Proton exchange membrane (PEM) cells – PEM cells are widely used in automotive and portable applications due to their compact size, fast start-up, and high power density.

Proton Exchange Membrane (PEM) fuel cells, also known as Polymer Electrolyte Membrane fuel cells, are the most commercially mature type, particularly favored for transportation and portable applications. Their distinguishing qualitative feature is the use of a solid, proton-conducting polymer membrane (often a perfluorosulfonic acid polymer like Nafion) as the electrolyte. This solid electrolyte makes them inherently simpler and more robust than liquid-electrolyte fuel cells. PEM cells operate at relatively low temperatures, typically between 60∘C and 80∘C, which allows for rapid startup and a quick response to changes in power demand, essential for dynamic applications like vehicles.

The low operating temperature, however, requires the membrane to be constantly humidified with water to maintain its conductivity—a critical system management challenge. This low temperature also necessitates the use of highly active catalysts, predominantly platinum, to drive the electrochemical reactions at the anode and cathode. This reliance on a costly material is the single greatest qualitative challenge to cost reduction for PEM cells. The inherent design offers a high power density (power per unit volume), making them compact and lightweight, which is why they dominate the Fuel Cell Electric Vehicle (FCEV) segment, as well as drone and backup power applications. Current research efforts in PEM technology focus on developing High-Temperature PEM (HT-PEM) cells that can operate at temperatures above 100∘ C, which would simplify the cooling and water management systems, improve tolerance to fuel impurities (like carbon monoxide), and ultimately reduce the system's complexity and cost. The success of PEM cells in the mobility sector will largely determine the trajectory of the entire fuel cell market.

Proton Exchange Membrane (PEM) Cells: FAQs
Q1: What is the primary advantage of PEM cells that makes them ideal for transportation?
The primary advantage is their low operating temperature and high power density, enabling a fast startup and quick response to changes in power demand, all within a compact and lightweight package.

Q2: Why do PEM cells face challenges regarding the catalyst material?
PEM cells operate at a low temperature, which requires the use of highly active and expensive catalysts, predominantly platinum, to facilitate the electrochemical reactions, posing a major barrier to cost reduction.

Q3: What is the function of the polymer membrane in a PEM cell?
The polymer membrane serves as the solid electrolyte, which is responsible for conducting protons (H+) from the anode to the cathode while simultaneously acting as a barrier to prevent the flow of electrons and reactant gases (hydrogen and oxygen).