NOVELTY - Altering the surface composition of an alloy comprises: (a) providing an alloy comprising at least two metals; (b) exposing the alloy to an oxidizing agent where to cause oxidation of at least one of the metals to form at least one metal oxide on a surface of the alloy; and (c) exposing the resulting alloy to a reducing agent where to reduce the metal oxide.    USE - The method is useful for altering the surface composition of alloy. The surface-modified alloy is useful as a catalyst, where the catalyst is a heterogeneous catalyst. The catalyst is useful for automobile exhaust emission control, ammonia oxidation, methanol oxidation, methanol reformation, or Fischer-Tropsch catalysis (all claimed).    ADVANTAGE - The method has significant potential in producing catalytic nanoparticles having unique surface structures. By varying the initial alloying elements, along with fine-tuning the oxidation/reduction exposure conditions, it is possible to produce nano-engineered catalyst structures from initially homogeneous alloys, with each structure optimized for use in a specific catalytic application. The method also serves to reduce the cost of catalytic materials.    DETAILED DESCRIPTION - Altering the surface composition of an alloy comprises: (a) providing an alloy comprising at least two metals; (b) exposing the alloy to an oxidizing agent where to cause oxidation of at least one of the metals to form at least one metal oxide on a surface of the alloy; and (c) exposing the resulting alloy to a reducing agent where to reduce the metal oxide; where the metals are each independently selected from groups 6, 7, 8, 9, 10 and 11 of the Periodic table and include at least one metal selected from platinum (Pt), palladium (Pd), rhodium (Rh) and ruthenium (Ru), and further where the alloy is not a platinum-rhodium (Pt-Rh) alloy. INDEPENDENT CLAIMS are:    (1) a surface-modified alloy obtainable by the method above; or a surface-modified alloy comprising two or more metals, where the alloy has at least one surface comprising island structures of at least one metal, where the metals are each independently selected from groups 6, 7, 8, 9, 10 and 11 of the Periodic table and include at least one metal selected from platinum (Pt), palladium (Pd), rhodium (Rh) and ruthenium (Ru), and further where the alloy is not a platinum-rhodium (Pt-Rh) alloy; and    (2) a catalytic converter or fuel cell comprising the surface-modified alloy, e.g. in nanoparticulate form.