Electrolyte Management in Liquid Electrolyte Fuel Cells

Abstract

Currently there are three major liquid-electrolyte fuel cells: alkaline (AFC), phosphoric (PAFC) and carbonate fuel cells, utilizing liquid electrolytes KOH, H3PO4 and M2CO3 (M: alkali ions), respectively. The electrolytes provide ionic conduction, reactant gas separation, and electrochemical kinetics. The electrolyte inventory and distribution in operating fuel-cell electrochemically-active cell components (electrodes and electrolyte matrix) need to be carefully managed to achieve desired performance and life. There are many similarities in physicochemical/electrochemical processes as well as electrolyte management schemes in these fuel cells. Internal-reforming carbonate fuel cell (Direct Fuel Cell, DFC®) is being commercially deployed by FuelCell Energy (FCE), its German subsidiary FCES (FuelCell Energy Solutions), and South Korean partner POSCO Energy. Successful electrolyte management schemes had allowed DFC stacks to achieve commercial stack performance and endurance goals. In this paper, electrolyte processes and management schemes in these three major liquid-electrolyte fuel cells are reviewed.