicated for 30 minutes. The obtained suspension was transferred to a 100 mL reactor and reacted at 170°C for 3 hours. After cooling to room temperature, the obtained product was centrifuged, washed, and dried to obtain a powder.

[0036] Figure 1The XRD pattern of the catalyst prepared in Example 1 is obtained by an X-ray diffractometer. Compared with the standard PDF card, it can be seen that the main phase of Example 1 and Example 2 is BiF3, without obvious impurity peaks, and good crystallinity. First, we perform XRD analysis on the prepared halogen-modified Bi nanosheet catalyst to understand its phase composition and structural information. Figure 4 As shown in Figure 1, from left to right, there are eight clear diffraction peaks at 26.32°, 30.48°, 43.64°, 51.68°, 54.17°, 63.43°, 69.90°, and 71.99°, which correspond to the (111), (200), (220), (311), (222), (400), (331), and (420) crystal planes of BiF3, respectively. Among them, the (111) crystal plane occupies a dominant position. It can be seen from the obvious BiF3 diffraction peaks (BiF3 PDF#73-1988).

[0037] Example 3

[0038] Weigh 0.11 g of ammonium bifluoride and dissolve it in 50 ml of DMF. Stir and ultrasonicate the solution until it becomes clear. Take 2.91 g of Bi(NO 3 ) 3 ·5H 2 O was dispersed in the above solution to obtain a suspension; then ultrasonicated for 30 minutes. The obtained suspension was transferred to a 100 mL reactor and reacted at 180°C for 2 hours. After cooling to room temperature, the obtained product was centrifuged, washed, and dried to obtain a powder.

[0039] Example 4

[0040] Weigh 0.22g of ammonium bifluoride and dissolve it in 50ml of DMF, stir and ultrasonicate the solution until it is clear; take 1.94g of Bi(NO 3 ) 3 ·5H 2 O was dispersed in the above solution to obtain a suspension; then ultrasonicated for 30 minutes. The obtained suspension was transferred to a 100 mL reactor and reacted at 180°C for 2 hours. After cooling to room temperature, the obtained product was centrifuged, washed, and dried to obtain a powder.

[0041] Example 5

[0042] Weigh 0.33 g of ammonium bifluoride and dissolve it in 50 ml of DMF. Stir and ultrasonicate the solution until it becomes clear. Take 2.91 g of Bi(NO 3 ) 3 ·5H 2O was dispersed in the above solution to obtain a suspension; then ultrasonicated for 30 minutes. The obtained suspension was transferred to a 100 mL reactor and reacted at 180°C for 2 hours. After cooling to room temperature, the obtained product was centrifuged, washed, and dried to obtain a powder.

[0043] The catalyst prepared in Example 1-2 was tested in an H-type electrolytic cell using a three-electrode system, including an Ag / AgCl reference electrode, a Pt sheet counter electrode, and a working electrode. 2 Saturated 0.5M KHCO 3 solution as electrolyte.

[0044] Figure 2 , 3 The carbon paper loaded BiF obtained in Example 1 and Example 2 3 SEM image of nanosheets. It can be seen that the morphology of the catalysts obtained in Example 1 is similar to that in Example 2. 3 The nanosheets are evenly distributed on the carbon paper with low contrast. 3 The particle size of the nanosheets is controlled between 50 and 100 nm. Fluorine doping makes the catalytic site BiF 3 The adsorption capacity of reactant CO and intermediate *COOH is improved, and the desorption capacity of product carbon monoxide is also improved, which is beneficial to the accumulation of formic acid. The larger electrochemical active area is beneficial to improve the electron transfer efficiency and optimize the adsorption of CO. 2 adsorption and activation, thereby improving material performance.

[0045] Figure 4 , 5 The TEM images of the BiF3 nanosheet catalysts obtained in Example 2 and Example 3 show that the fluorine-modified Bi nanosheet catalysts of different sizes observed through high-resolution transmission electron microscopy results show that fluorine doping gives it a nanosheet structure, and at a size of 5nm, the (111) crystal plane spacing of BiF3 is 0.1706nm, which is consistent with the XRD results.

[0046] Electrochemical testing

[0047] 10 mg of the catalyst obtained in Examples 1-3 was mixed with 0.7 mL of deionized water, 0.25 mL of ethanol and 0.05 mL of 5 wt% Nafion 117 solution to obtain a catalyst dispersion; the catalyst dispersion was then dripped onto a carbon paper electrode (0.5×2 cm) and dried in air to finally obtain a catalyst loading of 0.28 mg / cm 2 working electrode.

[0048] During the entire test, the carbon dioxide gas flow was kept constant at 50 mL min -1The electrolytic cell is fed with KHCO at a rate of 0.5 mol / L at the cathode and cathode of the electrolytic cell respectively. 3 Electrolyte.

[0049] The above molar ratios can synthesize BiF 3 When testing the Faraday efficiency of electrocatalysts, the working electrode was kept at a constant potential for 30 minutes, the potential and current data were collected using an electrochemical workstation, and the gas products produced were detected using a GC9790Ⅱ gas chromatograph. The applied voltage range during the test was -0.8V to -1.3V; the gas products were only CO and H 2 The electrocatalytic activities of fluorine-modified Bi and monomeric Bi were evaluated, and the Faraday efficiencies of the gas and liquid products of the two catalysts were tested in the potential range of -0.8V to -1.2V. 3 The carbon dioxide reduction products on the nanosheet catalyst were characterized by online GC9790Ⅱplus and 1H nuclear magnetic resonance. The results showed that the introduction of halogen fluorine was crucial for inhibiting the hydrogen evolution reaction (HER) and improving the selectivity of formic acid. In the entire potential range, the formic acid selectivity of BiF3 was higher than that of Bi (75.36%), with a maximum of 95.8%. Between -1.0V and -1.2V, the hydrogen Faraday efficiency was significantly suppressed, with a minimum of 4.85%. The carbon monoxide Faraday efficiency had different trends compared with monomer Bi at different potentials, and carbon monoxide (2.26%) was suppressed at high potential. It is speculated that F may improve its selectivity by promoting the activation of water and the conversion of active hydrogen species from CO* intermediates into formic acid.

[0050] Figure 6 Carbon paper loaded with BiF obtained in Examples 1, 4 and 5 3 The Faraday efficiency bar graph of the nanosheet catalyst products, the test potential distribution is between -0.8V vs.RHE and -1.3V vs.RHE. For both materials, the products are mainly formic acid (root) and hydrogen with a very small amount of carbon monoxide. As the overvoltage increases, the Faraday efficiency of formic acid (root) production increases significantly. For BiF 3 , FEHCOO at -1.0 V vs. RHE potential - It can reach a maximum value of 93.8% and has a Faradaic efficiency of more than 90% within a wide potential range of 300mv.

[0051] Table 1-1 BiF 3 Electrocatalyst synthesis conditions

[0052]

[0053] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the specification of the present invention, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A method for preparing carbon paper loaded BiF3, characterized in that: The steps include: (1) dispersing a fluorine source in DMF, adding a bismuth source and uniformly dispersing by ultrasonication, transferring to a high temperature reactor, and subjecting to a solvent thermal reaction at 160-180° C. for 2-4 h, wherein the molar volume ratio of the fluorine source, bismuth source and DMF is 3-5 mmoL:1-1.6 mmoL:50-150 mL; wherein the fluorine source is any one of ammonium bifluoride, ammonium fluoride, sodium fluoride and potassium fluoride, and the bismuth source is bismuth chloride or bismuth nitrate; (2) The obtained product was filtered, washed, and dried under vacuum at 60°C to obtain BiF3 nanoparticles; (3) The prepared BiF3 nanoparticles are uniformly dispersed in a mixed solution of deionized water, ethanol and 5wt% Nafion 117, and dropped onto the surface of the cleaned carbon paper. After drying, carbon paper-loaded bismuth trifluoride is obtained, wherein the mass volume ratio of the BiF3 nanoparticles to deionized water, ethanol and 5wt% Nafion 117 is 10 mg:0.7 mL:0.25 mL:0.05 mL.

2. The method for preparing BiF3 supported on carbon paper according to claim 1, characterized in that: In step (1), the fluorine source is dispersed in DMF, the bismuth source is added and ultrasonically dispersed uniformly, and the mixture is transferred to a high-temperature reactor and subjected to solvent thermal reaction at 160° C. for 4 h. The molar volume ratio of the fluorine source, bismuth source and DMF is 3 mol:1 mol:50 mL.

3. The method for preparing carbon paper loaded BiF3 according to claim 1, characterized in that: The fluorine source in step (1) is ammonium bifluoride.

4. The method for preparing carbon paper loaded BiF3 according to claim 1, characterized in that: The bismuth source in step (1) is bismuth nitrate.

5. The method for preparing carbon paper-supported BiF3 according to claim 1, characterized in that: The power of the ultrasonic dispersion in step (1) is 500-600 W, and the time of ultrasonic mixing is 20-60 min.

6. The method for preparing carbon paper loaded BiF3 according to claim 1, characterized in that: The particle size of the BiF3 nanoparticles prepared in step (2) is 50 to 100 nm.

7. The method for preparing BiF3 supported on carbon paper according to claim 1, characterized in that: The cleaned carbon paper in step (3) is cleaned by ultrasonic cleaning with acetone and water in sequence.

8. Carbon paper loaded with BiF3 prepared according to any one of claims 1 to 7.

9. An application of BiF3 loaded on carbon paper as claimed in claim 8, characterized in that: Application in electrocatalytic carbon dioxide production.

Images