Catalyst Design: X-rays Cross-examine the Fuel Cell Volcano Plot

Changing the electronic structure of a metal in order to “tune ” its affinity to catalytic reac-tion intermediates is a key element in catalyst design. Tailor-made catalysts with a carefully adjusted ratio of two or more different alloy components are particularly needed in fuel cells, which could efficiently power electric vehicles – without the range limitations of current batteries. Both convert chemically stored energy into electricity, but in batteries this storage is limited to the electrode materials themselves, while fuel cells draw hydrogen or methanol from a tank and oxygen from air. While the overall chemical reaction in a fuel cell is the same as in a combustion engine, its energy conversion is much more efficient since the reaction is separated in oxidation of the fuel at the anode, and the oxygen reduction reaction (ORR) at the cathode; the reaction free enthalpy is therefore directly converted into electricity. However, especially for the ORR an extremely careful design of catalyst materials is needed in order to meet two require-ments: high catalytic activity to minimize costly use of its active component, Pt, and, at the same time, high stability to prevent catalyst degradation during long-term operation in a corrosive environment