CN116575057A - Modified porous diffusion layer, preparation method thereof and electrolytic cell - Google Patents
Modified porous diffusion layer, preparation method thereof and electrolytic cell Download PDFInfo
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Classifications
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- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
- C25B1/00—Electrolytic production of inorganic compounds or non-metals
- C25B1/01—Products
- C25B1/02—Hydrogen or oxygen
- C25B1/04—Hydrogen or oxygen by electrolysis of water
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
- C25B11/00—Electrodes; Manufacture thereof not otherwise provided for
- C25B11/02—Electrodes; Manufacture thereof not otherwise provided for characterised by shape or form
- C25B11/03—Electrodes; Manufacture thereof not otherwise provided for characterised by shape or form perforated or foraminous
- C25B11/031—Porous electrodes
- C25B11/032—Gas diffusion electrodes
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
- C25B9/00—Cells or assemblies of cells; Constructional parts of cells; Assemblies of constructional parts, e.g. electrode-diaphragm assemblies; Process-related cell features
- C25B9/17—Cells comprising dimensionally-stable non-movable electrodes; Assemblies of constructional parts thereof
- C25B9/19—Cells comprising dimensionally-stable non-movable electrodes; Assemblies of constructional parts thereof with diaphragms
Abstract
The application relates to a modified porous diffusion layer, a preparation method thereof and an electrolytic cell, wherein the modified porous diffusion layer comprises the following components: a substrate; the base layer is covered on the surface of the base material, the material of the base layer comprises at least one of a first metal oxide and an alloy, the metal element in the first metal oxide comprises at least one of Nb, ta, hf and Ti, and the metal element in the alloy comprises at least two of Nb, ta, au, pt, hf and Ti; the surface layer is covered on the surface of one side of the bottom layer, which is far away from the base material, the material of the surface layer comprises a second metal oxide, the second metal oxide contains nonmetallic doping elements, and the thermal expansion coefficient of the bottom layer is between the thermal expansion coefficient of the porous base material and the thermal expansion coefficient of the surface layer.
Description
Technical Field
The application relates to the technical field of porous diffusion layer coatings of electrolytic cells, in particular to a modified porous diffusion layer, a preparation method thereof and an electrolytic cell.
Background
Traditional fossil fuel (coal, oil, natural gas, etc.) combustion has caused serious environmental pollution and global warming and other problems, and these energy sources are not sustainable in the future and cannot solve the fundamental contradiction. Clean energy sources such as hydrogen energy and the like have easy availability and high energy density, and are the best choice for replacing energy sources. The proton exchange membrane electrolyzed water (Proton Exchange Membrane water electrolysis, PEMWE) has the characteristics of compact structure, high hydrogen production efficiency and the like, and is considered to be the most potential electrolyzed water hydrogen production technology. PEMWE generates hydrogen gas precipitation (HER) reaction at a cathode and oxygen gas precipitation (OER) reaction at an anode through the action of an external potential and a catalyst, so that high-purity hydrogen energy is generated.
Porous diffusion layers (PTL), sometimes also referred to as liquid/gas diffusion layers (LGDL), are one of the key components of PEMWE cells, in which the PTL is located between the flow field and the catalyst layer. They provide electrical conductivity and water/gas transport, and therefore, the porous diffusion layers should have suitable electrical conductivity, thermal conductivity, mechanical strength, water/gas transport efficiency, and corrosion resistance, while the porous diffusion layers should also remain in interfacial contact with adjacent components. In addition, as the anode of the PEMWE has high potential, acidic environment, high temperature and other corrosion environments, the problem of contact resistance rise caused by corrosion of the porous diffusion layer can be accelerated in the use process of the electrolytic cell, and the incomplete infiltration of the porous diffusion layer can cause certain mass transfer resistance at the anode, so that the service life of the PEMWE is greatly limited. It is therefore necessary to develop a hydrophilic, electrically conductive, corrosion resistant porous diffusion layer coating.
Therefore, how to increase the service life of the porous diffusion layer is a critical issue for the electrolytic cell industry.
Disclosure of Invention
In view of the above, the application provides a modified porous diffusion layer, a preparation method thereof and an electrolytic cell, which can improve the conductivity, corrosion resistance, hydrophilicity of the porous diffusion layer, the binding force between a coating and a porous substrate and the deposition uniformity of the coating in the porous substrate, thereby prolonging the service life of the porous diffusion layer.
In a first aspect, embodiments of the present application provide a modified porous diffusion layer comprising:
a porous substrate;
the bottom layer is covered on the surface of the porous substrate, the material of the bottom layer comprises at least one of a first metal oxide and an alloy, the metal element in the first metal oxide comprises at least one of Nb, ta, hf and Ti, and the metal element in the alloy comprises at least two of Nb, ta, au, pt, hf and Ti;
the surface layer is covered on the surface of one side of the bottom layer, which is far away from the porous substrate, and the material of the surface layer comprises a second metal oxide which contains nonmetallic doping elements;
wherein the bottom layer has a coefficient of thermal expansion that is between the coefficient of thermal expansion of the porous substrate and the coefficient of thermal expansion of the surface layer.
In some embodiments, the modified porous diffusion layer includes at least one of the following features (1) - (3):
(1) The nonmetallic doping elements include at least one of S, N and P;
(2) The atom ratio of the nonmetallic doping element in the surface layer is 5at% -20 at%;
(3) The second metal oxide includes at least one of titanium oxide and niobium oxide.
In some embodiments, the modified porous diffusion layer includes at least one of the following features (1) - (5):
(1) The first metal oxide comprises TiO 2 、Nb 2 O 5 、HfO 2 And Ta 2 O 5 At least one of (a) and (b);
(2) The alloy comprises at least one of Nb-Ti alloy, ta-Ti alloy, hf-Ta alloy, ti-Au alloy and Ti-Pt alloy;
(3) The thickness of the bottom layer is 50 nm-5 mu m;
(4) The thickness of the surface layer is 10 nm-1 mu m;
(5) The porous substrate is made of at least one of titanium, titanium alloy and doped titanium.
In some embodiments, the contact resistance of the substrate is less than 2mΩ cm at a pressure of 1.4MPa 2 。
In some embodiments, the skin layer has a contact resistance of less than 2mΩ cm at a pressure of 1.4MPa 2 。
In some embodiments, the surface layer has a water contact angle of less than 40 °.
In some embodiments, the modified porous diffusion layer includes at least one of the following features (1) - (3):
(1) The thermal expansion coefficient of the porous substrate is 8E -6 /K～10E -6 /K；
(2) The thermal expansion coefficient of the bottom layer is 6E -6 /K～9E -6 /K；
(3) The thermal expansion coefficient of the surface layer is 5E -6 /K～7E -6 /K。
In some embodiments, the porous substrate is a porous fibrous substrate, the surface of the porous substrate in contact with the bottom layer has a region of thickness of 2mm, and the thickness variation of the filling thickness of the bottom layer and the surface layer in the region is less than 10%.
In a second aspect, an embodiment of the present application provides a method for preparing a modified porous diffusion layer, including the steps of:
providing a porous substrate;
providing a first metal oxide and/or an alloy, wherein metal elements in the first metal oxide comprise at least one of Nb, ta, hf and Ti, metal elements in the alloy comprise at least two of Nb, ta, au, pt, hf and Ti, and soaking the porous substrate by adopting a salt solution of the first metal oxide and/or the alloy and performing first deposition treatment to obtain a bottom layer coated on the surface of the porous substrate;
providing a second metal oxide, wherein the second metal oxide contains non-metal doping elements, and carrying out second deposition treatment and heat treatment on the bottom layer covered on the surface of the porous substrate by adopting the second metal oxide to obtain the modified porous diffusion layer.
In a third aspect, an embodiment of the present application further provides an electrolytic cell, including the modified porous diffusion layer according to the first aspect or the modified porous diffusion layer prepared by the preparation method according to the second aspect.
The technical scheme of the application has at least the following beneficial effects:
the bottom layer is arranged between the porous base material and the surface layer, and the thermal expansion coefficient of the bottom layer is arranged between the thermal expansion coefficient of the porous base material and the thermal expansion coefficient of the surface layer, so that the porous base material, the bottom layer and the surface layer form a gradient transition structure, the structure can reduce the internal stress of the second metal oxide surface layer and the porous base material, and the distribution uniformity of the composite coating formed by the bottom layer and the surface layer on the surface of the porous base material and the binding force of the composite coating formed by the bottom layer and the surface layer and the porous base material are improved. In addition, the first metal oxide of at least one of Nb, ta, hf and Ti and/or the alloy containing at least two metal elements of Nb, ta, au, pt, hf and Ti is/are used as a bottom layer, and Nb, ta, hf and Ti are low in price compared with noble metals such as Au, ag and the like, are high in stability compared with metals such as Ni, cr and Mn and the like, and are not easy to corrode in high-potential, acidic environment and high-temperature environment, so that the corrosion resistance of the modified porous diffusion layer in use can be improved. The second metal oxide of the nonmetallic doping element serves as a surface layer, which can secure corrosion resistance while having good adsorption ability to a liquid (e.g., water), thereby being capable of improving hydrophilicity of the modified porous diffusion layer. According to the modified porous diffusion layer, the bottom layer and the surface layer are in synergistic effect, so that the contact resistance of the porous diffusion layer can be reduced, meanwhile, the wettability of liquid to the porous diffusion layer can be improved, the hydrophilicity and the distribution uniformity of the modified porous diffusion layer are improved, and the service life of the modified porous diffusion layer is prolonged.
Drawings
For a clearer description of embodiments of the application or of the prior art, the drawings that are used in the description of the embodiments or of the prior art will be briefly described, it being apparent that the drawings in the description below are only some embodiments of the application, and that other drawings can be obtained from them without inventive effort for a person skilled in the art.
FIG. 1 is a schematic diagram of the structure of a modified porous diffusion layer of the present application;
FIG. 2 is a cross-sectional view of a modified porous diffusion layer prepared in example 1 of the present application;
FIG. 3 is a cross-sectional elemental analysis chart of a modified porous diffusion layer coating prepared in example 1 of the present application;
FIG. 4 is a graph showing the corrosion of the modified porous diffusion layer prepared in example 1 of the present application before and after the corrosion;
FIG. 5 is a graph showing the contact resistance of the modified porous diffusion layer prepared in example 1 of the present application before and after etching.
In the figure:
1-a surface layer;
2-a bottom layer;
3-porous substrate.
Detailed Description
For a better understanding of the technical solution of the present application, the following detailed description of the embodiments of the present application refers to the accompanying drawings.
It should be understood that the described embodiments are merely some, but not all, embodiments of the application. All other embodiments, which can be made by those skilled in the art based on the embodiments of the application without making any inventive effort, are intended to be within the scope of the application.
The terminology used in the embodiments of the application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used in this application and the appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.
It should be understood that the term "and/or" as used herein is merely one relationship describing the association of the associated objects, meaning that there may be three relationships, e.g., a and/or B, may represent: a exists alone, A and B exist together, and B exists alone. In addition, the character "/" herein generally indicates that the front and rear associated objects are an "or" relationship.
At present, the porous diffusion layer material is fibrous titanium, namely titanium felt, and the preparation process of the titanium felt is usually a fibrous porous material formed by sintering or spraying, which provides a passage for reactant water for a catalytic layer and an ion passage for generated product gas in an electrolytic tank, so that the porosity and the ventilation water capability of the porous diffusion layer material become important performance indexes of the porous diffusion layer, however, the current preparation process of the porous diffusion layer cannot ensure the uniformity and the hydrophobicity of the surface of the material, so that the porous diffusion layer cannot meet the requirement of maintaining good hydrophilic characteristics (good reactant passage and product leaving passage) on the basis of electric conduction and corrosion resistance, and cannot ensure the drainage and exhaust performance of the surface of the porous diffusion layer. In addition, carbonization and oxidation of the porous diffusion layer during the high temperature process under the use conditions also reduce the corrosion resistance of the porous diffusion layer under acidic conditions, and thus, it is now highly desirable to provide a modified diffusion layer having better conductive corrosion resistance and excellent hydrophilicity.
In view of this, the applicant proposes a modified porous diffusion layer, as shown in fig. 1, which is a schematic structural diagram of the modified porous diffusion layer according to an embodiment of the present application, where the modified porous diffusion layer includes:
a porous substrate 3;
a bottom layer 2 covered on the surface of the porous substrate 3, wherein the material of the bottom layer 2 comprises at least one of a first metal oxide and an alloy, the metal element in the first metal oxide comprises at least one of Nb, ta, hf and Ti, and the metal element in the alloy comprises at least two of Nb, ta, au, pt, hf and Ti;
the surface layer 1 is covered on the surface of one side of the bottom layer 2, which is far away from the porous substrate 3, and the material of the surface layer 1 comprises a second metal oxide which contains nonmetallic doping elements;
wherein the thermal expansion coefficient of the bottom layer 2 is between the thermal expansion coefficient of the porous substrate 3 and the thermal expansion coefficient of the surface layer 1.
In the above scheme, the bottom layer 2 is between the porous substrate 3 and the surface layer 1, and the thermal expansion coefficient of the bottom layer 2 is between the thermal expansion coefficient of the porous substrate 3 and the thermal expansion coefficient of the surface layer 1, so that the porous substrate 3, the bottom layer 2 and the surface layer 1 form a gradient transition structure, and the structure can reduce the internal stress of the second metal oxide surface layer 1 and the porous substrate 3, thereby being beneficial to improving the distribution uniformity of the composite coating formed by the bottom layer 2 and the surface layer 1 on the surface of the porous substrate 3 and the bonding force of the composite coating formed by the bottom layer and the surface layer and the porous substrate 3. In addition, the first metal oxide of at least one of Nb, ta, hf and Ti and/or the alloy containing at least two metal elements of Nb, ta, au, pt, hf and Ti is/are used as the underlayer 2, and Nb, ta, hf and Ti are less expensive than noble metals such as Au, ag and the like, are more stable than metals such as Ni, cr and Mn and are less likely to be corroded in high potential, acidic environment and high temperature environment, so that the corrosion resistance of the modified porous diffusion layer in use can be improved. The second metal oxide of the nonmetallic doping element, which is the surface layer 1, can secure corrosion resistance while having good adsorption ability to a liquid (e.g., water), so that the hydrophilicity of the modified porous diffusion layer can be improved. According to the modified porous diffusion layer, the bottom layer 2 and the surface layer 1 are in synergistic effect, so that the contact resistance of the porous diffusion layer can be reduced, meanwhile, the wettability of liquid to the porous diffusion layer can be improved, the hydrophilicity and the distribution uniformity of the modified porous diffusion layer are improved, and the service life of the modified porous diffusion layer is prolonged.
In the present application, the metal oxide of the nonmetallic doping element is formed by substituting an oxygen atom in the metal oxide with a nonmetallic element.
In some embodiments, if the first metal oxide and the second metal oxide are the same, the modified porous diffusion layer may be considered as a single layer coating structure disposed on the surface of the porous substrate 3.
In some embodiments, the nonmetallic doping elements include at least one of S, N and P. The non-polarity of the N element, the S element and the P element is greater than that of O, so that the N element, the S element and the P element replace the oxygen element in the second metal oxide, and the hydrophilicity of the porous diffusion layer can be improved.
In some embodiments, the atomic ratio of the nonmetallic doping element in the surface layer 1 is 5at% to 20at%, specifically, may be 5at%, 8at%, 10at%, 12at%, 15at%, 18at%, or 20at%, etc., and of course, may be other values within the above range. If the atomic ratio of the nonmetallic doping element in the surface layer 1 is less than 5at%, the conductivity of the porous diffusion layer is insufficient, and the contact angle adjustment degree is poor; if the atomic ratio of the nonmetallic doping element in the surface layer 1 is more than 20at%, the corrosion resistance of the material is reduced, so that the porous diffusion layer is easy to corrode and lose under the high-potential use condition.
In some embodiments, the second metal oxide comprises at least one of titanium oxide and niobium oxide.
In some embodiments, the first metal oxide comprises TiO 2 、Nb 2 O 5 、HfO 2 And Ta 2 O 5 At least one of them.
In some embodiments, the alloy includes at least one of a Nb-Ti alloy, a Ta-Ti alloy, a Hf-Ta alloy, a Ti-Au alloy, and a Ti-Pt alloy.
In some embodiments, the thickness of the underlayer 2 is 50nm to 5 μm, specifically 50nm, 100nm, 500nm, 800nm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, etc., but other values within the above range are also possible.
In some embodiments, the thickness of the surface layer 1 is 10nm to 1 μm, specifically 10nm, 50nm, 100nm, 300nm, 500nm, 800nm, 1 μm, or the like, but other values within the above range are also possible.
In some embodiments, the material of the substrate 1 includes pure titanium plate, titanium alloy and doped titanium. The doped titanium is a doped alloy material formed by various other metal elements and titanium, and other elements can be Ni, co, mn and the like.
In some embodiments, the substrate 1 with the underlayer 2 is tested electrochemically for corrosion conductivity, and the results indicate that the underlayer 2 has a contact resistance of less than 2mΩ cm at a pressure of 1.4MPa 2 Specifically, it may be 0.5mΩcm 2 、0.8mΩcm 2 、1mΩcm 2 、1.2mΩcm 2 、1.5mΩcm 2 、1.7mΩcm 2 Or 1.9mΩ cm 2 And the like, but may be other values within the above range.
In some embodiments, the corrosion conductivity of the skin layer 1 is tested electrochemically under the following conditions: 2.5Vvs. NHE (Standard calomel electrode), which shows that the contact resistance of the surface layer 1 at 1.4MPa is less than 2mΩ cm 2 Specifically, it may be 0.5mΩ cm 2 、0.8mΩcm 2 、1mΩcm 2 、1.2mΩcm 2 、1.5mΩcm 2 、1.7mΩcm 2 Or 1.9mΩ cm 2 And the like, but may be other values within the above range.
In summary, the composite coating formed by the surface layer and the bottom layer has excellent corrosion resistance.
In some embodiments, the contact angle measurement is performed by using a contact angle measuring instrument, and the result shows that the water contact angle of the surface layer 1 of the present application is less than 40 °, specifically may be 20 °, 23 °, 25 °, 28 °, 32 °, 35 °, 38 ° or 39 °, and may of course be other values within the above range. In the above-mentioned limit range, it shows that the surface layer of the application has a lower contact angle, which can be the formation of a water film, so that the modified porous diffusion layer can be quickly infiltrated in the use process, the reactant can enter the surface of the catalyst through the porous diffusion layer, the drainage and exhaust treatment capacity of the surface of the porous diffusion layer is improved, and the problem of insufficient reactant supply under high electric density is solved.
In some embodiments, the modified porous diffusion layer is potentiostatic tested using an electrochemical workstation, corroding the media: sulfuric acid with pH value of 3, test potential of not less than 2.5V, polarization time of not less than 100h, determination:
the modified porous diffusion layer has a corrosion current density of less than 1 μA/cm 2 Specifically, it may be 0.2. Mu.A/cm 2 、0.3μA/cm 2 、0.4μA/cm 2 、0.5μA/cm 2 、0.6μA/cm 2 、0.7μA/cm 2 、0.8μA/cm 2 Or 0.9. Mu.A/cm 2 Etc. of course, it may also be within the above-mentioned rangeHis value.
The contact resistance of the modified porous diffusion layer after corrosion under the pressure of 1.4MPa is less than 3mΩ cm 2 Specifically, it may be 0.5mΩ cm 2 、1mΩcm 2 、1.5mΩcm 2 、1.8mΩcm 2 、2.2mΩcm 2 、2.5mΩcm 2 Or 2.8mΩ cm 2 And the like, but may be other values within the above range.
The water contact angle of the modified porous diffusion layer is less than 40 °, specifically, 20 °, 23 °, 25 °, 28 °, 32 °, 35 °, 38 °, 39 °, or the like, but other values within the above range are also possible.
In some embodiments, the porous substrate 3 has a coefficient of thermal expansion of 8E -6 /K～10E -6 K, which may be in particular 8E -6 /K、8.5E -6 /K、9E -6 /K、9.5E -6 K or 10E -6 K, etc., but may be any other value within the above range.
In some embodiments, the bottom layer 2 has a coefficient of thermal expansion of 6E -6 /K～9E -6 K, which may be in particular 6E -6 /K、6.5E -6 /K、7E -6 /K、7.5E -6 /K、8E -6 /K、8.5E -6 /K or 9E -6 K, etc., but may be any other value within the above range.
In some embodiments, the skin layer 1 has a coefficient of thermal expansion of 5E -6 /K～7E -6 K, which may be in particular 5E -6 /K、5.5E -6 /K、6E -6 /K、6.5E -6 K or 7E -6 K, etc., but may be any other value within the above range.
In some embodiments, the porous substrate 3 is a porous fibrous substrate, the surface of the porous substrate 3 contacting the bottom layer 2 has a region with a thickness of 2mm, the thickness deviation of the filling thickness of the bottom layer 2 and the surface layer 1 in the region is less than 10%, specifically, the thickness deviation of the filling thickness of the bottom layer 2 and the surface layer 1 in the region may be 1%, 3%, 5%, 8%, etc. The thickness deviation of the filling thickness of the base layer 2 and the surface layer 1 in the above-described region means: the surface of the porous substrate 3 in contact with the under layer 2 is exemplified by a region of the surface having a thickness of 2mm at four corners thereof as a measurement region, the filling thickness of the under layer 2 and the surface layer 1 in the above region is measured, the thicknesses H1, H2, H3 … … of at least 10 different portions are measured, the average value of the thicknesses of the above different portions is calculated as X (mm), and the result calculated by the formula (2-X)/2 is the thickness deviation. The thickness deviation of the porous base material is within the above-mentioned limit range, which shows that the composite coating formed by the bottom layer 2 and the surface layer 1 can be embedded into the surface porous fiber of the porous fiber base material, and the thickness distribution in the surface porous fiber is uniform, which is beneficial to improving the hydrophilicity of the inside of the porous diffusion layer, reducing the resistance of the water solution diffusing from the outer surface of the porous diffusion layer to the inside, and realizing the rapid passing of water. The prior modified porous diffusion layer is formed by overlapping fibers, pores among fiber materials are smaller, a conventional physical vapor deposition process is adopted for deposition coating on the surface of the porous fiber base material, and the conventional physical vapor deposition process is concentrated on the surface for film forming, so that the porous fiber on the surface of the porous fiber base material cannot be filled to obtain a coating with uniform thickness.
The embodiment of the application provides an electrolytic cell, which comprises the modified porous diffusion layer. The modified porous diffusion layer is applied to the electrolytic cell, so that the stability of the electrolytic cell in an electrochemical corrosion environment is improved, the high potential resistance capability of the electrolytic cell can be enhanced, and the service life of the electrolytic cell is prolonged.
The embodiment of the application provides a preparation method of the modified porous diffusion layer, which comprises the following steps:
s100, providing a porous substrate 3;
s200, providing a first metal oxide and/or an alloy, wherein the metal element in the first metal oxide comprises at least one of Nb, ta, hf and Ti, the metal element in the alloy comprises at least two of Nb, ta, au, pt, hf and Ti, and the porous substrate 3 is subjected to soaking treatment and first deposition treatment by adopting a salt solution of the first metal oxide and/or the alloy to obtain a bottom layer 2 coated on the surface of the porous substrate 3;
s300, providing a second metal oxide, wherein the second metal oxide contains nonmetallic doping elements, and carrying out second deposition treatment and heat treatment on the bottom layer 2 covered on the surface of the porous substrate 3 by adopting the second metal oxide to obtain the modified porous diffusion layer.
In the scheme, the porous base material 3 is used as the substrate, and the bottom layer 2 and the surface layer 1 are sequentially deposited on the surface of the porous base material 3, so that the prepared modified porous diffusion layer is not easy to corrode in high potential, acidic environment and high temperature environment, and the corrosion resistance of the modified porous diffusion layer in the use process can be improved. The second metal oxide of the nonmetallic doping element is deposited on the surface of the underlayer 2, which can secure corrosion resistance while having good adsorption ability to a liquid (e.g., water), thereby being capable of improving the hydrophilicity of the modified porous diffusion layer. In addition, before the first deposition treatment, the salt solution of the first metal oxide and/or alloy is adopted for soaking treatment, so that liquid phase molecules of the salt solution enter the porous diffusion layer, the surface of the porous substrate 3 is provided with a bottom layer 2 capable of being processed and grown, and further, after the second deposition treatment, the heat treatment is carried out, so that the ordering and the homogenization of phases of the surface layer 1 and the bottom layer 2 can be enhanced, and the thickness uniformity and the comprehensive performance of the modified porous diffusion layer are improved. In a word, the bottom layer 2 and the surface layer 1 of the modified porous diffusion layer of the application cooperate to reduce the contact resistance of the porous diffusion layer, and simultaneously promote the wettability of liquid to the porous diffusion layer, and promote the hydrophilicity and the distribution uniformity of the modified porous diffusion layer, thereby prolonging the service life of the modified porous diffusion layer.
The preparation method of the present application will be described in detail below according to specific preparation steps.
S100, providing a porous substrate 3.
In some embodiments, the porous substrate 3 comprises at least one of pure titanium plate, titanium alloy and doped titanium. The doped titanium is a doped alloy material formed by various other metal elements and titanium, and other elements can be Ni, co, mn and the like.
In some embodiments, the step of surface treating the porous substrate 3 is further included after providing the porous substrate 3, specifically including: the surface of the porous substrate 3 is subjected to plasma cleaning, the plasma cleaning includes at least one of ion source cleaning, high-voltage discharge cleaning, radio frequency cleaning and bias cleaning, the specific parameters of the plasma cleaning are not limited in the application, and a person skilled in the art can perform treatment according to conventional parameters, and the surface of the porous substrate 3 is treated to remove impurity oxides, grease, surface fragments and the like on the surface of the porous substrate 3, so that the surface roughness of the porous substrate 3 is increased, and the subsequent bonding performance between the coating and the porous substrate 3 is improved.
S200, providing a first metal oxide and/or an alloy, wherein a metal element in the first metal oxide comprises at least one of Nb, ta, hf and Ti, a metal element in the alloy comprises at least two of Nb, ta, au, pt, hf and Ti, and performing soaking treatment and first deposition treatment on the porous substrate 3 by adopting a salt solution of the first metal oxide and/or the alloy to obtain a bottom layer 2 coated on the surface of the porous substrate 3.
In some embodiments, when the feedstock for the first deposition process includes a first metal oxide, the process of the first deposition process includes at least one of electrodeposition and micro-arc oxidation (microplasma oxidation), and illustratively, the first metal oxide is deposited on the surface of the porous substrate 3 by electrodeposition: soaking the porous substrate 3 in a salt solution (pH is controlled to be 5-10) containing a first metal oxide for 3h or more, then taking the salt solution of the first metal oxide as a negative electrode, taking a graphite rod as a positive electrode, controlling the deposition current to be 0.01 mA-2A, and the deposition time to be 5 min-120 min, and after deposition, placing the obtained product into a high-temperature furnace, and treating for 30 min-24 h at 400-1200 ℃ to obtain the bottom layer 2.
In some embodiments, when the feedstock for the first deposition process comprises an alloy, the process of the first deposition process comprises at least one of magnetron sputtering, electrodeposition, medium frequency sputtering, radio frequency sputtering, multi-arc ion plating, high power pulsed sputtering, plasma-assisted deposition, chemical vapor deposition, and pulsed laser deposition. Illustratively, the electrodeposition method is exemplified as follows: soaking the porous substrate 3 in a salt solution containing alloy elements for 3 hours or longer, taking the salt solution containing alloy elements as a negative electrode, taking a graphite rod as a positive electrode, controlling the deposition current to be 0.01 mA-2A, controlling the deposition time to be 5 min-120 min, placing the obtained product into a high-temperature furnace after deposition, and treating for 30 min-24 hours at 400-1200 ℃ to obtain a bottom layer.
In some embodiments, the soaking time is greater than or equal to 3h, specifically, 3h, 4h, 5h, 6h, 7h or 8h, and of course, other values within the above range are also possible, and the present application is not limited herein. If the soaking treatment is not performed, the underlayer grown inside the surface layer of the porous substrate 3 cannot be formed or the thickness deviation of the formed underlayer is large, and the demand cannot be satisfied.
S300, providing a second metal oxide, wherein the second metal oxide contains nonmetallic doping elements, and carrying out second deposition treatment and heat treatment on the bottom layer 2 covered on the surface of the porous substrate 3 by adopting the second metal oxide to obtain the modified porous diffusion layer.
In some embodiments, the process of the second deposition process includes at least one of magnetron sputtering, medium frequency sputtering, radio frequency sputtering, multi-arc ion plating, high power pulsed sputtering, plasma-assisted deposition, chemical vapor deposition, and pulsed laser deposition. Illustratively, magnetron sputtering is used as an example:
in the multifunctional vacuum coating equipment, a PECVD technology is adopted to deposit a metal target material to be deposited on a porous substrate 3 containing a bottom layer 2, wherein the deposition process is that the temperature is 400-600 ℃, the pressure is 0.1-10 pa, and the time is 15-60 min; introducing inert gas (such as Ar) and O into the multi-cavity equipment after deposition 2 And at least one of S, N and P elements, wherein the treatment temperature is 500-1000 ℃ and the treatment time is 15-60 min, thus obtaining the surface layer 1.
The thickness of the surface layer 1 and the bottom layer 2 can be controlled by the amount and time of the reactants introduced.
In some embodiments, the temperature of the heat treatment is 500 ℃ to 1000 ℃, specifically 500 ℃, 600 ℃, 700 ℃, 800 ℃, 900 ℃ or 1000 ℃, but may be other values within the above range, and the application is not limited thereto. If the heat treatment is not carried out, the ionization degree of the gas is low, the doping concentration of the formed doped titanium oxide coating is low, the conductivity and the hydrophilic performance of the coating are reduced, and the thickness uniformity of the modified porous diffusion layer is reduced.
Embodiments of the present application will be further described below with reference to a number of examples. The embodiments of the present application are not limited to the following specific examples.
Example 1
The embodiment provides a preparation method of a modified porous diffusion layer, which comprises the following steps:
(1) Titanium alloy with uniform thickness is selected as a porous fiber base material, and the titanium alloy is subjected to ultrasonic cleaning in ethanol and water to remove grease and surface scraps on the surface.
(2) Fixing titanium alloy substrate on electrode holder, soaking in TiCl 4 Soaking for 3 hours, wherein the positive electrode is a graphite rod, the negative electrode is a titanium alloy substrate, controlling the deposition current to be 0.5A, and the deposition time to be 30 minutes, and drying after the deposition is completed to obtain the bottom layer.
(3) Fixing the material obtained in the step (2) on a hanger, moving to a closed reaction chamber, vacuumizing the inside of the reaction chamber, starting a heater to heat to 500 ℃ when the vacuum is pumped to 1Pa, preserving heat for a period of time, and then introducing Ar gas and O into the chamber through a gas path and a gas hole 2 、N 2 TiF (titanium-tin-iron) alloy 4 Steam, controlling the vacuum degree of the process to be 5pa through an air extraction system, and carrying out Ar gas and O at the deposition temperature of 500 DEG C 2 、N 2 TiF (titanium-tin-iron) alloy 4 The steam is cracked in a high-temperature environment, a nonmetallic N-doped titanium oxide layer is formed on the surface, and then H is injected into a reaction chamber 2 And heating to 600 ℃, performing heat treatment for 30min, and gradually cooling to room temperature to obtain the modified porous diffusion layer.
In this embodiment, the modified porous diffusion layer comprises a titanium alloy porous substrate and TiO sequentially laminated 2 Layer and N-TiO doped with N element 2 The layer, as shown in fig. 2, is a cross-sectional view of the modified porous diffusion layer prepared in this example, and fig. 3 is a distribution diagram of interface elements of the modified porous diffusion layer prepared in this example, as can be seen from fig. 2 and 3: this embodiment1, the thickness uniformity of the coating on the surface of the prepared porous substrate is good. N element in TiO 2 The atomic ratio of (C) is 7at%, tiO 2 The thickness of the layer is 300nm, N-TiO 2 The layer thickness was 100nm. The titanium alloy substrate has a thermal expansion coefficient of 8.2 and TiO 2 The thermal expansion coefficient of the layer was 7.6, N-TiO doped with N element 2 The thermal expansion coefficient of the layer was 5.1.
Example 2
(1) Pure titanium with uniform thickness is selected as a porous substrate, and is subjected to ultrasonic cleaning in ethanol and water to remove grease and surface scraps on the surface.
(2) Fixing titanium alloy substrate on electrode holder, soaking in TiCl 4 Soaking for 3h, wherein the positive electrode is a graphite rod, the negative electrode is a titanium alloy substrate, controlling the deposition current to be 0.5A, and the deposition time to be 30min, and drying after the deposition is completed to obtain the surface layer.
(3) Fixing the material obtained in the step (2) on a hanger, moving to a closed reaction chamber, vacuumizing the inside of the reaction chamber, starting a heater to heat to 500 ℃ when the vacuum is pumped to 1Pa, preserving heat for a period of time, and then introducing Ar gas and O into the chamber through a gas path and a gas hole 2 、SO 2 TiF (titanium-tin-iron) alloy 4 Steam, controlling the vacuum degree of the process to be 5pa through an air extraction system, and carrying out Ar gas and O at the deposition temperature of 500 DEG C 2 、SO 2 TiF (titanium-tin-iron) alloy 4 The steam is cracked in a high-temperature environment, a nonmetallic S-doped titanium oxide layer is formed on the surface, and then H is injected into a reaction chamber 2 And heating to 600 ℃, performing heat treatment for 30min, and gradually cooling to room temperature to obtain the modified porous diffusion layer.
In this embodiment, the modified porous diffusion layer comprises a porous pure titanium substrate and TiO sequentially laminated 2 Layer and S-TiO doped with S element 2 Layer, S element in TiO 2 The atomic ratio of (C) is 8%, tiO 2 The thickness of the layer is 500nm, and the S element doped TiO 2 The thickness of the layer was 100nm. The thermal expansion coefficient of the porous pure titanium substrate is 8.4, and the TiO is 2 The thermal expansion coefficient of the layer is 7.5, S element doped S-TiO 2 The thermal expansion coefficient of the layer was 5.8.
Example 3
(1) Pure titanium with uniform thickness is selected as a porous substrate, and is subjected to ultrasonic cleaning in ethanol and water to remove grease and surface scraps on the surface.
(2) Fixing pure titanium on electrode clamp, fixing on hanger, moving to close reaction chamber, vacuumizing the interior, and vacuumizing to 10 -3 When Pa, starting a heater to heat; when the temperature in the reaction chamber reaches the designated temperature, preserving heat for a period of time, then introducing Ar into the chamber through the gas circuit and the air hole, maintaining vacuum of-0.6 pa, controlling sputtering current of the Ti-Nb alloy target, and depositing for 45min to obtain a bottom layer.
(3) Fixing the material obtained in the step (2) on a hanger, moving to a closed reaction chamber, vacuumizing the inside of the reaction chamber, starting a heater to heat to 500 ℃ when the vacuum is vacuumized to 1Pa, preserving heat for a period of time, then introducing reaction Ar gas into the chamber through a gas path and a gas hole, controlling the vacuum degree of the process to be 0.6Pa through a gas extraction system, and controlling sputtering Nb at the deposition temperature of 500 DEG C 2 O 5 Target current and N is introduced into 2 Treating for 30min, and finally introducing H 2 And heating to 500 ℃, performing heat treatment for 30min, and gradually cooling to room temperature to obtain the modified porous diffusion layer.
In this embodiment, the modified porous diffusion layer comprises a pure titanium porous substrate, a Ti-Nb alloy layer and N-Nb doped with N element, which are sequentially stacked 2 O 5 A layer in which N is Nb 2 O 5 The atomic ratio of the alloy is 10%, the thickness of the Ti-Nb alloy layer is 2 mu m, and the N element doped N-Nb 2 O 5 The thickness of the layer was 1 μm. The thermal expansion coefficient of the pure titanium porous substrate is 8.1, the thermal expansion coefficient of the Ti-Nb alloy layer is 7.4, and the N element doped N-Nb 2 O 5 The thermal expansion coefficient of the layer was 6.8.
Example 4
(1) Titanium alloy with uniform thickness is selected as a porous substrate, and the titanium alloy is subjected to ultrasonic cleaning in ethanol and water to remove grease and surface scraps on the surface.
(2) Fixing titanium alloy to electrode holder, immersingBubble to Hf (NO) 3 ) 4 Soaking for 4 hours, wherein the positive electrode is a graphite rod, the negative electrode is a titanium alloy substrate, controlling the deposition current to be 0.5A, and the deposition time to be 30 minutes, and drying after the deposition is completed to obtain the bottom layer.
(3) Fixing the material obtained in the step (2) on a hanger, moving to a closed reaction chamber, vacuumizing the inside of the reaction chamber, starting a heater to heat to 500 ℃ when the vacuum is pumped to 1Pa, preserving heat for a period of time, and then introducing Ar gas and O into the chamber through a gas path and a gas hole 2 、P 2 O 5 TiF (titanium-tin-iron) alloy 4 Steam, controlling the vacuum degree of the process to be 5pa through an air extraction system, and carrying out Ar gas and O at the deposition temperature of 500 DEG C 2 、P 2 O 5 TiF (titanium-tin-iron) alloy 4 The steam is cracked in a high-temperature environment to form nonmetal P doped TiO on the surface 2 An oxide layer, and then H is injected into the reaction chamber 2 And heating to 600 ℃, performing heat treatment for 30min, and gradually cooling to room temperature to obtain the modified porous diffusion layer.
In this embodiment, the modified porous diffusion layer includes a titanium alloy substrate and HfO laminated in this order 2 Layer and P-TiO doped with P element 2 Layer, P element in TiO 2 The atomic ratio of (1) to (11), hfO 2 The thickness of the layer is 600nm, and the S element doped TiO 2 The thickness of the layer was 500nm. The titanium alloy porous substrate has a thermal expansion coefficient of 8.2, hfO 2 The thermal expansion coefficient of the layer was 6.9, P-TiO 2 The thermal expansion coefficient of the layer was 5.8.
Comparative example 1
The comparative example provides a method for preparing a porous diffusion layer, comprising the following steps:
titanium alloy with uniform thickness is selected as a porous diffusion layer, and ultrasonic cleaning is carried out on the titanium alloy in ethanol and water so as to remove grease and surface scraps on the surface.
Comparative example 2
Unlike example 1, step (2) was not performed.
Comparative example 3
Unlike example 1, step (3) was not performed.
Performance testing
(1) The thickness of each of the modified porous diffusion layers was tested by SEM electron microscopy.
(2) The corrosion conductivity of the metal plate substrates of the examples and comparative examples was tested electrochemically, with the corrosion medium: and in a ph 3-sulfuric acid environment, the test potential is more than or equal to 2.5V, the polarization time is more than or equal to 100h, and then the stability of the contact resistance of the coating before and after corrosion is evaluated through a surface contact resistance test, wherein the test pressure is 0.6MPa.
(3) The contact angle of the modified porous diffusion layer was measured using a contact angle meter.
(4) The thermal expansion coefficients of the respective layers were measured by a thermo-mechanical analyzer (TMA) method.
(5) And measuring the binding force of the modified porous diffusion layer by adopting a nano scratch method.
(6) The thickness deviation of the underlayer and the surface layer in the above-mentioned region was measured by interface element analysis for measuring a region of 2mm in thickness of the surface of the porous substrate in the modified porous diffusion layer.
The test results are shown in Table 1.
TABLE 1 Performance test of porous diffusion layers prepared in examples and comparative examples
As can be seen from the data in table 1: according to the embodiment 1-4 of the application, the specific bottom layer and the specific surface layer are arranged, and the contact resistance can be reduced and the wettability of the liquid to the modified porous diffusion layer can be improved through the synergistic effect of the bottom layer and the surface layer, so that the hydrophilicity and the thickness distribution uniformity of the modified porous diffusion layer are improved, and the service life of the modified porous diffusion layer is prolonged.
Fig. 4 is a graph showing the corrosion resistance of the product prepared in example 1 of the present application before and after corrosion, and fig. 5 is a graph showing the contact resistance of the product prepared in example 1 before and after corrosion, as shown in fig. 4 and 5, wherein the corrosion current density of the modified porous diffusion layer of example 1 before and after corrosion is maintained to be stable.
In comparative example 1, the titanium alloy substrate was directly used as the porous diffusion layer, and the resistance increased significantly after corrosion.
In comparative example 2, only the surface layer is provided in the modified porous diffusion layer, so that the surface layer is directly combined with the porous substrate, and the combination property of the coating is low because of the large difference of the thermal expansion coefficients of the surface layer and the porous substrate, so that the modified porous diffusion layer is easy to cause the problem of falling off the film in the environments of alternating temperature change of an electrolytic tank and the like, and meanwhile, the uniformity of the surface layer in the thickness area of 2mm of the porous substrate is poor, and the hydrophilic property is poor.
In comparative example 3, only the bottom layer is arranged in the modified porous diffusion layer, and the bottom layer is extremely easy to generate a thicker oxide layer under a high-potential environment, so that electron transmission of the modified porous diffusion layer is blocked, a larger internal resistance is formed, and the energy consumption of the modified porous diffusion layer is reduced, and the utilization rate is low.
The foregoing description of the preferred embodiments of the application is not intended to be limiting, but rather is intended to cover all modifications, equivalents, alternatives, and improvements that fall within the spirit and scope of the application.
Claims (10)
1. A modified porous diffusion layer, the modified porous diffusion layer comprising:
a porous substrate;
the bottom layer is covered on the surface of the porous substrate, the material of the bottom layer comprises at least one of a first metal oxide and an alloy, the metal element in the first metal oxide comprises at least one of Nb, ta, hf and Ti, and the metal element in the alloy comprises at least two of Nb, ta, au, pt, hf and Ti;
the surface layer is covered on the surface of one side of the bottom layer, which is far away from the porous substrate, and the material of the surface layer comprises a second metal oxide which contains nonmetallic doping elements;
wherein the bottom layer has a coefficient of thermal expansion that is between the coefficient of thermal expansion of the porous substrate and the coefficient of thermal expansion of the surface layer.
2. The modified porous diffusion layer of claim 1, wherein the modified porous diffusion layer comprises at least one of the following features (1) - (3):
(1) The nonmetallic doping elements include at least one of S, N and P;
(2) The atom ratio of the nonmetallic doping element in the surface layer is 5at% -20 at%;
(3) The second metal oxide includes at least one of titanium oxide and niobium oxide.
3. The modified porous diffusion layer of claim 1, wherein the modified porous diffusion layer comprises at least one of the following features (1) - (5):
(1) The first metal oxide comprises TiO 2 、Nb 2 O 5 、HfO 2 And Ta 2 O 5 At least one of (a) and (b);
(2) The alloy comprises at least one of Nb-Ti alloy, ta-Ti alloy, hf-Ta alloy, ti-Au alloy and Ti-Pt alloy;
(3) The thickness of the bottom layer is 50 nm-5 mu m;
(4) The thickness of the surface layer is 10 nm-1 mu m;
(5) The porous substrate is made of at least one of titanium, titanium alloy and doped titanium.
4. The modified porous diffusion layer of claim 1, wherein the underlayer has a contact resistance of less than 2mΩ cm at a pressure of 1.4MPa 2 。
5. The modified porous diffusion layer of claim 1, wherein the skin layer has a contact resistance of less than 2mΩ cm at a pressure of 1.4MPa 2 。
6. The modified porous diffusion layer of claim 1, wherein the surface layer has a water contact angle of less than 40 °.
7. The modified porous diffusion layer of claim 1, wherein the modified porous diffusion layer comprises at least one of the following features (1) - (3):
(1) The thermal expansion coefficient of the porous substrate is 8E -6 /K～10E -6 /K；
(2) The thermal expansion coefficient of the bottom layer is 6E -6 /K～9E -6 /K；
(3) The thermal expansion coefficient of the surface layer is 5E -6 /K～7E -6 /K。
8. The modified porous diffusion layer of claim 1, wherein the porous substrate is a porous fibrous substrate, the surface of the porous substrate in contact with the bottom layer has a region of thickness 2mm, and the thickness variation of the filling thickness of the bottom layer and the surface layer in the region is less than 10%.
9. A method for preparing a modified porous diffusion layer, comprising the steps of:
providing a porous substrate;
providing a first metal oxide and/or an alloy, wherein metal elements in the first metal oxide comprise at least one of Nb, ta, hf and Ti, metal elements in the alloy comprise at least two of Nb, ta, au, pt, hf and Ti, and soaking the porous substrate by adopting a salt solution of the first metal oxide and/or the alloy and performing first deposition treatment to obtain a bottom layer coated on the surface of the porous substrate;
providing a second metal oxide, wherein the second metal oxide contains non-metal doping elements, and carrying out second deposition treatment and heat treatment on the bottom layer covered on the surface of the porous substrate by adopting the second metal oxide to obtain the modified porous diffusion layer.
10. An electrolytic cell comprising a modified porous diffusion layer according to any one of claims 1 to 8 or a modified porous diffusion layer produced by the production method according to claim 9.
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| CN117026171B (en) * | 2023-08-16 | 2024-02-06 | 上海亿氢能源科技有限公司 | Method for preparing PEM electrolytic cell porous diffusion layer based on pulse laser deposition technology |
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