Exploring the development of corrosion-resistant coatings for bipolar plates in PEM fuel cells - a comprehensive review of materials, methods, and performance metrics
Bipolar plates are the workhorses of PEM fuel cells, performing several critical functions simultaneously. Think of them as the cardiovascular and nervous systems of the fuel cell rolled into one component 1 2 .
They channel hydrogen fuel and oxygen through tiny flow channels, much like arteries carrying blood 2 .
They collect and conduct the electrical current generated by electrochemical reactions 6 .
They provide structural integrity to the entire fuel cell stack under varying conditions 1 .
The environment inside an operating PEM fuel cell is particularly harsh—acidic, humid, and electrochemically aggressive 4 . While metals like stainless steel and titanium offer excellent mechanical strength and electrical conductivity, they face a formidable adversary in this environment: corrosion.
Corroding plates release metal ions that can contaminate the membrane electrode assembly (MEA), poisoning the entire fuel cell 2 4 .
Corrosion leads to surface oxides that act as insulators, reducing power output significantly 4 .
Continuous corrosion weakens the structural integrity of bipolar plates over time.
The quest for the perfect bipolar plate coating has led researchers down multiple pathways, each with unique advantages and trade-offs.
TiN, CrN, WC create a barrier layer with excellent corrosion resistance and conductivity 2 .
Noble metals like gold provide exceptional performance but at higher cost 4 .
Conductive polymers like polyaniline offer economical protection 4 .
| Method | Process Description | Advantages | Limitations |
|---|---|---|---|
| Physical Vapor Deposition (PVD) | Vaporizing coating material in vacuum which then condenses on the substrate 2 | Dense, uniform coatings; Excellent adhesion | High equipment cost; Limited scalability |
| Chemical Vapor Deposition (CVD) | Chemical reactions of vapor precursors on heated substrate 2 | Conformal coatings on complex shapes | High temperatures required; Expensive gases |
| Electroplating | Electrochemical deposition from solution 2 | Cost-effective; Scalable for mass production | Thicker coatings may affect dimensions |
| Doctor-Blade Coating | Spreading slurry-like coating material with a precise blade gap 9 | Ambient conditions; Low cost; Highly scalable | Primarily for carbon-based coatings |
While vacuum-based deposition methods like PVD and CVD have dominated coating research, a recent experiment demonstrates how alternative approaches might offer better scalability and cost-effectiveness 9 .
Titanium substrates were cleaned and prepared to ensure optimal adhesion.
A porous titanium dioxide layer was developed to enhance bonding.
A specialized ink was formulated with carbon particles, solvents, and binders.
Carbon slurry was applied using a doctor-blade set to a precise gap.
Coated plates underwent controlled heat treatment to solidify the carbon layer.
Researchers evaluate bipolar plate coatings against well-established performance metrics, with interfacial contact resistance (ICR) and corrosion current density being particularly critical 2 .
| Property | Unit | DOE 2025 Target |
|---|---|---|
| Electrical Conductivity | S cm⁻¹ | >100 |
| Areal Specific Resistance | Ω cm² | <0.01 |
| Hydrogen Permeability | cm³ s⁻¹ cm⁻² | <2 × 10⁻⁶ |
| Contact Resistance | Ω cm² | <0.01 |
| Corrosion Current Density | μA cm⁻² | <1 |
| Cost | $ per kW | <5 |
| Flexural Strength | MPa | >45 |
| Coating Type | Substrate | Corrosion Current Density (μA/cm²) | Interfacial Contact Resistance (mΩ·cm²) |
|---|---|---|---|
| CrN/CrC Multilayer | Stainless Steel | 0.12-0.35 | 5-8 |
| Amorphous Carbon | Stainless Steel | 0.5-1.0 | 6-12 |
| TiN | Titanium | 0.8-1.5 | 10-20 |
| Doctor-Blade Carbon | Titanium with TiO₂ | <1.0 | <10 |
| Conductive Polymer | Aluminum | 1.0-2.0 | 15-30 |
Next-generation coatings designed to actively manage water, enhance heat transfer, or catalyze species recombination 8 .
Combining different coating types to balance cost and performance 4 .
Research into coating materials that are abundant and environmentally benign.
Machine learning algorithms to screen potential coating compositions and structures.
At currently <$5 per kW 6 , coating costs still need to decrease further for fuel cells to compete with incumbent technologies.
Developing coating processes that maintain consistent quality at high production volumes .
Real-world validation over thousands of hours of operation is still needed for newer coating technologies.
The growth of the bipolar plate market is linked to hydrogen refueling infrastructure expansion .
The market for fuel cell bipolar plates is projected to reach USD 6.5 billion by 2035 , highlighting the growing importance of these coating technologies.
The development of corrosion-resistant coatings for bipolar plates represents a perfect example of how materials science innovation enables technological revolutions. What began as a fundamental challenge has evolved into a sophisticated field of research yielding remarkable solutions.
From the intricate multilayer coatings deposited in high-tech vacuum chambers to the elegantly simple doctor-blade approach, these protective layers, though measured in micrometers or even nanometers, stand as critical enablers of the hydrogen economy. They embody the incremental progress that collectively transforms energy systems—the quiet breakthroughs that make loud impacts.
The next time you see a hydrogen fuel cell vehicle silently gliding down the street, remember the microscopic marvels working inside—the corrosion-resistant coatings that protect the heart of the fuel cell, ensuring that the only emission from its tailpipe is pure, clean water.