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Most recent posting below. See other articles in the column to the right.

Hydrogen Cars

May 12, 2008

Hydrogen cars have been in the news lately as another alternative to gasoline or diesel vehicles.

Some are afraid of the hydrogen vehicle concept, so in this article we look at exactly what a hydrogen vehicle is and how it runs.

One way a hydrogen car makes energy is by using a fuel cell to create electricity.

A fuel cell is an electrochemical energy conversion device, a mechanism that changes hydrogen and oxygen into water; that water is then used to create electricity, which is used to power electric motors.

This process is called fuel cell conversion; it produces energy without pollution and its only waste materials are water and heat.

There are various types of fuel cells; polymer exchange membrane fuel cells (PEMFC), solid oxide fuel cells (SOFC), alkaline fuel cells (AFC), molten-carbonate fuel cells (MCFC), phosphoric acid fuel cells (PAFC) and direct methanol fuel cells (DMFC).

Now that all that’s out of the way, we’ll talk about the one most commonly used in vehicles—the PEMFC.

A polymer exchange membrane fuel cell has many parts; an anode, cathode, electrolyte, and catalyst. The anode is the negative post; it guides free hydrogen electrons to an external circuit.

It uses canals that are carved into it to diffuse the hydrogen gas uniformly over the face of the catalyst. The cathode is the positive negative post; it uses canals carved into it to disperse oxygen to the face of the catalyst. It also directs the electrons back from the external circuit to the catalyst so they can mix with hydrogen ions and oxygen to create water.

The electrolyte is a proton exchange membrane; it is a specially treated material that directs positively charged ions and obstructs electrons.

The catalyst is another special material that hosts the reaction of oxygen and hydrogen, and its surface is coarse and absorbent so that the greatest surface area can be exposed to the hydrogen or oxygen.

In order for a hydrogen car to make energy, pressurized hydrogen gas enters the fuel cell on the anode side. The gas is forced through the catalyst by the pressure.

When these molecules come in contact with the catalyst, it splits into two hydrogen ions and electrons. The electrons are led through the anode, make their way through the external circuit where, among other things, they provide the energy to crank the motor, and return to the cathode side of the fuel cell.

At the same time on the cathode side of the fuel cell, pressurized oxygen gas is traveling through the catalyst, where it splits into two oxygen atoms with negative charges. These negative charges attract the two hydrogen ions through the membrane, where they mix with an oxygen atom and two electrons from the external circuit and make a new water molecule.

All this work creates less than 1 volt of electricity, so to boost this output separate fuel cells are combined to create a full cell stack, which provides enough energy to power a vehicle.

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