An exhaust
system 20 for an
internal combustion engine comprises a) a first catalysed substrate
monolith 12 comprising a first washcoat
coating disposed in a first washcoat zone 16 of the substrate
monolith and a second washcoat
coating disposed in a second washcoat zone 18 of the substrate
monolith, wherein the first washcoat
coating comprises a catalyst composition comprising at least one
platinum group
metal (PGM) and at least one support material, wherein at least one PGM in the first washcoat coating is liable to volatilise when the first washcoat coating is exposed to relatively extreme conditions including relatively high temperatures, wherein the second washcoat coating comprises at least one material supporting
copper for
trapping volatilised PGM and wherein the second washcoat coating is oriented to contact
exhaust gas that has contacted the first washcoat; and b) a second catalysed substrate monolith 14 comprising a catalyst for selectively catalysing the reduction of oxides of
nitrogen to dinitrogen with a nitrogenous reductant disposed downstream from the first catalysed substrate monolith.