Why do fuel cells exhibit efficiency improvements with increasing operating pressure?
The dependence of the reversible cell potential is given by the Nernst equation which describes mathematically the theoretical operation of a fuel cell. This equation shows that as the operating pressure increases the reversible cell potential or voltage also increases. The rate of cell potential increase does decline at high pressures. Enhanced cell voltages are due largely to the increase in reactant partial pressures and the resulting improvements in mass transport rates. This phenomenon has lead to the use of hybrid systems that marry gas turbines and fuel cells together. The gas turbine provides a high pressure environment for the fuel cell while using on the fuel cell waste thermal energy as its energy source.
