A platinum-based encapsulated mesoporous titanium dioxide electrocatalyst, its preparation method and application

Abstract

This invention relates to a platinum-based encapsulated mesoporous titanium dioxide electrocatalyst, its preparation method, and its applications, relating to the field of energy material preparation. The defective mesoporous titanium dioxide microspheres possess mesoporous channels radiating radially from the center; their surface is loaded with Pt single-atom / sub-nanometer clusters. The preparation method involves first dissolving a nonionic surfactant, metal salt, organic compound, and chelating agent in an organic solvent, then slowly evaporating the solvent to form stable composite micelles as building blocks, assembling them hydrothermally, and finally calcining them at high temperature in air to remove the surfactant, forming a mesoporous structure, thus obtaining defective mesoporous titanium dioxide microspheres encapsulated with Pt. The microspheres prepared by this invention have a large specific surface area, abundant accessible active sites, and rapid charge transport capabilities, showing broad application prospects in the field of energy catalysis.

Description

Technical Field

[0001] This invention relates to the field of energy material design and synthesis technology, specifically to a platinum-based encapsulated mesoporous titanium dioxide electrocatalyst, its preparation method, and its application. Background Technology

[0002] The energy crisis and global warming caused by the continuous consumption of fossil fuels have become a focus of global attention. This ever-increasing demand for fossil fuels and their non-renewable nature have exacerbated the energy crisis. The need for renewable energy sources that can be integrated into power generation systems is more urgent than ever before. To this end, researchers are constantly exploring methods for developing and applying renewable energy sources such as hydropower and wind power. However, due to the spatiotemporal discontinuous nature of these renewable energy sources, their energy transmission efficiency is low. Therefore, there is an urgent need to develop related energy storage technologies.

[0003] Among numerous energy carriers, hydrogen is an ideal energy carrier with extremely high energy density, and its utilization is of great significance for solving energy crises and environmental problems. Of the many hydrogen production methods, electrocatalytic water splitting represents the most scalable technology, characterized by its environmental friendliness, high efficiency, and controllability, making it a key strategy for producing green hydrogen. This technology can utilize renewable energy sources such as solar and wind power to split water into hydrogen and oxygen, thereby obtaining high-energy-density, pollution-free, easily stored, and transportable hydrogen to meet people's growing energy demands. Simultaneously, using electricity generated from renewable resources to produce "green hydrogen" will significantly alleviate environmental problems caused by carbon emissions. However, the hydrogen production efficiency of this method is still limited. This limitation stems from the slow kinetics of the two half-reactions in water electrolysis for hydrogen production: the oxygen evolution reaction (OER) and the hydrogen evolution reaction (HER).

[0004] The key to overcoming this slow kinetic process is the development of advanced electrocatalysts for electrocatalytic water splitting. Electrocatalysts accelerate the reaction process, reducing the additional energy required to achieve a water splitting process that is closest to the ideal state. To date, Pt-based catalysts are still considered the optimal choice for HER catalysts due to their best hydrogen binding energy. However, they face problems such as resource scarcity, high cost, and poor long-term cycling stability, which limit the practical application of Pt-based catalysts in the field of electrocatalytic water splitting.

[0005] Therefore, many researchers have proposed two approaches: first, to find alternatives, such as the large number of highly stable non-noble metal-based electrocatalysts synthesized through modified design; however, despite this, the performance of non-noble metal-based catalysts in practical applications still cannot compare with that of Pt-based catalysts. Second, to improve utilization efficiency, such as through ultrafine Pt nanostructures, including single atoms (SAs), sub-nano clusters (SNCs), and nanoparticles, aiming to significantly improve catalytic activity and maximize the utilization efficiency of precious Pt. Ultrafine nanostructures possess unique electronic structures, geometric properties, tunable coordination environments, and high atomic utilization efficiencies. However, due to their high surface free energy, ultrafine nanostructures often undergo irreversible structural changes under reaction conditions, such as dissolution, Ostwald ripening, and aggregation. This leads to a precipitous drop in performance. Furthermore, in practical applications, the catalytic activity of Pt-based catalysts at industrial-scale current densities is fundamentally limited, with excessive bubble generation hindering the efficient transfer of electrolyte to active sites.

[0006] Among the many strategies under investigation, strong metal-support interaction (SMSI), particularly through the encapsulation of metal nanostructures to enhance catalyst stability, has attracted considerable attention. Among various support materials, mesoporous materials, especially mesoporous titanium dioxide (TiO2), have shown promise as ideal supports for high-performance electrocatalysts due to their large specific surface area, rich and tunable pore structure, natural abundance, and excellent corrosion resistance. In recent years, a soft-template method based on solution evaporation-induced micelle self-assembly has been developed for the synthesis of mesoporous titanium dioxide. A large variety of mesoporous titanium dioxide has been synthesized using this method. Using mesoporous titanium dioxide as a support and loading ultrafine Pt nanostructures through strong metal-support interaction can significantly improve the material's stability while maintaining the high activity of Pt as an active site, providing guidance for the development of electrocatalysts with both high activity and high stability. Summary of the Invention

[0007] To address the problems of existing technologies, this invention provides a method for preparing a platinum-based encapsulated mesoporous titanium dioxide electrocatalyst.

[0008] The specific technical solution of the present invention is as follows:

[0009] A method for preparing a platinum-based encapsulated mesoporous titanium dioxide electrocatalyst is characterized by the following steps: dissolving a nonionic surfactant in an organic solvent and continuously stirring until dissolved; adding hydrochloric acid and acetic acid to the mixed solution and continuously stirring until homogeneous; then adding an organic compound and continuously stirring until dissolved; finally, adding a metal salt and the organic compound to the mixed solution and continuously stirring to obtain a precursor solution. At a certain temperature, the organic solvent is preferentially evaporated to form a composite soft micelle hydrogel. The composite soft micelle hydrogel is added to a hydrothermal reactor for hydrothermal treatment to obtain low-crystallinity platinum-based encapsulated mesoporous titanium dioxide microspheres. The low-crystallinity platinum-based encapsulated mesoporous titanium dioxide microspheres are then calcined at high temperature to obtain a platinum-based encapsulated mesoporous titanium dioxide electrocatalyst material.

[0010] The method for preparing the platinum-based encapsulated mesoporous titanium dioxide electrocatalyst is characterized by specifically including the following steps:

[0011] S1 At room temperature, a nonionic surfactant is dissolved in an organic solvent. Acetic acid and hydrochloric acid are then added to the solvent as additives to inhibit hydrolysis and complexation, and mixed evenly. 2-Ethylimidazole is then dissolved in the mixed solution as a defect inducer. Finally, platinum metal salt and tetrabutyl titanate are added as metal sources, and the mixture is stirred and mixed evenly to obtain a clear orange solution.

[0012] S2. The clarified solution is placed at a certain temperature. Through the preferential evaporation of the solvent, the block copolymer and the metal precursor in the solution self-assemble into composite micelles. After a certain evaporation time, a composite micelle orange hydrogel is formed.

[0013] S3 Add the above orange gel into the Teflon liner of the high-pressure hydrothermal reactor, seal the high-pressure hydrothermal reactor, and place it in an electric heating drying oven for reaction;

[0014] S4 The product obtained after hydrothermal treatment is calcined in a muffle furnace at a certain temperature to remove the template agent, thereby obtaining defective mesoporous titanium dioxide microspheres encapsulating Pt.

[0015] More preferably, in step S1, the organic solvent is tetrahydrofuran (THF), and the metal precursor is hydrated platinum chloride (PtCl4·H2O). In step S2, the evaporation temperature is 30-50 °C, and the evaporation time is 20-26 h. In step S3, the hydrothermal temperature is 60-80 °C, and the hydrothermal time is 20-26 h. In step S4, the calcination temperature is 400-450 °C, the temperature program is 1-2 °C / min, and the calcination time is 2-4 h.

[0016] Preferably, the nonionic surfactant is a triblock copolymer, polyethylene glycol-polypropylene glycol-polyethylene glycol, wherein the triblock copolymer mainly includes Pluronic F127 (EO). 106PO 70 EO 106 ), Pluronic P123 (EO 20 PO 70 EO 20 The preferred option is Pluronic F127 (EO). 106 PO 70 EO 106 ).

[0017] A platinum-based encapsulated mesoporous titanium dioxide electrocatalyst prepared by the above method has a specific surface area of ​​40-50 m². 2 / g, with pore size in the range of 9-12 nm.

[0018] A platinum-based encapsulated mesoporous titanium dioxide electrocatalyst prepared by the above method is used as a cathode catalyst material for electrocatalytic water splitting to produce hydrogen under acidic conditions.

[0019] An application of a platinum-based encapsulated mesoporous titanium dioxide electrocatalyst prepared by the above method is characterized in that: the platinum-based encapsulated mesoporous titanium dioxide electrocatalyst material is mixed with Nafion solvent and isopropanol solvent to form a catalyst slurry, which is then drop-coated onto a rotating disk electrode for electrocatalytic application using a three-electrode system.

[0020] The application of the platinum-based encapsulated mesoporous titanium dioxide electrocatalyst prepared by the above method is characterized by specifically including the following steps:

[0021] S1 The platinum-based encapsulated mesoporous titanium dioxide electrocatalyst material is taken in 4-6 mg as the catalytic active material;

[0022] S2 Take 5-20 μL of Nafion solvent and 480-500 μL of isopropanol solvent and the catalytic active material described in S1 respectively, and prepare a catalyst slurry by physical mixing;

[0023] S3 Take 5-20 μL of the above catalyst slurry and drop it onto the glassy carbon active surface of the rotating disk electrode. After the slurry dries to form a film, it is then used.

[0024] S4. Using the prepared rotating disk electrode as the working electrode, the Ag / AgCl electrode as the reference electrode, and the carbon rod as the counter electrode, a 1.0 M perchloric acid solution was selected as the electrolyte. The three-electrode system was assembled and applied to the electrocatalytic water splitting for hydrogen production under acidic conditions.

[0025] This invention utilizes an inorganic-organic co-assembly soft template self-assembly method and a solution evaporation-induced single-micelle self-assembly synthesis strategy to controllably synthesize defective mesoporous titanium dioxide microspheres encapsulated with Pt. Using material characterization techniques such as TEM, SEM, and an electrochemical workstation, a novel synthetic method for platinum-based encapsulated mesoporous titanium dioxide electrocatalysts was developed. The application of this material as a cathode for acidic electrocatalytic water splitting was investigated, the influence of material structure on performance was examined, and the structure-property relationship between material structure and performance was established.

[0026] Compared with the prior art, the present invention has the following advantages:

[0027] 1. This invention utilizes nonionic surfactants as structure directing agents and employs a solution evaporation-induced single micelle self-assembly synthesis strategy to synthesize defective mesoporous titanium dioxide microspheres encapsulating Pt. The process is simple and convenient, and the obtained product has a large specific surface area, high charge transport efficiency, and many accessible active sites.

[0028] 2. This invention utilizes a mesoporous structure with abundant pores to encapsulate high-performance particles through strong metal-carrier interaction, ensuring both the excellent performance of the material and its long-term stable application.

[0029] 3. This invention exhibits excellent catalytic performance in the application of acidic electrocatalytic water splitting cathodes and can be used stably for a long time in highly corrosive environments;

[0030] 4. The raw materials of this invention are readily available, the method is simple, and it has a wide range of applications in many fields such as energy storage and conversion, and catalysis. Attached Figure Description

[0031] Figure 1 Optical images of defective mesoporous titanium dioxide microspheres encapsulating Pt prepared in Example 1 at each synthesis stage;

[0032] Figure 2 Scanning electron microscope (SEM) and transmission electron microscope (TEM) images of defective mesoporous titanium dioxide microspheres encapsulating Pt prepared in Example 1;

[0033] Figure 3 The X-ray diffraction (XRD) patterns of defective mesoporous titanium dioxide microspheres (Pt@DMTO) and titanium dioxide particles (TiO2) encapsulated with Pt prepared in Example 1 are shown.

[0034] Figure 4 Characteristic nitrogen adsorption-desorption isotherms and pore size distribution curves of defective mesoporous titanium dioxide microspheres (Pt@DMTO) and titanium dioxide particles (TiO2) encapsulated with Pt prepared in Example 1;

[0035] Figure 5The linear sweep voltammetry (LSV) curves of the electrocatalytic water desorption hydrogen cathode catalysts obtained in Example 2 are shown below, which are comparison samples of defective mesoporous titanium dioxide microspheres (Pt@DMTO), defective mesoporous titanium dioxide microspheres (DMTO), mesoporous titanium dioxide microspheres (MTO), nano-titanium dioxide particles (P25), and commercial platinum-carbon catalyst (Pt / C).

[0036] Figure 6 The Tafel plots of the defective mesoporous titanium dioxide microspheres (Pt@DMTO), defective mesoporous titanium dioxide microspheres (DMTO), and commercial platinum-carbon catalyst (Pt / C) obtained in Example 2 are shown as the cathode catalysts for electrocatalytic water desorption hydrogenation under acidic conditions.

[0037] Figure 7 The Nyquist electrochemical impedance spectroscopy (EIS) spectra of the following samples obtained in Example 2: defective mesoporous titanium dioxide microspheres (Pt@DMTO), defective mesoporous titanium dioxide microspheres (DMTO), mesoporous titanium dioxide microspheres (MTO), nano-titanium dioxide particles (P25), and commercial platinum-carbon catalyst (Pt / C), used as cathode catalysts for electrocatalytic water desorption hydrogenation under acidic conditions.

[0038] Figure 8 The image shows a comparison of the linear sweep voltammetry (LSV) stability of the defective mesoporous titanium dioxide microspheres (Pt@DMTO) and the commercial platinum-carbon catalyst (Pt / C) obtained in Example 2 as electrocatalysts for water desorption hydrogenation under acidic conditions before and after 10,000 cycles. Detailed Implementation

[0039] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. The following embodiments are implemented based on the technical solution of the present invention, providing detailed implementation methods and specific operating procedures; however, the scope of protection of the present invention is not limited to the following embodiments.

[0040] Example 1: Synthesis of platinum-based encapsulated mesoporous titanium dioxide electrocatalyst.

[0041] In a tetrahydrofuran solvent (30 mL), 1.6 g of triblock copolymer F127, 2.6 mL of acetic acid, and 3.2 mL of concentrated hydrochloric acid were added sequentially, and a colorless and transparent solution was formed under stirring. Then, 0.5 g of 2-ethylimidazole was added and stirred until dissolved. Finally, 0.072 g of PtCl4 and 3 mL of TBOT were added and stirred for 5 min to form an orange and transparent solution. The mixture was then transferred to two 15 mL evaporation flasks, and tetrahydrofuran was preferentially evaporated at 40 °C for 24 h to form an orange Pt@F127 / TiO2 composite single-micelle hydrogel. The composite single-micelle hydrogel was then transferred to a 100 mL Teflon-lined container, sealed in a stainless steel high-pressure reactor, and reacted at 70 °C for 24 h. After cooling to room temperature, the product within the Teflon liner was collected and placed in a crucible. The crucible was then placed in a muffle furnace and calcined at 400 °C for 3 h under air at a heating rate of 1 °C / min to obtain defective mesoporous titanium dioxide microspheres encapsulated with Pt (Pt@DMTO). Optical images of each synthesis stage are shown. Figure 1 SEM and TEM images can be found here. Figure 2 SEM and TEM images confirm that the mesoporous microspheres possess good uniformity and radially radiating mesoporous channels from the center outwards, and that a large number of Pt single-atom / sub-nanometer clusters are loaded on the TiO2 surface (circled in orange in the images). Furthermore, XRD comparison images are shown below. Figure 3 As can be seen, the original titanium dioxide crystal phase was not changed after loading. See the nitrogen adsorption-desorption curves and pore size distribution diagram. Figure 4 The obtained two-dimensional mesoporous titanium dioxide nanosheets have a specific surface area of ​​46 m². 2 / g, pore size is 11.2 nm.

[0042] Example 2: The platinum-based encapsulated mesoporous titanium dioxide electrocatalyst synthesized in Example 1 was applied to the acidic hydrogen evolution reaction.

[0043] 5.0 mg of Pt-encapsulated defective mesoporous titanium dioxide microspheres (Pt@DMTO) were dispersed in a mixture of 10 μL Nafion solution and 490 μL ethanol solution. The mixture was sonicated for 30 min, ensuring a constant temperature throughout the sonication process, to prepare a catalyst ink slurry. Subsequently, 10 µL of the ink slurry was pipetted onto the working area of ​​a glassy carbon electrode (GCE) and dried at room temperature. The dried glassy carbon electrode served as the working electrode (WE), a graphite rod as the counter electrode (CE), and a silver / silver chloride (Ag / AgCl) electrode as the reference electrode (RE). A 1.0 M perchloric acid (HClO4) solution was used as the electrolyte. The prepared electrolyte was purged with nitrogen for 1 h before use. The electrodes and electrolyte were assembled into a three-electrode electrolytic cell, and electrochemical tests were performed using a Metrohm NovaN402 electrochemical workstation. Linear sweep voltammetry (LSV) curves were plotted at 5 mV s⁻¹. -1 The scan rate was measured. Since the solution interphase resistance affects the actual performance results, the test results were corrected using iR drop compensation, with a correction margin of 90%. After correction, the defective mesoporous titanium dioxide microspheres encapsulated with Pt showed performance at 10 mA cm⁻¹. -2 At current densities, it can achieve a low overpotential of 7 mV, lower than commercial platinum-carbon (Pt / C) and other comparative samples. Figure 5 ).and Figure 6 Analysis of the Tafel slope showed that the reaction kinetics of Pt@DMTO were superior to those of commercial Pt / C catalysts. Electrochemical impedance spectroscopy (EIS) was performed at a potential of -0.80 V for a reversible hydrogen electrode, with a frequency range of 0.01 Hz to 100 kHz. The results were fitted and analyzed using Zview software. The defective mesoporous titanium dioxide microspheres encapsulating Pt exhibited a charge transfer resistance of only 0.68 Ω, significantly lower than that of commercial Pt / C catalysts. Figure 7 After 10,000 cyclic voltammetry (CV) tests, comparing the linear sweep voltammetry (LSV) curves before and after the tests, the performance of the defective mesoporous titanium dioxide microspheres encapsulating Pt showed almost no degradation, exhibiting excellent stability. Figure 8 ).

[0044] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. Those skilled in the art can readily make various modifications to these embodiments and apply the general principles described herein to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A method for preparing a platinum-based encapsulated mesoporous titanium dioxide electrocatalyst, characterized in that: S1 At room temperature, a nonionic surfactant is dissolved in an organic solvent. Acetic acid and hydrochloric acid are then added to the solvent as additives to inhibit hydrolysis and complexation, and mixed evenly. 2-Ethylimidazole is then dissolved in the mixed solution as a defect inducer. Finally, platinum metal salt and tetrabutyl titanate are added as metal sources, and the mixture is stirred and mixed evenly to obtain a clear orange solution. S2 places the clarified solution at a certain temperature, and through the preferential evaporation of the solvent, the block copolymer in the solution and the metal precursor form a composite micelle self-assemble. After a certain evaporation time, a composite micelle orange hydrogel is formed. S3. The above-mentioned orange gel was added into the Teflon liner of the high-pressure hydrothermal reactor, the high-pressure hydrothermal reactor was sealed, and the reactor was placed in an electric heating drying oven for reaction. S4 calcined the product obtained after hydrothermal treatment in a muffle furnace at a certain temperature to obtain a platinum-based encapsulated mesoporous titanium dioxide electrocatalyst. In step S1, the organic solvent is tetrahydrofuran, and the metal precursor is hydrated platinum chloride; in step S2, the evaporation temperature is 30-50 ℃, and the evaporation time is 20-26 h; in step S3, the hydrothermal temperature is 60-80 ℃, and the hydrothermal time is 20-26 h; in step S4, the calcination temperature is 400-450 ℃, the heating program is 1-2 ℃ / min, and the calcination time is 2-4 h. The nonionic surfactant is a triblock copolymer, which is selected from Pluronic F127 and Pluronic P123.

2. The platinum-based encapsulated mesoporous titanium dioxide electrocatalyst prepared according to the preparation method of claim 1, characterized in that, It has a spherical morphology, a radially divergent mesoporous structure with a pore size of 9-12 nm, and is loaded with Pt single-atom / sub-nanometer clusters.

3. The application of the platinum-based encapsulated mesoporous titanium dioxide electrocatalyst according to claim 2, characterized in that, To develop cathode catalyst materials for electrocatalytic water splitting to produce hydrogen under acidic conditions.

4. The application of the platinum-based encapsulated mesoporous titanium dioxide electrocatalyst according to claim 3, characterized in that, Specifically, the following steps are included: S1. Take 4-6 mg of the platinum-based encapsulated mesoporous titanium dioxide electrocatalyst material as the catalytic active material; S2. Take 5-20 μL of Nafion solvent and 480-500 μL of isopropanol solvent and the catalytic active material described in S1, respectively, and prepare a catalyst slurry by physical mixing; S3. Take 5-20 μL of the above catalyst slurry and drop it onto the glassy carbon active surface of the rotating disk electrode. After the slurry is dried into a film, it is used; S4. Use the rotating disk electrode after the slurry in S3 is dried as the working electrode, the Ag / AgCl electrode as the reference electrode, and the carbon rod as the counter electrode. The electrolyte is a 1.0 M perchloric acid solution. Assemble the three-electrode system for electrocatalytic water splitting to produce hydrogen under acidic conditions.

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