SIGRACET^??Fuel Cell Components

SGL Carbon develops and commercializes carbon-based products for?Polymer-Electrolyte-Membrane Fuel Cells (PEMFC)?:

Gas Diffusion Layers (GDL)
Foils used as separator plates for fuel cells and redox-flow batteries (Expanded Graphite)

SGL Carbon's Gas Diffusion Layers (GDL)

GDLs are typically designed as a bilayer structure consisting of a macro-porous backing material (carbon fiber paper support) and a micro-porous, carbon-based layer (MPL). The fibrous backing material governs the mechanical properties of the GDL (behavior upon compression, bending and shear strength, etc.) while the MPL ensures intimate contact to the catalyst layers, protects the delicate proton exchange membrane against perforation and plays an active role with respect to the water management in the cell during operation. There is consensus that this heterogeneous porosity brought about by this structure (hydrophilic/hydrophobic and various pore sizes) is advantageous for the performance.

Sketch of the bilayer structure of Gas Diffusion Layers

Hydrophobic properties in the backing and the MPL are maintained by adding defined amounts of polytetrafluoroethylene (PTFE) to both sublayers. Various types of carbon particles (carbon blacks, graphite) can be used in the MPL in order to produce different levels of hydrophobicity. Furthermore, the MPL can be used as substrate to deposit catalyst particles for the manufacture of gas diffusion electrodes (GDEs).

SGL Carbon has been producing fully-treated SIGRACET^??gas diffusion layers by reel-to-reel processes since 1999. Carbon paper-type (prepared by wet-laying of chopped PAN-based carbon fibers) gas diffusion layers are the preferred solution since they can be manufactured at high volumes (scalability) and low thickness. The following figures show the whole value chain of GDL manufacturing. All commercially available GDL materials to date are based on carbon fibers derived from polyacrylonitrile (PAN). PAN (co)polymers are processed into precursor fibers by wet-spinning. Subsequent stabilization and pyrolysis yields high tensile (HT) carbon fibers which are sized and chopped to enable suitable processing by means of papermaking technologies.

Carbon Fiber Production

Manufacturing of SIGRAFIL^??chopped carbon fibers

A primary carbon fiber web is laid by a papermaking technology and subsequent thermobonding. Thereafter, the obtained raw paper is impregnated with carbonisable thermoset resins (with optional addition of carbon fillers), cured and re-carbonized/graphitized. This serves to enhance the mechanical stability and conductivity as well as to adjust the desired porosity level.

Carbon Paper Substrate

Manufacturing route of SIGRACET^??(carbon paper-based) gas diffusion layer backings

Finishing of GDL comprises hydrophobic treatment of the substrate with PTFE and coating with a microporous layer (MPL).

Finishing Treatment

Finishing treatments of SIGRACET^??(carbon paper-based) gas diffusion layers

A loading of the substrate with 5% (w/w) PTFE has proven to be sufficient for obtaining a pronounced hydrophobicity. MPLs typically contain 20 to 25% PTFE. This MPL composition has been identified as the optimum ratio for PEMFC performance across a broad range of operating conditions. Mean pore diameters of SIGRACET^??GDLs are typically in a range from 0.1 to 0.3 μm (Hg-Porosimetry) or 1.5 to 3 μm (calculated from capillary flow porometry). The hydrophobic treatment produces water repellent properties for the substrate and for the MPL (water contact angles by sessile drop method > 130°).

Typical properties of standard SIGRACET^??GDL grades.

??	Unit	22BB	36BB
Basic parameters	??	??	??
Thickness	μm	215	280
Area weight	g m^-2	70	105

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SIGRACET?^?燃料電池組件

SGL Carbon 為聚合物-電解質-膜燃料電池 (PEMFC)開發和商業化碳基產品：

氣體擴散層 (GDL)
用作燃料電池和氧化還原液流電池隔板的箔（膨脹石墨）

SGL Carbon 的氣體擴散層 (GDL)

GDL 通常設計為雙層結構，由大孔背襯材料（碳纖維紙載體）和微孔碳基層 (MPL) 組成。纖維背襯材料控制 GDL 的機械性能（壓縮、彎曲和剪切強度等），而 MPL 確保與催化劑層的緊密接觸，保護脆弱的質子交換膜免受穿孔，并在尊重方面發揮積極作用用于操作期間電池中的水管理。一致認為，這種結構（親水/疏水和各種孔徑）帶來的這種異質孔隙率有利于性能。

氣體擴散層的雙層結構示意圖

背襯和 MPL 的疏水性通過在兩個亞層中添加規定量的聚四氟乙烯 (PTFE) 來保持。MPL 中可使用各種類型的碳顆粒（炭黑、石墨）以產生不同水平的疏水性。此外，MPL 可用作沉積催化劑顆粒的基底，用于制造氣體擴散電極 (GDE)。

自 1999 年以來，西格里碳素一直在通過卷對卷工藝生產經過全面處理的 SIGRACET?^?氣體擴散層。碳紙型（通過濕法鋪設短切 PAN 基碳纖維制備）氣體擴散層是首選解決方案，因為它們可以大批量（可擴展性）和低厚度制造。下圖顯示了 GDL 制造的整個價值鏈。迄今為止，所有市售 GDL 材料均基于源自聚丙烯腈 (PAN) 的碳纖維。PAN（共）聚合物通過濕法紡絲加工成前體纖維。隨后的穩定化和熱解產生高強度 (HT) 碳纖維，這些碳纖維經過上漿和切碎，以通過造紙技術進行合適的加工。

碳纖維生產

SIGRAFIL?^?短切碳纖維
的制造

通過造紙技術和隨后的熱粘合鋪設初級碳纖維網。此后，用可碳化的熱固性樹脂（任選添加碳填料）浸漬獲得的原紙，固化并再碳化/石墨化。這用于提高機械穩定性和導電性以及調整所需的孔隙率水平。

碳紙基材

SIGRACET?^?（碳紙基）氣體擴散層背襯的
制造路線

GDL 的精加工包括用 PTFE 對基材進行疏水處理和用微孔層 (MPL) 進行涂層。

整理處理

SIGRACET?^?（碳紙基）氣體擴散層的
精加工處理

事實證明，在基材上裝載 5% (w/w) PTFE 足以獲得明顯的疏水性。MPL 通常含有 20% 到 25% 的 PTFE。這種 MPL 組合物已被確定為 PEMFC 在廣泛的操作條件下性能的最佳比例。^{SIGRACET ?}?GDL 的平均孔徑通常在 0.1 到 0.3 μm（Hg-Porosimetry）或 1.5 到 3 μm（根據毛細管流動孔隙度法計算）的范圍內。疏水處理使基材和 MPL 具有防水性能（通過固著滴法得到的水接觸角 > 130°）。

標準 SIGRACET?^??GDL 牌號的典型特性。

??	單元	22BB	36BB
基本參數	??	??	??
厚度	微米	215	280
面積權重	通用^-2	70	105

?Polymer Electrolyte Membrane Fuel Cells (PEMFC)

Fuel cells have the potential to revolutionize energy conversion and distribution. Vehicle propulsion, stationary cogeneration of heat and electricity, and power supply in mobile applications are current focus areas of fuel cell technology.

Polymer Electrolyte Membrane Fuel Cells (PEMFC)

Gas diffusion layers (GDLs) are vital components in Polymer Electrolyt Membrane Fuel Cells (PEMFC) modulating all relevant transport processes comprising fuel, oxidants, reaction products, electricity and heat. Gas diffusion layers serve as a functional interface between the gas distribution compartments (structural cell parts,?macroscopic scale) and the electrochemically active catalyst layers (reaction layers,?processes occurring at the nanoscale). GDLs direct fuels and oxidants to the active sites whilst removing heat and reaction products and electrically wiring the reaction layers with the current collectors.

Sketch of a single cell of a fuel cells stack with gas diffusion layers (GDL)

聚合物電解質膜燃料電池 (PEMFC)

燃料電池有可能徹底改變能量轉換和分配。車輛推進、固定式熱電聯產以及移動應用中的電源是燃料電池技術的當前重點領域。

氣體擴散層 (GDL) 是聚合物電解質膜燃料電池 (PEMFC) 中的重要組成部分，可調節包括燃料、氧化劑、反應產物、電和熱在內的所有相關傳輸過程。氣體擴散層充當氣體分配室（結構電池部分，宏觀尺度）和電化學活性催化劑層（反應層，發生在納米尺度的過程）之間的功能界面。GDL 將燃料和氧化劑引導至活性位點，同時去除熱量和反應產物，并將反應層與集電器電氣連接。

具有氣體擴散層 (GDL) 的燃料電池堆的單個電池的示意圖

https://www.sglcarbon.com/en/markets-solutions/material/sigracet-fuel-cell-components/

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