Surface-modified porous titanium diffusion layer, preparation method and application

Abstract

The invention discloses a surface-modified porous titanium diffusion layer which comprises a porous titanium substrate and a TiC coating growing on the surface of the porous titanium substrate in situ. The preparation method comprises the following steps: 1, carrying out heat treatment on the porous titanium substrate to obtain a TiO2 / Ti precursor; 2, embedding the TiO2 / Ti precursor by adopting titanium powder and polyethylene glycol powder, and then carrying out heat treatment; the invention further discloses application of the surface-modified porous titanium diffusion layer in a fuel cell and a water electrolysis device. The oxidized porous titanium substrate is embedded in the porcelain boat containing the polyethylene glycol powder and the titanium powder for heat treatment, so that the preparation temperature and the reaction time of the TiC coating are effectively reduced, the preparation process is simplified, and the surface-modified porous titanium diffusion layer with high conductivity and good corrosion resistance is obtained; the metal gas diffusion layer shows excellent performance in fuel cells and water electrolysis devices, and a technical route with low cost and large-scale feasibility is provided for surface modification of the metal gas diffusion layer.

Description

Technical Field

[0001] The invention belongs to the technical field of hydrogen energy, and in particular relates to a surface-modified porous titanium diffusion layer, a preparation method and an application thereof. Background Art

[0002] Hydrogen is considered an ideal energy carrier due to its zero pollution and high energy density. In the context of hydrogen economy, water electrolysis hydrogen production technology has become one of the efficient energy conversion processes for obtaining high-purity hydrogen fuel, and hydrogen energy will eventually be promoted through renewable energy conversion technologies such as fuel cells. As one of the core components in fuel cells and water electrolysis devices, metal-based gas diffusion layers usually need to be modified with precious metal (Ir or Pt) coatings on the porous titanium surface due to strong acidity and high oxidation potential working conditions to improve the conductivity and service life of the gas diffusion layer. However, there are problems such as large amount of precious metals used and high production costs.

[0003] In view of the high cost of surface coating technology for titanium diffusion layer components in current fuel cells and water electrolysis devices, it is urgent to develop low-cost, high-performance titanium porous transport layer surface modification technology. Titanium carbide (TiC) has high chemical stability and good conductivity. Surface modification of porous titanium substrates by titanium carbide coating is an effective and economical way to modify the surface of porous titanium diffusion layers. The traditional carbon thermal reduction of TiO2 requires high temperature (1700℃~2100℃) and long-term heat preservation (10h~24h), and the product is prone to problems such as large agglomeration and uneven particle shape.

[0004] Therefore, it is necessary to develop a surface modification technology with simple operation process and high-quality TiC coating under low reaction temperature and short reaction time conditions. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a surface-modified porous titanium diffusion layer in view of the deficiencies of the above-mentioned prior art. The method embeds the oxidized porous titanium substrate in a porcelain boat containing polyethylene glycol powder and titanium powder for heat treatment, effectively reducing the preparation temperature and reaction time of the TiC coating, simplifying the preparation process, and obtaining a surface-modified porous titanium diffusion layer with high conductivity and good corrosion resistance, thereby solving the problems of high temperature and long heat preservation time in the existing preparation process, which leads to easy agglomeration of the product and uneven particle shape.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is: a surface-modified porous titanium diffusion layer, characterized in that it includes a porous titanium substrate and a TiC coating grown in situ on the surface of the porous titanium substrate.

[0007] The above-mentioned surface-modified porous titanium diffusion layer is characterized in that the porous titanium substrate is a titanium mesh, sintered porous titanium, titanium felt or foamed titanium. The porous titanium diffusion layer of the present invention is applicable to a variety of substrates, which improves the practicability of the present invention.

[0008] At the same time, the present invention also discloses a method for preparing the surface-modified porous titanium diffusion layer as described above, characterized in that the method comprises the following steps:

[0009] Step 1, heat-treating the porous titanium substrate in air to obtain a TiO2 / Ti precursor;

[0010] Step 2: Use titanium powder and polyethylene glycol powder to embed the TiO2 / Ti precursor obtained in step 1 in a magnetic boat in the order of titanium powder-polyethylene glycol powder-TiO2 / Ti precursor-polyethylene glycol powder-titanium powder, and then place it in a tubular furnace for heat treatment in an inert atmosphere to form a surface-modified porous titanium diffusion layer.

[0011] During the heat treatment process of the present invention, firstly, the polyethylene glycol powder is thermally decomposed at a high temperature to produce a large amount of amorphous carbon, thereby providing a high-concentration reducing atmosphere for the TiO2 / Ti precursor. At the same time, the amorphous carbon produced by the decomposition of the polyethylene glycol powder is "locked" by the loose titanium powder, thereby prolonging the residence time of the amorphous carbon on the surface of the TiO2 / Ti precursor and ensuring the duration of the high-concentration reducing atmosphere. Under the continuous high-concentration reducing atmosphere, small-molecule amorphous carbon can quickly enter the TiO2 lattice of the TiO2 / Ti precursor, thereby effectively reducing the preparation temperature and reaction time of TiC and forming a surface-modified porous titanium diffusion layer with high conductivity and good corrosion resistance.

[0012] The above method is characterized in that the temperature of the heat treatment in step 1 is 300°C to 600°C and the heat treatment time is 2h to 10h. The present invention controls the thickness of the TiO2 oxide layer in the TiO2 / Ti precursor by controlling the temperature and time of the heat treatment oxidation.

[0013] The above method is characterized in that the molecular weight of the polyethylene glycol powder in step 2 is 2000 to 10000. Since the interaction between high molecular weight polyethylene glycol molecules is strong, the polyethylene glycol with a higher molecular weight has a higher decomposition temperature. The present invention controls the high molecular weight of the polyethylene glycol powder to ensure that it is thermally decomposed in large quantities at high temperatures to produce high-concentration amorphous carbon, which is used in the reduction process of the TiO2 oxide layer in the TiO2 / Ti precursor.

[0014] The above method is characterized in that the inert atmosphere in step three is nitrogen or argon.

[0015] The above method is characterized in that the heat treatment process described in step 2 is: firstly heating to 350°C at a heating rate of 5°C / min and keeping it for 1h, and then heating to 700°C-1000°C at a heating rate of 10°C / min and keeping it for 2h-8h. The present invention controls the heating rate, reaction temperature and time during the heat treatment process to regulate the thickness of the TiC coating in the surface-modified porous titanium diffusion layer and the particle size of the particles in the coating; as the temperature increases and the insulation time increases, the thickness of the TiC coating increases and the particle size in the coating gradually increases, thereby obtaining a surface-modified porous titanium diffusion layer with different roughness, different conductivity and different corrosion resistance.

[0016] At the same time, the present invention also discloses an application of the surface-modified porous titanium diffusion layer in a fuel cell and a water electrolysis device.

[0017] Compared with the prior art, the present invention has the following advantages:

[0018] 1. The present invention embeds the TiO2 / Ti precursor obtained after heat treatment and oxidation in a porcelain boat containing polyethylene glycol powder and titanium powder for heat treatment, and uses the amorphous carbon produced by the decomposition of the polyethylene glycol powder as a carbon source to provide a continuous high-concentration reducing atmosphere for the reduction of TiO2, thereby improving the uniformity of the TiC coating grown in situ on the surface of the porous titanium substrate, effectively reducing the preparation temperature and reaction time of the TiC coating, and obtaining a surface-modified porous titanium diffusion layer with high conductivity and good corrosion resistance, thereby greatly simplifying the preparation process.

[0019] 2. The preparation method of the present invention only involves a simple heat treatment process and is simple to operate, providing a low-cost and scalable technical route for surface modification of metal gas diffusion layers.

[0020] 3. The surface-modified porous titanium diffusion layer prepared by the present invention has high conductivity and good corrosion resistance, and exhibits excellent performance in fuel cells and water electrolysis devices.

[0021] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is the XRD pattern of the surface-modified porous titanium diffusion layer prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0023] Example 1

[0024] The surface-modified porous titanium diffusion layer of this embodiment includes sintered porous titanium with a thickness of 0.5 mm and a TiC coating layer grown in situ on the surface of the sintered porous titanium, and the porosity of the sintered porous titanium is 28%.

[0025] The preparation method of the surface-modified porous titanium diffusion layer of this embodiment comprises the following steps:

[0026] Step 1: heat-treating 0.5 mm thick sintered porous titanium in air at 400° C. for 4 h to obtain a TiO2 / Ti precursor;

[0027] Step 2: Use titanium powder and polyethylene glycol powder with a molecular weight of 4000 to embed the TiO2 / Ti precursor obtained in step 1 in a magnetic boat in the order of titanium powder-polyethylene glycol powder-TiO2 / Ti precursor-polyethylene glycol powder-titanium powder, and then place it in a tubular furnace for heat treatment in argon: first heat to 350°C at a heating rate of 5°C / min and keep warm for 1h, then heat to 800°C at a heating rate of 10°C / min and keep warm for 4h to form a surface-modified porous titanium diffusion layer.

[0028] Figure 1 The XRD pattern of the surface-modified porous titanium diffusion layer prepared in this embodiment is shown in FIG. Figure 1 It can be seen that by analyzing the diffraction peak positions, it is determined that the phase of the surface-modified porous titanium diffusion layer is composed of close-packed hexagonal structure Ti (PDF#44-1294) and face-centered cubic structure TiC (PDF#32-1383), without other impurity phases.

[0029] Example 2

[0030] The surface-modified porous titanium diffusion layer of this embodiment includes a titanium felt with a thickness of 0.25 mm and a TiC coating layer grown in situ on the surface of the titanium felt, and the porosity of the titanium felt is 65%.

[0031] The preparation method of the surface-modified porous titanium diffusion layer of this embodiment comprises the following steps:

[0032] Step 1: heat-treating a titanium felt having a thickness of 0.25 mm in air at 300° C. for 10 h to obtain a TiO2 / Ti precursor;

[0033] Step 2: Use titanium powder and polyethylene glycol powder with a molecular weight of 2000 to embed the TiO2 / Ti precursor obtained in step 1 in a magnetic boat in the order of titanium powder-polyethylene glycol powder-TiO2 / Ti precursor-polyethylene glycol powder-titanium powder, and then place it in a tubular furnace for heat treatment in argon: first heat to 350°C at a heating rate of 5°C / min and keep warm for 1h, then heat to 1000°C at a heating rate of 10°C / min and keep warm for 2h to form a surface-modified porous titanium diffusion layer.

[0034] Example 3

[0035] The surface-modified porous titanium diffusion layer of this embodiment includes a titanium mesh with a thickness of 1 mm and a TiC coating layer grown in situ on the surface of the titanium mesh, and the porosity of the titanium mesh is 50%.

[0036] The preparation method of the surface-modified porous titanium diffusion layer of this embodiment comprises the following steps:

[0037] Step 1: heat-treating a titanium mesh with a thickness of 1 mm in air at 500° C. for 8 h to obtain a TiO2 / Ti precursor;

[0038] Step 2: Use titanium powder and polyethylene glycol powder with a molecular weight of 8000 to embed the TiO2 / Ti precursor obtained in step 1 in a magnetic boat in the order of titanium powder-polyethylene glycol powder-TiO2 / Ti precursor-polyethylene glycol powder-titanium powder, and then place it in a tubular furnace for heat treatment in nitrogen: first heat to 350°C at a heating rate of 5°C / min and keep warm for 1h, then heat to 700°C at a heating rate of 10°C / min and keep warm for 8h to form a surface-modified porous titanium diffusion layer.

[0039] Example 4

[0040] The surface-modified porous titanium diffusion layer of this embodiment includes 2 mm thick titanium foam and a TiC coating layer grown in situ on the surface of the titanium foam, and the porosity of the titanium foam is 55%.

[0041] The preparation method of the surface-modified porous titanium diffusion layer of this embodiment comprises the following steps:

[0042] Step 1: heat-treating 2 mm thick titanium foam in air at 600°C for 2 h to obtain a TiO2 / Ti precursor;

[0043] Step 2: Use titanium powder and polyethylene glycol powder with a molecular weight of 10,000 to embed the TiO2 / Ti precursor obtained in step 1 in a magnetic boat in the order of titanium powder-polyethylene glycol powder-TiO2 / Ti precursor-polyethylene glycol powder-titanium powder, and then place it in a tubular furnace for heat treatment in nitrogen: first heat to 350°C at a heating rate of 5°C / min and keep warm for 1h, then heat to 800°C at a heating rate of 10°C / min and keep warm for 5h to form a surface-modified porous titanium diffusion layer.

[0044] The above is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent change made to the above embodiment according to the technical essence of the invention still falls within the protection scope of the technical solution of the present invention.

Claims

1. A surface-modified porous titanium diffusion layer, characterized in that: The invention comprises a porous titanium substrate and a TiC coating in-situ grown on the surface of the porous titanium substrate.

2. The surface-modified porous titanium diffusion layer according to claim 1, characterized in that: The porous titanium substrate is titanium mesh, sintered porous titanium, titanium felt or foamed titanium.

3. A method for preparing a surface-modified porous titanium diffusion layer as claimed in claim 1 or 2, characterized in that: The method comprises the following steps: Step 1, heat-treating the porous titanium substrate in air to obtain a TiO2 / Ti precursor; Step 2: Use titanium powder and polyethylene glycol powder to embed the TiO2 / Ti precursor obtained in step 1 in a magnetic boat in the order of titanium powder-polyethylene glycol powder-TiO2 / Ti precursor-polyethylene glycol powder-titanium powder, and then place it in a tubular furnace for heat treatment in an inert atmosphere to form a surface-modified porous titanium diffusion layer.

4. The method according to claim 3, characterized in that The heat treatment temperature in step 1 is 300° C. to 600° C., and the heat treatment time is 2 h to 10 h.

5. The method according to claim 3, characterized in that: The molecular weight of the polyethylene glycol powder in step 2 is 2000-10000.

6. The method according to claim 3, characterized in that The inert atmosphere in step 3 is nitrogen or argon.

7. The method according to claim 3, characterized in that The heat treatment process in step 2 is: firstly heat to 350°C at a heating rate of 5°C / min and keep warm for 1 hour, then heat to 700°C-1000°C at a heating rate of 10°C / min and keep warm for 2h-8h.

8. Use of the surface-modified porous titanium diffusion layer according to claim 1 or 2 in fuel cells and water electrolysis devices.

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