stevenf: answer to your question
stevenf: It seems no one has actually answered your first question, "How does a fuel cell work?"
Reading all the posts, I observed that members are discussing two different technologies as one.
The two are:
1) Hydrolysis
2) Oxidation
HYDROLYSIS
A "fuel cell" is of the "hydrolysis" (or electrolysis) type. This is the technology used in the Honda FCX. In the process of hydrolysis, electrical current is passed through water to break it down into hydrogen and oxygen according to the following reaction: 2H2O + electricity --> 2H2 + O2. A small amount of electricity is generated, and this is what is used to power the car. More specifically: pressurized hydrogen gas (H2) enters the fuel cell on the anode side. This gas is forced through the catalyst by the pressure. When an H2 molecule comes in contact with the platinum on the catalyst, it splits into two H+ ions and two electrons (e-). The electrons are conducted through the anode, where they make their way through the external circuit (doing useful work such as turning a motor) and return to the cathode side of the fuel cell.
Meanwhile, on the cathode side of the fuel cell, oxygen gas (O2) is being forced through the catalyst, where it forms two oxygen atoms. Each of these atoms has a strong negative charge. This negative charge attracts the two H+ ions through the membrane, where they combine with an oxygen atom and two of the electrons from the external circuit to form a water molecule (H2O).
This reaction in a single fuel cell produces only about 0.7 volts. To get this voltage up to a reasonable level, many separate fuel cells must be combined to form a fuel-cell stack.
OXIDATION
Oxidation is the combustion technology (think Hindenberg), and is used in the BMW H2R engine. The combustion (oxidation) of hydrogen is the process by which energy is created according to the following formula:
2H2 + O2 --> 2H2O + energy. The only by-product of this reaction is water.
This technology, however, requires a supply of hydrogen, which must be generated somewhere, at significant infusion of energy.
CONSIDERATIONS
Whether electrical current is used in the hydrolysis method to split the hydrogen molecule, or energy is used to generate hydrogen to be combusted in the oxidation method, energy is required to initiate either process, and is a contributor to the inefficiency of both methods.
1st edit: remove *; add "CONSIDERATIONS"