Preparation method and application of zinc selenide catalyst for electroreduction of CO2 to formic acid

Abstract

The present invention belongs to the field of catalyst technology, and particularly relates to a preparation method and application of a zinc selenide catalyst for electroreduction of CO2 to formic acid. A preparation method of a zinc selenide catalyst, wherein the raw materials include selenium powder and ZIF‑8; the mass ratio of selenium powder and ZIF‑8 is (0.15‑2.2): 1. When preparing a zinc selenide catalyst for electroreduction of CO2 to formic acid, the present invention adds selenium powder and ZIF‑8, and the mass ratio of selenium powder and ZIF‑8 is (0.15‑2.2): 1, and prepares a zinc selenide material by controlling the amount of reactants and the reaction temperature. The zinc selenide material has the ability to electrochemically reduce CO2 to formic acid, and the catalyst has a high faradaic efficiency and a large current density when electroreducing CO2 to formic acid. The faradaic efficiency exceeds 50%, and the faradaic efficiency even reaches 60.5% at a voltage of ‑1.2V vs.RHE, and the current density is 41.6mA cm ‑2 .

Description

Technical Field

[0001] The present invention belongs to the technical field of catalysts, and in particular relates to a preparation method and application of a zinc selenide catalyst for producing formic acid by electroreduction of CO2. Background Art

[0002] Currently, the continued consumption of natural fossil fuels such as oil and coal has led to excessive CO2 emissions, disrupting the natural carbon cycle and causing global climate change. The environmental problems caused by excessive emissions of the greenhouse gas CO2 have become a focus of worldwide attention. Direct conversion of excess CO2 is one of the important measures to alleviate this problem. It can restore the carbon cycle and produce valuable chemicals to meet the needs of modern society. In particular, the electrocatalytic CO2 reduction reaction (CO2RR) has attracted attention because it can effectively convert CO2 into fuels and energy-intensive products powered by clean and renewable electricity. Accordingly, CO2 resource recovery technology has also become a research hotspot. Among them, the electrocatalytic CO2 reduction reaction has attracted increasing attention due to its simple device, high environmental compatibility, and the possibility of combining with renewable solar or wind energy under mild reaction conditions. It is considered a promising strategy.

[0003] Formic acid (HCOOH) is a basic organic chemical raw material widely used in industries such as pesticides, leather, dyes, pharmaceuticals, and rubber. Studies have shown that Sn, Bi, In, Hg, and Pb catalysts have high selectivity for the production of formic acid. Sn has high formic acid selectivity but poor stability. Bi is unstable and easily oxidized in air, making it difficult to determine the active site of its reaction. In has good formic acid selectivity, conductivity, and easy alloying properties, and has low toxicity. However, indium-based electrocatalysts have low Faradaic efficiency for the production of formic acid at negative potentials, poor durability, and high cost. Hg is extremely toxic and environmentally unfriendly. Pb has poor stability, low current density and product selectivity, and high intrinsic toxicity.

[0004] Therefore, there is an urgent need to provide a preparation method of a zinc selenide catalyst, which has a simple preparation process and the prepared zinc selenide catalyst has high Faradaic efficiency and large current density when used to catalyze CO2 to produce formic acid. Summary of the Invention

[0005] The present invention aims to solve one or more technical problems existing in the prior art and at least provide a beneficial alternative or create a condition. The present invention provides a method for preparing a zinc selenide catalyst. The method is simple, and the resulting zinc selenide catalyst exhibits high Faradaic efficiency and high current density when used to catalyze the conversion of CO2 to formic acid.

[0006] The inventive concept of the present invention is as follows: when preparing a zinc selenide catalyst for electroreduction of CO2 to formic acid, the present invention adds selenium powder and ZIF-8, and the mass ratio of selenium powder to ZIF-8 is (0.15-2.2):1. The zinc selenide material is prepared by controlling the amount of reactants added and the reaction conditions. Electrochemical testing shows that the zinc selenide material has the ability to electrochemically reduce CO2 to formic acid. Moreover, the zinc selenide catalyst has high Faradaic efficiency and high current density when used in the electroreduction of CO2 to formic acid. The Faradaic efficiency exceeds 50%, and even reaches 60.5% at a voltage of -1.2 V vs. RHE, with a current density of 41.6 mA cm -2 In addition, selenium powder and ZIF-8 directly react to generate zinc selenide, which has a simple preparation method and is easy to industrialize.

[0007] Therefore, a first aspect of the present invention provides a method for preparing a zinc selenide catalyst for electroreduction of CO2 to formic acid.

[0008] Specifically, a method for preparing a zinc selenide catalyst for electroreduction of CO2 to formic acid is provided, wherein the raw materials for preparing the zinc selenide catalyst include selenium powder and ZIF-8; the mass ratio of the selenium powder to the ZIF-8 is (0.15-2.2):1.

[0009] Preferably, the mass ratio of the selenium powder to the ZIF-8 is (0.2-2):1.

[0010] Preferably, the preparation method comprises the following steps:

[0011] The selenium powder and the ZIF-8 are mixed and reacted to prepare the zinc selenide catalyst.

[0012] Preferably, the selenium powder and the ZIF-8 are placed in two porcelain boats respectively, and the two porcelain boats are placed side by side in a tube furnace for reaction.

[0013] Preferably, the reaction temperature is 450-950°C, the reaction time is 1.5-5h, and the heating rate is 2-10°C min -1 .

[0014] More preferably, the reaction temperature is 500-900°C, the reaction time is 2-4h, and the reaction heating rate is 3-9°C min -1 .

[0015] Preferably, the reaction is carried out in a gas atmosphere, and the gas is selected from at least one of N2 and Ar.

[0016] Preferably, the preparation method of ZIF-8 comprises the following steps:

[0017] The Zn(NO3)2 solution and the dimethylimidazole solution are mixed and reacted to obtain the ZIF-8.

[0018] Preferably, the Zn(NO3)2 solution is formed by dissolving Zn(NO3)2·6H2O in methanol; and the dimethylimidazole solution is formed by dissolving dimethylimidazole in methanol.

[0019] Preferably, during the mixing, the dimethylimidazole solution is added to the Zn(NO3)2 solution within 20-30 seconds.

[0020] Preferably, the molar ratio of Zn(NO3)2·6H2O to dimethylimidazole is (0.125-8):1.

[0021] Preferably, the reaction temperature is 5-35° C., and the reaction time is 11-25 h; further preferably, the reaction temperature is 6-34° C., and the reaction time is 12-24 h.

[0022] Preferably, the reaction further includes centrifugation, washing, and vacuum drying to obtain the ZIF-8.

[0023] Preferably, the centrifugal speed is 7800-11000 rpm, and the centrifugal time is 3-10 min.

[0024] More preferably, the centrifugal speed is 8000-10000 rpm, and the centrifugal time is 4-9 min.

[0025] Preferably, the washing is performed with methanol, and the number of washing times is 3-5 times.

[0026] Preferably, the vacuum degree of the vacuum drying is 0.08-0.1 MPa; the temperature of the vacuum drying is 35-85° C.; and the time of the vacuum drying is 7-13 h.

[0027] Further preferably, the vacuum degree of the vacuum drying is 0.085-0.09 MPa; the temperature of the vacuum drying is 40-80° C.; and the time of the vacuum drying is 8-12 h.

[0028] The second aspect of the present invention provides an application of a zinc selenide catalyst prepared by the method for preparing a zinc selenide catalyst for electroreduction of CO2 to produce formic acid according to the first aspect of the present invention in the electroreduction of CO2 to produce formic acid.

[0029] Preferably, the reaction temperature is 10-30° C.; the reaction time is 0.5-1 h; and the applied voltage of the reaction is -0.7 to -1.3 V vs. RHE.

[0030] Further preferably, the reaction temperature is 15-25° C.; the reaction time is 0.6-0.9 h; and the applied voltage of the reaction is -0.8 to -1.2 V vs. RHE.

[0031] Preferably, the working electrode of the electroreduction is a platinum sheet electrode containing a zinc selenide catalyst prepared by the preparation method of a zinc selenide catalyst for electroreduction of CO2 to formic acid described in the first aspect of the present invention, the counter electrode is a platinum sheet electrode, and the reference electrode is an Ag / AgCl electrode.

[0032] Preferably, the electroreduction electrolyte is selected from at least one of KHCO3, KOH, and NaHCO3.

[0033] Preferably, the concentration of the electrolyte is 0.1-1M.

[0034] Compared with the prior art, the technical solution provided by the present invention has the following beneficial effects:

[0035] (1) In the present invention, when preparing a zinc selenide catalyst for electroreduction of CO2 to formic acid, selenium powder and ZIF-8 are added, and the mass ratio of selenium powder to ZIF-8 is (0.15-2.2):1. The zinc selenide material is prepared by controlling the amount of reactants added and the reaction temperature. The zinc selenide material has the ability to electrochemically reduce CO2 to formic acid. The zinc selenide catalyst has high Faradaic efficiency and high current density when used in electroreduction of CO2 to formic acid. The Faradaic efficiency exceeds 50%, and even reaches 60.5% at a voltage of -1.2 V vs. RHE, and the current density is 41.6 mA cm -2 .

[0036] (2) The selenium powder and ZIF-8 of the present invention directly react to generate zinc selenide (ZnSe), and the preparation method is simple and easy to promote and realize industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 This is the XRD pattern of the zinc selenide catalyst prepared in Example 1 of the present invention;

[0038] Figure 2 This is a diagram of the Faraday efficiency and current density of the zinc selenide catalyst prepared in Example 1 of the present invention;

[0039] Figure 3 This is a diagram of the Faraday efficiency and current density of the zinc selenide catalyst prepared in Example 2 of the present invention;

[0040] Figure 4 This is a diagram of the Faraday efficiency and current density of the zinc selenide catalyst prepared in Example 4 of the present invention. DETAILED DESCRIPTION

[0041] In order to make the technical solution of the present invention more clearly understood by those skilled in the art, the following examples are given for illustration. It should be noted that the following examples do not limit the scope of protection claimed by the present invention.

[0042] Unless otherwise specified, the raw materials, reagents, or devices used in the following examples can be obtained from conventional commercial sources or by existing known methods.

[0043] Example 1

[0044] A method for preparing a zinc selenide catalyst for producing formic acid by electroreduction of CO2. The preparation raw materials include selenium powder and ZIF-8; the mass ratio of selenium powder to ZIF-8 is 10:23.

[0045] A method for preparing a zinc selenide catalyst for electroreduction of CO2 to formic acid comprises the following steps:

[0046] Weigh 100 mg of selenium powder and 230 mg of ZIF-8, place them in two porcelain boats, and put them in a tube furnace. -1 The temperature was raised to 700°C at a rate of 1000 ℃, reacted at 700°C for 3 hours, and then naturally cooled to room temperature to obtain a zinc selenide catalyst.

[0047] The preparation method of ZIF-8 comprises the following steps:

[0048] (1) Dissolve 5 mmol of Zn(NO3)2·6H2O in 50 mL of methanol to obtain solution A;

[0049] (2) Dissolve 40 mmol of dimethylimidazole in 50 mL of methanol to obtain solution B;

[0050] (3) Solution B was poured into solution A within 30 seconds to obtain a mixed solution, which was reacted at 25°C for 24 hours. The product was centrifuged at a centrifugal rate of 8000 rpm for 5 minutes and washed three times with methanol. It was vacuum dried at a vacuum degree of 0.085 MPa and a drying temperature of 60°C for 12 hours to obtain ZIF-8.

[0051] Example 2

[0052] A method for preparing a zinc selenide catalyst for producing formic acid by electroreduction of CO2. The preparation raw materials include selenium powder and ZIF-8; the mass ratio of selenium powder to ZIF-8 is 10:23.

[0053] A method for preparing a zinc selenide catalyst for electroreduction of CO2 to formic acid comprises the following steps:

[0054] Weigh 100 mg of selenium powder and 230 mg of ZIF-8, place them in two porcelain boats, and put them in a tube furnace. -1 The temperature was raised to 500° C. at a heating rate, reacted at 500° C. for 3 h, and then naturally cooled to room temperature to obtain a zinc selenide catalyst with a yield of 70%.

[0055] The preparation method of ZIF-8 comprises the following steps:

[0056] (1) Dissolve 5 mmol of Zn(NO3)2·6H2O in 50 mL of methanol to obtain solution A;

[0057] (2) Dissolve 40 mmol of dimethylimidazole in 50 mL of methanol to obtain solution B;

[0058] (3) Solution B was poured into solution A within 20 seconds to obtain a mixed solution, which was reacted at 20°C for 24 hours. The product was centrifuged at a centrifugal speed of 9000 rpm for 7 minutes and washed three times with methanol. It was vacuum dried at a vacuum degree of 0.09 MPa and a drying temperature of 80°C for 10 hours to obtain ZIF-8.

[0059] Example 3

[0060] A zinc selenide catalyst for electroreduction of CO2 to formic acid comprises ZnSe generated from selenium powder and ZIF-8; the mass ratio of the selenium powder to the ZIF-8 is 10:23.

[0061] A method for preparing a zinc selenide catalyst for electroreduction of CO2 to formic acid comprises the following steps:

[0062] Weigh 100 mg of selenium powder and 230 mg of ZIF-8, place them in two porcelain boats, and put them in a tube furnace in an Ar atmosphere at 6 ° C min -1 The temperature was raised to 700°C at a rate of 1000 ℃, reacted at 700°C for 3 hours, and then naturally cooled to room temperature to obtain a zinc selenide catalyst.

[0063] The preparation method of ZIF-8 comprises the following steps:

[0064] (1) Dissolve 5 mmol of Zn(NO3)2·6H2O in 50 mL of methanol to obtain solution A;

[0065] (2) Dissolve 40 mmol of dimethylimidazole in 50 mL of methanol to obtain solution B;

[0066] (3) Solution B was poured into solution A within 25 seconds to obtain a mixed solution, which was reacted at 25°C for 24 hours. The product was centrifuged at a centrifugal rate of 9500 rpm for 5 minutes and washed three times with methanol. It was vacuum dried at a vacuum degree of 0.085 MPa and a drying temperature of 60°C for 12 hours to obtain ZIF-8.

[0067] Example 4

[0068] A zinc selenide catalyst for electroreduction of CO2 to formic acid comprises ZnSe generated from selenium powder and ZIF-8; the mass ratio of selenium powder to ZIF-8 is 30:23.

[0069] A method for preparing a zinc selenide catalyst for electroreduction of CO2 to formic acid comprises the following steps:

[0070] Weigh 300 mg of selenium powder and 230 mg of ZIF-8, place them in two porcelain boats, and put them in a tube furnace. -1 The temperature was raised to 700°C at a rate of 1000 ℃, reacted at 700°C for 3 hours, and then naturally cooled to room temperature to obtain a zinc selenide catalyst.

[0071] The preparation method of ZIF-8 comprises the following steps:

[0072] (1) Dissolve 5 mmol of Zn(NO3)2·6H2O in 50 mL of methanol to obtain solution A;

[0073] (2) Dissolve 40 mmol of dimethylimidazole in 50 mL of methanol to obtain solution B;

[0074] (3) Solution B was poured into solution A within 30 seconds to obtain a mixed solution, which was reacted at 30°C for 24 hours. The product was centrifuged at 8000 rpm for 6 minutes and washed three times with methanol. The product was vacuum dried at a vacuum degree of 0.09 MPa and a drying temperature of 40°C for 13 hours to obtain ZIF-8.

[0075] Performance testing:

[0076] XRD test

[0077] The zinc selenide catalyst prepared in Example 1 was subjected to XRD test, and the XRD curve is shown in FIG. Figure 1 As shown, the ordinate represents intensity (au) and the abscissa represents 2θ (°). Figure 1 It can be seen that the XRD diffraction peak of the zinc selenide catalyst in Example 1 is consistent with the standard XRD pattern of zinc selenide, indicating that the catalyst obtained in Example 1 is a zinc selenide catalyst.

[0078] Performance test of zinc selenide catalyst for electroreduction of CO2 to formic acid

[0079] The zinc selenide catalysts prepared in Example 1 and Example 2 were subjected to CO2RR tests at -0.8, -1.0, and -1.2 V vs. RHE voltages, respectively. The electrodes were then removed and rinsed three times with deionized water before being directly placed in fresh electrolyte for further CO2RR testing. All electrochemical tests were performed using a Chenhua CHI 760e electrochemical workstation. An H-type electrolytic cell was used, and the cathode and anode chambers were separated by a Nafion 117 proton exchange membrane. During the test, the electrolytes in the cathode and cathode chambers each contained 17.5 mL, and the upper cavity volume was 20.5 mL. A three-electrode system was used for electrochemical characterization. A platinum electrode containing a zinc selenide catalyst was used as the working electrode, a platinum electrode was used as the counter electrode, an Ag / AgCl electrode (filled with a saturated KCl solution) was used as the reference electrode, and the electrolyte was a 0.5 M KHCO3 solution. The conversion between the Ag / AgCl electrode and the standard hydrogen electrode is: E(vs. RHE) = E(vs. Ag / AgCl) + 0.059 × pH + 0.197. At room temperature, CO2 gas is continuously introduced into the electrolytic cell for 30 minutes and then sealed to obtain a CO2-saturated electrolyte solution, producing formic acid.

[0080] The Faraday efficiency and current density of the zinc selenide catalysts prepared in Examples 1 and 2 are shown in FIG. Figure 2 and Figure 3 As shown, Figure 2 and Figure 3 The CO and H2 in the solution are both reduction products at the cathode. Figure 2 The horizontal axis represents the potential (Vvs.RHE), the vertical axis on the left represents the Faraday efficiency (%), and the vertical axis on the right represents the current density (mAcm -2 ), the bar graph represents the Faradaic efficiency, and the curve represents the current density; Figure 3 The horizontal axis represents the potential (Vvs.RHE), the vertical axis on the left represents the Faraday efficiency (%), and the vertical axis on the right represents the current density (mAcm -2 ), the bar graph represents the Faradaic efficiency, and the curve represents the current density.

[0081] Depend on Figure 2 and Figure 3 It can be seen that under the optimal conditions, that is, under the conditions of Example 1, the maximum Faradaic efficiency of formic acid production can reach 60.5%, and the current density is 41.6 mA cm -2 The maximum Faraday efficiency of formic acid produced under the conditions of Example 2 can reach 30.5%, and the current density is 40.5 mA cm -2 Changing the components will reduce the performance of the catalyst, the Faraday efficiency and current density of the zinc selenide catalyst prepared in Example 4, as shown Figure 4As shown, Figure 4 The CO and H2 in the solution are both reduction products at the cathode. Figure 4 The horizontal axis represents the potential (Vvs.RHE), the vertical axis on the left represents the Faraday efficiency (%), and the vertical axis on the right represents the current density (mAcm -2 ), the bar graph represents the Faraday efficiency, and the curve represents the current density. Figure 4 It can be seen that the highest Faradaic efficiency for producing formic acid under the conditions of Example 4 can reach 30.0%, and the current density is 39.5 mA cm -2 .

[0082] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a zinc selenide catalyst and its application in the electroreduction of CO2 to produce formic acid, characterized in that: The raw materials for preparing the zinc selenide catalyst include selenium powder and ZIF-8; the mass ratio of the selenium powder to the ZIF-8 is 0.15:1-10:23; The reaction temperature is 15-25° C.; the reaction time is 0.6-0.9 h; and the applied voltage is -0.8 to -1.2 V vs. RH.

2. The use according to claim 1, characterized in that The following steps are involved: The selenium powder and the ZIF-8 are mixed and reacted to prepare the zinc selenide catalyst.

3. The use according to claim 2, characterized in that The reaction temperature is 450-950°C; the reaction time is 1.5-5h; the heating rate of the reaction is 2-10°C min -1 .

4. The use according to claim 2, characterized in that The preparation method of ZIF-8 comprises the following steps: The Zn(NO3)2 solution and the dimethylimidazole solution are mixed and reacted to obtain the ZIF-8.

5. The use according to claim 4, characterized in that The Zn(NO3)2 solution is formed by dissolving Zn(NO3)2·6H2O in methanol; the dimethylimidazole solution is formed by dissolving dimethylimidazole in methanol; the molar ratio of the Zn(NO3)2·6H2O to dimethylimidazole is (0.125-8):

1.

6. The use according to claim 4, characterized in that The reaction temperature is 5-35° C.; the reaction time is 11-25 h.

7. The use according to claim 1, characterized in that The working electrode of the electroreduction is a platinum sheet electrode containing the zinc selenide catalyst, the counter electrode is a platinum sheet electrode, and the reference electrode is an Ag / AgCl electrode; The electroreduction electrolyte is selected from at least one of KHCO3, KOH, and NaHCO3.

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