Polymer Electrolyte Membrane Fuel Cell developed by ISRO

Context: The Indian Space Research Organisation (ISRO) has effectively conducted a trial of a 100 W-class Power System utilising Polymer Electrolyte Membrane Fuel Cell (PEMFC) technology on its orbital platform, POEM3.

About Polymer Electrolyte Membrane Fuel Cell 

A Polymer Electrolyte Membrane (PEM) fuel cell is a type of electrochemical cell that converts chemical energy from the reaction of hydrogen with oxygen or another oxidising agent into electrical energy. 

The key component of a PEM fuel cell is the polymer electrolyte membrane, which serves as the electrolyte.

Key feature of PEM fuel cells

1. Polymer Electrolyte Membrane (PEM): The PEM is a solid polymer electrolyte typically made of a perfluorosulfonic acid material, such as Nafion. 
2. Use of Polymer Electrolyte Membrane: This membrane allows protons to pass through while blocking the passage of electrons. It plays a crucial role in separating the anode and cathode reactions.

Components and Working of Polymer Electrolyte Membrane (PEM) Fuel Cell

Anode and Cathode: At the anode, hydrogen gas is typically supplied, and it undergoes electrochemical oxidation to produce protons (H⁺) and electrons (e⁻). The electrons flow through an external circuit, creating an electric current.

Catalysts: Platinum or other platinum-group metals are commonly used as catalysts on the anode and cathode to facilitate the electrochemical reactions.

Electrochemical Reactions:

At the anode: 2H₂→4H⁺ + 4e^-

At the cathode: O₂ + 4H⁺ + 4e^- →2H₂O

Proton Exchange: Protons generated at the anode move through the PEM to the cathode, while electrons flow through an external circuit, creating an electrical current.

Characteristics of Polymer Electrolyte Membrane Cell (PEMC) 

• Operating Temperature: PEM fuel cells operate at relatively low temperatures (typically between 60 to 80 degrees Celsius), allowing for quick start-up times (less warm up time) and increased efficiency in certain applications.
• Catalyst Requirement: To facilitate the separation of electrons and protons in hydrogen, PEM fuel cells use a noble-metal catalyst, typically platinum leading to high cost.
• Carbon Monoxide Sensitivity: The platinum catalyst in PEM fuel cells is highly sensitive to carbon monoxide (CO) poisoning. If the hydrogen used in the fuel cell is derived from a hydrocarbon fuel, it may contain trace amounts of carbon monoxide. The presence of CO can significantly degrade the performance of the platinum catalyst, leading to a decrease in fuel cell efficiency.
• Carbon Monoxide Reduction Reactor: To address the issue of carbon monoxide poisoning, an additional reactor is often employed to reduce the levels of carbon monoxide in the fuel gas before it reaches the fuel cell. This reactor adds complexity and cost to the overall system.
• Water Management: PEM fuel cells require effective water management to maintain the hydration level of the polymer electrolyte membrane. Water produced during the electrochemical reactions needs to be removed from the membrane to prevent flooding.

Applications of Polymer Electrolyte Membrane (PEM) Fuel Cell

• PEM fuel cells are commonly used in various applications, including transportation (such as fuel cell vehicles), stationary power generation (backup power systems, distributed generation), and portable electronic devices. 
• These fuel cells are known for their high efficiency, fast start-up times, and ability to operate under varying loads. 
• However, challenges such as cost, durability, and sensitivity to contaminants in the hydrogen fuel remain areas of ongoing research and development.