Hydrogen Fuel Cell Automobiles

With gasoline now more than $2.00 a gallon, alternate automobile technologies will be discussed with greater interest and developed with more urgency. For our government, the hydrogen fuel cell-powered automobile is at the top of the list of future technologies. This paper presents a simple description of the principles behind this technology and a brief discussion of the pros and cons. It is also an extension on my previous paper on the physics of the automobile engine.1 There have been numerous articles on the hydrogen fuel cell automobile. Strong supporters of the hydrogen fuel cell automobile include Amory Lovins2 and Joan Ogden.3 A more balanced approach comes from Mathew Wald4 and the American Physical Society.5 Robert Service6 and Steven Ashley7 take a more skeptical position. I probably fall in the skeptical camp, but I leave it to the reader to make his or her own evaluation. The hydrogen fuel cell is fundamentally a battery that operates with H2 and air (O2) as its fuel, electricity as its output, and water and heat as its exhaust. This article will focus on the proton-exchange membrane (PEM) fuel cell, which is the type most readily usable and currently being road tested in automobiles.8 Each PEM fuel cell has a sandwich structure with five layers, as seen in Fig. 1.9 The two outer layers are the backing layers. They are both porous to gases and electrically conducting, and are usually made of carbon paper or carbon cloth. The anode-backing layer allows hydrogen gas to reach the anode and collects electrons from the anode. The cathode-backing layer allows air (oxygen) to reach the cathode, water vapor to leave the cathode, and electrons to flow to the cathode. Layers two and four are the anode and cathode, which usually consist of platinum nanoparticles embedded in a carbon substrate. On the platinum surfaces in the anode, the hydrogen molecules are split into two protons and two electrons. On the platinum surfaces of the cathode, the oxygen molecules, protons, and electrons combine to form water molecules. The middle layer is a thin polymer electrolyte membrane, similar