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0Computational and experimental studies of bipolar plates for proton exchange membrane fuel cells, creation of a prototype
D.K.Grebtsov1, I.A.Lomakin2, Yu.A.Dobrovolsky1,3
1 Moscow Institute of Physics and Technology, Moscow, Russia 2Bauman Moscow State Technical University, Moscow, Russia 2Federal Research Center for Problems of Chemical Physics and Medical Chemistry, Russian Academy of Sciences, Chernogolovka, Russia.
e-mail: grebtsov.dk@mipt.ru
DOI 10.24412/cl-37211-FC-2024.18
The performance of a proton exchange membrane fuel cell (PEMFC) depends on the efficiency of reagent transport and water removal. As one of the key components of PEMFC, bipolar plates (BPs) provide reagent transport, water removal, heat removal, electron transfer, and are also the load-bearing frame of the fuel cell. Thus, one of the key challenges to achieve high performance of fuel cells is to design the BPs taking into account all the above functions.
This work was carried out in order to identify the most effective geometries of closed cathode fuel cells according to the above parameters, taking into account the manufacturability and cost of production as well as to perform the production of a prototype of the selected geometry for further laboratory tests.
The existing geometries of BP channels, as well as variants of their application on the BP plane of both hydrogen (anode) and oxygen (cathode) parts were studied by analyzing the literature. Thus, the work [1] presents studies of three main geometries of BP channels -serpentine, parallel, interfinger. In [2] the influence of channel height and width on the performance of serpentine channel is investigated. Taking into account scientific publications, as well as the world experience of serially produced BPs for hydrogen transportation, it was decided to produce a BP with serpentine pattern as a prototype.
The geometry of the polar plates has been constructed, and current density calculations have been performed depending on the voltage. The resulting polarization curves at different points and distributions are shown in Figure 1.
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Fig. 1. Polarization curves at different points.
Also, the materials used for manufacturing of BPs were analyzed [3]. The production of BPs with closed cathode is usually carried out using metallic materials copper, aluminum, stainless steel, titanium and others. Titanium is the most preferred as it is well processable, has good conductivity and low weight. The disadvantages of using titanium are high cost and formation of oxides on the surface of the metal, which reduces its conductivity. To improve
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conductivity, as well as to reduce susceptibility to corrosion, BPs made of titanium and other metals are coated with special protective coatings. One of the most common and successful options is a carbon nanocoating called Pi conjugated amorphous carbon (PAC). The use of this coating instead of precious metal coating allows for cheaper BP production as well as increased conductivity of the electrode.
Based on the performed analysis, titanium of VT1-0 grade was chosen as a model material for the production of a prototype BP. The samples were manufactured using laser marking technology - by removing a part of the material and forming channels in the form of recesses
Fig. 2. Process of BP sample manufacturing by laser marking method.
The advantage of this technology is the ability to quickly reconfigure the equipment to obtain the required geometry. However, the time spent for manufacturing one wafer is quite significant (about 10-12 hours), which does not allow using this technology for industrial mass production of BPs.
Taking into account the peculiarities of this method, a 0.8 mm-thick titanium sheet was selected for obtaining 550 p,m deep channels. However, as a result of laser processing, mechanical overstresses of the metal occurred and deformations appeared, which violated the flatness of the workpiece. To level the distortions of geometry, a titanium sheet of the same grade with a thickness of 2 mm was taken as a basis, the processing of which did not lead to deformations.
After engraving, mechanical grinding of the product surface was carried out, as well as laser polishing. The 3d-scan of the channels obtained on the laser profilometer is shown in Figure 3. The channel profile of the manufactured sample is shown in Figure 4.
Fig. 3. 3D-scan of the surface of the manufactured specimen.
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Fig. 4. Channel profile of the BP sample.
Thus, in this work the fabrication of a prototype BP by laser marking method was realized. The next stage of the ongoing research is devoted to the development of the technology of applying a protective carbon coating on BPs, the study of mechanical and electrical characteristics of this coating, testing the anti-corrosion properties of coated BPs, as well as the assembly of a single BTE cell in order to study its operating parameters with the manufactured BPs.
References
[1] Son Jonghyun, Um Sukkee u Kim Young-Beom Numerical analysis of the effect of anisotropic gas diffusion layer permeability on polymer electrolyte membrane fuel cell performance with various channel types [Journal] // Fuel. - [Journal] : Elsevier BV, April 2021.
- T. 289. - pages. 119888. - ISSN: 0016-2361.
[2] Jiao Kui [et al.] Designing the next generation of proton-exchange membrane fuel cells [Journal] // Nature. - [Journal] : Springer Science and Business Media LLC, July 2021. - T. 595.
- pages. 361-369. - ISSN: 1476-4687.
[3] Dobrovolsky Yu. [et al.] Materials for bipolar fuel cell plates based on proton-conducting membranes [Journal] // Russian Chemical Journal. - 2006.
