Domestic gas diffusion layer "hard battle"

With the rise of the domestic fuel cell vehicle market, the gas diffusion layer (GDL), which is the key material of the stack membrane electrode, is accelerating the localization, and the domestic gas diffusion layer enterprises represented by general hydrogen energy are accelerating the launch of batch products.

"At present, the company's gas diffusion layer has been tested and verified in head fuel cell companies such as Ballard, Jie Hydrogen Technology, Weichai Power, etc., and some companies have been verified for more than 6 months." Dr. Yao Keguang, general manager of Shenzhen General Hydrogen Energy Technology Co., Ltd. (hereinafter referred to as "General Hydrogen Energy"), told Gaogong Hydrogen That it is expected that in the second half of this year, it will be able to open a batch supply through the verification period.

For the localization of the core components and key materials of the fuel cell, it has now progressed to the most core part of the membrane electrode: compared with the proton exchange membrane, catalyst and gas diffusion layer, the Chinese proton exchange membrane and catalyst have realized the application of small batches in the past year, and the domestic gas diffusion layer is also expected to truly achieve batch commercialization this year, thus breaking through the last barrier of fuel cell localization.

The problem of preparing gas diffusion layers

The gas diffusion layer plays an important role in supporting the catalytic layer, collecting current, conducting gas and discharging reaction product water in fuel cells.

Due to the characteristics above the gas diffusion layer, it is required to have good mass transfer, heat transfer, and conductive properties, coupled with the need for it to have a certain mechanical strength to support the membrane electrode, good mechanical strength is naturally essential. Therefore, it is not easy to do a good job of gas diffusion layer.

"To do a good gas diffusion layer, you first need to have a good gas diffusion layer material." Yao Keguang said that the material selection of the gas diffusion layer has higher requirements.

From the perspective of material sources, GDL is roughly divided into four types, carbon fiber paper, carbon fiber woven fabric, non-woven fabric and carbon black paper. Due to the difference in raw materials and preparation processes, the properties of the obtained diffusion layer materials are also different.

In the long-term experiment and application process, it was found that due to the light weight, flat surface, corrosion resistance, uniform porosity and high strength of carbon fiber paper, the thickness can be adjusted according to the requirements of use, which is more suitable for the use of durable fuel cells. Carbon paper has also become the mainstream choice of gas diffusion layer materials because of its mature manufacturing process and stable performance.

"The substrate of carbon paper comes from carbon fiber, and making carbon fiber into carbon paper is the core difficulty." Wang Tianxi, deputy general manager of the technology center of Shanghai Yi hydrogen technology co., Ltd., told Gaogong Hydrogen Electric that Japan's Toray is relying on its profound technical accumulation to produce carbon fiber and carbon paper to become a leading enterprise in the field of gas diffusion layer.

In addition to carbon fiber substrates, mastering the structure of materials and hydrothermal management is also quite critical, and there is a certain gap between the domestic gas diffusion layer and the advanced level of foreign countries at this stage.

"Judging from the technical indicators of the gas diffusion layer, the current density of the foreign advanced level has reached 2.5-3.0A/cm, and the domestic progress has been very fast in the past year, and it has reached the medium level of imported products." The technical person in charge of a domestic membrane electrode enterprise believes that the domestic gas diffusion layer has reached the standard technically, and it is also necessary to open the verification barrier, and this verification cycle needs to be close to one year.

The commercial acceleration of domestic gas diffusion layers

The cost of the gas diffusion layer accounts for a relatively high proportion of fuel cells, and to reduce the cost of fuel cells, it is an inevitable option to achieve this part of the localization breakthrough.

According to the U.S. Department of Energy (DOE), large-scale production of GDL will bring significant cost reductions. For every 100,000 sets of proton exchange membrane fuel cell systems produced, GDL accounts for 9%, and for every 500,000 sets of proton exchange membrane fuel cell systems produced, GDL accounts for 6%.

At this stage, most of the fuel cell manufacturers use the gas diffusion layer products of Japan's Toray, the United States Avcarb, Germany's SGL and other manufacturers, of which Japan's Toray and Avcarb occupy a large market share. Toray and SGL's product value chain begins with their own production of carbon fiber carbon paper and continues to microporous MPL coating, with deep basic carbon material development and large-scale production capabilities.

Gaogong Hydrogen Power learned that only a few enterprises in China, such as General Hydrogen Energy, Jiangsu Tianniao, and Shanghai Jiazi, are involved in the research and development of gas diffusion layers, and most of them are in the state of small batch sample trial production. Among them, general hydrogen energy has developed rapidly in the past two years, and its products have been tested and verified by many domestic fuel cell companies, and a batch production line has been prepared to prepare for the next batch supply.

"At present, the company has received a lot of intentional orders, the production line in Shenzhen has built an annual output of 100,000 square meters of gas diffusion layer production capacity, the company is currently purchasing equipment, plans to build a production line of 1 million square meters in the second half of the year in the production base in Tianjin." Yao Keguang said that from the perspective of contact with downstream customers, everyone's recognition of domestic GDL is not bad, and some customers can gradually supply in batches after completing the verification cycle this year.

"Judging from the company's testing, the domestic gas diffusion layer has gradually approached the imported brand in terms of technical indicators." Wang Tianxi believes that the policy of fuel cell vehicle demonstration application city cluster encourages the application of domestic materials, and Yi hydrogen technology has enabled domestic materials in proton exchange membranes and catalysts, and is trying to introduce domestic gas diffusion layer products.

According to the subsidy policy of the demonstration period, the introduction of domestic gas diffusion layer into operation hydrogen fuel cell vehicles can get a reward of 0.3 points, which also leaves a 4-year time window for the domestic gas diffusion layer to catch up with imported brands.

"For the domestic gas diffusion layer to make a commercial breakthrough, the most critical thing is to solve the two core problems of supply chain management and quality control." Dr. Zou Yuquan, CEO of Hongji Chuangneng, believes that it is not difficult to make microporous layer MPL coating, GDL only from the carbon fiber level to open up the localization of carbon paper, in order to have the advantage of autonomy, Hongji Chuangneng plans to introduce a domestic gas diffusion layer in a membrane electrode product in the second half of this year.

Although the localization breakthrough of the gas diffusion layer is a difficult process, companies such as General Hydrogen energy are on the road of accelerating catch-up, and the core components and materials of fuel cells are not far from conquering the last barrier of localization.