Current research is centred upon making compact
cells of high efficiency. They are described in terms
of the electrolyte that is used. The principle types
arealkali(AFC), described above, with aqueous
KOH as electrolyte transferring OH- ions; proton
exchange membrane(PEMFC), using a solid polymer electrolyte that conducts H+
ions; phosphoricacid fuel cell (PAFC), using phosphoric acid as
electrolyte in a matrix of silicon carbide to transfer