Titanium Oxide Carbon Bilayer Coatings for Fuel Cell Bipolar Plates
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Solution Overview
Problem
Bipolar plates in fuel cells face challenges with high contact resistance and corrosion, particularly due to the passive oxide film on metallic surfaces, which requires expensive coatings and is not adequately addressed by existing titanium nitride coatings.
Innovation Solution
A titanium oxide-coated carbon bilayer is applied to the metal plates, reducing contact resistance to less than 40 mohm-cm2 and improving corrosion resistance by forming a hydrophilic surface with a contact angle less than 30 degrees, effectively managing water and reducing metal ion release.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If metallic bipolar plates are used for mechanical strength, then structural integrity is improved, but contact resistance increases due to passive oxide film formation
Solution Approach 1:
The patent applies a composite coating structure consisting of a carbon layer and a titanium oxide layer on metallic bipolar plates. The carbon layer provides electrical conductivity to reduce contact resistance, while the titanium oxide layer offers corrosion resistance. This composite approach allows the metallic plate to maintain its mechanical strength while the coating system addresses the electrical and chemical stability issues.
Solution Approach 2:
The patent modifies the surface properties of the metallic bipolar plate by applying coatings that change the electrical and chemical parameters of the surface. The carbon layer alters the electrical conductivity parameter to reduce contact resistance, while the titanium oxide layer modifies the chemical stability parameter to prevent corrosion and metal ion release.
2Reliability
If expensive electrically conductive coatings like gold or polymeric carbon are applied, then contact resistance is reduced, but manufacturing cost increases
Solution Approach 1:
The patent uses a composite coating of carbon and titanium oxide layers that provides effective electrical conductivity and corrosion protection at lower cost than gold coatings. The carbon layer specifically addresses the contact resistance issue while being more cost-effective than precious metal coatings.
Solution Approach 2:
The patent employs cost-effective coating materials (carbon and titanium oxide) that can be applied through relatively simple processes, replacing expensive materials like gold. The coating system provides sufficient performance for the application while significantly reducing material and manufacturing costs.
3Ease of manufacture
If titanium nitride coatings are applied for corrosion resistance, then cost is reduced, but water affinity deteriorates with contact angle close to 60 degrees
Solution Approach 1:
The patent combines carbon and titanium oxide layers to achieve both cost-effectiveness and improved water affinity. The titanium oxide component provides hydrophilic surface properties with lower contact angle than titanium nitride, while the carbon layer maintains electrical conductivity. This composite structure addresses both the cost and water management requirements.
Solution Approach 2:
The patent changes the surface chemical composition by using titanium oxide instead of titanium nitride in the coating system. This parameter change in the coating material composition results in improved hydrophilicity with a lower contact angle, enhancing water affinity while maintaining cost-effectiveness.
4Strength
If metal bipolar plates are used, then mechanical strength is improved, but corrosion resistance worsens due to metal dissolution releasing iron, chromium and nickel ions
Solution Approach 1:
The patent applies a composite coating system where the titanium oxide layer serves as a protective barrier against corrosion, preventing direct contact between the corrosive environment and the metallic substrate. This preserves the mechanical strength of the metal while protecting against metal ion release through the corrosion-resistant oxide layer.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The titanium oxide-coated carbon bilayer significantly reduces contact resistance and enhances corrosion protection, improving the efficiency and durability of fuel cell performance while minimizing the need for costly coatings.
Implementation Method 1
improving corrosion resistance by forming a hydrophilic surface with a contact angle less than 30 degrees
Implementation Method 2
A titanium oxide-coated carbon bilayer is applied to the metal plates
Data Source
AI summary
A flow field plate for fuel cell applications includes a metal with a carbon layer disposed over at least a portion of the metal plate. The carbon layer is overcoated with a titanium oxide layer to form a titanium oxide/carbon bilayer. The titanium oxide/carbon bilayer may be activated to increase hydrophilicity. The flow field plate is included in a fuel cell with a minimal increase in contact resistance. Methods for forming the flow field plates are also provided.