CATALYTIC REQUIREMENTS FOR MIXED REACTANT FUEL CELLS

Abstract

Significant advantage could be achieved if mixed reactant fuel cells, MR-FC, were functioning. These cells are intended to operate on a mixture of air and fuel introduced into both the cathode and anode compartment. Symmetry is broken by using different electrode materials exhibiting special and different catalytic properties. No high temperature fuel cell was reported to date to function as a true MR-FC and only one, low temperature type, did function properly. We discuss the required catalytic properties which are unique in that they promote electrochemical reactions and suppress chemical ones as well as possible ways to search for them. The chemical reaction which has to be suppressed is the direct reaction of fuel and oxygen as the two components are premixed and the mixture is then introduced into the fuel cell at both electrode compartments. The electrochemical reactions that should be promoted are the reduction of oxygen at the cathode and the oxidation of fuel at the anode only by oxygen ions that emerge from the solid electrolyte. Conditions to promote this selectivity are discussed. These are derived from the theory of chemisorption as applied to heterogeneous catalysis.