An indium oxide-bismuth oxide composite oxide with (111) crystal plane and its preparation method

Abstract

The present invention relates to the field of catalyst preparation, and specifically discloses an indium oxide-bismuth oxide composite oxide with (111) crystal plane and a preparation method thereof. Indium nitrate, bismuth nitrate and urea are dissolved in a mixed solvent containing ethylene glycol and water, and heated for reaction to obtain a reaction solution containing the indium oxide-bismuth oxide composite oxide with (111) crystal plane. In the mixed solvent, the volume ratio of water is 3% - 10%. The method provided by the present invention has the advantages of simple preparation process, good repeatability, and convenient batch synthesis of the composite oxide catalyst without a carrier. Moreover, during the reduction preparation of formic acid, the catalyst has high selectivity for formic acid, and the Faraday efficiency of CO2 electroreduction to formic acid is about 90%. This catalyst is expected to be widely used in the field of electrocatalysis.

Description

Technical Field

[0001] The present invention relates to the field of catalyst preparation, and particularly relates to an indium oxide-bismuth oxide composite oxide with a (111) crystal plane and a preparation method thereof. Background Art

[0002] What is provided in this part is only background information related to the present disclosure, and it is not necessarily prior art.

[0003] With the increasingly serious global climate change problem, CO 2 emission reduction and resource utilization have become one of the important issues that need to be solved urgently in today's society. CO 2 electroreduction (CO 2 RR) technology has attracted much attention because it can convert CO 2 into high-value-added chemicals and fuels, such as formic acid, methanol, etc., under mild conditions. Formic acid is not only an important chemical raw material but also can be used as a hydrogen source for fuel cells, with broad application prospects. In recent years, as a low-toxic p-group metal, indium metal has attracted extensive attention from researchers because it has a relatively high overpotential for the hydrogen evolution reaction and can electroreduce CO 2 to formic acid with high selectivity and reach a relatively high current density. However, the relatively high overpotential and unsatisfactory stability of indium-based catalysts themselves limit their further development. Constructing bimetallic oxides can stabilize intermediates and inhibit the hydrogen evolution reaction, thereby improving the electroreduction reaction activity of CO 2

[0004] In recent years, the composite oxides of indium and bismuth have shown good application prospects in CO2 electroreduction due to their different surface electronic structures and diverse active sites. The synergistic effect of indium and bismuth can effectively stabilize the CO 2 reduction intermediates and inhibit the hydrogen evolution reaction, thereby increasing the yield and Faraday efficiency of formic acid. However, current research mostly focuses on the simple composite of indium oxide and bismuth oxide (X. Chen, Journal of Colloid and Interface Science, 2025,678; CN 109939670 A), while ignoring the profound influence of their crystal plane structure on catalytic performance. Crystal plane regulation technology can enhance the density of active centers on the catalyst surface by selectively exposing specific crystal planes, thereby enhancing the adsorption, activation, and electron transfer processes of CO 2 molecules, and thus significantly improving the reaction activity and selectivity of the catalyst. Therefore, optimizing and improving the composite oxide material of indium oxide and bismuth oxide based on the crystal plane selection strategy to enhance its performance in the reaction of electroreducing CO 2 to formic acid has important research significance and application value. Summary of the Invention ​

[0005] Objective of the Invention: Aiming at the deficiencies of the prior art, the technical problem to be solved by the present invention is to provide an indium oxide-bismuth oxide composite oxide with (111) crystal plane, a preparation method thereof, and its application in the electroreduction of CO 2 to formic acid.

[0006] To solve the above technical problems, the present invention discloses the following technical solutions:

[0007] In the first aspect, the present invention discloses an indium oxide-bismuth oxide composite oxide with (111) crystal plane and a preparation method thereof.

[0008] In the preparation method, ethylene glycol and water are used as a mixed solvent, indium nitrate and bismuth nitrate are used as indium and bismuth sources respectively, and urea is used as an alkali source.

[0009] Specifically, the preparation method of the indium oxide-bismuth oxide composite oxide with (111) crystal plane includes ultrasonic dissolving of indium nitrate, bismuth nitrate and urea in a mixed solvent containing ethylene glycol and water, mixing evenly, heating and reacting to obtain a reaction solution containing the indium oxide-bismuth oxide composite oxide with (111) crystal plane; the obtained reaction solution is cooled to room temperature, successively washed thoroughly with deionized water and absolute ethanol, centrifuged, dried, and calcined at 300-600 °C for 2-5 hours to obtain the indium oxide-bismuth oxide composite oxide with (111) crystal plane.

[0010] Among them, in the mixed solvent, the volume ratio of water is 3% - 10%, such as 5%, 7%, 9%.

[0011] Among them, the molar volume ratio of indium nitrate to the mixed solution is 0.2 - 2 mmol: 29 - 30 mL, such as 0.5 mmol: 29 - 30 mL, 1.5 mmol: 29 - 30 mL.

[0012] Among them, the molar ratio of indium nitrate to bismuth nitrate is 1:3 - 3:1.

[0013] Among them, the ratio of the total molar amount of indium nitrate and bismuth nitrate to the molar amount of urea is 1:5 - 7, such as 1:6.

[0014] Among them, the temperature of the heating reaction is 120 - 130 °C.

[0015] Among them, the time of the heating reaction is 16 - 18 h.

[0016] In the second aspect, the present invention discloses the application of the above indium oxide-bismuth oxide composite oxide with (111) crystal plane as a catalyst in the electroreduction of CO 2 to formic acid.

[0017] Among them, the potential for preparing formic acid by electroreduction is -0.8~-1.4.

[0018] Wherein, the catalyst loading is 0.5-1.5 mg / cm 2 , such as 1 mg / cm 2 .

[0019] Beneficial effects:

[0020] 1. The method provided by the present invention has the advantages of simple preparation process, good repeatability, and convenient batch synthesis of composite oxide catalysts without carriers, and the catalyst has high selectivity for formic acid in the process of reducing and preparing formic acid.

[0021] 2. The present invention prepares a composite oxide of indium oxide and bismuth oxide having a (111) crystal plane, CO 2 The Faradaic efficiency of electroreduction of formic acid is about 90%, and the catalyst is expected to be widely used in the field of electrocatalysis. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments, and the above and / or other advantages of the present invention will become more clear.

[0023] Figure 1 It is the X-ray diffraction pattern of the indium oxide-bismuth oxide catalyst prepared in Example 1 of the present invention.

[0024] Figure 2 The figures are scanning electron microscope images (a) and transmission electron microscope images (b) of the indium oxide-bismuth oxide catalyst prepared in Example 1 of the present invention.

[0025] Figure 3 It is a formic acid Faraday efficiency diagram of the indium oxide-bismuth oxide catalyst prepared in the present invention.

[0026] Figure 4 This is the X-ray diffraction pattern of the indium oxide-bismuth oxide catalyst prepared in Example 2 of the present invention. DETAILED DESCRIPTION

[0027] The present invention can be better understood according to the following examples. However, it is easy for those skilled in the art to understand that the contents described in the examples are only used to illustrate the present invention, and should not and will not limit the present invention described in detail in the claims.

[0028] The experimental methods described in the following examples are conventional methods unless otherwise specified; the reagents and materials described are commercially available unless otherwise specified.

[0029] The following examples provide a method for preparing indium oxide-bismuth oxide composite oxides with (111) crystal planes. This method can rapidly synthesize a large amount of CO electroreduction reaction catalysts with (111) crystal planes, good dispersibility, high repeatability, and high selectivity within a wide range of molar ratios of indium oxide to bismuth oxide using a simple hydrothermal process. 2 Electroreduction reaction catalyst.

[0030] Example 1

[0031] Mix 28 mL of ethylene glycol and 1 mL of deionized water evenly to form a mixed solvent. Then add 1.0 mmol of indium nitrate, 1.0 mmol of bismuth nitrate, and 0.70 g of urea, and ultrasonically dissolve until completely dissolved. Stir well for 1 hour until the mixed solution is completely homogeneous. Transfer the obtained mixed solution to a 50 mL stainless steel reaction kettle with a polytetrafluoroethylene liner, place it in a forced-air drying oven, and carry out a hydrothermal reaction at 120 °C for 17 hours. Then naturally cool to room temperature, wash the obtained precipitate successively with deionized water and absolute ethanol, centrifuge and separate, and dry in an oven at 60 °C for 12 hours to obtain a precursor product. Transfer the precursor product to a tubular furnace and calcine in air at 600 °C for 2 hours to obtain indium oxide-bismuth oxide composite oxides with (111) crystal planes.

[0032] CO 2 CO electroreduction reaction evaluation: Use 10 mg of indium oxide-bismuth oxide composite oxide catalyst with (111) crystal planes, add 20 μL of 5% Nafion solution and 1000 μL of isopropanol to prepare an ink solution, ultrasonically disperse evenly for 30 minutes, take 25 μL of the ink solution and disperse it on a 0.25 cm 2 carbon paper, and the catalyst loading is about 1 mg / cm 2 , and dry under an infrared lamp for 10 min. Test in a three-electrode system of an H-type electrolytic cell. The CO 2 flow rate is 20 sccm, 0.1 M KHCO 3 is used as the electrolyte, electrolyze for 60 min, the gaseous products H 2 and CO are detected by gas chromatography, the liquid products are detected by liquid nuclear magnetic resonance, and the entire electrochemical reaction process applies a voltage through an electrochemical workstation and records the current-time curve.

[0033] The X-ray diffraction pattern of indium oxide-bismuth oxide composite oxides with (111) crystal planes is shown in Figure 1 , and the positions and intensities of each diffraction peak are consistent with the indium oxide standard card (JCPDS 06-0416) and the bismuth oxide standard card (JCPDS 27-0050). Its scanning electron micrograph is shown in Figure 2 Figure (a), showing that the size and morphology of indium oxide-bismuth oxide are uniform granular. The high-magnification transmission electron micrograph is shown in Figure 2(b) Similarly, it can also be confirmed that the mainly exposed surface is the (111) crystal plane.

[0034] The indium oxide-bismuth oxide catalyst is used for the 2 electroreduction reaction of CO. The catalytic results are shown in Figure 3 Example 1. At a relatively wide potential range, the product is formic acid, and its Faraday efficiency exceeds 90%.

[0035] Example 2

[0036] Mix 29 mL of ethylene glycol and 1 mL of deionized water evenly to form a mixed solvent. Then add 0.5 mmol of indium nitrate, 1.5 mmol of bismuth nitrate and 0.65 g of urea, and ultrasonically dissolve until completely dissolved. Stir well for 1 hour until the mixed solution is completely homogeneous. Transfer the obtained mixed solution to a 50 mL stainless steel reaction kettle with a polytetrafluoroethylene lining, place it in a forced-air drying oven, and carry out hydrothermal reaction at 130 °C for 16 hours. Then naturally cool to room temperature, wash the obtained precipitate thoroughly with deionized water and absolute ethanol in sequence, centrifuge and separate, and dry in an oven at 60 °C for 12 hours to obtain a precursor product. Transfer the precursor product to a tubular furnace and calcine in air at 600 °C for 2 hours to obtain the indium oxide-bismuth oxide catalyst. The X-ray diffraction pattern of the indium oxide-bismuth oxide catalyst is shown in Figure 4 , the proportion of the (111) crystal plane decreases, and the 2 Faraday efficiency of electroreduction of CO to formic acid is shown in Figure 3 Example 2, which is about 80%.

[0037] Example 3

[0038] Mix 28 mL of ethylene glycol and 1 mL of deionized water evenly to form a mixed solvent. Then add 1.5 mmol of indium nitrate, 0.5 mmol of bismuth nitrate and 0.75 g of urea, and ultrasonically dissolve until completely dissolved. Stir well for 1 hour until the mixed solution is completely homogeneous. Transfer the obtained mixed solution to a 50 mL stainless steel reaction kettle with a polytetrafluoroethylene lining, place it in a forced-air drying oven, and carry out hydrothermal reaction at 130 °C for 18 hours. Then naturally cool to room temperature, wash the obtained precipitate thoroughly with deionized water and absolute ethanol in sequence, centrifuge and separate, and dry in an oven at 60 °C for 12 hours to obtain a precursor product. Transfer the precursor product to a tubular furnace and calcine in air at 600 °C for 2 hours to obtain the indium oxide-bismuth oxide composite oxide with the (111) crystal plane. Its 2 Faraday efficiency of electroreduction of CO to formic acid is shown in Figure 3 Example 3. At a potential of -1.0~-1.1 V, the Faraday efficiency reaches 90%, and then it maintains at about 80% in the subsequent potential window.

[0039] Comparative Example 1

[0040] Mix 27 mL of ethylene glycol and 3 mL of deionized water evenly to form a mixed solvent, then add 1 mmol of indium nitrate and 0.40 g of urea, and ultrasonically dissolve until completely dissolved. Stir well for 1 hour until the mixed solution is completely homogeneous. Transfer the obtained mixed solution to a 50 mL stainless steel autoclave with a polytetrafluoroethylene lining, place it in a forced-air drying oven, and carry out a hydrothermal reaction at 130 °C for 18 hours. Then naturally cool to room temperature, wash the obtained precipitate thoroughly with deionized water and absolute ethanol in sequence, centrifuge and separate, and dry in an oven at 60 °C for 12 hours to obtain a precursor product. Transfer the precursor product to a tube furnace and calcine in air at 600 °C for 5 hours to obtain indium oxide with a (111) crystal plane. Its CO 2 The Faraday efficiency of electroreduction to formic acid is shown in Figure 3 For Comparative Example 1, the initial potential increased slightly, and the Faraday efficiency of formic acid was between 70% and 80%.

[0041] Comparative Example 2

[0042] Mix 29 mL of ethylene glycol and 1 mL of deionized water evenly to form a mixed solvent, then add 1 mmol of bismuth nitrate and 0.30 g of urea, and ultrasonically dissolve until completely dissolved. Stir well for 1 hour until the mixed solution is completely homogeneous. Transfer the obtained mixed solution to a 50 mL stainless steel autoclave with a polytetrafluoroethylene lining, place it in a forced-air drying oven, and carry out a hydrothermal reaction at 120 °C for 17 hours. Then naturally cool to room temperature, wash the obtained precipitate thoroughly with deionized water and absolute ethanol in sequence, centrifuge and separate, and dry in an oven at 60 °C for 12 hours to obtain a precursor product. Transfer the precursor product to a tube furnace and calcine in air at 600 °C for 2 hours to obtain bismuth oxide. Its CO 2 The Faraday efficiency of electroreduction to formic acid is shown in Figure 3 For Comparative Example 2, the Faraday efficiency of formic acid was between 70% and 80%.

[0043] Comparative Example 3

[0044] Same as Example 1, except that 28 mL of ethylene glycol and 1 mL of deionized water were replaced with 28 mL of ethylene glycol, and indium oxide-bismuth oxide composite oxide could not be synthesized.

[0045] Comparative Example 4

[0046] Same as Example 1, except that 28 mL of ethylene glycol and 1 mL of deionized water were replaced with 5 mL of ethylene glycol and 24 mL of water, and as a result, the Faraday efficiency of formic acid was only about 60%.

[0047] It can be seen that the present invention provides a nanomaterial with crystal plane selectivity, in particular, an indium oxide-bismuth oxide composite oxide with (111) crystal plane, and has high selectivity for formic acid. Specifically, the present invention does not require any template or structure-directing agent. By using the ethylene glycol-water mixed solvent thermal method and regulating the ratio of urea to metal precursor salts, hydrothermal temperature and synthesis time, an indium oxide-bismuth oxide composite oxide with (111) crystal plane can be obtained. This synthesis method has the advantages of simple process, low cost, relatively uniform product morphology and size, can be synthesized in large quantities and has good repeatability. The indium oxide and bismuth oxide composite oxide synthesized by this method has high selectivity in the 2 CO electroreduction reaction. In an H-type electrolytic cell, the Faraday efficiency of the product formic acid is measured to be above 80%.

[0048] The above embodiments only represent several implementation manners of the present invention. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the present invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several deformations and improvements can be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention patent shall be subject to the appended claims.

Claims

1. A method for preparing an indium oxide-bismuth oxide composite oxide having a (111) crystal face for preparing formic acid by CO2 electroreduction, characterized in that: Indium nitrate, bismuth nitrate and urea are dissolved in a mixed solvent containing ethylene glycol and water, and heated to react to obtain a reaction solution containing the indium oxide-bismuth oxide composite oxide with a (111) crystal face; the volume ratio of water in the mixed solvent is 3% to 10%; the temperature of the heating reaction is 120 to 130° C., and the time of the heating reaction is 16 to 18 hours.

2. The method according to claim 1, characterized in that The molar ratio of indium nitrate to bismuth nitrate is 1:3 to 3:

1.

3. The method according to claim 1, characterized in that The ratio of the total molar amount of the indium nitrate and the bismuth nitrate to the molar amount of urea is 1:5-7.

4. The method according to claim 1, characterized in that: After the heating reaction is completed, the mixture is cooled, washed, dried and calcined to obtain an indium oxide-bismuth oxide composite oxide having a (111) crystal plane.

5. The method according to claim 4, characterized in that The calcination is carried out at 300-600° C. for 2-5 hours.

6. An indium oxide-bismuth oxide composite oxide having a (111) crystal plane prepared by the method according to any one of claims 1 to 5.

7. Use of the indium oxide-bismuth oxide composite oxide having a (111) crystal plane as claimed in claim 6 in the preparation of formic acid by CO2 electroreduction.

8. The use according to claim 7, characterized in that: The potential for preparing formic acid by electroreduction is -0.8~-1.4.

Images