Preparation method of conductive oxide supported palladium ethanol fuel cell anode catalyst

Abstract

The invention belongs to the field of fuel cells, and relates to a preparation method of a conductive oxide supported palladium ethanol fuel cell anode catalyst, the catalyst is a Pd / c-TiO2 (at) MoO3 catalyst, the preparation method comprises the following steps: mixing TiO2 and a molybdenum source, roasting to obtain TiO2 (at) MoO3, and carrying out chemical reduction to obtain conductive c-TiO2 (at) MoO3; after dispersing, adding a palladium precursor for adsorption, reducing by a reducing agent, washing and drying to obtain a Pd / c-TiO2 / MoO3 anode catalyst, and loading the Pd / c-TiO2 / MoO3 anode catalyst on an electrode substrate for activation to obtain the working electrode. The method is simple in process and high in controllability, and the obtained catalyst is excellent in conductivity and catalytic performance, can be used for direct ethanol fuel cell anode catalytic ethanol oxidation reaction and is good in application prospect. The invention provides a novel and feasible solution for the stability problem of the anode catalyst of the direct ethanol fuel cell, and is expected to promote the industrial application process of the direct ethanol fuel cell.

Description

Technical Field

[0001] This invention belongs to the field of fuel cells and relates to a method for preparing a conductive oxide-supported palladium ethanol fuel cell anode catalyst. Background Technology

[0002] A direct ethanol fuel cell (DEFC) is a primary battery device that converts the chemical energy of ethanol into electrical energy. DEFCs use biorenewable ethanol as fuel, and the energy conversion process is not limited by the Carnot cycle in a heat engine, promising a clean and efficient energy conversion process. DEFCs mainly involve two key reactions: the ethanol oxidation reaction (EOR) at the anode and the oxygen reduction reaction at the cathode. However, the commercialization of DEFCs is still hindered by efficiency and cost, one of the key factors being the development of a highly efficient and stable electrocatalytic EOR catalyst.

[0003] Supports are a crucial component of EOR electrocatalysts and a key factor in improving catalyst performance. They not only provide anchoring sites for catalytic activity centers but also influence electron transport and surface reaction kinetics. Common electrocatalyst supports are carbon materials, such as activated carbon, graphene, and carbon nanotubes, which possess advantages like high conductivity and low cost, making them widely used in electrocatalysis. However, in anodic catalysis, when carbon-based materials are used as supports, prolonged oxidation at the oxidation potential leads to oxidation and structural damage, resulting in reduced catalyst activity and stability. To address this issue, researchers have replaced carbon materials with other support materials. For example, the patent titled "A Method for Preparing a Self-Regenerating Ethanol Fuel Cell Anode Catalyst" (patent number: CN108550863B) modifies TiO2 with silicon-based materials to obtain f-TiO2 as a support, achieving good stability in EOR; the patent titled "A Direct Ethanol Fuel Cell Electrocatalyst with a Functional Support and its Preparation Method" (patent number: CN115000434B) uses AlTi@AlTiO2... x The functional support supporting platinum nanoparticles promoted the breakage of cyclophosphamide (CC) during ethanol oxidation, enhancing the acid resistance and stability of the EOR catalyst. Therefore, modifying acid- and alkali-resistant stable oxides such as TiO2 shows promise as an electrocatalytic support to improve the stability and activity of EOR. However, oxides such as TiO2 have low conductivity, and synthesizing conductive metal oxide electrocatalytic supports for efficient and stable EOR remains a challenge. Summary of the Invention

[0004] To address the issues of unstable operation of anode catalysts in direct ethanol fuel cells under long-term oxidation potential and insufficient conductivity of oxide electrocatalytic supports, this paper provides a method for preparing a conductive oxide-supported palladium ethanol fuel cell anode catalyst, an anode working electrode prepared from the catalyst, and the application of the catalyst or the anode working electrode in the preparation of direct ethanol fuel cells. The aim is to solve the stability defects of existing anode catalysts and improve the electrochemical performance of the battery.

[0005] To achieve the above objectives, in a first aspect, a method for preparing an electrocatalyst is provided, wherein the electrocatalyst is a Pd / c-TiO2@MoO3 catalyst, and the preparation method includes the following steps: S1: Preparation of MoO3-modified TiO2 composite material TiO2@MoO3: TiO2 and molybdenum source were mixed evenly, calcined at a set temperature, and cooled to obtain TiO2@MoO3; S2: Preparation of conductive c-TiO2@MoO3 composite material: The TiO2@MoO3 composite material prepared in S1 was subjected to reduction treatment to obtain conductive c-TiO2@MoO3 composite material; S3: Preparation of Pd / c-TiO2@MoO3 catalyst: The conductive c-TiO2@MoO3 composite material obtained in S2 was dispersed in a solvent, a palladium precursor was added, and the mixture was stirred and adsorbed. Then, the first reducing agent was added to carry out the reduction reaction. After washing and drying, the Pd / c-TiO2@MoO3 catalyst was obtained.

[0006] In some embodiments of the first aspect, in S1, the cooling specifically refers to natural cooling to 15-30°C, for example, it can be 15°C, 16°C, 17°C, 18°C, 19°C, 20°C, 21°C, 22°C, 23°C, 24°C, 25°C, 26°C, 27°C, 28°C, 29°C, or 30°C.

[0007] In some embodiments of the first aspect, in S1, the molybdenum source is selected from one or more of molybdenum trioxide, ammonium orthomolybdate, ammonium paramolybdate, ammonium tetramolybdate, molybdenum acetate, and molybdenum formate.

[0008] In some embodiments of the first aspect, in S1, the ratio of TiO2 to the molybdenum source is: based on the complete conversion of the molybdenum source to MoO3, the mass ratio of TiO2 to MoO3 is 1:0.05 to 1:0.3, for example, it can be 1:0.05, 1:0.1, 1:0.15, 1:0.2, 1:0.25, or 1:0.3.

[0009] In some embodiments of the first aspect, in S1, the mixing method is selected from one or more of ball milling, grinding, impregnation and evaporation, and ultrasonic precipitation; and / or In some embodiments of the first aspect, in S1, the calcination temperature is 300–500 °C. 0 C, for example, could be 300 0 C, 350 0 C, 400 0 C, 450 0 C, 500 0 C.

[0010] In some embodiments of the first aspect, in S1, the calcination time is 1 to 10 hours, for example, 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, or 10 hours.

[0011] In some embodiments of the first aspect, in S3, the palladium precursor is sodium chloropalladium.

[0012] In some embodiments of the first aspect, in S3, the temperature of the stirring adsorption is 15-30°C, for example, it can be 15°C, 16°C, 17°C, 18°C, 19°C, 20°C, 21°C, 22°C, 23°C, 24°C, 25°C, 26°C, 27°C, 28°C, 29°C, or 30°C.

[0013] In some embodiments of the first aspect, in S3, the stirring and adsorption time is 0.5-5h, for example, it can be 0.5h, 1h, 1.5h, 2h, 2.5h, 3h, 3.5h, 4h, 4.5h, or 5h.

[0014] In some embodiments of the first aspect, in S3, the reduction reaction time is 0.1-2h, for example, it can be 0.1h, 0.2h, 0.3h, 0.4h, 0.5h, 1h, 1.5h, or 2h.

[0015] In some embodiments of the first aspect, in S3, the solvent is selected from one or more of water, methanol, ethanol, and ethylene glycol.

[0016] In some embodiments of the first aspect, in S3, the first reducing agent is selected from one or more of sodium borohydride and hydrazine hydrate.

[0017] In some embodiments of the first aspect, in S3, the amount of the first reducing agent added is 1 to 100 times the amount of palladium atoms, for example, it can be 1, 2, 3, 4, 5, 10, 15, 20, 25, 30, 40, 50, 60, 70, 80, 90, or 100 times.

[0018] In some embodiments of the first aspect, in S3, the loading of Pd is 5 to 20% of the mass of the Pd / c-TiO2@MoO3 composite material, for example, it can be 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, or 20%.

[0019] In some embodiments of the first aspect, in S2, the reduction treatment method is a solid-liquid phase chemical reduction method, which specifically involves: ultrasonically dispersing the TiO2@MoO3 composite material uniformly in a solvent, slowly adding a second reducing agent under stirring conditions at a temperature of 15-30°C, continuously stirring and reacting for 0.5-5 hours, and then washing and drying to obtain c-TiO2@MoO3; preferably, the temperature can be 15°C, 16°C, 17°C, 18°C, 19°C, 20°C, 21°C, 22°C, 23°C, 24°C, 25°C, 26°C, 27°C, 28°C, 29°C, or 30°C, and the reaction time can be 0.5 hours, 1 hour, 1.5 hours, 2 hours, 2.5 hours, 3 hours, 3.5 hours, 4 hours, 4.5 hours, or 5 hours.

[0020] In some embodiments of the first aspect, the second reducing agent is selected from one or more of sodium borohydride and hydrazine hydrate.

[0021] In some embodiments of the first aspect, the amount of the second reducing agent added is 0.1 to 10 times the amount of molybdenum atoms, for example, it can be 0.1 times, 0.2 times, 0.3 times, 0.4 times, 0.5 times, 0.6 times, 0.7 times, 0.8 times, 0.9 times, 1 times, 2 times, 3 times, 4 times, 5 times, 6 times, 7 times, 8 times, 9 times, or 10 times.

[0022] In a second aspect, an anode working electrode is provided, the preparation method of which includes: suspending and dispersing the Pd / c-TiO2@MoO3 catalyst obtained by the method described in the first aspect in a mixed solution of water and ethanol to form a uniform suspension, loading the suspension onto the surface of an electrode substrate, drying it, and then activating it to obtain the anode working electrode.

[0023] In some embodiments of the second aspect, the volume ratio of water to ethanol in the mixed solution is 1:2 to 2:1, preferably 1:1.

[0024] In some embodiments of the second aspect, the suspension dispersion method is ultrasound.

[0025] In some embodiments of the second aspect, the method of loading the suspension onto the surface of the electrode substrate is selected from one or more of drop coating, spin coating, and spray coating.

[0026] In some embodiments of the second aspect, the concentration of Pd / c-TiO2@MoO3 in the suspension is 0.1–10 mg / mL, for example, it can be 0.1 mg / mL, 0.2 mg / mL, 0.3 mg / mL, 0.4 mg / mL, 0.5 mg / mL, 0.6 mg / mL, 0.7 mg / mL, 0.8 mg / mL, 0.9 mg / mL, 1 mg / mL, 2 mg / mL, 3 mg / mL, 4 mg / mL, 5 mg / mL, 6 mg / mL, 7 mg / mL, 8 mg / mL, 9 mg / mL, or 10 mg / mL.

[0027] In some embodiments of the second aspect, the electrode substrate is selected from glassy carbon electrode, carbon paper electrode, and nickel foam.

[0028] Thirdly, the use of the Pd / c-TiO2@MoO3 catalyst obtained by the method described in the first aspect or the anode working electrode described in the second aspect in the preparation of a battery is provided.

[0029] In some embodiments of the third aspect, the battery is a direct ethanol fuel cell.

[0030] This invention uses MoO3-modified TiO2 as an electrocatalytic support. First, a high-temperature calcination process in air is used to spontaneously disperse MoO3 on the TiO2 surface, forming a stable coating structure (TiO2@MoO3). The excellent acid and alkali resistance of TiO2 is utilized to improve the stability of MoO3 in the acid-base electrolyte of the fuel cell. Subsequently, a chemical reduction treatment is used to partially reduce MoO3, enhancing the material's conductivity and obtaining a conductive c-TiO2@MoO3 support that meets the conductivity requirements of the electrocatalytic reaction. Finally, Pd catalytic active centers are loaded onto this conductive support to prepare a Pd / c-TiO2@MoO3 anode catalyst.

[0031] Compared with the prior art, a certain embodiment of the present invention includes at least one of the following beneficial effects: (1) The synthesis method is simple and easy to operate, without the need for complex equipment and harsh reaction conditions. The steps such as calcination, reduction and loading are easy to scale up for production, which is conducive to low-cost production. (2) Using TiO2, which is resistant to acids and alkalis and has strong stability, as a substrate, the reduced MoO3 enhances the conductivity, so that the prepared Pd / c-TiO2@MoO3 catalyst has excellent acid and alkali resistance and long-term oxidation potential stability, effectively solving the technical problem that existing anode catalysts are prone to deactivation during long-term operation. (3) The surface of c-TiO2@MoO3 support has excellent oxygen-loving properties, which can promote the generation of OH- adsorbed species during the reaction process, thereby rapidly oxidizing and removing CO intermediate products adsorbed on the catalyst surface, enhancing the catalyst's resistance to CO poisoning, and further improving the catalyst's service life and catalytic activity.

[0032] This invention features a simple and highly controllable process, yielding a catalyst with excellent electrical conductivity and catalytic performance. It can be used for the anode catalytic oxidation of ethanol in direct ethanol fuel cells, showing promising application prospects. This invention provides a novel and feasible solution to the stability problem of anode catalysts in direct ethanol fuel cells, and is expected to promote the industrial application of direct ethanol fuel cells.

[0033] Terminology Explanation The term "M" refers to mol / L.

[0034] It is important to note that, in the context of this invention, all figures disclosed herein are approximate values, regardless of whether words such as "approximately" or "about" are used. The value of each figure may vary by 1%, 2%, 5%, 7%, 8%, 10%, 15%, or 20%, etc. Whenever a figure with a value of N is disclosed, any figure having a value of N+ / -1%, N+ / -2%, N+ / -3%, N+ / -5%, N+ / -7%, N+ / -8%, N+ / -10%, N+ / -15%, or N+ / -20% is explicitly disclosed, where "+ / -" indicates addition or subtraction. Whenever a lower limit, RL, and an upper limit, RU, of a numerical range are disclosed, any value within that disclosed range is explicitly disclosed. In particular, the following value is included within this range: R = RL + K * (RU - RL), where K is a variable increasing in 1% increments from 1% to 100%. For example: 1%, 2%, 3%, 4%, 5%, 50%, 51%, 52%, 95%, 96%, 97%, 98%, 99%, or 100%. In addition, the numerical ranges defined by the two R numbers disclosed herein are also specifically included. Attached Figure Description

[0035] Figure 1 The XPS peak spectrum of the Mo 3d orbital of the Pd / c-TiO2@MoO3 sample in Example 1 is shown.

[0036] Figure 2 The XPS peak spectrum of the Ti 2p orbital of the Pd / c-TiO2@MoO3 sample in Example 1 is shown.

[0037] Figure 3 The cyclic voltammetry curve of the Pd / c-TiO2@MoO3 sample in Example 1 in 1M KOH+1M C2H5OH solution is shown.

[0038] Figure 4 The cyclic voltammetry curve of the Pd / c-TiO2@MoO3 sample in Example 2 in 1M KOH+1M C2H5OH solution is shown.

[0039] Figure 5 The cyclic voltammetry curve of the Pd / c-TiO2@MoO3 sample in Example 3 in 1M KOH+1M C2H5OH solution is shown.

[0040] Figure 6 The cyclic voltammetry curve of the Pd / c-TiO2@MoO3 sample in Example 4 in 1M KOH+1M C2H5OH solution is shown.

[0041] Figure 7 The cyclic voltammetry curve of the Pd / c-TiO2@MoO3 sample in Example 5 in 1M KOH+1M C2H5OH solution is shown.

[0042] Figure 8 The cyclic voltammetry curve of the Pd / c-TiO2@MoO3 sample in Example 6 in 1M KOH+1M C2H5OH solution is shown. Detailed Implementation

[0043] The present invention will be further described in detail below with reference to the embodiments and accompanying drawings, but the embodiments of the present invention are not limited thereto.

[0044] Example 1: 1) Weigh 200 mg TiO2 and 40 mg MoO3 into a mortar, add 0.5 mL of ethanol, grind until powder is formed, dry again, transfer to a crucible, and heat in a muffle furnace at 450 °C. 0 Calcination at C for 2 hours followed by natural cooling yields the product TiO2@MoO3.

[0045] 2) Disperse 50 mg TiO2@MoO3 in 25 mL of water, add 4 mL of 0.01 M NaBH4 solution dropwise while stirring, react at 15-30 °C for 1 h, filter, wash and dry to obtain product c-TiO2@MoO3.

[0046] 3) Disperse 8 mg of c-TiO2@MoO3 in 16 mL of water, add 200 µL of Na2PdCl4 solution with 5 mg / mL Pd, stir and adsorb at 15-30 °C for 1 h, then add 4 mL of 0.01 M NaBH4 solution, react at 15-30 °C for 1 h, filter, wash and dry to obtain the product Pd / c-TiO2@MoO3.

[0047] 4) Weigh 2 mg of Pd / TiO2@MoO3 and add it to 2 mL of a 1:1 water:ethanol mixture. Disperse the mixture evenly and drop it onto a glassy carbon electrode. After drying, test the ethanol oxidation performance in a 1 M ethanol + 1 M KOH solution.

[0048] Example 1: XPS peak fractionation of Mo 3d orbitals in Pd / c-TiO2@MoO3 sample (see [reference]). Figure 1 This proves that the Mo element in Pd / c-TiO2@MoO3 exhibits both +6 and +4 valences, proving that Mo... 4+ The presence of [a certain substance] may affect the conductivity of oxides. See the XPS peak pattern of the Ti 2p orbitals for the Pd / c-TiO2@MoO3 sample in Example 1. Figure 2 This demonstrates that Ti in Pd / c-TiO2@MoO3 exhibits a +4 valence, indicating that Ti exists in the form of TiO2, and the conductivity exhibited by the support does not originate from the change in the valence state of Ti. Example 1: Cyclic voltammetry curves of the Pd / c-TiO2@MoO3 sample in 1M KOH + 1M C2H5OH solution are shown below. Figure 3 This demonstrates that it has excellent ethanol oxidation activity.

[0049] Example 2: The difference between this embodiment and Embodiment 1 is that the mass of MoO3 used in step 1) is 20 mg.

[0050] Example 2: Cyclic voltammetry curves of Pd / c-TiO2@MoO3 sample in 1M KOH + 1M C2H5OH solution are shown below. Figure 4 This demonstrates that it has excellent ethanol oxidation activity.

[0051] Example 3: The difference between this embodiment and Embodiment 1 is that the roasting temperature used in step 1) is 400°C. 0 C.

[0052] Example 3: Cyclic voltammetry curves of Pd / c-TiO2@MoO3 sample in 1M KOH + 1M C2H5OH solution are shown below. Figure 5 This demonstrates that it has excellent ethanol oxidation activity.

[0053] Example 4: The difference between this embodiment and Embodiment 1 is that the MoO3 used in step 1) is replaced with ammonium molybdate.

[0054] Example 5: The difference between this embodiment and embodiment 1 is that the roasting time used in step 1) is changed from 2 hours to 10 hours.

[0055] Example 6: The difference between this embodiment and embodiment 1 is that the NaBH4 used in step 2) is replaced with hydrazine hydrate.

[0056] from Figures 6-8 It can be seen that Examples 4-6 also have excellent ethanol oxidation activity.

Claims

1. A method for preparing an electrocatalyst, characterized in that, The electrocatalyst is a Pd / c-TiO2@MoO3 catalyst, and the preparation method includes the following steps: S1: Preparation of MoO3-modified TiO2 composite material TiO2@MoO3: TiO2 and molybdenum source were mixed evenly, calcined at a set temperature, and cooled to obtain TiO2@MoO3; S2: Preparation of conductive c-TiO2@MoO3 composite material: The TiO2@MoO3 composite material prepared in S1 was subjected to reduction treatment to obtain conductive c-TiO2@MoO3 composite material; S3: Preparation of Pd / c-TiO2@MoO3 catalyst: The conductive c-TiO2@MoO3 composite material obtained in S2 was dispersed in a solvent, a palladium precursor was added, and the mixture was stirred and adsorbed. Then, the first reducing agent was added to carry out the reduction reaction. After washing and drying, the Pd / c-TiO2@MoO3 catalyst was obtained.

2. The method according to claim 1, characterized in that: In S1, the cooling specifically refers to natural cooling to 15-30°C; and / or In S1, the molybdenum source is selected from one or more of molybdenum trioxide, ammonium molybdate, ammonium parmolybdate, ammonium tetramolybdate, molybdenum acetate, and molybdenum formate; and / or In S1, the ratio of TiO2 to molybdenum source is as follows: based on the complete conversion of molybdenum source to MoO3, the mass ratio of TiO2 to MoO3 is 1:0.05 to 1:0.3; and / or In S1, the mixing method is selected from one or more of ball milling, grinding, impregnation and evaporation, and ultrasonic precipitation; and / or In S1, the calcination temperature is 300-500°C. 0 C; and / or In S1, the calcination time is 1–10 h; and / or In S3, the palladium precursor is sodium chloropalladium; and / or In S3, the temperature for stirring and adsorption is 15-30℃; and / or In S3, the stirring and adsorption time is 0.5-5 hours; and / or In S3, the reduction reaction is carried out at a temperature of 15-30°C; and / or In S3, the reduction reaction takes 0.1-2 hours; and / or In S3, the solvent is selected from one or more of water, methanol, ethanol, and ethylene glycol; and / or In S3, the first reducing agent is selected from one or more of sodium borohydride and hydrazine hydrate; and / or In S3, the amount of the first reducing agent added is 1 to 100 times the amount of palladium atoms; and / or In S3, the loading of Pd is 5 to 20% of the mass of the Pd / c-TiO2@MoO3 composite material.

3. The method according to claim 2, characterized in that, In S2, the reduction treatment method is solid-liquid phase chemical reduction method. Specifically, the solid-liquid phase chemical reduction method is as follows: the TiO2@MoO3 composite material is ultrasonically and uniformly dispersed in a solvent, and a second reducing agent is slowly added under stirring conditions at a temperature of 15-30℃. After continuous stirring and reaction for 0.5-5 hours, c-TiO2@MoO3 is obtained after washing and drying.

4. The method according to claim 3, characterized in that, The second reducing agent is selected from one or more of sodium borohydride and hydrazine hydrate; and / or The amount of the second reducing agent added is 0.1 to 10 times the amount of molybdenum atoms.

5. An anode working electrode, characterized in that, Its preparation methods include: The Pd / c-TiO2@MoO3 catalyst obtained by the method according to any one of claims 1-4 is suspended and dispersed in a mixed solution of water and ethanol to form a uniform suspension. The suspension is loaded onto the surface of an electrode substrate, dried, and then activated to obtain the anode working electrode.

6. The anode working electrode according to claim 5, characterized in that, In the mixed solution, the volume ratio of water to ethanol is 1:2 to 2:1; and / or The suspension dispersion method is ultrasound; and / or The method for loading the suspension onto the electrode substrate surface is selected from one or more of the following: drop coating, spin coating, and spray coating; and / or The concentration of Pd / c-TiO2@MoO3 in the suspension is 0.1–10 mg / mL; and / or The electrode substrate is selected from one of glassy carbon electrode, carbon paper electrode, and nickel foam.

7. Use of a Pd / c-TiO2@MoO3 catalyst obtained by the method of any one of claims 1-4 or an anode working electrode as described in claim 5 or 6 in the preparation of a battery.

8. The use according to claim 7, characterized in that, The battery is a direct ethanol fuel cell.

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