The necessity for a better understanding of the basic processes that
determine the operation of fuel cells became evident during the devel-
opment of practical units in the last three decades. The search for
efficient electrocatalysts in low-temperature fuel cells intensified the
general study of the nature and the role of the electrode material. Re-
search on the complex mechanisms of the anodic oxidation of different
fuels and of the reduction of molecular oxygen on solid electrodes was
stimulated, and the strong influence of adsorbed species on the
electrode reaction in question was investigated. Suitable electrolytes
had to be found for the high-temperature fuel cells. The use of
electrodes with large internal surface lead to the development of models
of porous electrode. structures and to the mathematical analysis of the
operation of these models under certain conditions. While the chapters I
to III introduce the reader to the general field offuel cells, the
progress made in the understanding of the basic problems in the
electrochemistry of fuel cells since the end of the second world war is
reviewed in chapters IV to XVI of this monograph. In contrast, the
technological aspects necessary for the development of practical units
are not covered here. The open literature published as books or as
papers in scientific journals has been considered up to the time of the
writing of the final draft of the specific chapter, at least till the
end of 1967.