Active Area Name

The area of a fuel cell electrode which is electrochemically active and able to produce electricity from the supplied fuel.


The fuel electrode in a fuel cell at which oxidation occurs.

APU - Auxiliary Power Unit

An auxiliary power unit or APU (for example a fuel cell) provides electricity and is supplemental to the main power source of a vehicle (such as an internal combustion engine).

Bipolar Plate

A fuel cell stack component which allows electricity to be conducted between adjacent fuel cell membrane electrode assemblies in a stack. They are often designed to channel the flow of gases and heat to and from the cell.


The balance of plant (BoP) in a fuel cell system is the auxiliary equipment required to ensure the fuel cell operates as a reliable power source. This may include fuel reformers and pumps, for example.


A catalyst increases the rate of a reaction without itself being consumed. In a fuel cell catalysts are used for the electrodes (to break down hydrogen into electrons and protons).

Catalyst loading

The catalyst loading refers to the mass of catalyst per unit area of a fuel cell electrode.


The oxygen/air electrode in a fuel cell where reduction occurs.


CCM stands for Catalyst coated membrane.


Combined heat and power (CHP) is a way to make even more efficient use of fuel cells. The waste heat from the electricity production is used to heat water or for space heating.

Direct methanol fuel cell (DMFC)

A direct methanol fuel cell (DMFC) functions in a similar way to a PEMFC and uses the same electrolyte, but reforms methanol directly on its electrode to form hydrogen.


The electrode is where reaction of a chemical species occurs and electrons are either released or accepted. Typically this will be a metal, such as platinum in PEMFC.


An electrochemical device which works like a fuel cell in reverse and can split water into its constituent molecules, hydrogen and oxygen, by passing an electric current through it.


A substance which carries charge via the migration of ions; together with the external connections of a fuel cell, an electrical circuit can be created.


Fuel cell vehicle.

Fuel Cell

A fuel cell is an electrochemical device, which converts chemical energy to electrical energy without combustion. Unlike a battery, a fuel cell will continuously produce electricity as long as fuel is supplied and the catalyst remains active.

Fuel cell supplier

See Fuel Cell Manufacturers.

Fuel cell manufacturers

Fuel cell manufacturers are companies that develop, produce and sell fuel cells. Fuel cell manufacturers themselves source required fuel cell components from suppliers like Freudenberg FCCT.


Gas diffusion electrode i.e. catalyst is coated onto the GDL


Gas diffusion layers, typically made out of carbon paper or cloth, play a number of important roles in a fuel cell, such as structural support, reactant transport, water removal, and heat conduction.


Hydrogen is the fuel most commonly used in fuel cells.


High temperature proton exhange membrane fuel cell (HT PEMFC). A variant of the PEMFC which uses a mineral acid based electrolyte rather than an aqueous one and can operate at temperatures up to 200°C. These cells are more tolerant to impurities in the fuel as a result.


Kilowatt, a unit of power equal to 1,000 watts.


Kilowatt electric, a measure of electric power output.


Kilowatt-hour, a unit of energy. A device with a power output of one kilowatt running for one hour would generate one kilowatt-hour of energy.

kWth or kWt

Kilowatt thermal, a unit of thermal (heat) power output.


This separates two electrodes of a fuel cell, acting as the electrolyte and allowing passage of ions between the electrodes.

Membrane Electrode Assemblies - MEA

Membrane electrode assembly or MEA, a structured component in a PEMFC and DMFC, consisting of a membrane with an electrode on each side.


Methanol, a fuel that is used in DMFCs.


Micro-combined heat and power fuel cells refer to stationary units designed to provide electricity, hot water and sometimes space heating. These can either be for residential use or for small offices and commercial buildings.


Palladium is one of the platinum group metals and can be used for the purification of reformed hydrogen for fuel cells.

Pemfc fuel cell

Proton exchange or polymer electrolyte membrane fuel cells or (PEMFC) use a solid acid membrane as the electrolyte. PEMFC operate at low temperatures (100°C) and use platinum-containing electrodes.


Polymer electrolyte membranes based on perfluorosulfonic acid.

Polarisation curve

A measure of cell performance that indicates the relationship between current density and voltage across a fuel cell.

Power density

The power density of a fuel cell is the power produced in relation to the active area or volume of the cell, expressed in W/m2 or W/m3 respectively.

Proton exchange membrane (PEM)

Proton exchange membranes, also referred to as polymer electrolyte membranes due to their composition, separate the feed gases in a PEMFC or DMFC and act as the electrolyte by allowing the passage of protons.

Proton exchange membranes, also referred to as polymer electrolyte membranes due to their composition, separate the feed gases in a PEMFC or DMFC and act as the electrolyte by allowing the passage of protons.

Proton exchange membrane fuel cells

Proton exchange or polymer electrolyte membrane fuel cells (PEMFC) use a solid acid membrane as the electrolyte. PEMFC operate at low temperatures (100°C) and use platinum-containing electrodes.


Platinum is a commonly used catalyst material for PEMFC and DMFC technologies.


Reformate is the output of a fuel reformer. Such a gas stream often contains hydrogen, carbon monoxide and carbon dioxide. This reformate gas can be fed to a fuel cell, generally after some degree of cleanup.

Reversible fuel cell

A reversible, or regenerative, fuel cell can operate as a fuel cell, or in reverse like an electrolyser.


Ruthenium is a member of the platinum group of metals and is used in DMFC to assist with internal fuel reforming.

Separator plates

Separator plates are used to separate fuel cells from one another arranged in a fuel cell stack.

Single cell

A single cell is the smallest and most basic form of fuel cell. It is useful for testing and development purposes to predict how stacks will perform.


A fuel cell stack is an arrangement of individual fuel cells, usually in series to provide a useful output voltage.

Thermal efficiency

The thermal efficiency of a fuel cell system is the ratio between the output of the system (as heat and power) and the


Uninterruptible power supply.


Watt, a unit of power. It is a measure of the rate of energy conversion or generation, equivalent to one joule per second.

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