TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preparation (Claimed): Preparation (M1) of the composite catalyst involves providing a metal alloy; de-alloying the metal alloy to provide a porous metal catalyst that catalyzes several reactants to provide a reaction product; and adding a reaction-enhancing material to the porous metal catalyst such that the reaction-enhancing material is disposed within pores defined by the porous metal catalyst. In the method (M1), adding the reaction-enhancing material adds a liquid reaction-enhancing material that is drawn into and held within the pores defined by the porous metal catalyst by capillary forces. Preferred Components: When the porous metal catalyst catalyzes an oxygen reduction reaction to provide H2O as a reaction product, O2 is more soluble in the reaction-enhancing material than H2O, and the reaction-enhancing material is hydrophobic. The porous metal catalyst has a specific surface area of 5-100 (preferably 40-50, especially 44) m2/g. The porous metal catalyst comprises platinum (Pt). The porous metal catalyst comprises a metal selected from titanium, iron, cobalt, nickel, copper, iridium, rhenium, aluminum, manganese, palladium, osmium, rhodium, vanadium and/or chromium. The porous metal catalyst has an ensemble average pore diameter of less than 10 mu m (preferably less than 100 nm, more preferably 1-50 nm, especially 1-4 nm, particularly 2-3 nm). The porous metal catalyst has an average ligament diameter of 2-3 nm.    TECHNOLOGY FOCUS - METALLURGY - Preferred Components: The porous metal catalyst is an alloy that further comprises nickel (Ni). The porous metal catalyst is an alloy consisting of platinum and nickel. The porous metal catalyst is an alloy further satisfying formula PtxNi1-x.x=0.6-1 (preferably 0.67).    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Components: The reaction-enhancing material is a liquid in which the reactant is more soluble than a local environment that exposes the composite catalyst to the reactant. The reaction-enhancing material is a liquid in which the reaction product is less soluble than a local environment that receives the reaction product. The reaction-enhancing material is an ionic liquid (preferably (7-methyl-1,5,7-triazabicyclo(4.4.0)dec-5-ene)(bis(perfluoroethylsulfonyl)imide) ((MTBD)(beti)) or (7-methyl-1,5,7-triazabicyclo(4.4.0)dec-5-ene)(bis(trifluoromethylsulfonyl)imide) ((MTBD)(Tf2N))). EXAMPLE - No suitable example given.