The Environmental Engineering Hub

Most fuel cells use hydrogen as fuel because of its high reactivity for the electrochemical reaction in the anode and the water release from oxidation, which is harmless to the environment. Thus, vehicles that employ PEMFCs (Proton-exchange Membrane Fuel Cells) may be classified as zero-emission. However, hydrogen is not readily available in most places and it has be generated before fuel cells can be used. One common way of producing hydrogen is through the electrolysis of water, which is the reverse process of a fuel cell. Even though the method may seem perverse, it is in fact a very convenient way of providing hydrogen for mobile fuel cells. Another method of providing fuel is through biological processes that can break down fossil or bio-fuel. Some of these methods are based on enzymes, bacteria or light. In other cases, hydrogen is produced in large central plants, or by electrolysers and is stored for use in fuel cells. There is already something of an infrastruct...

Most of the time, the designer doesn't have the choice between air and oxygen when assembling a PEM fuel cell. Oxygen is employed in systems that don't depend on air to operate, such as submarine and spacecraft (when that is not the case, air is used). However, the performance of a PEM fuel cell is greatly improved when oxygen is used. That happens because of three factors: The increase in partial pressure of oxygen makes the 'no loss' open circuit voltage rise, as appointed by the Equation of Nernst (https://en.wikipedia.org/wiki/Nernst_equation). Use of better catalyst sites reduces the activation over-voltage. The mass transport or concentration over-voltage losses are reduced by the increase in the limiting current, which is an event caused by the absence of nitrogen(a gas that contributes for this kind of loss at high current densities. Some results have showed that the change from air to oxygen in a PEMFC can increase performance by as much as 30%.  R...