A photoelectrocatalyst and its preparation method

Abstract

This invention discloses a photoelectrocatalyst and its preparation method, wherein the photoelectrocatalyst comprises Zn 2+ Ce 4+ Au; Zn 2+ Including ammonium acetate, zinc nitrate, and hexamethylenetetramine; Ce 4+ Including cerium nitrate, ammonium chloride, and potassium chloride; Au includes PVP, sodium citrate, potassium bromide, and chloroauric acid; Zn 2+ Ce 4+ The molar ratio of Au to Zn is... 2+ Ce 4+ Au = 1:0.5 ~ 1:2.5 * 10 ‑7 ~7.5*10 ‑7 This method uses electrodeposition to prepare ZnO as a substrate. Its vertically aligned one-dimensional (1D) nanostructures exhibit quantum size-dependent effects, effectively shortening the carrier diffusion distance. CeO2 coats the ZnO, forming a stable, acid- and alkali-resistant substrate material. CeO2 traps electrons from Ce... 4+ Restored to Ce 3+ This forms oxygen voids and Ce 3+ / Ce 4+ Electron pairs produce high catalytic activity.

Description

Technical Field

[0001] This invention relates to the field of CO2 reduction technology, specifically to a photoelectrocatalyst and its preparation method. Background Technology

[0002] Carbon dioxide is a major greenhouse gas, with a concentration of approximately 410 ppm (2019 data) in the Earth's atmosphere, totaling about 3200 Gt. According to the targets set by the Paris Agreement, the increase in global average temperature should be limited to well below 2°C above pre-industrial levels by 2100. It is estimated that to achieve this goal, the global net emission allowance for carbon dioxide will be approximately 800 Gt by 2100. However, current global net carbon dioxide emissions are approximately 41 Gt per year. In other words, if the current rate of net emissions continues, the net emission allowance will be exhausted within 20 years. Environmental pollution caused by excessive carbon dioxide emissions is one of the major problems facing human society today.

[0003] Currently, carbon dioxide can be recovered and recycled through artificial carbon fixation technology. Photoelectrocatalytic CO2 reduction is a feasible technology for alleviating environmental problems, converting carbon dioxide into high-value-added chemicals, and improving the storage efficiency of renewable energy. Among many related technologies, photoelectrocatalytic carbon dioxide reduction occurs under relatively mild conditions and has good compatibility and complementarity with new renewable energy sources (such as solar, wind, and hydropower). It can convert solar and electrical energy and store it in chemical bonds, while simultaneously obtaining a series of economically valuable reduction products. Therefore, photoelectrocatalytic carbon dioxide reduction technology has received widespread attention from the scientific and industrial communities in recent years. However, during the reduction process, due to the stable structure of carbon dioxide molecules, the catalytic conversion process requires overcoming a high energy barrier. Furthermore, the diverse products of carbon dioxide reduction (formic acid, carbon monoxide, methane, methanol, etc.) and the similar redox potentials of the products lead to low product selectivity. Therefore, the carbon dioxide reduction reaction suffers from low catalytic efficiency and poor product selectivity. To address this, we propose a photoelectrocatalyst and its preparation method. Summary of the Invention

[0004] (a) Technical problems to be solved

[0005] To address the shortcomings of existing technologies, this invention provides a photoelectrocatalyst and its preparation method. ZnO, prepared by electrodeposition, serves as the substrate. Its vertically aligned one-dimensional (1D) nanostructures exhibit quantum size-dependent effects, effectively shortening the diffusion distance of charge carriers. CeO2 coats the ZnO, forming a stable and acid / alkali-resistant substrate material, which is beneficial for further hydrothermal growth of Au nanoparticles. Compared to CeO2 / ZnO, the Au-CeO2 / ZnO modified with the co-catalyst Au exhibits a synergistic effect between the two components. Specifically, after activation under xenon lamp irradiation, Au significantly promotes the separation of photogenerated charge carriers, and CeO2 captures electrons from CeO2. 4+ Restored to Ce 3+ This forms oxygen voids and Ce 3+ / Ce 4+ Electron pairs facilitate oxygen escape, leading to higher catalytic activity. This invention provides a photoelectrocatalyst for CO2 reduction that exhibits excellent catalytic performance, good selectivity and stability, a simple and controllable preparation process, and is easily mass-producible industrially. The technical solution employed in this invention operates under relatively mild conditions, is simple to operate, and is easily scaled up for industrial production.

[0006] (II) Technical Solution

[0007] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0008] A photoelectrocatalyst comprising Zn 2+ Ce 4+ and Au;

[0009] Zn 2+ Including ammonium acetate, zinc nitrate, and hexamethylenetetramine;

[0010] Ce 4+ Including cerium nitrate, ammonium chloride, and potassium chloride;

[0011] Au includes PVP, sodium citrate, potassium bromide, and chloroauric acid;

[0012] Zn 2+ Ce 4+ The molar ratio of Au to Zn is... 2+ Ce 4+ Au = 1:0.5 ~ 1:2.5 * 10 -7 ~7.5*10 -7 .

[0013] Preferred, Zn 2+ The mass concentrations of ammonium acetate, zinc nitrate, and hexamethylenetetramine were 0.39 g / 500 mL, 2.97 g / 500 mL, and 0.70 g / 500 mL, respectively.

[0014] The mass ratio of ammonium acetate, zinc nitrate, and hexamethylenetetramine is ammonium acetate: zinc nitrate: hexamethylenetetramine = 1:7.62:1.79.

[0015] Preferred, Ce 4+ The mass concentration of cerium nitrate in the solution is 1.09 g / 250 mL, the mass concentration of ammonium chloride is 1.34 g / 250 mL, and the mass concentration of potassium chloride is 0.93 g / 250 mL.

[0016] The mass concentration ratio of cerium nitrate, ammonium chloride, and potassium chloride is cerium nitrate:ammonium chloride:potassium chloride = 1.17:1.44:1.

[0017] Preferably, the mass concentration of PVP in Au is 1 g / 100 mL, the mass concentration of potassium citrate is 1 g / 100 mL, the mass concentration of potassium bromide is 3 g / 100 mL, and the mass concentration of chloroauric acid is 0.25–0.75 μmol / 100 mL.

[0018] A method for preparing a photoelectrocatalyst includes the following steps:

[0019] Step 1: Dissolve ammonium acetate, zinc nitrate, and hexamethylenetetramine in deionized water to obtain Zn. 2+ The plating solution will contain Zn 2+ The electrolytic cell of the plating solution was transferred to an oil bath for heating. Then, a conductive glass plate was placed into the electrolytic cell and electroplated using a constant current electrodeposition method. After that, the FTO conductive glass plate was removed and rinsed with deionized water to obtain a white thin film of ZnONRAs.

[0020] Step 2: Dissolve cerium nitrate, ammonium chloride, and potassium chloride in deionized water to obtain Ce. 4+ The plating solution will contain Ce 4+ The electrolytic cell of the plating solution was transferred to an oil bath for heating, and then ZnO NRAs were placed in the electrolytic cell. Electroplating was performed using a constant current electrodeposition method. After the plating was completed, the material was removed and rinsed with deionized water to obtain a white thin film of CeO2 / ZnO.

[0021] Step 3: Dissolve PVP, sodium citrate, potassium bromide and chloroauric acid in deionized water to obtain Au plating solution. Transfer the solution to an oil bath and heat it. Then add the obtained CeO2 / ZnO into the Au plating solution and stir slowly. After the process is complete, remove the material and rinse it with deionized water to obtain a white film-like Au-CeO2 / ZnO.

[0022] Preferably, the heating temperature in the first step is 90°C;

[0023] The electroplating current was -2.0mA, and the electroplating temperature and time were 90℃ and 50min, respectively.

[0024] Preferably, the heating temperature in the second step is 70°C;

[0025] The electroplating current is 0.5mA, the electroplating temperature is 70℃, and the electroplating time is 20min.

[0026] Preferably, the heating temperature in the third step is 80°C;

[0027] The stirring time is 30 minutes.

[0028] (III) Beneficial Effects

[0029] Compared with the prior art, the photoelectrocatalyst and preparation method provided by the present invention have the following beneficial effects:

[0030] 1. This photoelectrocatalyst and its preparation method: This invention prepares Au-CeO2 / ZnO by first constructing CeO2 / ZnO and then modifying it with Au nanoparticles. Compared with ZnO NRAs and CeO2 / ZnO, the obtained Au-CeO2 / ZnO shows stronger photoelectrocatalytic ability in CO2 reduction. This invention provides a new idea for the selection of photoelectrocatalytic CO2 reduction catalysts and provides more references for the preparation of CO2 reduction photoelectrocatalysts.

[0031] 2. Application of the photoelectrocatalyst and its preparation method in catalytic CO2 reduction: Photoelectrocatalysts have considerable practical application prospects in photoelectrocatalytic CO2 reduction.

[0032] 3. This photoelectrocatalyst and its preparation method select cerium dioxide (CeO2) as the main catalyst for photoelectrocatalytic CO2 reduction due to its unique variable valence property (Ce(IV)-Ce(III)), which gives CeO2 a strong oxygen storage and release capacity and provides redox sites that can be used for catalytic reactions. Furthermore, after CeO2 reacts with other metals to form a supported cerium-based catalyst, it can generate strong metal-support interactions, creating a large number of surface oxygen vacancies, which helps activate oxygen-containing reactants (such as CO2 molecules) and exhibit superior catalytic performance.

[0033] 4. The photoelectrocatalyst and its preparation method employ a hydrothermal method to deposit Au nanoparticles loaded on the surface of CeO2. By reducing the reaction overpotential, promoting the separation of photogenerated carriers, and suppressing the occurrence of side reactions and reverse reactions, the catalytic performance of the CeO2 catalyst is effectively regulated, thereby improving catalytic activity and stability. Attached Figure Description

[0034] Figure 1 Scanning electron microscope images of ZnO NARs magnified at different magnifications prepared for embodiments of the present invention;

[0035] Figure 2X-ray diffraction patterns of Au-CeO2 / ZnO prepared with different amounts of chloroauric acid in the embodiments of the present invention;

[0036] Figure 3 The X-ray photoelectron spectrum of the photoelectron catalyst in an embodiment of the present invention is shown below.

[0037] Figure 4 The linear voltammetric curves of Au-CeO2 / ZnO tested in N2 and CO2 saturated KHCO3 solutions are shown in the embodiments of the present invention.

[0038] Figure 5 The products and Faraday efficiencies of carbon dioxide reduction were tested using Au-CeO2 / ZnO and CeO2 / ZnO catalysts prepared with different amounts of chloroauric acid in the embodiments of the present invention. Detailed Implementation

[0039] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0040] Please see Figure 1-5 The photoelectrocatalyst and method provided by this invention are detailed in the following three sets of examples:

[0041] Example 1

[0042] The photoelectrocatalyst provided in this embodiment includes Zn 2+ Ce 4+ and Au; of which Zn 2+ Made from ammonium acetate, zinc nitrate, and hexamethylenetetramine; Ce 4+ Made from cerium nitrate, ammonium chloride, and potassium chloride; Au is made from PVP, sodium citrate, potassium bromide, and chloroauric acid; Zn 2+ Ce 4+ The molar ratio of Au to Zn is... 2+ Ce 4+ Au = 1:(0.5~1):(2.5*10 -7 ~7.5*10 -7 ).

[0043] The Zn 2+ The mass concentrations of ammonium acetate, zinc nitrate, and hexamethylenetetramine were 0.39 g / 500 mL, 2.97 g / 500 mL, and 0.70 g / 500 mL, respectively.

[0044] The mass ratio of ammonium acetate, zinc nitrate, and hexamethylenetetramine is ammonium acetate: zinc nitrate: hexamethylenetetramine = 1:7.62:1.79.

[0045] The Ce 4+ The mass concentration of cerium nitrate in the solution is 1.09 g / 250 mL, the mass concentration of ammonium chloride is 1.34 g / 250 mL, and the mass concentration of potassium chloride is 0.93 g / 250 mL.

[0046] The mass concentration ratio of cerium nitrate, ammonium chloride, and potassium chloride is cerium nitrate:ammonium chloride:potassium chloride = 1.17:1.44:1.

[0047] The Au contains PVP at a mass concentration of 1 g / 100 mL, potassium citrate at a mass concentration of 1 g / 100 mL, potassium bromide at a mass concentration of 3 g / 100 mL, and chloroauric acid at a mass concentration of 0.25–0.75 μmol / 100 mL.

[0048] The preparation method of the photoelectrocatalyst provided in this embodiment includes the following specific components, proportions, and steps:

[0049] (1) Dissolve 0.39g ammonium acetate, 2.97g zinc nitrate and 0.70g hexamethylenetetramine in deionized water and make up to 500mL of ZnO plating solution. Transfer the electrolytic cell containing about 50mL of plating solution to an oil bath and heat to 90°C. Then put a conductive glass plate into the electrolytic cell and use the constant current electrodeposition method with a current of -2.0mA at 90°C for 50min. After that, take out the FTO conductive glass plate and rinse it with deionized water to obtain white thin film ZnO NRAs.

[0050] (2) Dissolve 1.09g cerium nitrate, 1.34g ammonium chloride and 0.93g potassium chloride in deionized water and make up to 250mL of CeO2 plating solution. Transfer the electrolytic cell containing about 50mL of plating solution to an oil bath and heat it to 70°C. Then put the ZnO NRAs obtained in step (1) into the above electrolytic cell and electroplate for 20min using the constant current electrodeposition method. After the electrolytic cell is finished, take out the material and rinse it with deionized water to obtain a white film-like CeO2 / ZnO.

[0051] (3) Dissolve 1g PVP, 1g sodium citrate, 3g potassium bromide and 0.25μmol chloroauric acid in 100mL of deionized water, transfer to an oil bath and heat to 80℃, then put the CeO2 / ZnO obtained in step (2) into the solution and stir slowly for 30min. After the end, take out the material and rinse with deionized water to obtain a white film Au-CeO2 / ZnO.

[0052] Example 2

[0053] The preparation method of the photoelectrocatalyst provided in this embodiment, based on Example 1, has the following specific components, proportions, and steps:

[0054] (1) Dissolve 0.39g ammonium acetate, 2.97g zinc nitrate and 0.70g hexamethylenetetramine in deionized water and make up to 500mL of ZnO plating solution. Transfer the electrolytic cell containing about 50mL of plating solution to an oil bath and heat to 90°C. Then put a conductive glass plate into the electrolytic cell and use the constant current electrodeposition method with a current of -2.0mA at 90°C for 50min. After that, take out the FTO conductive glass plate and rinse it with deionized water to obtain white thin film ZnO NRAs.

[0055] (2) Dissolve 1.09g cerium nitrate, 1.34g ammonium chloride and 0.93g potassium chloride in deionized water and make up to 250mL of CeO2 plating solution. Transfer the electrolytic cell containing about 50mL of plating solution to an oil bath and heat it to 70°C. Then put the ZnO NRAs obtained in step (1) into the above electrolytic cell and electroplate for 20min using the constant current electrodeposition method. After the electrolytic cell is finished, take out the material and rinse it with deionized water to obtain a white film-like CeO2 / ZnO.

[0056] (3) Dissolve 1g PVP, 1g sodium citrate, 3g potassium bromide and 0.5μmol chloroauric acid in 100mL of deionized water, transfer to an oil bath and heat to 80℃, then put the CeO2 / ZnO obtained in step (2) into the solution and stir slowly for 30min. After the end, take out the material and rinse with deionized water to obtain a white film Au-CeO2 / ZnO.

[0057] Example 3

[0058] The preparation method of the photoelectrocatalyst provided in this embodiment, based on Example 1, has the following specific components, proportions, and steps:

[0059] (1) Dissolve 0.39g ammonium acetate, 2.97g zinc nitrate and 0.70g hexamethylenetetramine in deionized water and make up to 500mL of ZnO plating solution. Transfer the electrolytic cell containing about 50mL of plating solution to an oil bath and heat to 90°C. Then put a conductive glass plate into the electrolytic cell and use the constant current electrodeposition method with a current of -2.0mA at 90°C for 50min. After that, take out the FTO conductive glass plate and rinse it with deionized water to obtain white thin film ZnO NRAs.

[0060] (2) Dissolve 1.09g cerium nitrate, 1.34g ammonium chloride and 0.93g potassium chloride in deionized water and make up to 250mL CeO2 plating solution. Transfer the electrolytic cell containing about 50mL of plating solution to an oil bath and heat to 70°C. Then put the ZnO NRAs obtained in step (1) into the above electrolytic cell and electroplate for 20min using the constant potential electrodeposition method. After the electrolytic cell is finished, take out the material and rinse it with deionized water to obtain a white film-like CeO2 / ZnO.

[0061] (3) Dissolve 1g PVP, 1g sodium citrate, 3g potassium bromide and 0.75μmol chloroauric acid in 100mL of deionized water, transfer to an oil bath and heat to 80℃, then put the CeO2 / ZnO obtained in step (2) into the solution and stir slowly for 30min. After the end, take out the material and rinse with deionized water to obtain a white film Au-CeO2 / ZnO.

[0062] Attached image description: Figure 1 a, Figure 1 b shows scanning electron microscope (SEM) images of ZnO NARs at different magnifications; Figure 1 c. Figure 1 d represents SEM images of CeO2 / ZnO magnified at different magnifications; Figure 1 e Figure 1 f represents SEM images of Au-CeO2 / ZnO at different magnifications;

[0063] Figure 2 X-ray diffraction (XRD) patterns of Au-CeO2 / ZnO prepared with different chloroauric acid dosages; all catalysts contained both CeO2 and ZnO phases, and no diffraction peaks attributable to Au were detected due to the very low dosage of chloroauric acid.

[0064] Figure 3 The image shows the X-ray photoelectron spectroscopy (XPS) spectrum of the photoelectrocatalyst of this invention, wherein... Figure 3 a shows the Au 4f XPS spectra of Au-CeO2 / ZnO and CeO2 / ZnO; Figure 3 b shows the Ce 3d XPS spectra of Au-CeO2 / ZnO and CeO2 / ZnO; Figure 3 c represents the Zn 2p XPS spectra of Au-CeO2 / ZnO and CeO2 / ZnO; Figure 3 d shows the O1s XPS spectra of Au-CeO2 / ZnO and CeO2 / ZnO;

[0065] Figure 4 a represents the linear voltammetric curves (LSV) of Au-CeO2 / ZnO in N2 and CO2 saturated KHCO3 solutions, respectively. Figure 4b shows the linear current-voltage (LSV) curves of Au-CeO2 / ZnO under dark and light conditions, respectively, indicating that Au-CeO2 / ZnO is responsive to CO2 and light. Figure 4 c represents the linear voltammetric curves (LSV) of Au-CeO2 / ZnO and CeO2 / ZnO in CO2-saturated KHCO3, indicating that Au-CeO2 / ZnO has stronger stability.

[0066] Figure 5 a and Figure 5 b represents the carbon dioxide reduction products and Faraday efficiencies obtained by testing Au-CeO2 / ZnO and CeO2 / ZnO catalysts prepared with different chloroauric acid dosages under 300W xenon lamp irradiation and at a voltage of -1.4V vs. Ag / AgCl.

[0067] As can be seen from the above embodiments of the present invention, the photoelectrocatalyst, preparation method, and accompanying drawings show that the ZnO prepared by electrodeposition is used as the substrate. Its vertically arranged one-dimensional (1D) nanostructures exhibit quantum size-dependent effects, effectively shortening the diffusion distance of charge carriers. CeO2 coats the ZnO, forming a stable and acid- and alkali-resistant substrate material, which is beneficial for further hydrothermal growth of Au nanoparticles. Compared with CeO2 / ZnO, the Au-CeO2 / ZnO modified with the co-catalyst Au exhibits a synergistic effect between the two components. Its characteristic is that after Au is activated under xenon lamp irradiation, it significantly promotes the separation of photogenerated charge carriers, and CeO2 captures electrons from Ce... 4+ Restored to Ce 3+ This forms oxygen voids and Ce 3+ / Ce 4+ Electron pairs facilitate oxygen spillover, thereby resulting in higher catalytic activity.

[0068] It should be noted that, within the scope described above, other technical solutions obtained by selecting different components, proportions, and preparation processes can achieve the technical effects of this invention, and therefore will not be listed one by one.

[0069] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a CO2 reduction photoelectrocatalyst, characterized in that, Includes the following steps: Step 1: Dissolve ammonium acetate, zinc nitrate, and hexamethylenetetramine in deionized water to obtain Zn. 2+ The plating solution will contain Zn 2+ The electrolytic cell of the plating solution was transferred to an oil bath for heating. Then, a conductive glass plate was placed into the electrolytic cell and electroplated using a constant current electrodeposition method. After that, the FTO conductive glass plate was removed and rinsed with deionized water to obtain a white thin film of ZnO NRAs. Step 2: Dissolve cerium nitrate, ammonium chloride, and potassium chloride in deionized water to obtain Ce. 4+ The plating solution will contain Ce 4+ The electrolytic cell of the plating solution was transferred to an oil bath for heating, and then ZnO NRAs were placed in the electrolytic cell. Electroplating was performed using a constant current electrodeposition method. After the plating was completed, the material was removed and rinsed with deionized water to obtain a white thin film of CeO2 / ZnO. Step 3: Dissolve PVP, sodium citrate, potassium bromide and chloroauric acid in deionized water to obtain Au plating solution. Transfer the solution to an oil bath and heat it. Then add the obtained CeO2 / ZnO into the Au plating solution and stir slowly. After the process is complete, remove the material and rinse it with deionized water to obtain a white film-like Au-CeO2 / ZnO.

2. The method for preparing a CO2 reduction photoelectrocatalyst according to claim 1, characterized in that: The Zn 2+ The plating solution contained ammonium acetate at a mass concentration of 0.39 g / 500 mL, zinc nitrate at a mass concentration of 2.97 g / 500 mL, and hexamethylenetetramine at a mass concentration of 0.70 g / 500 mL.

3. The method for preparing a CO2 reduction photoelectrocatalyst according to claim 1, characterized in that: The Ce 4+ The plating solution contained 1.09 g / 250 mL of cerium nitrate, 1.34 g / 250 mL of ammonium chloride, and 0.93 g / 250 mL of potassium chloride.

4. The method for preparing a CO2 reduction photoelectrocatalyst according to claim 1, characterized in that: The Au plating solution contains PVP at a mass concentration of 1 g / 100 mL, potassium citrate at a mass concentration of 1 g / 100 mL, potassium bromide at a mass concentration of 3 g / 100 mL, and chloroauric acid at a mass concentration of 0.25–0.75 μmol / 100 mL.

5. The method for preparing a CO2 reduction photoelectrocatalyst according to claim 1, characterized in that: The heating temperature in the first step is 90℃; the electroplating current is -2.0mA, and the electroplating temperature and time are 90℃ and 50min, respectively.

6. The method for preparing a CO2 reduction photoelectrocatalyst according to claim 1, characterized in that: The heating temperature in the second step is 70℃; the electroplating current is 0.5mA, the electroplating temperature is 70℃, and the electroplating time is 20min.

7. The method for preparing a CO2 reduction photoelectrocatalyst according to claim 1, characterized in that: The heating temperature in the third step is 80℃; the stirring time is 30 minutes.

8. The CO2 reduction photocatalyst prepared by the preparation method according to any one of claims 1-7.

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