Bismuth-based electrochemical reduction catalyst as well as preparation method and application thereof
By using bismuth-based electrochemical reduction catalyst in acidic media, the problems of insufficient catalytic activity and poor stability of bismuth-based catalysts in acidic media are solved through the organic phosphoric acid complexing agent and constant current electrolytic activation technology, and the formic acid product is significantly improved Selectivity and stability, suitable for a variety of electrocatalytic reactions.
Patent Information
- Application Number
- CN202411344361.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-25
- Publication Date
- 2024-12-27
AI Technical Summary
In acidic media, the existing bismuth-based catalysts have insufficient catalytic activity and poor stability in electrocatalytic CO2 reduction reaction, and high concentrations of alkali metal cations lead to precipitation of carbonate and bicarbonate, affecting the reaction efficiency.
Using a preparation method of bismuth-based electrochemical reduction catalyst, bismuth nitrate and organic phosphoric acid complexing agent are mixed at low temperature to form a bismuth-based electrochemical reduction catalyst precursor, and bismuth-based electrochemical reduction is obtained by constant current electrolytic activation. Catalysts use phosphate groups to adsorb alkali metal cations, inhibit competitive hydrogen evolution reactions, and improve catalytic activity and stability.
The selectivity and stability of formic acid products are significantly improved, and the CO2 reduction reaction activity of the catalyst in acidic media is enhanced. The method is simple to operate and can be widely used in a variety of electrocatalytic reactions.
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Figure CN119194466A_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of catalyst materials, and in particular relates to a bismuth-based electrochemical reduction catalyst and a preparation method and application thereof. Background Art
[0002] Currently, electrochemical carbon dioxide reduction reaction (CO 2 RR) has emerged as a promising solution to mitigate the growing greenhouse gas emissions and energy crisis while producing valuable chemicals that meet the needs of modern society. 2 The electrolysis system of RR mainly uses alkaline or neutral electrolytes. 2 Molecular and local / bulk OH - The species react to form carbonates, which in turn cause CO 2 The problems of raw material consumption and reduced carbon utilization efficiency severely limit the basic / neutral CO 2 Industrial prospects of RR systems. 3 O + Or H 2 O as a proton source), low pH conditions can fully inhibit the formation of carbonates.
[0003] In addition, formic acid (HCOOH) is an important chemical intermediate in many industrial processes and has been shown to be a CO 2 Technical and economical products in the reduction of CO. Electrolysis in acidic medium 2 Reduction can directly produce HCOOH instead of formate, thus saving the cost of product regeneration. Bismuth-based catalysts (including bismuth nanosheets, bismuth oxides, bismuth-based conductive metal skeleton materials and other bismuth-containing catalysts) are currently used for CO in acidic media. 2 However, due to the competitive hydrogen evolution reaction (HER) in acidic media, existing bismuth-based catalysts are not very effective in the electrocatalytic conversion of CO 2 During the reduction reaction, the catalytic activity for the HCOOH product needs to be further improved, and the stability problem under acidic conditions needs to be solved urgently.
[0004] At present, the local electrolyte environment on the catalyst surface can be regulated by alkali metal cations, which can significantly improve the electrocatalytic CO conversion in acidic media. 2 However, high concentrations of alkali metal cations can easily cause the precipitation of carbonates and bicarbonates under high current density and long reaction times, leading to poor stability and insufficient catalytic activity. Summary of the invention
[0005] In order to solve the above technical problems, the present invention proposes a bismuth-based electrochemical reduction catalyst and a preparation method and application thereof, wherein the bismuth-based electrochemical reduction catalyst has a high activity in an acidic medium for CO 2 The electrochemical reduction reaction has excellent catalytic activity and high selectivity for formic acid product.
[0006] To achieve the above object, the present invention provides a method for preparing a bismuth-based electrochemical reduction catalyst precursor, comprising the following steps:
[0007] S1: dissolving bismuth nitrate in ethylene glycol solution to obtain solution A; dissolving a complexing agent in ultrapure water to obtain solution B; the complexing agent is an organic phosphoric acid complexing agent or an organic phosphate complexing agent;
[0008] S2: adding the solution A dropwise to the solution B at low temperature, and continuing stirring for 3-8 hours after the addition; and allowing to stand after the stirring;
[0009] S3: collecting the solid after filtering, washing the solid by centrifugation, and freeze-drying the solid after centrifugation to obtain the bismuth-based electrochemical reduction catalyst precursor.
[0010] Further, in step S1, the complexing agent is one or more of diethylenetriaminepenta(methylenephosphonic acid) (DTPMP), ethylenediaminetetra(methylenephosphonic acid) (EDTMP), biphenyldiphosphonic acid, and one or more corresponding organic phosphates.
[0011] Further, in step S2, the low temperature is 0°C.
[0012] The present invention also provides a bismuth-based electrochemical reduction catalyst precursor, which is prepared by the above-mentioned preparation method.
[0013] The present invention also provides a bismuth-based electrochemical reduction catalyst, which is obtained by subjecting the above-mentioned bismuth-based electrochemical reduction catalyst precursor to constant current electrolytic activation.
[0014] Furthermore, the step of constant current electrolytic activation comprises:
[0015] The bismuth-based electrochemical reduction catalyst precursor is prepared into a precursor slurry, and the precursor slurry is sprayed onto a hydrophobic carbon paper with a diffusion layer to obtain a precursor working electrode;
[0016] The precursor working electrode is assembled in a flow electrolytic cell using a potassium chloride solution acidified with sulfuric acid as an electrolyte, and is activated by constant current electrolysis to obtain a bismuth-based electrochemical reduction catalyst.
[0017] Furthermore, the method of preparing the bismuth-based electrochemical reduction catalyst precursor into a precursor slurry includes: uniformly dispersing 5 mg of the bismuth-based electrochemical reduction catalyst precursor in 1.8 mL of isopropanol and 0.2 mL of ultrapure water, ultrasonicating for 40 min, adding 30 μL of Nafion solution (5 wt.%), and ultrasonicating for 40 min.
[0018] Furthermore, in the potassium chloride solution acidified with sulfuric acid, the concentration of potassium chloride is 1 M, and sulfuric acid is added to make the pH of the potassium chloride solution 2;
[0019] The constant current electrolytic activation method comprises: assembling the precursor working electrode in a flow electrolytic cell at 10-100 mA / cm 2 Constant current electrolysis activation for 20 to 60 minutes.
[0020] The present invention also provides the use of the above-mentioned bismuth-based electrochemical reduction catalyst in the electrocatalytic reduction of carbon dioxide, wherein the electrocatalytic reduction of carbon dioxide is carried out in an acidic environment.
[0021] The present invention also provides a method for electrocatalytic reduction of carbon dioxide, comprising the following steps:
[0022] The bismuth-based electrochemical reduction catalyst is used as a cathode, and carbon dioxide is introduced into a reaction electrolytic cell to perform electrolysis.
[0023] Compared with the prior art, the present invention has the following advantages and technical effects:
[0024] The invention uses a simple method to prepare a bismuth-based electrochemical reduction catalyst for adsorbing phosphate groups, and the operation process is simple and has strong repeatability.
[0025] BiNPs-PO prepared by the present invention 3 Catalyst in acidic medium CO 2 The reduction reaction can significantly improve the selectivity and stability of formic acid products.
[0026] BiNPs-PO prepared by the present invention 3 The catalyst relies on the adsorption of phosphate groups on the surface of bismuth-based catalysts by adsorbing alkali metal cations (K + ), inhibiting the diffusion of protons to the catalyst surface to suppress the competing HER reaction and promote the catalytic reaction activity.
[0027] The preparation method of the present invention can be widely used in various types of electrocatalytic reactions by simply adjusting the metal type, including but not limited to oxygen reduction reaction (ORR), oxygen evolution reaction (OER), hydrogen evolution reaction (HER), nitrate reduction reaction (NO 3 RR) and urea oxidation reaction (UOR). BRIEF DESCRIPTION OF THE DRAWINGS
[0028] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.
[0029] Figure 1 From left to right are the precursor powders DTPMP-Bi (a) and BiNPs-PO prepared in Example 1. 3 (b) Transmission electron microscopy image;
[0030] Figure 2 From left to right, they are Bi in Comparative Example 1 2 O 2 CO 3 Transmission electron microscopy images of the precursor (a) and BiNSs (b);
[0031] Figure 3 DTPMP, DTPMP-Bi and Bi NPs-PO in Example 1 3 Infrared spectrum of
[0032] Figure 4 Bi NPs-PO 3 and ECSA normalized adsorption K of Bi NSs + Number chart;
[0033] Figure 5 Bi NPs-PO 3 Electrocatalytic CO generation of Bi NSs 2 RR performance diagram; where a is the current density curve, b is the Faraday efficiency diagram, c is the partial current density diagram, and d is the single-pass carbon efficiency (SPCE) diagram;
[0034] Figure 6 is the FE before and after the BiNSs catalyst adsorbs DTPMP in Example 2 HCOOH Comparison chart. DETAILED DESCRIPTION
[0035] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.
[0036] It should be understood that the terms described in the present invention are only for describing special embodiments and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. Each smaller range between the intermediate value in any stated value or stated range and any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.
[0037] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.
[0038] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to those skilled in the art. The present invention description and examples are exemplary only.
[0039] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.
[0040] Example 1
[0041] A bismuth-based electrochemical reduction catalyst Bi NPs-PO 3 The preparation method comprises the following steps:
[0042] (1) Weigh 0.970 g of bismuth nitrate (Bi(NO 3 ) 3 ) in a 100 mL beaker, add 15 mL of ethylene glycol, referred to as solution A, and stir thoroughly until bismuth nitrate is completely dissolved;
[0043] (2) Weigh 1.193 g of diethylenetriaminepenta(methylenephosphonic acid) (DTPMP) into a 100 mL beaker, add 15 mL of ultrapure water (referred to as solution B), and stir thoroughly until the DTPMP is completely dissolved;
[0044] (3) At 0°C, solution A is slowly added dropwise to solution B to obtain a mixed solution;
[0045] (4) stirring the mixed solution of step (3) at room temperature for 6 hours for reaction at a stirring speed of 600 rpm;
[0046] (5) After the reaction in step (4) is completed, the mixture is allowed to stand for 10 minutes, the filter cake is collected by filtration, and the filter cake is washed twice with ethanol and centrifuged;
[0047] (6) The solid product obtained by centrifugation in step (5) was subjected to vacuum freeze drying (freeze drying temperature -50°C, drying time 24h and vacuum degree 10Pa) to obtain complex precursor powder DTPMP-Bi;
[0048] (7) 5 mg of the precursor powder obtained in step (6) was uniformly dispersed in 1.8 mL of isopropanol and 0.2 mL of ultrapure water, and ultrasonicated for 40 min to make it uniformly mixed. 30 μL of Nafion solution (5 wt.%) was added, and ultrasonicated for 40 min to obtain a uniform precursor slurry. Then, 400 μL of the above precursor slurry was spread on a hydrophobic carbon paper (YLS-30T) with a diffusion layer and an exposed area of 1×1 cm at 60°C. 2 The precursor working electrode was obtained by spraying uniformly at room temperature and drying overnight; finally, potassium chloride solution (H 2 SO 4 +1M KCl, pH=2) as the electrolyte, and the precursor working electrode was assembled in a flow electrolytic cell at 100 mA / cm 2 The bismuth-based electrochemical reduction catalyst Bi NPs-PO was obtained by constant current electrolysis activation for 20 min. 3 .
[0049] Comparative Example 1
[0050] A method for preparing a bismuth-based electrochemical reduction catalyst Bi NSs, the steps are as follows:
[0051] 5 mg of commercial bismuth subcarbonate powder (Bi 2 O 2 CO 3 ) was uniformly dispersed in 1.8 mL of isopropanol and 0.2 mL of ultrapure water, and ultrasonicated for 40 min to make it uniformly mixed, and 30 μL of Nafion solution (5 wt.%) was added, and ultrasonicated for 40 min to obtain a uniform precursor slurry; then, at 60 ° C, 400 μL of the above precursor slurry was spread on a hydrophobic carbon paper (YLS-30T) with a diffusion layer and an exposed area of 1×1 cm 2 The precursor working electrode was obtained by spraying uniformly at room temperature and drying overnight; finally, potassium chloride solution (H 2 SO 4+1M KCl, pH=2) as the electrolyte, and the precursor working electrode was assembled in a flow electrolytic cell at 100 mA / cm 2 After constant current electrolysis activation for 20 min, bismuth-based electrochemical reduction catalyst Bi NSs was obtained.
[0052] Structural characterization:
[0053] The precursor powder DTPMP-Bi and bismuth-based electrochemical reduction catalyst Bi NPs-PO in Example 1 were observed by transmission electron microscopy. 3 and the commercial bismuth subcarbonate powder Bi in Comparative Example 1 2 O 2 CO 3 , bismuth-based electrochemical reduction catalyst Bi NSs were tested, and the transmission electron microscopy images were shown as follows: Figure 1 and Figure 2 shown.
[0054] The electrochemical performance of the bismuth-based electrochemical reduction catalysts prepared in Example 1 and Comparative Example 1 was tested, and the specific testing method was as follows:
[0055] The electrochemical performance test of the present invention was carried out on a CHI 760e (Shanghai Chenhua Instrument Co., Ltd.) electrochemical workstation, using a flow cell with a gas diffusion chamber as the electrolytic cell, and Ag / AgCl and IrO x / Ti mesh(2×2cm 2 ) are reference electrode and counter electrode respectively, wherein the preparation method of counter electrode and working electrode is as follows:
[0056] IrO was prepared by thermal decomposition method. x / Ti mesh anode. First, the titanium mesh was washed with ultrapure water and acetone several times, and etched in 6M hydrochloric acid for 1 hour at a temperature of 80-90°C. Then 30 mg IrCl 3 .xH 2 IrO was dissolved in 10 mL of isopropanol containing 10% concentrated hydrochloric acid. Subsequently, the etched Ti mesh was immersed in the solution, dried in an oven at 100 °C for 10 min, and calcined in a muffle furnace at 500 °C for 10 min under air atmosphere. The impregnation and calcination process was repeated until the catalyst IrO on Ti was x Loading up to 2mg / cm 2 Finally, the obtained IrO x / Ti mesh anode was used for electrochemical tests.
[0057] The carbon dioxide reduction activity and formic acid yield of bismuth-based electrochemical reduction catalysts in acidic media were tested by linear sweep voltammetry (LSV) and chronopotentiometry. The anolyte was an aqueous sulfuric acid solution (pH = 2), and the catholyte was an aqueous sulfuric acid solution with 1M potassium chloride (pH = 2). 30mL of electrolyte was added to both the anode and cathode bottles. A flowmeter was used to control the CO 2 RR gas flow rate. Before the test, CO was introduced into the electrolytic cell. 2 To achieve gas saturation. 2 The gas products produced during the RR process were detected by gas chromatography (GC-2014C, SHIMADAZU), and the liquid products were detected by nuclear magnetic resonance (NMR).
[0058] Figure 3 DTPMP, DTPMP-Bi and Bi NPs-PO 3 The infrared spectrum of the Bi nanocatalyst proves that after electrochemical reduction, the phosphate groups are still adsorbed on the surface of the Bi nanocatalyst.
[0059] Figure 4 This proves that the electrocatalytic CO 2 During the process, due to the Bi NPs-PO 3 The presence of phosphate groups in the catalyst can significantly promote the + The adsorption of formic acid can inhibit the proton diffusion process on the catalyst surface during the electrochemical process, thereby showing high selectivity for formic acid.
[0060] Figure 5 a is Bi NPs-PO 3 and Bi NSs as electrochemical reduction catalysts in CO 2 The current density curve of LSV test in saturated electrolyte shows that Bi NPs-PO 3 Catalyst in CO 2 The current density of the saturated electrolyte test is higher than that of the Bi NSs catalyst, indicating that the Bi NPs-PO 3 The catalyst has excellent electrochemical carbon dioxide reduction activity in acidic medium.
[0061] Figure 5 The Bi NPs-PO 3 The CO calculated by chronopotentiometry of the two catalysts, Bi NSs and Bi NSs, at different potentials 2 The Faradaic efficiency of the reduced liquid product formic acid (HCOOH) shows that Bi NSs has good formic acid selectivity in a wide potential range, with a maximum of 200 mA cm -2 The Faradaic efficiency of formic acid reached up to 96.3% at the current density. Figure 5c is the CO obtained by electrolysis using chronopotentiometry at a selected current 2 Partial current density of the reduction product formic acid (HCOOH), Bi NPs-PO 3 The catalyst has the best partial current density for formic acid among the two catalysts, reaching 932.80 mA / cm at -1.99 V vs. RHE. 2 . Figure 5 d shows the Bi NPs-PO in acidic medium. 3 and Bi NSs at 1000mA / cm 2 and the single pass carbon efficiency (SPCE) at different CO2 flow rates. Since the input of CO2 greatly exceeds the consumption, the SPCE will be relatively low at higher flow rates. 2 When the flow rate was reduced from 50 to 8 sccm, Bi NPs-PO 3 The SPCE of formic acid production in an acidic system is as high as 78.00%.
[0062] In order to further prove that the Bi-based electrochemical reduction catalyst with adsorbed phosphate groups can promote the electrocatalytic CO 2 To investigate the activity of Bi NSs, 50 mM DTPMP was added to the catholyte of Bi NSs, followed by circulation with a peristaltic pump at a flow rate of 10 mL / min for 30 min. 2 The test was carried out at a current density of Figure 6 As shown, the FE of Bi NSs after adsorption of DTPMP HCOOH It is proved that the adsorption of DTPMP can significantly promote the electrocatalytic CO 2 Converted to HCOOH.
[0063] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.
Claims
1. A method for preparing a bismuth-based electrochemical reduction catalyst precursor, characterized in that: The following steps are involved: S1: dissolving bismuth nitrate in ethylene glycol solution to obtain solution A; dissolving a complexing agent in ultrapure water to obtain solution B; the complexing agent is an organic phosphoric acid complexing agent or an organic phosphate complexing agent; S2: adding the solution A dropwise to the solution B at low temperature, and continuing stirring for 3-8 hours after the addition; and allowing to stand after the stirring; S3: collecting the solid after filtering, washing the solid by centrifugation, and freeze-drying the solid after centrifugation to obtain the bismuth-based electrochemical reduction catalyst precursor.
2. The method for preparing a bismuth-based electrochemical reduction catalyst precursor according to claim 1, characterized in that: In step S1, the complexing agent is one or more of diethylenetriaminepenta(methylenephosphonic acid), ethylenediaminetetra(methylenephosphonic acid), biphenyldiphosphonic acid, and one or more corresponding organic phosphates.
3. The method for preparing a bismuth-based electrochemical reduction catalyst precursor according to claim 1, characterized in that: In step S2, the low temperature is 0°C.
4. A bismuth-based electrochemical reduction catalyst precursor, characterized in that: The preparation method is described in any one of claims 1 to 3.
5. A bismuth-based electrochemical reduction catalyst, characterized in that: The bismuth-based electrochemical reduction catalyst precursor according to claim 4 is obtained by constant current electrolytic activation.
6. The bismuth-based electrochemical reduction catalyst according to claim 5, characterized in that: The step of constant current electrolytic activation comprises: The bismuth-based electrochemical reduction catalyst precursor is prepared into a precursor slurry, and the precursor slurry is sprayed onto a hydrophobic carbon paper with a diffusion layer to obtain a precursor working electrode; The precursor working electrode is assembled in a flow electrolytic cell using a potassium chloride solution acidified with sulfuric acid as an electrolyte, and is activated by constant current electrolysis to obtain a bismuth-based electrochemical reduction catalyst.
7. The bismuth-based electrochemical reduction catalyst according to claim 5, characterized in that: The method for preparing the bismuth-based electrochemical reduction catalyst precursor into a precursor slurry comprises: uniformly dispersing 5 mg of the bismuth-based electrochemical reduction catalyst precursor in 1.8 mL of isopropanol and 0.2 mL of ultrapure water, ultrasonicating for 40 minutes, adding 30 μL of Nafion solution (5 wt.%), and ultrasonicating for 40 minutes.
8. The bismuth-based electrochemical reduction catalyst according to claim 5, characterized in that: In the potassium chloride solution acidified by sulfuric acid, the concentration of potassium chloride is 1M, and sulfuric acid is added to make the pH of the potassium chloride solution 2; The constant current electrolytic activation method comprises: assembling the precursor working electrode in a flow electrolytic cell at 10-100 mA / cm 2 Constant current electrolysis activation for 20 to 60 minutes.
9. Use of the bismuth-based electrochemical reduction catalyst according to any one of claims 5 to 8 in electrocatalytic reduction of carbon dioxide, characterized in that: The electrocatalytic reduction of carbon dioxide is performed in an acidic environment.
10. A method for electrocatalytic reduction of carbon dioxide, characterized in that: The following steps are involved: The bismuth-based electrochemical reduction catalyst according to any one of claims 5 to 8 is used as a cathode, and carbon dioxide is introduced into a reaction electrolytic cell to perform electrolysis.