The hydrogen fuel cell uses hydrogen (H2) gas as the fuel. The gas can be obtained from a
number of sources ranging from natural gas to water.
The gas strikes a catalyst material, such as platinum, which causes the H2 molecule to split into two hydrogen protons (H+), and two electrons (e-). The electrons flow through the EV motor, and the protons are routed through a membrane and combined with oxygen. The result is water and power. It is very clean.
The schematic below shows the basic operational theory. Since one unit alone produces about 0.7 volts, the units in the schematic are repeated, or stacked, to form the fuel stack.
Types of fuel cells
There are variations on the basic hydrogen fuel cell above. These variations may include different elements used in the catalyst, and other types of membranes used to separate the hydrogen ions into protons and electrons.
Here are a few of the types of fuel cells and their current best uses:
- Polymer/proton exchange membrane fuel cell (PEMFC) - this fuel cell is currently the most promising for transport. Operating temperature is 175 degrees F. The new Honda Clarity features a PEMFC fuel cell stack.
- Solid oxide fuel cell (SOFC) - good for large scale power generating plants. Operating temperature is 1,800 degrees F.
- Alkaline fuel cell (AFC) - One of the oldest fuel cells used by NASA. Very expensive.
- Molten-carbonate fuel cell (MCFC) - Read molten - these cells work at 600 degrees Celsius. They are also used in large scale power generation. Operating temperature is 1,250 degrees F.
- Phosphoric-acid fuel cell (PAFC) - operates at 400 degrees F, and is best for small scale power generation stations
- Direct-methanol fuel cell (DMFC) - similar to the PEMFC, but needs platinum, which is expensive.
Research is ongoing by major auto manufacturers to improve the PEM cell for cars and trucks. So far, the main advantage of hydrogen fuel cells is their range. The main drawback of the fuel cell is their cost.
The catalyst for the EV fuel cell is likely to be made of platinum. The silvery metal costs more than gold, currently at nearly $1,800 per ounce.
Recent research has found a possible platinum substitute. Los Alamos scientists have discovered a catalyst using a low cost blend of iron, cobalt, and a form of carbon. The compounds may be derived from the substance polyaniline. Polyaniline is a common organic compound first produced from indigo.
The hydrogen fuel cell for cars has the potential to replace both the internal combustion engine, and the battery pack for cars. A fuel cell is basically a cell that produces electricity through electrochemical reaction - like a battery. All fuel cells operate on hydrogen fuel.
Fuel cells and batteries have a lot in common. Both the chemical battery and the fuel cell have an anode and cathode. The flow of negatively charged electrons in both the fuel cell and the battery produce the power used by the vehicle.