CN112993299B

CN112993299B - Silicon-doped niobium carbide coating of metal bipolar plate of fuel cell and preparation method thereof

Info

Publication number: CN112993299B
Application number: CN201911287548.8A
Authority: CN
Inventors: 邵志刚; 苟勇; 何良
Original assignee: Dalian Institute of Chemical Physics of CAS
Current assignee: Dalian Institute of Chemical Physics of CAS
Priority date: 2019-12-14
Filing date: 2019-12-14
Publication date: 2022-01-28
Anticipated expiration: 2039-12-14
Also published as: CN112993299A

Abstract

The invention belongs to the field of fuel cells, and particularly relates to a silicon-doped niobium carbide coating of a metal bipolar plate of a fuel cell and a preparation method thereof. And depositing a silicon-doped niobium carbide coating on the surface of the metal bipolar plate by adopting a technology combining multi-arc ion plating and magnetron sputtering. A small amount of silicon is doped on the basis of high-conductivity niobium carbide, so that on one hand, the growth of columnar grains in the coating is inhibited, the coating is more compact, on the other hand, the hardness of the coating is increased, the wear resistance of the coating is improved, and on the whole, the coating has better corrosion resistance and mechanical property on the premise of ensuring good conductivity.

Description

Silicon-doped niobium carbide coating of metal bipolar plate of fuel cell and preparation method thereof

Technical Field

The invention belongs to the field of fuel cells, and particularly relates to a silicon-doped niobium carbide coating of a metal bipolar plate of a fuel cell and a preparation method thereof.

Background

The bipolar plate is one of the key components of the fuel cell, mainly comprises three types of graphite, composite and metal materials, wherein the metal material has high strength and strong processability, is easy to produce into the ultrathin bipolar plate in a large scale, and is considered as an inevitable choice for improving the specific power of the fuel cell. However, bipolar plates typically operate with SO₄ ^2-、F^-In the high-temperature and high-humidity acidic environment of plasma, the metal material is faced with serious corrosion and passivation problems under the condition, the output power and the durability of the fuel cell are greatly influenced, and therefore, a conductive and corrosion-resistant coating needs to be prepared on the surface of the metal bipolar plate to improve the performance of the metal bipolar plate. The coatings currently used for fuel cell metal bipolar plates mainly include carbon-based coatings, noble metal coatings, conductive polymer coatings, and transition metal ceramic compound coatings. Research shows that the carbon coating and the noble metal coating have excellent conductivity and corrosion resistance, but have the problems of low deposition efficiency of the carbon coating and high cost of the noble metal material, and the conductive polymer coating has good corrosion resistance, but has large contact resistance with a diffusion layer and weak bonding force with a substrate. The transition metal ceramic compound coating has attracted much attention in recent years due to its high deposition efficiency, low material cost, good conductivity, and strong wear resistance.

Chinese patent CN109449457A discloses a method for preparing a metal bipolar plate by directly spraying corrosion-resistant and high-conductivity carbide particles on stainless steel by a metal spray method, which has the advantages of simple operation, stable and reliable process, high energy consumption and large internal stress of a coating. Chinese patent CN 110061257A discloses a metal-based bipolar plate for proton exchange membrane fuel cell and a preparation method thereof, wherein a conductive and corrosion-resistant molybdenum carbide coating is deposited on a metal substrate mainly by magnetron sputtering technology, and the coating can protect the metal bipolar plate from corroding with a current less than 1 muA/cm in the use environment of PEMFC²The resistance of the gas diffusion layer to the adjacent gas diffusion layer is lower than 10 m omega cm²However, magnetron sputtering is a low-temperature deposition technology, and the diffusion of molybdenum carbide in the deposition process is not enough to overcome the influence of surface geometric shadow, so that a columnar structure is easily formed, a low-density interface region is generated, and the excellent corrosion resistance of the coating can be difficult to maintain for a long time.

Disclosure of Invention

Aiming at the defects of the prior art, the invention provides a fuel cell metal bipolar plate silicon-doped niobium carbide coating with compact structure and good conductivity and wear resistance and a preparation method thereof.

In order to achieve the purpose, the technical scheme adopted by the invention is as follows:

a fuel cell metal bipolar plate silicon-doped niobium carbide coating comprises a metal substrate and a coating, and is characterized in that the material of the coating consists of elemental silicon and niobium carbide.

In the technical scheme, further, the silicon in the silicon-doped niobium carbide coating accounts for 0.1-30%.

In the technical scheme, further, the thickness of the silicon-doped niobium carbide coating is 50-3000 nm.

In the above technical solution, further, the niobium carbide includes NbC and Nb₂One or two of C, and does not exclude the presence of a part of simple carbon.

In the above technical solution, further, the metal substrate is one of stainless steel, titanium alloy, aluminum, and aluminum alloy.

A preparation method of a silicon-doped niobium carbide coating of a metal bipolar plate of a fuel cell mainly comprises the following steps:

(1) pretreatment: sequentially ultrasonically cleaning and drying a metal substrate in deionized water, ethanol and acetone;

(2) silicon-doped niobium carbide coating deposition: respectively taking a niobium target and a silicon target as evaporation sputtering sources, and depositing a silicon-doped niobium carbide coating on a metal substrate by adopting a technology of combining multi-arc ion plating and magnetron sputtering.

In the above technical solution, further, the silicon-doped niobium carbide in step (2) is prepared by co-deposition of magnetron sputtered silicon and multi-arc ion-plated niobium carbide.

In the above technical solution, further, the carbon source in the coating includes one of graphite target, methane, ethane, ethylene, and acetylene

The invention has the beneficial effects that: the doping of silicon in the coating can prevent the continuous growth of dominant crystal orientation during the deposition of niobium carbide, inhibit the generation of columnar crystal grains in the coating, enhance the compactness of the coating, better prevent corrosive media from permeating inwards, increase the hardness of the niobium carbide coating and improve the wear resistance of the coating, and in addition, silicon dioxide generated by oxidizing silicon has better passivation performance and can effectively improve the corrosion resistance of the coating.

Drawings

FIG. 1 is a schematic structural view of a bipolar plate according to the present invention, wherein 1 is a metal plate substrate, 2 is niobium carbide, 3 is silicon;

FIG. 2 is a scanning electron microscope cross-sectional view of the coating prepared in example 2;

FIG. 3 is a graph showing the proportions of the elements in the coatings prepared in the examples;

FIG. 4 is a graph of contact resistance between a bipolar plate and carbon paper prepared in each example as a function of pressure;

fig. 5 is a plot of potentiostatic polarization of bipolar plates prepared in each example under simulated fuel cell cathode conditions.

Detailed Description

The invention is further illustrated but is not in any way limited by the following specific examples.

Comparative example 1

Taking TA1 type pure titanium as a substrate, and ultrasonically cleaning and drying in deionized water, ethanol and acetone in sequence; mounting the substrate on a workpiece rack of an arc ion plating machine, and vacuumizing to 3 x 10^-3Pa below; introducing argon of 200 sccm into the vacuum chamber to keep the pressure at 0.5 Pa; taking a niobium target as an evaporation source, controlling the target current to be 60A, controlling the substrate bias voltage to be-600V, and carrying out sputtering cleaning for 5 min; then 15 sccm of acetylene gas is introduced into the vacuum chamber, the target current is controlled to be 100A, the substrate bias voltage is-200V, and the niobium carbide layer is deposited for 30 min; and cooling and taking out to obtain the metal plate with the modified surface coating, wherein the thickness of the coating is about 600 nm.

As shown in the figure, the contact resistance between the bipolar plate and the carbon paper is 0.97 m omega cm under 1.5 MPa²At 80 ℃ 0.5M H₂SO₄+5ppm F^-After the constant potential of 0.6V (vs. SCE) is corroded for 3 hours under the condition of air introduction, the corrosion current is 1.80 mu A/cm²。

Example 1

Taking TA1 type pure titanium as a substrate, and ultrasonically cleaning and drying in deionized water, ethanol and acetone in sequence; mounting the substrate on a workpiece frame of a magnetron sputtering ion composite coating machine, and vacuumizing to less than 3 x 10^-3Pa; introducing argon of 300 sccm into the vacuum chamber, and keeping the pressure at 0.8 Pa; taking a multi-arc niobium target as an evaporation source, controlling the target current to be 60A, controlling the substrate bias voltage to be-600V, and carrying out sputtering cleaning for 5 min; adjusting the bias voltage of the substrate to-100V, and depositing a niobium transition layer for 5 min; introducing acetylene gas of 9 sccm into the vacuum chamber, adjusting the niobium target current to 70A, introducing a silicon target sputtering source, controlling the target current to be 1.0A and the substrate bias voltage to be-150V, and depositing the silicon-doped niobium carbide coating for 40 min; and cooling and taking out to obtain the metal plate with the modified surface coating, wherein the thickness of the coating is about 400 nm.

As shown in the figure, the contact resistance between the bipolar plate and the carbon paper is 5.39 m omega cm under 1.5 MPa²At 80 ℃ 0.5M H₂SO₄+5ppm F^-Through airUnder the condition, after the constant potential of 0.6V (vs. SCE) is corroded for 3 hours, the corrosion current is 0.82 mu A/cm²Compared with the coating prepared in the comparative example 1, the corrosion current is obviously reduced, which shows that the corrosion resistance of the coating is improved by doping silicon.

Example 2

Taking TA1 type pure titanium as a substrate, and ultrasonically cleaning and drying in deionized water, ethanol and acetone in sequence; mounting the substrate on a workpiece frame of a magnetron sputtering ion composite coating machine, and vacuumizing to less than 3 x 10^-3Pa; introducing argon of 300 sccm into the vacuum chamber, and keeping the pressure at 0.8 Pa; taking a multi-arc niobium target as an evaporation source, controlling the target current to be 60A, controlling the substrate bias voltage to be-600V, and carrying out sputtering cleaning for 5 min; adjusting the bias voltage of the substrate to-100V, and depositing a niobium transition layer for 5 min; keeping the niobium target current unchanged, introducing 9 sccm acetylene gas into the vacuum chamber, introducing a silicon target sputtering source, controlling the target current to be 2.0A, biasing the substrate to be-150V, and depositing a silicon-doped niobium carbide coating for 40 min; and cooling and taking out to obtain the metal plate with the modified surface coating.

As shown in the figure, the thickness of the coating is about 400 nm, and the contact resistance between the bipolar plate and the carbon paper is 16.93 m omega cm under 1.5 MPa²At 80 ℃ 0.5M H₂SO₄+5ppm F^-After the constant potential of 0.6V (vs. SCE) is corroded for 3 hours under the condition of air introduction, the corrosion current is 1.14 mu A/cm²Compared with the coating prepared in the comparative example 1, the corrosion current is obviously reduced, which shows that the corrosion resistance of the coating is improved by doping silicon.

It will be apparent to those skilled in the art from this disclosure that many changes and modifications can be made, or equivalents modified, in the embodiments of the invention without departing from the scope of the invention. Therefore, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention shall still fall within the protection scope of the technical solution of the present invention, unless the contents of the technical solution of the present invention are departed.

Claims

1. A fuel cell metal bipolar plate silicon-doped niobium carbide coating comprises a metal substrate and a coating, and is characterized in that the material of the coating consists of elemental silicon and niobium carbide.

2. The fuel cell metal bipolar plate silicon-doped niobium carbide coating of claim 1, wherein the silicon-doped niobium carbide coating comprises 0.1% to 30% silicon.

3. The fuel cell metal bipolar plate silicon-doped niobium carbide coating of claim 1, wherein the thickness of the silicon-doped niobium carbide coating is 50 to 3000 nm.

4. The fuel cell metallic bipolar plate silicon-doped niobium carbide coating of claim 1, wherein said niobium carbide comprises NbC, Nb₂One or two of C.

5. The fuel cell metallic bipolar plate silicon doped niobium carbide coating of claim 1, wherein said metal substrate is one of stainless steel, titanium alloy, aluminum alloy.

6. The method for preparing a silicon-doped niobium carbide coating for a metal bipolar plate of a fuel cell according to any one of claims 1 to 5, which mainly comprises the following steps:

7. The method for preparing a silicon-doped niobium carbide coating of a metal bipolar plate for a fuel cell according to claim 6, wherein the silicon-doped niobium carbide in the step (2) is prepared by co-depositing magnetron-sputtered silicon and multi-arc ion-plated niobium carbide.

8. The method as claimed in claim 6, wherein the carbon source in the coating comprises one of graphite target, methane, ethane, ethylene, and acetylene.