Catalyst articles comprising palladium and related methods of preparation and use are disclosed. Disclosed is a catalyst article comprising a first catalytic layer formed on a substrate, wherein the first catalytic layer comprises palladium impregnated on a ceria-free oxygen storage component and platinum impregnated on a refractory metal oxide, and a second catalytic layer formed on the first catalytic layer comprising platinum impregnated on an oxygen storage component and rhodium impregnated on a zirconia-coated or yttria-coated alumina. The palladium component of the catalyst article is present in a higher proportion relative to the other platinum group metal components. The catalyst articles provide improved reductions in NOx in exhaust gases, particularly after lean-rich aging.