The invention provides a catalyst structure for catalytic reduction of nitrogen oxides in exhaust gases by supplying and subjecting fuel to combustion with periodic rich/lean excursions and contacting the resulting exhaust gases with the catalyst structure, wherein the catalyst structure comprises, on an inactive substrate: (A) an outer catalyst layer comprising an outer layer catalyst component wherein the outer layer catalyst component comprises a first catalyst component comprising a mixture or a composite oxide (except mixtures or composite oxides of cerium oxides and zirconium oxides) of (a) ceria and (b) at least one oxide of at least one element selected from zirconium, gadolinium, terbium, samarium and lanthanum, and a second catalyst component comprising (c) at least one catalyst component selected from rhodium, palladium and their oxides, and (B) an inner catalyst layer comprising an inner layer catalyst component wherein the inner layer catalyst component comprises (a) at least one catalyst component selected from platinum, rhodium, palladium and their oxides, and (b) a carrier material.