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.

Selective Electrodes for Mixed Reactant Fuel Cells

“…At the cathode oxygen ions have to be generated and be adsorbed hence hydrogen should not be chemically adsorbed. This can be controlled by the proper choice of the work function and affinity of the cathode material (9,13). At the anode oxygen ions originating from chemisorption of oxygen should be avoided.…”

“…At the anode oxygen ions originating from chemisorption of oxygen should be avoided. This can also be achieved by choice of the anode work function and ionization energy (9,13). This will allow the adsorbed hydrogen at the anode to only react with oxygen ions emerging from the solid electrolyte, as is desired.…”

Single chamber Solid Oxide Fuel Cells selective electrodes: A real chance with brownmillerite-based nanocomposites

“…Flow-through cells (also named Mixed Reactant Cell) in which the gas mixture is forced through repeated porous layers of cathode, electrolyte and anode are another possibility. [10] Riess [6,[11][12][13], stressed the importance of the selectivity of the electrodes on SC-SOFCs performance. A SC-SOFC is operated in an anomalous way compared to other cells.…”