A system, comprising: an exhaust aftertreatment system configured to treat emissions from a combustion engine, wherein the exhaust aftertreatment system comprises: a three-way catalyst assembly having a first outlet; an ammonia slip catalyst assembly configured to receive a fluid from the TWC assembly and to convert ammonia (NH 3) within the fluid into nitrogen (N 2), wherein the ASC assembly has an inlet and a second outlet; a fluid conduit disposed between the TWC assembly and the ASC assembly and configured to transfer the fluid from the TWC assembly to the ASC assembly; an oxidant injection system coupled to the fluid conduit and configured to inject oxidant into the fluid conduit to regulate a temperature of the fluid flowing into the inlet of the ASC assembly to regulate a catalytic activity in the ASC assembly that converts NH 3 into N 2; one or more transducers disposed throughout the exhaust aftertreatment system; and a controller coupled to the oxidant injection system and configured to receive signals from the one or more transducers representative of system parameters, to determine whether the catalytic activity in the ASC assembly has aged based on one of the system parameters, and - based on the determination that the catalytic activity in the ASC assembly has aged - to adjust an amount of oxidant injected into the fluid conduit by the oxidant injection system to adjust the temperature of the fluid flowing into the inlet of the ASC assembly to a desired adjusted temperature to increase the catalytic activity. an exhaust aftertreatment system configured to treat emissions from a combustion engine, wherein the exhaust aftertreatment system comprises: a three-way catalyst assembly having a first outlet; an ammonia slip catalyst assembly configured to receive a fluid from the TWC assembly and to convert ammonia (NH 3) within the fluid into nitrogen (N 2), wherein the ASC assembly has an inlet and a second outlet; a fluid conduit disposed between the TWC assembly and the ASC assembly and configured to transfer the fluid from the TWC assembly to the ASC assembly; an oxidant injection system coupled to the fluid conduit and configured to inject oxidant into the fluid conduit to regulate a temperature of the fluid flowing into the inlet of the ASC assembly to regulate a catalytic activity in the ASC assembly that converts NH 3 into N 2; one or more transducers disposed throughout the exhaust aftertreatment system; and a controller coupled to the oxidant injection system and configured to receive signals from the one or more transducers representative of system parameters, to determine whether the catalytic activity in the ASC assembly has aged based on one of the system parameters, and - based on the determination that the catalytic activity in the ASC assembly has aged - to adjust an amount of oxidant injected into the fluid conduit by the oxidant injection system to adjust the temperature of the fluid flowing into the inlet of the ASC assembly to a desired adjusted temperature to increase the catalytic activity. a three-way catalyst assembly having a first outlet; an ammonia slip catalyst assembly configured to receive a fluid from the TWC assembly and to convert ammonia (NH 3) within the fluid into nitrogen (N 2), wherein the ASC assembly has an inlet and a second outlet; a fluid conduit disposed between the TWC assembly and the ASC assembly and configured to transfer the fluid from the TWC assembly to the ASC assembly; an oxidant injection system coupled to the fluid conduit and configured to inject oxidant into the fluid conduit to regulate a temperature of the fluid flowing into the inlet of the ASC assembly to regulate a catalytic activity in the ASC assembly that converts NH 3 into N 2; one or more transducers disposed throughout the exhaust aftertreatment system; and a controller coupled to the oxidant injection system and configured to receive signals from the one or more transducers representative of system parameters, to determine whether the catalytic activity in the ASC assembly has aged based on one of the system parameters, and - based on the determination that the catalytic activity in the ASC assembly has aged - to adjust an amount of oxidant injected into the fluid conduit by the oxidant injection system to adjust the temperature of the fluid flowing into the inlet of the ASC assembly to a desired adjusted temperature to increase the catalytic activity.