Ce-doped Cu-based perovskite oxide catalyst and preparation method thereof

Abstract

The application discloses a Ce-doped Cu-based perovskite oxide catalyst and a preparation method thereof and belongs to the technical field of CO2 electrocatalysis, and comprises the following steps: Pr(NO3)3, Cu(NO3)2 and CeNO3 are added into a container, water is added to stir and dissolve, citric acid monohydrate is added to chelate metal cations after dissolution, the solution is adjusted to be neutral, and stirring is conducted until the solution is gelatinous; the gelatinous substance is pre-fired, and roasting is conducted after pre-firing, so that Pr2Cu 0.9 Ce 0.1 04 catalyst is obtained. 0.9 Ce 0.1 04(PCCe 0.1 ) has very good electroreduction performance on carbon dioxide in the application of CO2 electrocatalytic reduction. With the increase of applied potential, the FE of CO decreases, and the FE of C2H4 increases and then decreases. C2H4 is dominant at-1.2 V vs. RHE, which indicates that H2 is only inhibited at a proper applied potential, and the maximum FE% of C2H4 is 25% at-1.2 V vs. RHE; the FE% of the PC catalyst is improved by 10% after etching by acid, and the PC catalyst is improved by 66.7% compared with PC.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of CO2 electrocatalysis, and particularly relates to a Ce-doped Cu-based perovskite oxide catalyst and a preparation method thereof. BACKGROUND

[0002] CO2 electro-reduction (CO2RR) is a green and pollution-free catalytic conversion technology of CO2. Since C2H4 is an important industrial raw material, it has high practical use value and economic value to catalytically convert CO2 into C2H4. However, most of the catalysts commonly used to electrocatalytically convert CO2 into C2H4 are Cu-based catalysts, but in the reaction process, the crystal is restructured, resulting in low faradic efficiency and poor selectivity, which limits its large-scale use. It is of great significance to design and prepare a kind of copper-based catalyst with high selectivity and high faradic efficiency. Transition metals are low in price and are a kind of potential excellent electrocatalysts. However, transition metals have high adsorption capacity for H*, and are more likely to cause hydrogen evolution reaction, thereby reducing the selectivity of CO2 reduction products. Surface modification of transition metals can change the adsorption strength of intermediate species, thereby improving the CO2 reduction capacity. The Ce-doped Cu-based perovskite catalyst exhibits high CO2 reduction capacity, and the faradic efficiency for C2H4 reaches about 25%. Moreover, the perovskite catalyst is still in the early stage of research in the field of CO2, and there is no literature report on the Ce-doped Cu-based perovskite catalyst to enhance the CO2 reduction capacity. SUMMARY

[0003] In view of the deficiencies of the prior art, the purpose of the present application is to provide a Ce-doped Cu-based perovskite oxide catalyst and a preparation method thereof.

[0004] The purpose of the present application can be achieved by the following technical solutions.

[0005] A Ce-doped Cu-based perovskite oxide catalyst, the chemical formula of the catalyst is Pr2Cu 0.9 Ce 0.1 04.

[0006] A preparation method of a Ce-doped Cu-based perovskite oxide catalyst, comprising the following steps:

[0007] Pr(NO3)3, Cu(NO3)2 and CeNO3 are added to a container, and water is added to stir and dissolve, then citric acid monohydrate is added to chelate metal cations, after the solution is adjusted to neutral, stirring is performed until the solution becomes gelatinous, the gelatinous substance is pre-fired, and then calcination is performed to obtain a Pr2Cu 0.9 Ce 0.1 04 catalyst.

[0008] Further, the molar ratio of metal cation to citric acid in the solution is 1:1.5.

[0009] Further, the solution is adjusted to neutral with ammonia water.

[0010] Further, the Pr(NO3)3, Cu(NO3)2 and CeNO3 need to be stirred and dissolved at 80℃ after adding water.

[0011] Further, the solution needs to be stirred to be gelatinous, and the stirring needs to be carried out at a temperature of 80℃.

[0012] Further, the pre-burning is carried out at 250℃ for 4h in a muffle furnace.

[0013] Further, the calcination is carried out at 1000℃ in an air atmosphere for 8h in a muffle furnace.

[0014] Further, the pre-burning needs to be carried out after grinding, and the calcination needs to be carried out after grinding to obtain the final product.

[0015] Application of a Ce-doped Cu-based perovskite oxide catalyst in CO2 electrocatalytic reduction, the catalyst is Pr2Cu 0.9 Ce 0.1 04.

[0016] Advantages of the present application:

[0017] The Pr2Cu 0.9 Ce 0.1 04(PCCe 0.1 ) prepared in the present application has very good electro-reduction performance on carbon dioxide in the application of CO2 electrocatalytic reduction. With the increase of the applied potential, the FE of CO decreases, and the FE of C2H4 increases and then decreases. C2H4 is dominant at-1.2V vs. RHE, which indicates that H2 is only inhibited at a proper applied potential, and the maximum FE% of C2H4 is 25% at-1.2V vs. RHE, and the FE% of the PC catalyst is improved by 10% after acid etching, which is improved by 66.7% compared with PC. BRIEF DESCRIPTION OF DRAWINGS

[0018] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced below, and obviously, other drawings can also be obtained by those skilled in the art without creative labor on the basis of these drawings.

[0019] Figure 1 is the X-ray diffraction (XRD) pattern of the PCCe 0.1 prepared in Embodiment Two of the present application;

[0020] Figure 2 PC and PCCe prepared in Example 1 of the present application 0.1 TEM image of the electrocatalyst;

[0021] Figure 3 PCCe prepared in Example 2 of the present application 0.1 Elemental mapping of the electrocatalyst;

[0022] Figure 4 Faraday efficiency plot of the catalyst PC prepared in Example 1 of the present application for the CO2 electroreduction reaction to C2H4;

[0023] Figure 5 PCCe prepared in Example 2 of the present application 0.1 Faraday efficiency plot of the catalyst for the CO2 electroreduction reaction to C2H4. DETAILED DESCRIPTION

[0024] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative labor fall within the protection scope of the present application.

[0025] Ce-doped Cu-based perovskite oxide catalyst and preparation method thereof

[0026] Example 1

[0027] The Pr2CuO4 catalyst was prepared by a conventional sol-gel method. The corresponding metal salts (Pr(NO3)3 and Cu(NO3)2) of each element were added to a beaker in stoichiometric ratios, and stirred and dissolved at 80°C. After the metal salts were fully dissolved, one water citric acid with a molar ratio of 1:1.5 (metal ions: citric acid) was added to chelate the metal cations. Then, the solution was adjusted to neutral with ammonia water, and continued to be stirred at 80°C until the solution became gelatinous. The gelatinous substance was placed in a muffle furnace and pre-fired at 250°C for 4h (the heating and cooling rates were both 2°C h-1), to obtain a Pr2CuO4 precursor. The precursor was pretreated and ground in a mortar, and then placed in a muffle furnace and calcined at 1000°C in an air atmosphere for 8h. After cooling to room temperature, the black powder was further ground to obtain the Pr2CuO4 catalyst, which was denoted as PC.

[0028] Example 2

[0029] Pr2Cu 0.9 Ce 0.104catalyst was prepared by a conventional sol-gel method. The corresponding metal salts of each element (Pr(NO3)3, Cu(NO3)2and CeNO3) were added to a beaker according to the stoichiometric ratio, deionized water was added to dissolve at 80°C, after the metal salts were fully dissolved, one water citric acid with a molar ratio of 1:1.5 (metal ions: citric acid) was added to chelate metal cations, then the solution was adjusted to neutral with ammonia water, and continued to stir at 80°C until the solution was gelatinous. The gelatinous material was placed in a muffle furnace and pre-fired at 250°C for 4h (the heating and cooling rates were both 2°C / h -1 ), to obtain a black solid. The black solid was pretreated, ground thoroughly in a mortar, and then placed in a muffle furnace at 1000°C for 8h in an air atmosphere. After cooling to room temperature, the black powder was further ground to obtain a Pr2Cu 0.9 Ce 0.1 04catalyst, denoted as PCCe 0.1 .

[0030] The above example CO2reduction test conditions: 0.5mol KHCO3electrolyte, potential scanning range is -0.8--1.2V vs. RHE, scanning rate is 5mV / s. The carbon paper with catalyst drop-coated as the working electrode, Ag / AgCl as the reference electrode, graphite sheet as the auxiliary electrode, and different electrochemical techniques were used to test the electrochemical performance of the material in the H-type electrolytic cell. The H-type electrolytic cell uses nafion-117 proton exchange membrane to separate, to prevent the oxygen generated in the anode chamber from diffusing to the cathode chamber to oxidize the reduction product, and 25mL 0.5M KHCO3solution is added as the electrolyte solution in the two electrolytic chambers. The material electrochemical performance tester selects CHI-660E electrochemical workstation, and all electrochemical experiments are carried out at room temperature. Before electrochemical testing, CO2(20mL / min) or Ar is pre-inflated for at least 30min, which is to saturate the KHCO3solution and to eliminate the interference of the internal air of the system.

[0031] As shown in Figure 1 , the standard card including Pr2CuO4(JCPDS No. 79-0957). It was found that after doping, the positions at 23.59°, 31.48°, 31.92°, 43.82°, 45.77°, and 56.61° did not change, the structure was consistent with PC, and the space group was still I4 / mmm. The diffraction peaks of PCCe 0.1 in the figure corresponded to the peaks in the standard card one by one, indicating that the prepared catalyst was a pure phase without other impurity phases.

[0032] The TEM image of Pr2Cu 0.9 Ce 0.1 is as shown in Figure 2a, it can be seen that the lattice fringes are uniform and 0.29 nm, corresponding to the (110) plane of PC, and the selected area electron diffraction (SAED) pattern along the zone axis is further revealed by fast Fourier transform (FFT) mode Figure 2 d), the spots appearing are completely matched with the (110) plane, further confirming the tetragonal structure, indicating that the incorporation of Ce does not change the structure of PC. The TEM of PC is shown in Figure 2 e, it can also be seen from the figure that the lattice fringes are uniform and 0.28 nm, which is about 0.01 nm smaller than the PCCe 0.1 , because according to the Debye-Scherrer formula, the radius of Ce is larger than that of Cu, so the doping of Ce into the B site of PC will cause the lattice to expand and the lattice spacing to increase.

[0033] As shown in Figure 3 , it is confirmed that there is a small amount of Ce in PCCe 0.1 , and it can be seen that Pr, Cu and O are uniformly distributed, and there is no other impurity

[0034] Figure 4 is the product distribution diagram of PC at the same voltage, and the FE% of C2H4 is about 15% at -1.2 V vs. RHE

[0035] As shown in Figure 5 , with the increase of potential, the selectivity of C2H4 is enhanced, and it can be found that the selectivity of C2H4 is the highest at -1.2 V vs. RHE, about 25%. It can be seen that the PC catalyst after acid etching improves the FE% by 10%, which is increased by 66.7% compared with PC.

[0036] In the description of the present specification, the description of the terms "one embodiment", "example", "specific example" and the like means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In the present specification, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0037] The basic principles, main features and advantages of the present application are shown and described above. Those skilled in the art should understand that the present application is not limited by the above embodiments, and the above embodiments and descriptions in the specification are only to illustrate the principles of the present application. Without departing from the spirit and scope of the present application, various changes and improvements can be made to the present application, and these changes and improvements all fall within the scope of the claimed present application.

Claims

1. A Ce-doped Cu-based perovskite oxide catalyst, characterized in that, The catalyst has the chemical formula Pr₂Cu. 0.9 Ce 0.1 O4.

2. A method for preparing a Ce-doped Cu-based perovskite oxide catalyst, characterized in that, Includes the following steps: Pr(NO3)3, Cu(NO3)2, and CeNO3 were added to a container and dissolved by stirring with water. After dissolution, citric acid monohydrate was added to chelate the metal cations. The solution was adjusted to neutral and stirred until it became gel-like. The gel was then pre-calcined and subsequently roasted to obtain Pr2Cu. 0.9 Ce 0.1 O4 catalyst.

3. The method for preparing a Ce-doped Cu-based perovskite oxide catalyst according to claim 2, characterized in that, After adding citric acid to the solution, the molar ratio of metal cations to citric acid is 1:1.

5.

4. The method for preparing a Ce-doped Cu-based perovskite oxide catalyst according to claim 2, characterized in that, Adjust the solution to neutral using ammonia.

5. The method for preparing a Ce-doped Cu-based perovskite oxide catalyst according to claim 2, characterized in that, The Pr(NO3)3, Cu(NO3)2 and CeNO3 need to be dissolved by stirring at 80°C after adding water.

6. The method for preparing a Ce-doped Cu-based perovskite oxide catalyst according to claim 2, characterized in that, The solution is stirred until it becomes gel-like, which must be done at a temperature of 80°C.

7. The method for preparing a Ce-doped Cu-based perovskite oxide catalyst according to claim 2, characterized in that, The pre-firing is performed in a muffle furnace at 250°C for 4 hours.

8. The method for preparing a Ce-doped Cu-based perovskite oxide catalyst according to claim 2, characterized in that, The roasting was carried out in a muffle furnace at 1000°C in air atmosphere for 8 hours.

9. The method for preparing a Ce-doped Cu-based perovskite oxide catalyst according to claim 2, characterized in that, The pre-calcined product needs to be ground before being roasted again, and then ground again after roasting to obtain the final product.

10. The application of a Ce-doped Cu-based perovskite oxide catalyst in the electrocatalytic reduction of CO2, characterized in that, The catalyst is Pr₂Cu. 0.9 Ce 0.1 O4.

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