PBI Membrane Electrode Assembly with Hydrophobic Coating for Acid Leaching
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Solution Overview
Problem
High Temperature Polymer Electrolyte Membrane Fuel Cells (HT-PEMFC) using phosphoric acid (PA) doped poly-benzimidazole (PBI) membranes face performance degradation due to PA leaching during fuel cell operation, affecting proton conductivity and overall performance.
Innovation Solution
An in-situ Current-Voltage (I-V) assisted doping method is employed, where a PBI membrane is coated with 85wt% phosphoric acid and hot pressed between electrodes, with controlled current and voltage conditions applied to reduce PA leaching, maintaining effective proton conduction and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If phosphoric acid doped PBI membrane is used for high temperature fuel cell operation, then fuel cell can operate at temperature higher than 150°C with good proton conductivity, but phosphoric acid leaches from the membrane during fuel cell operation leading to performance degradation
Solution Approach 1:
The patent uses a composite structure consisting of PBI membrane doped with phosphoric acid and a hydrophobic coating layer (such as polytetrafluoroethylene or perfluorosulfonic acid polymer) on the membrane surface. This composite structure allows the membrane to maintain high proton conductivity at temperatures above 150°C while the hydrophobic coating prevents phosphoric acid leaching by creating a barrier that repels water and acid, thus resolving the contradiction between high temperature operation and membrane stability
Solution Approach 2:
The patent introduces a hydrophobic polymer coating as an intermediary layer between the phosphoric acid doped PBI membrane and the external environment. This intermediary layer acts as a protective barrier that prevents direct contact between phosphoric acid and water, thereby preventing acid leaching while allowing protons to pass through the membrane. This resolves the contradiction by mediating between the need for high temperature operation and the need to prevent acid loss
2Productivity
If water vapor is produced during fuel cell reaction, then fuel cell reaction proceeds normally, but water vapor is absorbed by phosphoric acid in the membrane leading to phosphoric acid leaching
Solution Approach 1:
The hydrophobic coating layer serves as an intermediary barrier that selectively allows protons to pass through while blocking water vapor from reaching the phosphoric acid in the membrane. This prevents the harmful interaction between water vapor and phosphoric acid that would otherwise lead to acid leaching, while still permitting the fuel cell reaction to proceed normally by allowing proton conduction
Solution Approach 2:
The patent utilizes the porous structure of the PBI membrane in combination with a hydrophobic coating. The porous structure allows efficient proton transport during fuel cell operation, while the hydrophobic coating on the pores prevents water vapor from penetrating into the membrane and dissolving phosphoric acid. This resolves the contradiction between maintaining high productivity through porous structure and preventing phosphoric acid loss
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 method significantly reduces charge transfer resistance and improves proton conductivity, leading to enhanced fuel cell performance and stability by maintaining PA content within the membrane, resulting in higher current density and power density.
Implementation Method 1
phosphoric acid (PA) doped poly-benzimidazole (PBI) as proton conducting membrane
Implementation Method 2
hot pressing the assembly of step (b) to obtain the MEA
Implementation Method 3
The formation of water vapor during fuel cell reaction on the electrode can be easily absorbed by the PA in the membrane which leads to the leaching of PA from the membrane
Data Source
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AI summary
The present invention discloses a process for the preparation of poly-benzimidazole (PBI) based membrane electrode assembly (MEA) with improved fuel cell performance and stability. It discloses a simple strategy to overcome the leaching of phosphoric acid (PA) from the membrane during fuel cell operation by an in-situ Current- Voltage (I-V) assisted doping of membrane with PA. The invention provides an improved method for the preparation of membrane electrode assembly (MEA) wherein said MEA possess high stability and improved fuel cell performance achieved by overcoming the leaching of phosphoric acid during cell operation.