Summary of proton exchange membrane knowledge

A proton exchange membrane is a thin layer of polymer electrolyte with cation exchange groups (sulfonic acid groups, carboxylic acid groups, phosphate groups, etc.). The cation exchange groups are chemically bonded to the polymer to form a single unit. This fixed connection method avoids the loss of small molecule electrolytes. Proton exchange membranes are divided into perfluorosulfonic acid membranes, partially fluorinated polymer membranes, new non-fluorinated polymer membranes, composite membranes, etc. according to the fluorine content. At present, perfluorinated proton exchange membrane is the mainstream technology with a high degree of industrialization. It is mainly used in downstream fuel cells, upstream electrolysis of water for hydrogen production, energy storage batteries and other fields.

The full name of PEMFC is proton exchange membrane fuel cell. The proton exchange membrane is the electrolyte of PEMFC, which plays the role of conducting hydrogen ions, isolating fuel and oxidants, and blocking electrons. It is the core component of PEMFC. Compared with other fuel cells, PEMFC has a higher power density due to the excellent performance of the proton membrane.

01

Perfluorosulfonic acid membrane

The perfluorosulfonic acid membrane is composed of a fluorocarbon backbone and an ether branch chain with a sulfonic acid group.

Characteristics: high mechanical strength, good chemical stability and high conductivity under high humidity conditions; high current density at low temperatures and low proton conduction resistance.

Advantages: high mechanical strength, good chemical stability, high electrical conductivity, high current density at low temperatures, low proton conduction resistance

Disadvantages: Proton conductivity deteriorates as temperature rises, chemical degradation is prone to occur at high temperatures, and the cost is high.

02

Non-perfluorinated proton exchange membrane

Use substituted chlorides instead of fluororesins, or blend fluorides with inorganic or other non-fluoride compounds.

Characteristics: Very low sulfonic acid group content and high working efficiency.

Advantages: low cost and high work efficiency.

Disadvantages: poor mechanical strength and chemical stability.

03

Fluoride-free proton exchange membrane

Composed of fluorinated hydrocarbon-free polymer membrane.

Advantages: low cost, little pollution

Disadvantages: Weak chemical stability

04

Composite film

Composite membrane composed of modified material and perfluorosulfonic acid resin.

Advantages: Improved mechanical properties, improved water transmission and distribution within the membrane, and reduced internal resistance of the proton exchange membrane

Disadvantages: high preparation technology requirements

Applications of proton exchange membranes

One of the main applications of proton exchange membranes is proton exchange membrane fuel cells. These fuel cells have a wide range of commercial and military applications, including the aerospace, automotive and energy industries. Early proton exchange membrane fuel cell applications were mainly concentrated in the aerospace industry. The higher capacity of fuel cells at the time made them an ideal choice compared to batteries.

PEM fuel cells are popular in automotive applications because they operate at relatively low temperatures and can start up quickly even in subfreezing conditions.