Method for preparing tungsten trioxide low-platinum electrocatalyst with core-shell structure through pulse Joule heating

Abstract

The invention discloses a method for preparing a tungsten trioxide low-platinum electrocatalyst with a core-shell structure through pulse Joule heating, and belongs to the field of electrochemical catalysts for electrolysis of water. The invention aims to solve the problems that controllable amorphization is difficult to realize on the WO3 surface and a crystal nucleus-amorphous shell composite structure cannot be effectively constructed in the prior art. The preparation method comprises the following steps: 1, preparing a tungsten trioxide carrier with a core-shell structure; and 2, loading a platinum source. The method is used for preparing the tungsten trioxide low-platinum electrocatalyst with the core-shell structure through pulse Joule heating.

Description

Technical Field

[0001] This invention belongs to the field of electrochemical catalysts for water electrolysis. Background Technology

[0002] Utilizing renewable energy for hydrogen production through acidic water electrolysis is a crucial pathway to achieving large-scale green hydrogen production. However, this process currently relies heavily on precious metal catalysts such as platinum (Pt), resulting in high hydrogen production costs and severely hindering its commercialization. To reduce dependence on platinum, developing efficient and stable electrocatalysts with low or no platinum content has become a key research focus.

[0003] Tungsten trioxide (WO3) is considered an ideal catalyst support material due to its good stability in acidic media and tunable electronic structure. However, intrinsic WO3 has poor conductivity and limited surface active sites, resulting in poor performance when directly used for electrocatalytic hydrogen evolution reaction. Existing modification strategies, including introducing defects and constructing heterojunctions, can improve the dispersion and utilization of platinum to some extent, but the material is still prone to dissolution, agglomeration, or activity decay under strongly acidic and high-potential operating environments. Amorphous materials, due to their long-range disordered atomic arrangement and high density of unsaturated coordination sites, show excellent potential in the field of electrocatalysis. Amorphous phases not only provide abundant active sites but also allow for optimization of the adsorption behavior of reaction intermediates through electronic structure regulation, thereby improving catalytic performance. However, overall amorphization of WO3 can weaken its overall structural stability and mechanical strength, which is detrimental to long-term durability. Therefore, the ideal strategy is to leverage the advantages of amorphous phases while retaining the structural stability of the crystalline core. The key lies in achieving controllable and uniform construction of the surface amorphous layer, forming a composite structure of "crystalline nucleus-amorphous shell". Currently, conventional amorphization methods (such as high-temperature annealing and melt quenching) are difficult to achieve controllable and localized amorphization on the surface of highly crystalline and thermally stable metal oxides like WO3, which makes it difficult to construct core-shell structures and restricts their further application in low-platinum catalysts.

[0004] Therefore, developing a method to precisely control the surface structure of WO3, construct a core-shell structure with a crystalline core and an amorphous outer shell, and then constructing a method for preparing a highly efficient, low-platinum catalyst based on this structure, has significant research value and practical application prospects. Summary of the Invention

[0005] This invention addresses the challenges of achieving controllable amorphization on WO3 surfaces and effectively constructing "nucleus-amorphous shell" composite structures in existing technologies. It provides a method for preparing core-shell structured tungsten trioxide electrocatalysts with low platinum loading using pulsed Joule heating. This method is simple, precisely controlled, and achieves excellent HER activity and stability even with extremely low platinum loading.

[0006] A method for preparing a core-shell structured tungsten trioxide low-platinum electrocatalyst by pulsed Joule heating, comprising the following steps:

[0007] 1. Dissolve the tungsten source compound in water to obtain a suspension. Add a dispersant to the suspension and sonicate to obtain a precursor solution. Coat the precursor solution onto a conductive substrate and dry it to obtain the precursor. Perform pulse Joule heating on the precursor to obtain a core-shell structured tungsten trioxide carrier.

[0008] The core-shell tungsten trioxide support has a crystalline tungsten trioxide core and an amorphous tungsten trioxide layer as the outer shell. Secondly, a platinum source solution is loaded onto the surface of the core-shell tungsten trioxide support, and then subjected to settling, washing, and drying to obtain a core-shell tungsten trioxide low-platinum electrocatalyst.

[0009] The beneficial effects of this invention are:

[0010] 1. This invention solves the technical challenge of achieving localized amorphization on the surface of highly crystalline oxides using traditional methods. By precisely controlling key parameters and methods through pulsed Joule heating technology, an amorphous shell layer is controllably constructed on the WO3 surface, forming a composite catalyst with a well-defined core-shell structure. This structure can significantly modulate the electronic structure, effectively suppress the competitive adsorption of hydrogen intermediates at the W sites of the catalyst, and optimize the hydrogen adsorption free energy of Pt species, thereby achieving excellent hydrogen evolution reaction activity and stability even with extremely low platinum loading.

[0011] 2. The preparation method proposed in this invention is simple, rapid, and highly controllable, requiring no complex post-processing, which is conducive to large-scale preparation and has good process applicability;

[0012] 3. Based on the electronic regulation advantages of the surface amorphous / crystalline core-shell structure, the catalyst exhibits excellent catalytic performance and stability under acidic conditions. Even with a platinum loading ≤0.3wt%, it can achieve catalytic performance at 10 mA cm⁻¹. -2 Achieving a low overpotential of 33mV at the current density significantly reduces catalyst costs and demonstrates outstanding potential for practical applications. Attached Figure Description

[0013] Figure 1 Scanning electron microscope (SEM) image of the core-shell structured tungsten trioxide low-platinum electrocatalyst prepared in Example 1;

[0014] Figure 2 High-resolution transmission electron microscopy (HRTEM) image of the core-shell structured tungsten trioxide low-platinum electrocatalyst prepared in Example 1;

[0015] Figure 3The X-ray photoelectron spectroscopy (XPS) spectra of the core-shell structured tungsten trioxide low-platinum electrocatalyst prepared in Example 1 and the crystalline tungsten trioxide electrocatalyst W 4f prepared in the comparative experiment are shown.

[0016] Figure 4 The X-ray photoelectron spectroscopy (XPS) spectra of the core-shell structured tungsten trioxide low-platinum electrocatalyst prepared in Example 1 and the crystalline tungsten trioxide electrocatalyst Pt 4f prepared in the comparative experiment are shown.

[0017] Figure 5 The polarization curves (LSV) are shown for the core-shell structured tungsten trioxide low-platinum electrocatalyst prepared in Example 1 and the crystalline tungsten trioxide electrocatalyst prepared in the comparative experiment.

[0018] Figure 6 The stability curve of the core-shell structured tungsten trioxide low-platinum electrocatalyst prepared in Example 1 is shown. Detailed Implementation

[0019] Specific Implementation Method 1: This implementation method is a method for preparing core-shell structured tungsten trioxide low-platinum electrocatalysts using pulsed Joule heating, characterized by the following steps:

[0020] 1. Dissolve the tungsten source compound in water to obtain a suspension. Add a dispersant to the suspension and sonicate to obtain a precursor solution. Coat the precursor solution onto a conductive substrate and dry it to obtain the precursor. Perform pulse Joule heating on the precursor to obtain a core-shell structured tungsten trioxide carrier.

[0021] The core-shell tungsten trioxide support has a crystalline tungsten trioxide core and an amorphous tungsten trioxide layer as the outer shell. Secondly, a platinum source solution is loaded onto the surface of the core-shell tungsten trioxide support, and then subjected to settling, washing, and drying to obtain a core-shell tungsten trioxide low-platinum electrocatalyst.

[0022] The beneficial effects of this embodiment are:

[0023] 1. This embodiment solves the technical challenge of achieving localized amorphization on the surface of highly crystalline oxides using traditional methods. By precisely controlling key parameters and methods through pulsed Joule heating technology, an amorphous shell layer is controllably constructed on the WO3 surface, forming a composite catalyst with a well-defined core-shell structure. This structure can significantly modulate the electronic structure, effectively suppress the competitive adsorption of hydrogen intermediates at the W sites of the catalyst, and optimize the hydrogen adsorption free energy of Pt species, thereby achieving excellent hydrogen evolution reaction activity and stability at extremely low platinum loading.

[0024] 2. The preparation method proposed in this embodiment is simple, rapid, and highly controllable, requiring no complex post-processing, which is conducive to large-scale preparation and has good process applicability;

[0025] 3. Based on the electronic regulation advantages of the surface amorphous / crystalline core-shell structure, this embodiment of the catalyst exhibits excellent catalytic performance and stability under acidic conditions. Even with a platinum loading ≤0.3wt%, it can achieve catalytic performance at 10 mA cm⁻¹. -2 Achieving a low overpotential of 33mV at the current density significantly reduces catalyst costs and demonstrates outstanding potential for practical applications.

[0026] Specific Implementation Method Two: This implementation method differs from Specific Implementation Method One in that: the tungsten source compound mentioned in step one is ammonium metatungstate, sodium tungstate, or tungstic acid; the dispersant mentioned in step one is ethanol or isopropanol; and the conductive substrate mentioned in step one is carbon cloth or titanium foam. Everything else is the same as in Specific Implementation Method One.

[0027] Specific Implementation Method Three: This implementation method differs from Specific Implementation Method One or Two in that: the concentration of tungsten ions in the suspension described in step one is 2 mol / L to 6 mol / L; and the volume ratio of the dispersant to the suspension described in step one is 1:(5~10). Everything else is the same as in Specific Implementation Method One or Two.

[0028] Specific Implementation Method Four: This implementation method differs from Specific Implementation Methods One to Three in that the ultrasonic treatment described in step one is specifically performed at an ultrasonic power of 100W to 300W for 3 to 5 minutes. Everything else is the same as in Specific Implementation Methods One to Three.

[0029] Specific Implementation Method Five: This implementation method differs from Specific Implementation Methods One to Four in that: in step one, the coating amount is 0.1 mL / cm². 2 ~0.2mL / cm 2 The precursor solution is coated onto a conductive substrate and then dried at a temperature of 25°C to 60°C for 15 to 45 minutes to obtain the precursor. Other steps are the same as in embodiments one through four.

[0030] Specific Implementation Method Six: This implementation method differs from Specific Implementation Methods One to Five in that the pulse Joule heating treatment described in step one is specifically performed as follows: a DC current of 25V~35V and 20A~30A is applied to the conductive substrate, causing the precursor temperature to reach 1100℃~1300℃, and the treatment lasts for 5s~10s. Everything else is the same as in Specific Implementation Methods One to Five.

[0031] Specific Implementation Method Seven: This implementation method differs from Specific Implementation Methods One to Six in that the platinum source in the platinum source solution described in step two is chloroplatinic acid or platinum acetylacetonate. Everything else is the same as in Specific Implementation Methods One to Six.

[0032] Specific Implementation Method Eight: This implementation method differs from Specific Implementation Methods One to Seven in that: in the core-shell structured tungsten trioxide low-platinum electrocatalyst described in step two, Pt accounts for 0.1% to 0.3% of the total mass of Pt and W elements. Everything else is the same as in Specific Implementation Methods One to Seven.

[0033] Specific Implementation Method Nine: This implementation method differs from Specific Implementation Methods One to Eight in that the core-shell structured tungsten trioxide low-platinum electrocatalyst described in step two is vertically grown on a conductive substrate in the form of a nanoneedle array. Everything else is the same as in Specific Implementation Methods One to Eight.

[0034] Specific Implementation Method Ten: This implementation method differs from Specific Implementation Methods One to Nine in that the length of the nanoneedles is 2.7μm to 4.5μm, and the diameter is 0.3μm to 1μm. Everything else is the same as Specific Implementation Methods One to Nine.

[0035] The beneficial effects of the present invention are verified using the following embodiments:

[0036] Example 1:

[0037] A method for preparing a core-shell structured tungsten trioxide low-platinum electrocatalyst by pulsed Joule heating, comprising the following steps:

[0038] 1. Dissolve the tungsten source compound in ultrapure water to obtain a suspension. Add a dispersant to the suspension and sonicate for 3 minutes at an ultrasonic power of 200 W to obtain a precursor solution. Apply the solution at a coating amount of 0.15 mL / cm³. 2 The precursor solution was coated onto a conductive substrate and dried at 60°C for 15 minutes to obtain the precursor. The precursor was then fixed in the fixture of a pulse Joule heating device, which consisted of a graphite block and copper electrodes. A DC current of 30V and 25A was applied to the conductive substrate to raise the temperature of the precursor to approximately 1200°C. After processing for 10 seconds, a core-shell structured tungsten trioxide carrier was obtained.

[0039] The core-shell structured tungsten trioxide carrier has a core of crystalline tungsten trioxide and an outer shell of amorphous tungsten trioxide layer with a thickness of approximately 3.5 nm.

[0040] The tungsten source compound is ammonium metatungstate; the dispersant is ethanol; and the conductive substrate is carbon cloth (2×5cm). 2 The concentration of tungsten ions in the suspension is 4 mol / L; the volume ratio of the dispersant to the suspension is 1:10.

[0041] 2. 0.1 mL of platinum source solution was added dropwise to the surface of the core-shell tungsten trioxide support and completely wetted. Then, the solution was allowed to stand at room temperature for 20 min, rinsed with pure water, and air-dried to obtain a core-shell tungsten trioxide low-platinum electrocatalyst.

[0042] The platinum source solution is a chloroplatinic acid hexahydrate solution with a platinum ion concentration of 0.046 mol / L;

[0043] Quantitative ICP-OES (Inductively Coupled Plasma Optical Emission Spectroscopy) analysis determined that the mass ratio of W to Pt in the core-shell structured tungsten trioxide low-platinum electrocatalyst was 99.7:0.3, meaning that Pt accounted for 0.3% of the total mass of Pt and W in the core-shell structured tungsten trioxide low-platinum electrocatalyst.

[0044] The core-shell structured tungsten trioxide low-platinum electrocatalyst described in step two is vertically grown on a conductive substrate in the form of a nanoneedle array.

[0045] The nanoneedles have a length of 2.7 μm to 4.5 μm and a diameter of 0.3 μm to 1 μm.

[0046] Comparative experiment:

[0047] A method for preparing a crystalline tungsten trioxide electrocatalyst, comprising the following steps:

[0048] 1. Dissolve the tungsten source compound in ultrapure water to obtain a suspension. Add a dispersant to the suspension and sonicate for 3 minutes at an ultrasonic power of 200 W to obtain a precursor solution. Apply the solution at a coating amount of 0.15 mL / cm³. 2 The precursor solution was coated onto a conductive substrate and then dried at 60°C for 15 min to obtain precursor A.

[0049] The tungsten source compound is ammonium metatungstate; the dispersant is ethanol; and the conductive substrate is carbon cloth (2×5cm). 2 The concentration of tungsten ions in the suspension is 4 mol / L; the volume ratio of the dispersant to the suspension is 1:10.

[0050] 2. Add 0.1 mL of platinum source solution to the surface of precursor A and completely wet it. Then, let it stand at room temperature for 20 min, rinse with pure water and air dry to obtain precursor B.

[0051] 3. Precursor B is placed in a muffle furnace and heat-treated at 400℃ for 5 hours. After removal, it is rinsed with pure water and air-dried to obtain crystalline tungsten trioxide electrocatalyst.

[0052] Since the introduction of platinum does not change the morphology of the core-shell tungsten trioxide support in step one, the morphology of the core-shell tungsten trioxide low-platinum electrocatalyst prepared in Example 1 was directly tested, and the test results are as follows: Figure 1 and Figure 2 As shown;

[0053] Figure 1 This is a scanning electron microscope (SEM) image of the core-shell structured tungsten trioxide low-platinum electrocatalyst prepared in Example 1. The surface morphology was observed and evaluated using a Carl Zeiss Gemini 560 scanning electron microscope at an accelerating voltage of 20 kV. As shown in the image, the surface morphology of the electrocatalyst material consists of a uniformly grown, vertically arranged array of nanoneedles on carbon cloth fibers. The nanoneedles have a length of 2.7 μm to 4.5 μm and a diameter of 0.3 μm to 1 μm. This structure helps to increase the effective contact area between the electrode and the electrolyte, promoting mass transfer during the electrochemical reaction process.

[0054] Figure 2 This is a high-resolution transmission electron microscope (HRTEM) image of the core-shell structured tungsten trioxide low-platinum electrocatalyst prepared in Example 1. As shown in the figure, the obtained material has a clear core-shell structure, namely a monoclinic WO3 core and an encapsulated amorphous outer shell of about 3.5 nm thickness.

[0055] Figure 3 The images show the X-ray photoelectron spectroscopy (XPS) spectra of the core-shell structured tungsten trioxide low-platinum electrocatalyst prepared in Example 1 and the crystalline tungsten trioxide electrocatalyst W 4f prepared in the comparative experiment. It can be seen that both the core-shell structured tungsten trioxide low-platinum electrocatalyst and the pure crystalline tungsten trioxide catalyst in the comparative sample exhibit typical W... 6+ Characteristic double peaks, corresponding to W4f 5 / 2 and W 4f 7 / 2 In pure crystalline tungsten trioxide catalysts, W 6+ The characteristic bimodal binding energies are located at approximately 35.6 eV and 37.7 eV; however, in the core-shell structured tungsten trioxide low-platinum electrocatalyst, the W 4f peak shifts overall towards lower binding energies by approximately 0.1 eV, with binding energies at approximately 35.5 eV and 37.6 eV, respectively. This negative shift indicates an increase in the electron cloud density of W, suggesting that the W sites in the core-shell structured tungsten trioxide low-platinum electrocatalyst have gained electrons, resulting in a change in the valence state environment and confirming the electron transfer process from Pt to W.

[0056] Figure 4 The images show the X-ray photoelectron spectroscopy (XPS) spectra of the core-shell structured tungsten trioxide low-platinum electrocatalyst prepared in Example 1 and the crystalline tungsten trioxide electrocatalyst Pt 4f prepared in the comparative experiment. In the core-shell structured tungsten trioxide low-platinum electrocatalyst, the Pt 4f spectrum can be fitted to indicate that it is mainly attributed to Pt. 4+ Characteristic peak (4f)7 / 2 Located at 75.5 eV, 4f 5 / 2 Located at 78.8 eV), with a small amount of Pt 2+ Species (72.6 eV); while in crystalline tungsten trioxide electrocatalysts, metallic Pt is the dominant species. 0 and Pt 4+ Coexistence is the dominant characteristic. In the core-shell structured tungsten trioxide low-platinum electrocatalyst, the valence state of Pt species is significantly increased, and the binding energy is relatively elevated, indicating that Pt loses electrons, further supporting the transfer of electrons from Pt to W. This electronic reconstruction effectively regulates the interfacial charge distribution and optimizes the hydrogen adsorption free energy, thereby significantly improving the catalyst's hydrogen evolution reaction activity and stability.

[0057] Figure 5 The polarization curves (LSVs) of the core-shell structured tungsten trioxide low-platinum electrocatalyst prepared in Example 1 and the crystalline tungsten trioxide electrocatalyst prepared in the comparative experiment are shown. A three-electrode system was tested using the electrocatalyst as the working electrode and a 0.5 mol / L H₂SO₄ solution as the electrolyte at a current density of 10 mA / cm². 2 Under certain conditions, the HER reaction of crystalline tungsten trioxide electrocatalyst requires an overpotential of 68 mV, while the HER reaction of core-shell tungsten trioxide low-platinum electrocatalyst requires only 33 mV, significantly reducing energy loss.

[0058] Figure 6 The stability curve of the core-shell structured tungsten trioxide low-platinum electrocatalyst prepared in Example 1 is shown below; the stability curve was measured using a potentiostatic chronometry method at a current density of 10 mA / cm². 2 Under these conditions, the hydrogen evolution reaction (HER) test was conducted continuously for 500 hours, and the material maintained stable performance throughout. The catalytic activity decay of the material was negligible, indicating that the prepared electrocatalyst material has excellent stability.

Claims

1. A method for preparing core-shell structured tungsten trioxide low-platinum electrocatalysts by pulsed Joule heating, characterized in that... It is done in the following steps:

1. Dissolve the tungsten source compound in water to obtain a suspension. Add a dispersant to the suspension and sonicate to obtain a precursor solution. Coat the precursor solution onto a conductive substrate and dry it to obtain the precursor. Perform pulse Joule heating on the precursor to obtain a core-shell structured tungsten trioxide carrier. The core-shell structured tungsten trioxide carrier has a core of crystalline tungsten trioxide and an outer shell of amorphous tungsten trioxide layer.

2. A platinum source solution is loaded onto the surface of a core-shell tungsten trioxide support, and then subjected to standing, washing and drying in sequence to obtain a core-shell tungsten trioxide low-platinum electrocatalyst.

2. The method for preparing core-shell structured tungsten trioxide low-platinum electrocatalysts by pulsed Joule heating according to claim 1, characterized in that... The tungsten source compound mentioned in step one is ammonium metatungstate, sodium tungstate, or tungstic acid; the dispersant mentioned in step one is ethanol or isopropanol; and the conductive substrate mentioned in step one is carbon cloth or titanium foam.

3. The method for preparing core-shell structured tungsten trioxide low-platinum electrocatalysts by pulsed Joule heating according to claim 1, characterized in that... The concentration of tungsten ions in the suspension mentioned in step one is 2 mol / L to 6 mol / L; the volume ratio of the dispersant to the suspension mentioned in step one is 1:(5~10).

4. The method for preparing core-shell structured tungsten trioxide low-platinum electrocatalysts by pulsed Joule heating according to claim 1, characterized in that... The ultrasonic treatment described in step one is specifically performed at an ultrasonic power of 100W~300W for 3min~5min.

5. The method for preparing core-shell structured tungsten trioxide low-platinum electrocatalysts by pulsed Joule heating according to claim 1, characterized in that... In step one, the coating amount is 0.1 mL / cm². 2 ~0.2mL / cm 2 The precursor solution is coated onto a conductive substrate and then dried at a temperature of 25℃~60℃ for 15min~45min to obtain the precursor.

6. The method for preparing core-shell structured tungsten trioxide low-platinum electrocatalyst by pulsed Joule heating according to claim 1, characterized in that... The pulse Joule heating treatment described in step one is carried out in the following steps: applying a DC voltage of 25V~35V and a current of 20A~30A to the conductive substrate, so that the precursor temperature reaches 1100℃~1300℃, and the treatment lasts for 5s~10s.

7. The method for preparing core-shell structured tungsten trioxide low-platinum electrocatalysts by pulsed Joule heating according to claim 1, characterized in that... The platinum source in the platinum source solution described in step two is chloroplatinic acid or platinum acetylacetonate.

8. The method for preparing core-shell structured tungsten trioxide low-platinum electrocatalysts by pulsed Joule heating according to claim 1, characterized in that... In the core-shell structured tungsten trioxide low-platinum electrocatalyst described in step two, Pt accounts for 0.1% to 0.3% of the total mass of Pt and W elements.

9. The method for preparing core-shell structured tungsten trioxide low-platinum electrocatalysts by pulsed Joule heating according to claim 1, characterized in that... The core-shell structured tungsten trioxide low-platinum electrocatalyst described in step two is vertically grown on a conductive substrate in the form of a nanoneedle array.

10. The method for preparing a core-shell structured tungsten trioxide low-platinum electrocatalyst by pulsed Joule heating according to claim 9, characterized in that... The nanoneedles have a length of 2.7 μm to 4.5 μm and a diameter of 0.3 μm to 1 μm.

Images