Fuel Cell Membrane Drying to Suppress Catalyst Dissolution
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Solution Overview
Problem
Electrochemical conversion assemblies with humidified membrane electrode assemblies experience significant start-up/shut down losses due to corrosion and catalyst dissolution caused by high voltages during the displacement of air in the anode flow field, leading to degradation of the support material and catalysts.
Innovation Solution
Implementing a shut down sequence where a substantially dry gas is driven through the cathode or anode flow fields to reduce the water content of the proton exchange membrane to below 5, suppressing catalyst dissolution and corrosion, and using an assembly controller to initiate this sequence to manage the water content effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a hydrogenous front is driven through the anode flow field during start-up, then the air in the anode flow field is displaced, but high voltages are developed on the cathode causing corrosion and catalyst dissolution
Solution Approach 1:
A dry gas is supplied to the cathode flow field before the hydrogenous front is driven through the anode flow field. This preliminary action removes water from the proton exchange membrane, creating conditions that suppress corrosion and catalyst dissolution during the subsequent high-voltage start-up phase.
Solution Approach 2:
The dry gas treatment creates a protective state in the membrane by reducing water content before the harmful high-voltage condition occurs. This preliminary anti-action counteracts the degrading effect of high voltage on the cathode, preventing corrosion and catalyst dissolution before they can occur.
2Power
If the proton exchange membrane is kept humidified for enhanced proton conductivity, then electrical performance is improved, but water content promotes corrosion and catalyst dissolution during start-up/shut down
Solution Approach 1:
The water content in the proton exchange membrane is dynamically adjusted based on operational phase. During normal operation, the membrane is kept humidified for optimal proton conductivity. During start-up and shut-down, the membrane is dried by supplying dry gas to the cathode flow field, suppressing corrosion while maintaining the ability to quickly restore humidity when needed.
Solution Approach 2:
The water content parameter of the proton exchange membrane is changed from high (humidified) to low (dry) depending on the operational state. By controlling the water content parameter through dry gas supply during critical phases, the system achieves both high proton conductivity during operation and corrosion protection during transitions.
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
This approach significantly mitigates degradation by reducing water content in the membrane electrode assembly, thereby extending the lifespan of the components and maintaining the electrochemical conversion assembly's efficiency over multiple cycles.
Implementation Method 1
a substantially dry gas is driven through the cathode flow field for an amount of time sufficient to reduce the water content of the proton exchange membrane
Data Source
AI summary
A method of operating an electrochemical conversion assembly is provided where a shut down sequence is introduced where a substantially dry gas is driven through the cathode flow field. The dry gas is supplied for an amount of time sufficient to reduce the water content of the proton exchange membrane to a level sufficient to suppress corrosion and catalyst dissolution in the membrane electrode assembly. Additional embodiments are disclosed.