A cadmium-bismuth alloy, a preparation method and application thereof

Abstract

The present application belongs to the technical field of catalysts, and particularly relates to a cadmium-bismuth alloy as well as a preparation method and application thereof. The present application provides a cadmium-bismuth alloy, which comprises cadmium and bismuth, and the molar percentage of the cadmium in the cadmium-bismuth alloy is 1-10%. The cadmium-bismuth alloy can greatly improve the selectivity of formate as a catalyst for electrocatalytic reduction of carbon dioxide to formate. The present application also provides a preparation method of the cadmium-bismuth alloy, which comprises the following steps: uniformly dispersing a bismuth salt in a first solvent to obtain a bismuth salt dispersion; dissolving a cadmium salt in a second solvent to obtain a cadmium salt solution; adding the bismuth salt dispersion and the cadmium salt solution into a reducing agent solution dropwise after mixing, and performing a reduction reaction to obtain the cadmium-bismuth alloy. The preparation method provided by the present application is simple and easy to operate, and can be used for industrial production.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of catalysts, and particularly relates to a cadmium-bismuth alloy and a preparation method and application thereof. BACKGROUND

[0002] Electrocatalytic reduction of carbon dioxide to generate high-value products is an effective strategy to reduce carbon emissions and achieve carbon neutrality. Formate as a product of carbon dioxide reduction has high economic value and wide industrial applications. In addition, liquid formate is easy to separate from reaction gas. In the process of preparing formate by electrocatalytic reduction of carbon dioxide, a catalyst is needed. Existing catalysts are mostly copper-based catalysts, tin-based catalysts or bismuth-based catalysts. Among them, bismuth-based catalysts have higher selectivity for catalytic reduction to prepare formate than tin-based catalysts and copper-based catalysts. However, the selectivity of pure bismuth metal catalyst is only 85.5%, and the selectivity of existing catalysts for catalytic reduction of carbon dioxide to prepare formate needs to be further improved. SUMMARY

[0003] Therefore, the application provides a cadmium-bismuth alloy and a preparation method and application thereof. The cadmium-bismuth alloy provided by the application can significantly improve the selectivity of electrocatalytic reduction of carbon dioxide to formate.

[0004] To solve the above technical problems, the application provides a cadmium-bismuth alloy, which comprises cadmium and bismuth. The molar percentage of cadmium in the cadmium-bismuth alloy is 1-10%.

[0005] Preferably, the molar percentage of cadmium in the cadmium-bismuth alloy is 3-10%.

[0006] The application also provides a preparation method of the cadmium-bismuth alloy.

[0007] The bismuth salt is dispersed in a first solvent to obtain a bismuth salt dispersion solution;

[0008] The cadmium salt is dissolved in a second solvent to obtain a cadmium salt solution;

[0009] The bismuth salt dispersion solution and the cadmium salt solution are mixed and then added dropwise into a reducing agent solution to perform a reduction reaction, thereby obtaining the cadmium-bismuth alloy.

[0010] Preferably, the reducing agent solution comprises a sodium borohydride aqueous solution or a potassium borohydride aqueous solution.

[0011] Preferably, the bismuth salt comprises bismuth sulfate, bismuth chloride or bismuth nitrate.

[0012] Preferably, the cadmium salt comprises cadmium sulfate, cadmium chloride or cadmium nitrate.

[0013] Preferably, the temperature of the reduction reaction is-1-1℃.

[0014] The time of the reduction reaction is 0.4-0.6 h.

[0015] Preferably, the reduction reaction is followed by water washing and acetone washing of the product after the reduction reaction.

[0016] The application also provides the use of the cadmium-bismuth alloy or the cadmium-bismuth alloy prepared by the preparation method as a catalyst.

[0017] Preferably, the catalyst is a catalyst for electrocatalytic reduction of carbon dioxide to form formate.

[0018] The application provides a cadmium-bismuth alloy, which comprises cadmium and bismuth; the molar percentage of the cadmium in the cadmium-bismuth alloy is 1-10%.

[0019] The application also provides a preparation method of the cadmium-bismuth alloy, which comprises the following steps: dispersing a bismuth salt in a first solvent to obtain a bismuth salt dispersion; dissolving a cadmium salt in a second solvent to obtain a cadmium salt solution; mixing the bismuth salt dispersion and the cadmium salt solution and then dropping into a reducing agent solution to perform a reduction reaction, so as to obtain the cadmium-bismuth alloy. DETAILED DESCRIPTION

[0020] The application provides a cadmium-bismuth alloy, which comprises cadmium and bismuth; the molar percentage of the cadmium in the cadmium-bismuth alloy is 1-10%, preferably 3-10%, and more preferably 3-5%.

[0021] The application limits the molar percentage of the cadmium in the cadmium-bismuth alloy to the above range, which is beneficial to achieving a uniform atomic dispersion level.

[0022] The application introduces a small amount of Cd metal into Bi metal, which can greatly realize the high selectivity of the catalyst material to electrocatalytic CO2 preparation of formate.

[0023] The application also provides a preparation method of the cadmium-bismuth alloy, which comprises the following steps:

[0024] dispersing a bismuth salt in a first solvent to obtain a bismuth salt dispersion;

[0025] dissolving a cadmium salt in a second solvent to obtain a cadmium salt solution;

[0026] The bismuth salt solution and cadmium salt solution are mixed and then added dropwise to a reducing agent solution to carry out a reduction reaction, thereby obtaining the cadmium-bismuth alloy.

[0027] Unless otherwise specified, all raw materials used in this invention are commercially available products.

[0028] This invention disperses a bismuth salt in a first solvent to obtain a bismuth salt dispersion. In this invention, the bismuth salt preferably includes bismuth sulfate, bismuth chloride, or bismuth nitrate, more preferably bismuth chloride. In this invention, the first solvent is preferably ethanol or acetone, more preferably ethanol. In this invention, the ethanol is preferably anhydrous ethanol. In this invention, the molar concentration of bismuth in the bismuth salt dispersion is preferably 0.3 mol / L to 0.5 mol / L, more preferably 0.4 mol / L. In this invention, the dispersion is preferably carried out under ultrasonic conditions, the ultrasonic power is preferably 30 to 40 kHz, more preferably 35 to 40 kHz; the ultrasonic time is preferably 8 to 12 min, more preferably 10 min.

[0029] This invention dissolves cadmium salt in a second solvent to obtain a cadmium salt solution. In this invention, the second solvent is preferably water or ethanol, more preferably water. In this invention, the cadmium salt preferably includes cadmium sulfate, cadmium chloride, or cadmium nitrate, more preferably cadmium chloride. In this invention, the molar concentration of cadmium in the cadmium salt solution is preferably 0.01–0.3 mol / L, more preferably 0.06–0.08 mol / L. This invention does not have special requirements for the dissolution process, as long as complete dissolution is achieved.

[0030] After obtaining the bismuth salt dispersion and the cadmium salt solution, the present invention mixes the bismuth salt dispersion and the cadmium salt solution and adds them dropwise to a reducing agent solution to carry out a reduction reaction, thereby obtaining the cadmium-bismuth alloy. In the present invention, the mixing is preferably carried out under ultrasonic conditions; the ultrasonic power is preferably 30-40 kHz, more preferably 35-40 kHz; the ultrasonic time is preferably 8-12 min, more preferably 10 min.

[0031] In this invention, the reducing agent solution preferably comprises an aqueous solution of sodium borohydride or potassium borohydride, more preferably an aqueous solution of sodium borohydride. In this invention, the molar concentration of the sodium borohydride aqueous solution is preferably 4.8–5.2 mol / L, more preferably 5 mol / L. In this invention, the volume ratio of the bismuth salt dispersion to the cadmium salt solution is preferably 6:1–4:1, more preferably 5:1. In this invention, the volume ratio of the bismuth salt dispersion to the reducing agent solution is preferably 5:3–5:2, more preferably 5:2. In this invention, the ratio of cadmium to bismuth in the cadmium-bismuth alloy is preferably controlled by controlling the content of bismuth ions and cadmium ions in the mixed solution obtained by mixing. In this invention, the dripping rate is preferably dropwise.

[0032] The mixing has no special requirements in the present application, as long as it can be uniformly mixed.

[0033] In the present application, the temperature of the reduction reaction is preferably -1-1℃, more preferably 0℃; the time of the reduction reaction is preferably 0.4-0.6h, more preferably 0.5h. The temperature of the reduction reaction is preferably provided by ice bath in the present application.

[0034] The reduction reaction in the present application can reduce cadmium ions and bismuth ions to form a cadmium-bismuth alloy.

[0035] In the present application, the reduction reaction preferably further comprises: performing solid-liquid separation on the system after the reduction reaction; and sequentially performing water washing and acetone washing on the solid obtained by the solid-liquid separation. In the present application, the solid-liquid separation is preferably centrifugation. The centrifugation has no special requirements in the present application, as long as it can separate the solid and the liquid. In the present application, the water used for the water washing is preferably deionized water. In the present application, the water washing removes water-soluble compounds in the remaining reactants; and the acetone washing removes acetone-soluble compounds in the remaining reactants.

[0036] The present application also provides the use of the cadmium-bismuth alloy in the above technical solution or the cadmium-bismuth alloy prepared by the preparation method in the above technical solution as a catalyst. In the present application, the catalyst is preferably a catalyst for electrocatalytic reduction of carbon dioxide to form formate. The present application has no special requirements for the method of electrocatalytic reduction of carbon dioxide to prepare formate, and a conventional method in the art can be used.

[0037] In order to further illustrate the present application, the technical solutions provided by the present application are described in detail below with reference to the examples, but they should not be understood as limiting the scope of protection of the present application.

[0038] Example 1

[0039] 630mg of bismuth chloride was dispersed in 5mL of ethanol, and ultrasonic treatment was performed for 10min under the condition of 40KHz to obtain a bismuth chloride dispersion liquid;

[0040] 4.6mg of cadmium chloride 2 / 5 hydrate was dissolved in 1mL of water to obtain a cadmium chloride solution;

[0041] 1mL of the cadmium salt solution was added to 5mL of the bismuth salt dispersion liquid, and ultrasonic treatment was performed for 10min under the condition of 40KHz to mix uniformly, and the mixed solution was added dropwise to 2mL of 5mol / L sodium borohydride aqueous solution under ice bath condition, and reduction was performed for 0.5h, and the system after the reduction reaction was centrifuged, and the solid obtained by the centrifugation was sequentially subjected to water washing and acetone washing to obtain a cadmium-bismuth alloy (Cd1Bi 99 ) with a cadmium molar percentage of 1%.

[0042] Example 2

[0043] A cadmium bismuth alloy with a cadmium molar percentage of 3% (Cd3Bi 97 ) was prepared according to the method of Example 1, except that 14.1 mg of cadmium chloride 2 / 5 hydrate was dissolved in 1 mL of water to obtain a cadmium chloride solution.

[0044] Example 3

[0045] A cadmium bismuth alloy with a cadmium molar percentage of 5% (Cd5Bi 95 ) was prepared according to the method of Example 1, except that 24 mg of cadmium chloride 2 / 5 hydrate was dissolved in 1 mL of water to obtain a cadmium chloride solution.

[0046] Example 4

[0047] A cadmium bismuth alloy with a cadmium molar percentage of 10% (Cd 10 Bi 90 ) was prepared according to the method of Example 1, except that 50.7 mg of cadmium chloride 2 / 5 hydrate was dissolved in 1 mL of water to obtain a cadmium chloride solution.

[0048] Comparative Example 1

[0049] Pure bismuth metal was used as a comparative example.

[0050] Comparative Example 2

[0051] Pure cadmium metal was used as a comparative example.

[0052] Comparative Example 3

[0053] A cadmium bismuth alloy with a cadmium molar percentage of 30% (Cd 30 Bi 70 ) was prepared according to the method of Example 1, except that 195.7 mg of cadmium chloride 2 / 5 hydrate was dissolved in 1 mL of water to obtain a cadmium chloride solution.

[0054] The catalytic performance of the alloys of Examples 1-4 and Comparative Examples 1-3 as catalysts was detected according to the following method. Description of the electrocatalytic device and reaction conditions: the electrocatalytic reduction of CO2 to form formate salt by the catalyst was carried out at room temperature and pressure. The electrocatalytic reduction reaction was carried out in an H-type electrolytic cell system using CO2 as the reaction gas. A proton exchange membrane was used to separate the cathode and anode compartments of the electrolytic cell, 15 mL of 0.5 mol / L KHCO3 was used as the electrolyte in the cathode compartment, 10 mL of 0.1 mol / L H2SO4 was used as the electrolyte in the anode compartment, and CO2 was continuously introduced into the cathode compartment during the reaction to carry out the catalytic reduction reaction.

[0055] The three-electrode system was used to apply the potential by the electrochemical workstation (CHI660E), 1 mg of catalyst was loaded on 1 cm 2 of carbon paper as the working electrode, silver-silver chloride electrode as the reference electrode, and platinum metal mesh as the counter electrode to measure the reaction current and calculate the current density. Among them, all the potentials were converted into the reversible hydrogen electrode potential using E RHE = E Ag / AgCl + 0.197 + pH x 0.059.

[0056] The product formate concentration was measured by using a nuclear magnetic resonance spectrometer, and the formate Faraday efficiency was calculated to measure the selectivity of the formate product, and the calculation formula is shown in formula 1:

[0057]

[0058] Among them, C 甲酸盐 is the concentration of formate, V is the volume of the cathode chamber electrolyte, I is the current, and t is the reaction time.

[0059] The catalytic performance results of the alloys of Examples 1-4 and Comparative Examples 1-3 are listed in Table 1.

[0060] Table 1 Catalytic performance of the alloys provided by Examples 1-4 and Comparative Examples 1-3

[0061]

[0062] As can be seen from the data in Table 1, compared with the pure bismuth metal catalyst, the introduction of a small amount of cadmium metal improves the selectivity of the bismuth-based catalyst for preparing formate, and when the doping cadmium molar content is in the range of 1-10%, the Faraday efficiency of formate is higher than 90%. It is proved that the introduction of cadmium has a promoting effect on the electrocatalytic preparation of formate from CO2. When the molar content of cadmium accounts for 3% of the alloy, the Faraday efficiency of formate is 99%, and the selectivity performance is optimal. At the same time, the bismuth-based catalyst containing cadmium metal is higher than-16 mAcm -2 in terms of formate partial current density. In the case of applying voltage close to each other, the current density performance of cadmium-bismuth alloy is on par with or even higher than some of the existing literature, which also shows that the alloy material provided by the present application can achieve high selectivity in the synthesis of formate at a lower voltage, while also reducing the energy consumption of electrochemical reduction.

[0063] Although the above examples have made a detailed description of the present application, it is only a part of the embodiments of the present application, but not all the embodiments, and other embodiments can be obtained according to the present embodiments without creativity, which all belong to the protection scope of the present application.

Claims

1. Use of a cadmium-bismuth alloy as a catalyst, characterized in that, The cadmium-bismuth alloy comprises cadmium and bismuth; the cadmium accounts for 1-10% of the cadmium-bismuth alloy in terms of mole percentage; The preparation method of the cadmium-bismuth alloy is performed according to the following steps: dispersing a bismuth salt in a first solvent to obtain a bismuth salt dispersion; dissolving a cadmium salt in a second solvent to obtain a cadmium salt solution; mixing the bismuth salt dispersion and the cadmium salt solution and then dropping into a reducing agent solution to perform a reduction reaction, thereby obtaining the cadmium-bismuth alloy.

2. Use according to claim 1, characterized in that, The cadmium accounts for 3-10% of the cadmium-bismuth alloy in terms of mole percentage.

3. Use according to claim 1, characterized in that, The reducing agent solution comprises a sodium borohydride aqueous solution or a potassium borohydride aqueous solution.

4. The use according to claim 1, characterized in that, The bismuth salt comprises bismuth sulfate, bismuth chloride or bismuth nitrate.

5. The use according to claim 1, characterized in that, The cadmium salt comprises cadmium sulfate, cadmium chloride or cadmium nitrate.

6. The use according to claim 1, characterized in that, The temperature of the reduction reaction is -1-1 ℃. The time of the reduction reaction is 0.4-0.6 h.

7. Use according to claim 1, characterized in that, After the reduction reaction, the product after the reduction reaction is sequentially subjected to water washing and acetone washing.

8. The use according to claim 1, characterized in that, The catalyst is a catalyst for electrocatalytic reduction of carbon dioxide to generate formate.

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