The research on the protective coating of fuel cell bipolar plates of Lanzhou Chemical Institute has made progress

Fuel cell is a chemical device that directly converts the chemical energy of fuel into electrical energy, also known as electrochemical generator
.
Fuel cells have the advantages of zero emissions and high efficiency in operation, and are one of the
important technologies to achieve low carbon emissions in the transportation field.
The bipolar plate is the core component of the hydrogen fuel cell, and its main function is to collect the current generated by the fuel cell, supply the reaction gas to the electrode, prevent the penetration of the reactive substances between the poles, and support and strengthen the fuel cell
.
However, due to the acidic working environment of fuel cells, bipolar plates are susceptible to corrosion
.
Therefore, the development of new bipolar plates with excellent electrical conductivity and corrosion resistance is an important task
in this field.

In recent years, the nano-lubrication research group of the Advanced Lubrication and Protective Materials Research and Development Center of Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences has been committed to the design and process technology development of new bipolar plate film/coating for hydrogen, methanol and phosphoric acid fuel cells, and has made a series of research progress
.

In view of the low deposition efficiency and poor conductivity of carbon film, the research team used catalytic reaction magnetron sputtering to prepare conductive and corrosion-resistant carbon film (Figure 1).

The study relies on bridging nanocopper clusters and graphene-like carbon structures to form a spatial network in the bulk phase, which imparts good conductivity
to the sample.
At the same time, the bridged nano-copper clusters are isolated by graphene-like carbon structures and amorphous carbon clusters, thereby protecting the nano-copper clusters from contact with corrosive liquids and giving the sample excellent corrosion
resistance 。 The research results were published in Materials Today Chemistry under the title Electronic conductive and corrosion mechanisms of dual nanostructure CuCr-doped hydrogenated carbon films for SS316L bipolar plates
.

Researchers have found that CrN films have excellent corrosion resistance, conductivity and low cost characteristics, but the preparation window of CrN films is very narrow, and few films can meet the DOE 2025 standards for contact resistance and corrosion current density at the same time, and cannot achieve the commercialization
of bipolar plates.
In order to solve these problems, the amorphous nanocrystalline diffusion structure is proposed to break through the contradiction
of the unity of conductivity and corrosion resistance.
The researchers used high-power micropulse magnetron sputtering (HiPIMS) to deposit CrN films with high conductivity (as low as 6.
14 mΩ·^cm2at 1.
4 MPa) and strong corrosion resistance (corrosion current density less than 1 μA·^cm-2, as low as 0.
086 μA·cm-2) under wide_N2/Ar ratio (^4-10%)
。 The results show that thanks to the high plasma density and ionic energy of HiPIMS, the growth of Cr 2Nwith high metal characteristics and stability can be regulated, giving the film good electrical conductivity, and at the same time inhibiting the growth of the columnar structure of the CrN film, forming the spatial network structure of amorphous coated Cr_2Nnanoclusters, which improves the corrosion resistance of the film (Figure 2).

The research results were published in Materials & Design as_{Nano-Cr 2}N-dominated films with high conductivity and strong corrosion resistance for Ti bipolar plates
.

The research team prepared TiN films by HiPIMS, and systematically studied the effects of nitrogen flow rate on the surface microstructure, corrosion resistance, surface conductivity and water contact angle of
the deposited films.
The change of nitrogen gas flow causes the change of the internal degree of freedom of the molecular gas and affects the kinetic energy, thereby affecting the nucleation and growth of TiN, and then affecting the surface microstructure
of the TiN film.
Through the calculation of texture coefficient and grain scale, it is proved that the kinetic energy of incident particles is an important factor controlling the optimal orientation and crystallinity of TiN coating (Figure 3).

This study confirms that high-energy plasma regulation can achieve uniform conductivity and corrosion resistance over a wide process range (_N2/Ar ratio (4-10%)
).
。 The research results were published in the International Journal of Hydrogen Energy under the title Adjustable TiN coatings deposited with HiPIMS on titanium bipolar plates for PEMFC
.

Recently, the research team made a prospective review of the protective film/coating properties, material synthesis methods and applications of fuel cell metal bipolar plates, entitled Protective coatings for metal bipolar plates of fuel cells: A review, published in the International Journal of Hydrogen Energy
。

At present, the scientific research team has obtained 3 Chinese invention patents in fuel cell bipolar plate thin film/coating, and 1 Chinese invention patent authorization in bipolar plate coating equipment, and is actively seeking industrial cooperation
.
The research work is supported
by the High-tech Industrialization Project of Science and Technology Cooperation between Jilin Province and the Chinese Academy of Sciences, the Cooperation Fund of the Clean Energy Innovation Institute of the Chinese Academy of Sciences, and the Excellent Member Program of the Youth Innovation Promotion Association of the Chinese Academy of Sciences.

Figure 1.
Preparation process, electrochemical performance and conductive corrosion resistance mechanism of CrCu-doped conductive and corrosion-resistant carbon film

Figure 2.
HiPIMS prepared a highly conductive and corrosion-resistant CrN film and its performance analysis

Figure 3.
Mechanism of the effect of_N2 flow rate on TiN film growth

Figure 4.
Development history of fuel cell bipolar plates