Inside This Release
This release introduces engineers, scientists, and industry professionals to porous carbon materials as transport layers (PTLs) for electrolyzers and highlights key characteristics for optimal performance.
Introduction
AvCarb is excited to unveil its newest innovations in porous transport layer (PTL) carbon materials, designed to enhance the efficiency and durability of electrolyzer systems. Engineered for applications such as Proton Exchange Membrane (PEM), Alkaline Water Electrolysis (AWE), Anion Exchange Membrane (AEM), and CO₂ electrolysis, these advanced PTLs offer superior conductivity, optimized mass transport, and long-term stability under demanding conditions.
As the need for scalable hydrogen production grows, AvCarb is pushing the boundaries of electrolysis innovation, delivering high-performance carbon solutions in multiple form factors to drive efficiency and reliability. This paper examines the role of carbon materials in a standard electrolyzer system, from where it can be used effectively to the specific properties that influence performance. Our product spotlight looks at the newest of our rollable carbon paper, manufactured continuously on rolls over 1000 linear meters long and 850 mm wide, that is designed to perform in electrolyzer systems.
Inside the Electrolyzer: Understanding the Critical Components
Electrolyzers are critical technologies for hydrogen and chemical production, using electrical energy to split water (or CO₂ in specialized applications) into its constituent elements. Various electrolyzer types—including Proton Exchange Membrane (PEM), Alkaline Water Electrolysis (AWE), Anion Exchange Membrane (AEM), and CO₂ electrolyzers—each have unique designs, operating conditions, and material requirements. However, all electrolyzers share common components that define their functionality: electrodes, an electrolyte or membrane, a porous transport layer
Core Components of Electrolyzers
Electrodes
Electrodes facilitate the electrochemical reactions that generate hydrogen and oxygen (or other chemical products in CO₂ electrolysis). They are typically coated with catalysts to enhance reaction kinetics. The choice of electrode materials varies by electrolyzer type, with noble metals such as platinum and iridium commonly used in PEM electrolyzers, while transition metal-based catalysts are employed in AWE and AEM systems.
Electrolyte (Liquid or Membrane)
The electrolyte is responsible for ionic conduction between the electrodes. The electrolyte can change depending on the type of electrolyzer. AWEs use liquid alkaline electrolytes, while PEM and AEM use special polymer electrolytes that can transport either H+ ions (e.g., Nafion) or OH- ions (e.g., PBI, DAPP, etc.). Alternatively, CO2 electrolyzers can use a variety of different electrolyte materials depending on cell design and the desired product being produced.
Bipolar Plates
Bipolar plates (BPPs) serve as current collectors, providing structural integrity and facilitating fluid distribution. They are typically made from stainless steel, titanium, or graphite, depending on the electrolyzer type and operating conditions.
Porous Transport Layer (PTL)
The PTL plays a vital role in gas diffusion, electrical conduction, and water/gas transport within the electrolyzer. While the anode side of the electrolyzer is usually metallic (titanium or coated nickel), the cathode side can use a more flexible format and lower cost carbon-based material. These PTLs are essential for optimizing gas-liquid transport, electrical connectivity, and mechanical stability in electrolyzers. AvCarb’s carbon-based PTLs are engineered to:
With flexibility in material thickness, product format, compressibility, and microporous layer coatings with AvCarb carbon PTLs provide a unique solution for any given application. From enabling proper sealing by compressing enough to account for thickness variation between parts to providing a smooth surface to ensure good contact with the membrane during assembly AvCarb carbon PTLs can be designed for cell needs. Carbon-based PTLs are particularly beneficial in electrolyzers due to their compatibility with both acidic and alkaline environments without the need for precious metal coatings or reinforcement like metallic PTLs.
Carbon in Electrolysis: The Ideal Cathode PTL Material
Carbon Materials for Porous Transport Layers
Electrolyzers are at the heart of the hydrogen economy, enabling the production of clean hydrogen for energy storage, transportation, and industrial applications. As global demand for hydrogen grows, mass production of electrolyzers is essential, requiring advancements in materials and manufacturing to reduce costs and improve scalability. One of the critical components influencing electrolyzer performance and efficiency is the porous transport layer (PTL), which facilitates electron transport, gas diffusion, and water distribution. Utilizing optimized PTL materials such as the advanced carbon-based solutions from AvCarb provides product and system design flexibility, at a lower manufacturing price point, ultimately improving overall system efficiency and cost. Here we will look at the innovations in PTL technology at AvCarb and how they play a key role in making hydrogen production more cost-effective and accelerating the transition to a sustainable energy future.
Flexibility in Material Design – Thickness, Compressibility, Porosity
AvCarb has a long history of producing carbon-based materials for electrochemical devices such as GDLs for fuel cell systems, electrodes for battery systems, oxygen depolarized cathodes (ODCs) for chlor-alkali processes, as well as PTLs for electrolyzer systems. These materials range from: 1) woven carbon fabrics with various weave patterns to alter porosity or contact area, 2) wet-laid carbon papers with different thicknesses and compressibility, 3) needled felt with higher surface area and thicknesses, 4) rigid carbon-carbon composites known as molded graphite laminates engineered for optimal thickness and density. Regardless of the system needs for thickness, compressibility, porosity, or contact area, AvCarb has a material that can meet your needs.
Stability - Corrosion Resistance
AvCarb carbon-based PTLs provide stability and performance in a variety of harsh environments ranging from highly acidic (e.g., PAFC, PEM, etc.) to highly alkaline (e.g., AFC, AWE, AEM, etc.). For example, AvCarb MB-30 had a corrosion current of <1 A/cm2 and a mass loss of 0.11 g/cm2-hr when tested in an acidic environment (pH 3), with 0.1 ppm HF at 80°C, (at +0.6V (Ag/AgCl)). Carbon based PTLs are chemically compatible with most materials and can be used in moderately high temperature systems (up to 400°C in air). Carbon based PTLs are not harmful in microbial systems and do not suffer from hydrogen embrittlement ensuring long-term stability and performance for any electrochemical system.
Enhanced Performance – Conductivity, Porosity, and Surface Treatments
Carbon materials can offer superior electrical conductivity compared to titanium or nickel PTLs in electrolyzer systems without precious metal coatings. This translates to lower resistance in the device and potentially higher system efficiency. AvCarb’s manufacturing process gives total control over the porosity and hydrophobicity of the material for improve control reactant and product transport, maximizing cell performance. This control extends to unique options such as altering pore size distributions, creating porosity gradients, or enhancing compressive strength. Carbon materials can be easily functionalized or treated to enhance their surface properties (e.g., hydrophobic or hydrophilic coatings) reducing bubble size and improving mass transport within the cell and subsequently system efficiency.
Carbon in Electrolysis: The Ideal Cathode PTL Material
Microporous Layers – Surface Roughness
Microporous layer (MPL) coatings applied to the carbon-based PTLs can significantly improve system efficiency by improving many aspects of the PTL performance. Most commonly, MPLs are known to provide a smoother surface for lower contact resistance, improved catalyst utilization by preventing catalyst intrusion into the PTL and acting as a protective layer to prevent damage to sensitive components like membranes or separators. MPLs help to create a more uniform distribution of reactants at the catalyst layer, maximizing the active sites and improving catalyst utilization. MPLs also mitigate flooding by optimizing water transport and preventing gas bubble accumulation. MPL coatings also provide structural stability and can improve the durability of PTLs, extending the lifespan of the electrolyzer. These benefits make MPL-coated PTLs particularly valuable in high-performance electrolysis applications, such as PEM and AEM electrolyzers.
Advanced Design Considerations
Stacking Materials
While AvCarb offers a wide range of carbon materials for use within an electrolyzer system, often a single solution is not adequate for specific design needs. AvCarb products can be combined to create unique PTL designs to fit specific design requirements. Combining a thick rigid MGL panel with a thin compressible rollable paper with an MPL may provide the structural support and gas distribution network while providing more compressibility for intimate contact and a smoother surface for water distribution and membrane protection. Similarly placing a compressible carbon fabric between two rigid MPL panels can provide system compressibility without bowing or channel intrusion.
Electrode Encapsulation
In addition to stacking, some PTLs or electrodes may be encapsulated to simplify assembly and prevent leaking. Encapsulation can prevent carbon dust or debris from coming loose, help parts maintain form and fit for assembly, and provide good contact for sealing. Encapsulation designs are customized for specific applications, so please contact the AvCarb team to discuss specific system needs and design options.
AvCarb New Product Spotlight: PTLXXXX
Microporous Layers – Surface Roughness
AvCarb, a leading innovator in advanced materials for electrochemical applications, is proud to announce the launch of its first rollable carbon Porous Transport Layer (PTL) designed specifically for electrolyzer systems, PTLXXXXX. This cutting-edge PTL is combines the latest carbon substrate with a new microporous layer (MPL) optimized for use as the cathode PTL in an electrolyzer system.
AvCarb’s new rollable PTL offers several key advantages:
AvCarb is thrilled to introduce this game-changing PTL to the electrolyzer market. This innovation represents a significant advancement in PTL technology, enabling our customers to achieve higher performance, lower costs, and increased production efficiency in their electrolyzer systems.
Typical Properties
Physical Compressibility and Electrical Resistivity
Sizing Availability
AvCarb PTLXXXX is manufactured continuously in a rolled format at a standard width of 800 mm and a standard length of 1,000 LM. AvCarb has the capability to slit the rolls to any width between 150 – 750 mm and can cut down rolls to manageable lengths from 50 LM to 600 LM for improved handling. Rolls are typically shipped on 6” cardboard cores set on a fixed hub and spoke setting placed within a box or crate. AvCarb rolls are uniform in both the cross-web and down-web direction allowing for more versatility in post-processing to increase yields and throughput rates.
