Fuel Cell Reactions and Thermodynamic Efficiencies

In the case of H2-O2 fuel cells, the thermodynamic efficiency or the ideal efficiency of the energy conversion is always related to the reaction enthalpy of the chemical process involved. The ideal thermal efficiency of the cell can be expressed as follows  

For this particular fuel cell reaction, the chemical reaction equation can be written as follows  

This clearly shows that the by-product of this chemical reaction is water. 

In an Hj-Oj fuel cell, typical cell voltage EP°) under standard conditions or under normal temperature and pressure conditions is typically 1.23 V, and the thermodynamic cell voltage E° ) is about 1.48 V. For almost all fuel cell reactions, one can expect the reaction entropy AS) to be less than zero. This means the amount of heat generated in the surrounding areas will be a product of temperature T) and reaction entropy AS). With the conversion of the chemical energy into the 

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