A method for improving the glycerol electrooxidation reaction activity of Bi-modified Pt catalysts

Abstract

The present invention discloses a method for improving the activity of a Bi-modified Pt catalyst in a glycerol electro-oxidation reaction, and belongs to the technical field of glycerol electro-oxidation conversion. Specifically, the Bi-modified Pt catalyst is placed in a KOH solution for cyclic voltammetry scanning or constant potential pretreatment, and then applied to the glycerol electro-oxidation reaction. By electrochemically pretreating the Bi-modified Pt catalyst, the catalytic activity of the catalyst is significantly improved, solving the problem of low activity of existing liquid alcohol fuel cell catalysts. The method of the present invention is simple and easy to implement.

Description

Technical Field

[0001] The invention belongs to the technical field of glycerol electro-oxidation conversion, and particularly relates to a method for improving the activity of a Bi-modified Pt catalyst in a glycerol electro-oxidation reaction. Background Art

[0002] As environmental pollution and energy problems continue to intensify, low-pollution, high-efficiency fuel cells have received widespread attention. Compared with hydrogen fuel cells, direct alcohol fuel cells are convenient to transport and store as liquids, have high energy density, and are widely available. In particular, while polyol glycerol is electro-oxidized and converted into electricity, its partial oxidation products are mostly high-value-added fine chemicals. However, glycerol electro-oxidation is a multi-electron transfer process with slow catalytic kinetics and a high energy barrier for CC bond rupture; and glycerol, as a polyol, has a complex reaction path and a variety of oxidation products and adsorbed intermediates. Therefore, the development of efficient catalysts for electro-catalytic oxidation of glycerol is of great significance for promoting the development and application of fuel cells.

[0003] The electrocatalytic oxidation of anodic glycerol is a structure-sensitive reaction, and its reaction activity and product distribution are closely related to the reaction system and the structure and properties of the catalyst. Supported Pt catalyst is the most effective catalyst for the electrocatalytic oxidation of alcohols, but it is expensive and easily deactivated by poisoning, which limits its commercial application. Therefore, it is of great practical significance to effectively modify and regulate the structure of supported Pt catalysts and improve their catalytic performance. Summary of the invention

[0004] Based on the above content, the present invention provides a method for improving the glycerol electrooxidation reaction activity of a Bi-modified Pt catalyst.

[0005] To achieve the above object, the present invention provides the following solutions:

[0006] A method for improving the activity of a Bi-modified Pt catalyst in a glycerol electrooxidation reaction comprises the following steps:

[0007] Before application, the Bi-modified Pt catalyst was placed in KOH solution for cyclic voltammetry scanning or constant potential pretreatment.

[0008] Furthermore, the Bi-modified Pt catalyst includes a supported PtBi catalyst and an adsorbed PtBi catalyst. Preferably, the supported PtBi catalyst is a PtBi catalyst supported on the surface of a carbon material, the Pt loading is 2-10wt.%, preferably 5wt.%; the Bi loading is 2-10wt.%, preferably 1wt.%; the carbon material is any one of carbon nanotubes, graphene, carbon fiber, activated carbon, graphite, and carbon black.

[0009] The preparation methods of Bi-modified Pt catalysts include chemical reduction, impregnation, H 2 Preferably, the Pt catalyst is prepared by ethylene glycol reduction method, and the Bi modification method is impregnation method.

[0010] Furthermore, the concentration of the KOH solution is 0.002-0.4M, preferably 0.1M.

[0011] Furthermore, the scanning potential of the cyclic voltammetry scan is -1 to 0.45 V, and the number of scans is 1 to 100 times, preferably 10 times.

[0012] Furthermore, the potential of the constant potential pretreatment is -1 to -0.4 V, and the treatment time is 50 to 4000 s. Preferably, the potential is -1 V, and the treatment time is 250 s.

[0013] The present invention also provides a three-electrode system, with glycerol electro-oxidation reaction liquid as liquid, a glass electrode loaded with Bi-modified Pt catalyst as a working electrode, a carbon rod as a counter electrode, and KCl-saturated Ag / AgCl as a reference electrode.

[0014] Furthermore, the glycerol electro-oxidation reaction liquid contains glycerol and potassium hydroxide solution.

[0015] Furthermore, the glycerol concentration in the glycerol electro-oxidation reaction solution is 1M, and the concentration of the potassium hydroxide solution is 1M.

[0016] Technical concept of the present invention:

[0017] Glycerol electro-oxidation reaction is a structure-sensitive reaction, and its catalytic performance is closely related to the structure of the catalyst and the catalytic microenvironment. Pre-loaded and pre-adsorbed Bi on the Pt catalyst can significantly improve the performance of the Pt catalyst in catalyzing glycerol electro-oxidation, but the structure and catalytic microenvironment of the Bi-modified Pt catalyst undergo certain dynamic structural changes during the electro-oxidation reaction. Therefore, the present invention utilizes the Bi-modified Pt catalyst to undergo cyclic voltammetry scanning or constant potential pretreatment in potassium hydroxide electrolyte, and the geometric structure, Bi species and species ratio of Bi on or adjacent to Pt will undergo certain dynamic changes, thereby further regulating and optimizing the catalytic performance of glycerol electro-oxidation.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] The present invention provides a method for improving the activity of a Bi-modified Pt catalyst in a glycerol electrooxidation reaction, by electrochemically pretreating the PtBi catalyst, the catalytic activity of the Bi-modified Pt catalyst is significantly improved, and the problem of low activity of existing liquid alcohol fuel cell catalysts is solved. At the same time, the problem of poisoning and deactivation of the Pt catalyst can also be alleviated.

[0020] The method of the invention is simple and easy to implement. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] 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.

[0022] Figure 1 cyclic voltammogram of glycerol electrooxidation based on Pt catalyst in Examples 1-7 of the present invention;

[0023] Figure 2 This is a CO-stripping diagram based on Pt catalyst in Examples 1-7 of the present invention. DETAILED DESCRIPTION

[0024] 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.

[0025] 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.

[0026] 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.

[0027] 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 application description and examples are exemplary only.

[0028] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0029] The "room temperature" in the present invention refers to 15-30°C unless otherwise specified.

[0030] The raw materials used in the embodiments of the present invention can be purchased from commercial sources.

[0031] Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the present technical field.

[0032] A method for improving the activity of a Bi-modified Pt catalyst in a glycerol electrooxidation reaction comprises the following steps:

[0033] Before application, the Bi-modified Pt catalyst was placed in KOH solution for cyclic voltammetry scanning or constant potential pretreatment.

[0034] In some preferred embodiments, the Bi-modified Pt catalyst includes a supported PtBi catalyst and an adsorbed PtBi catalyst. Preferably, the supported PtBi catalyst is a PtBi catalyst supported on the surface of a carbon material, the Pt loading is 2-10wt.%, preferably 5wt.%; the Bi loading is 2-10wt.%, preferably 1wt.%; the carbon material is any one of carbon nanotubes, graphene, carbon fiber, activated carbon, graphite, and carbon black.

[0035] The preparation methods of Bi-modified Pt catalysts include chemical reduction, impregnation, H 2 Preferably, the Pt catalyst is prepared by ethylene glycol reduction method, and the Bi modification method is impregnation method.

[0036] In some preferred embodiments, the concentration of the KOH solution is 0.002-0.4 M, preferably 0.1 M.

[0037] In some preferred embodiments, the scanning potential of the cyclic voltammetry scan is -1 to 0.45 V, and the number of scans is 1 to 100 times, preferably 10 times.

[0038] In some preferred embodiments, the potential of the constant potential pretreatment is -1 to -0.4 V, and the treatment time is 50 to 4000 s. The preferred potential is -1 V, and the preferred treatment time is 250 s.

[0039] The present invention also provides a three-electrode system, with glycerol electro-oxidation reaction liquid as liquid, a glass electrode loaded with Bi-modified Pt catalyst as a working electrode, a carbon rod as a counter electrode, and KCl-saturated Ag / AgCl as a reference electrode.

[0040] In some preferred embodiments, the glycerol electro-oxidation reaction solution contains glycerol and potassium hydroxide solution.

[0041] In some preferred embodiments, the glycerol concentration in the glycerol electro-oxidation reaction solution is 0.2-1.5M, preferably 1.0M; the concentration of the potassium hydroxide solution is 0.2-1.5M, preferably 1.0M.

[0042] The Bi-modified Pt catalyst used in the embodiment of the present invention is a Pt catalyst prepared by ethylene glycol reduction method, and the Bi modification method is an impregnation method. The specific preparation process is:

[0043] 1) Pour carbon nanotubes into ethylene glycol solvent at a ratio of 100 mg: 60 mL, and disperse them uniformly by ultrasonication to obtain a carbon material dispersion. 2 PtCl 6 The powder was added to the carbon material dispersion, and then the pH was adjusted to 8.5 with KOH solution (concentration of 0.04 M), stirred and refluxed at 140°C for 2 hours, filtered and rinsed after cooling to room temperature, vacuum dried at 75°C, and ground to obtain a Pt catalyst.

[0044] 2) Take 40 mg of the prepared Pt catalyst and add it to 40 mL of distilled water, stir and ultrasonicate to obtain a Pt catalyst dispersion. 3 ) 3 ·5H 2 O (1mM) solution was added to the Pt catalyst dispersion, and then stirred at 60°C for 6h after ultrasonic stirring. After cooling to room temperature, the mixture was filtered, rinsed, vacuum dried at 75°C, and ground. The ground catalyst was calcined in an Ar atmosphere (temperature: 300°C, time: 2h) to obtain a Bi-modified Pt catalyst, and the theoretical Bi loading was 1wt.%.

[0045] Example 1

[0046] The Pt catalyst prepared in step (1) above is directly applied to the glycerol electro-oxidation reaction. The reaction adopts a three-electrode system, wherein the glass electrode with the catalyst to be tested on the surface is the working electrode, the Ag / AgCl saturated with KCl is the reference electrode, and the carbon rod is the counter electrode. The glycerol electro-oxidation reaction solution is 1.0M glycerol and 1.0M KOH, the scanning voltage is -1 to 0.45V, and the scanning rate is 100mV / s.

[0047] Example 2

[0048] The Bi-modified Pt catalyst prepared in step (2) above is directly applied to the glycerol electro-oxidation reaction. The reaction adopts a three-electrode system, wherein the glass electrode with the catalyst to be tested on the surface is the working electrode, the Ag / AgCl saturated with KCl is the reference electrode, and the carbon rod is the counter electrode. The glycerol electro-oxidation reaction solution is 1.0 M glycerol and 1.0 M KOH, the scanning voltage is -1 to 0.45 V, and the scanning rate is 100 mV / s.

[0049] Example 3

[0050] The Bi-modified Pt catalyst was subjected to cyclic voltammetry scanning in a KOH solution with a concentration of 0.1 M, with a scanning potential of -1 to 0.45 V and a scanning number of 10 times, to obtain a pretreated Bi-modified Pt catalyst.

[0051] The pretreated Bi-modified Pt catalyst was applied to the glycerol electrooxidation reaction. The reaction used a three-electrode system, with a glass electrode carrying the catalyst to be tested as the working electrode, KCl-saturated Ag / AgCl as the reference electrode, and a carbon rod as the counter electrode. The glycerol electrooxidation reaction solution was 1.0M glycerol and 1.0M KOH, the scanning voltage was -1 to 0.45V, and the scanning rate was 100mV / s.

[0052] Example 4

[0053] The Bi-modified Pt catalyst was subjected to constant potential pretreatment in a 0.1 M KOH solution at a potential of -1 V for a treatment time of 250 s to obtain a pretreated Bi-modified Pt catalyst.

[0054] The pretreated Bi-modified Pt catalyst was applied to the glycerol electrooxidation reaction. The reaction used a three-electrode system, with a glass electrode carrying the catalyst to be tested as the working electrode, KCl-saturated Ag / AgCl as the reference electrode, and a carbon rod as the counter electrode. The glycerol electrooxidation reaction solution was 1.0M glycerol and 1.0M KOH, the scanning voltage was -1 to 0.45V, and the scanning rate was 100mV / s.

[0055] Example 5

[0056] The Bi-modified Pt catalyst was subjected to constant potential pretreatment in a 0.1 M KOH solution at a potential of -0.8 V for a treatment time of 250 s to obtain a pretreated Bi-modified Pt catalyst.

[0057] The pretreated Bi-modified Pt catalyst was applied to the glycerol electrooxidation reaction. The reaction used a three-electrode system, with a glass electrode carrying the catalyst to be tested as the working electrode, KCl-saturated Ag / AgCl as the reference electrode, and a carbon rod as the counter electrode. The glycerol electrooxidation reaction solution was 1.0M glycerol and 1.0M KOH, the scanning voltage was -1 to 0.45V, and the scanning rate was 100mV / s.

[0058] Example 6

[0059] The Bi-modified Pt catalyst was subjected to constant potential pretreatment in a 0.1 M KOH solution at a potential of -0.6 V for a treatment time of 250 s to obtain a pretreated Bi-modified Pt catalyst.

[0060] The pretreated Bi-modified Pt catalyst was applied to the glycerol electrooxidation reaction. The reaction used a three-electrode system, with a glass electrode carrying the catalyst to be tested as the working electrode, KCl-saturated Ag / AgCl as the reference electrode, and a carbon rod as the counter electrode. The glycerol electrooxidation reaction solution was 1.0M glycerol and 1.0M KOH, the scanning voltage was -1 to 0.45V, and the scanning rate was 100mV / s.

[0061] Example 7

[0062] The Bi-modified Pt catalyst was subjected to constant potential pretreatment in a 0.1 M KOH solution at a potential of -0.4 V for a treatment time of 250 s to obtain a pretreated Bi-modified Pt catalyst.

[0063] The pretreated Bi-modified Pt catalyst was applied to the glycerol electrooxidation reaction. The reaction used a three-electrode system, with a glass electrode carrying the catalyst to be tested as the working electrode, KCl-saturated Ag / AgCl as the reference electrode, and a carbon rod as the counter electrode. The glycerol electrooxidation reaction solution was 1.0M glycerol and 1.0M KOH, the scanning voltage was -1 to 0.45V, and the scanning rate was 100mV / s.

[0064] Figure 1 1 is the cyclic voltammogram of glycerol electrooxidation based on Pt catalyst in Example 1-7. Figure 1 It can be seen that the Bi-modified Pt catalyst can significantly improve the glycerol electro-oxidation performance of the Pt catalyst. In addition, the glycerol electro-oxidation peak current density of the Bi-modified Pt catalyst pretreated by cyclic voltammetry scanning in a certain concentration of KOH electrolyte solution is 2.3 times higher than that of the untreated Bi-modified Pt catalyst. Pretreatment of the Bi-modified Pt catalyst in 0.1M KOH solution at constant potentials of -1.0V and -0.8V can improve the catalytic activity of the Bi-modified Pt catalyst to a certain extent, and the more negative the pretreatment potential, the more obvious the performance improvement.

[0065] Figure 2 The CO-stripping diagram based on Pt catalyst in Examples 1-7. The CO-stripping technique is used to analyze the coverage of Bi on Pt. Figure 2 It can be seen that the CO oxidation peak area of ​​the Bi-modified Pt catalyst is significantly reduced, indicating that Bi has obvious coverage on Pt and changes the geometric structure of the Pt catalyst. In addition, compared with the untreated Bi-modified Pt catalyst, the CO oxidation peak and the characteristic peak of Bi of the Bi-modified Pt catalyst pretreated by cyclic voltammetry or constant potential in KOH solution have no significant changes, indicating that the reason for the improvement of the performance of the Bi-modified Pt catalyst after pretreatment may be the change of the catalytic microenvironment of the catalyst, such as the species adsorbed on the catalyst surface.

[0066] Example 8

[0067] Same as Example 3, except that during the pretreatment process, the concentration of the KOH solution is 0.002M.

[0068] Example 9

[0069] Same as Example 3, except that, during the pretreatment process, the number of scans of the cyclic voltammetry scan is 1.

[0070] Example 10

[0071] Same as Example 4, except that during the constant potential pretreatment, the potential is -0.2V.

[0072] Embodiment 11

[0073] Same as Example 4, except that during the constant potential pretreatment process, the treatment time is 50 s.

[0074] Comparative Example 1

[0075] Same as Example 3, except that during the pretreatment process, the concentration of the KOH solution is 1M.

[0076] The catalytic activity of glycerol electrooxidation after cyclic voltammetry pretreatment of PtBi catalyst in Examples 8-9 and Comparative Example 1 was lower than that in Example 3.

[0077] The catalytic activity of glycerol electro-oxidation after constant potential pretreatment of PtBi catalyst in Examples 10-11 was lower than that in Example 4.

[0078] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for improving the activity of a Bi-modified Pt catalyst in a glycerol electrooxidation reaction, characterized in that: The following steps are involved: Before application, the Bi-modified Pt catalyst was placed in a KOH solution for constant potential pretreatment; The concentration of the KOH solution is 0.1M; The potential of the constant potential pretreatment is -1V, and the treatment time is 250s; The specific preparation process of the Bi-modified Pt catalyst is as follows: 1) Pour carbon nanotubes into ethylene glycol solvent at a ratio of 100 mg: 60 mL, and disperse them uniformly by ultrasonication to obtain a carbon material dispersion; add H2PtCl6 powder with a theoretical loading of 5 wt.% to the carbon material dispersion, and then adjust the pH to 8.5 with KOH solution (concentration of 0.04 M), stir and reflux at 140°C for 2 h, cool to room temperature, filter, rinse, vacuum dry at 75°C, and grind to obtain a Pt catalyst; 2) Take 40 mg of the Pt catalyst prepared above and add it to 40 mL of distilled water, stir and ultrasonicate to obtain a Pt catalyst dispersion; measure 2 mL of Bi(NO3)3·5H2O (1 mM) solution and add it to the Pt catalyst dispersion, ultrasonically stir and then stir at a constant temperature of 60°C for 6 h, cool to room temperature and filter, rinse, vacuum dry at 75°C, and grind; calcine the ground catalyst at 300°C under Ar atmosphere for 2 h to obtain a Bi-modified Pt catalyst with a theoretical Bi loading of 1 wt.%.

2. The method for improving the activity of Bi-modified Pt catalyst in glycerol electrooxidation reaction according to claim 1, characterized in that: The Bi-modified Pt catalyst includes a supported PtBi catalyst and an adsorbed PtBi catalyst.

3. A three-electrode system, characterized in that: The glycerol electro-oxidation reaction liquid is used as liquid, the glass electrode loaded with the Bi-modified Pt catalyst according to any one of claims 1 to 2 is used as a working electrode, the carbon rod is used as a counter electrode, and KCl-saturated Ag / AgCl is used as a reference electrode.

4. The three-electrode system according to claim 3, characterized in that: The glycerol electro-oxidation reaction liquid contains glycerol and potassium hydroxide solution.

5. The three-electrode system according to claim 4, characterized in that: The glycerol concentration in the glycerol electro-oxidation reaction solution is 1M, and the concentration of the potassium hydroxide solution is 1M.

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