Thermodynamics of Fuel Cells

Fuel cells replace uncontrolled combustion with controlled reactions, hence promise efficient use of fuels. In this chapter we apply our understanding of thermodynamics to evaluate fuel cell operation. The high theoretical efficiency of reversible fuel cells is reduced by losses due to mass transfer, resistance, and activation overpotential. To describe the latter, we present a derivation of the Butler-Volmer equation. Electrolyzers, which are used for sustainable production of hydrogen, follow the inverse process and are subject to the same suite of irreversible losses.