Methods and systems are provided for an emissions aftertreatment device. In one example, the emissions aftertreatment device may include a catalyst and a high entropy oxygen storage material formed of at least five metal oxides in equal molar proportions. The at least five metal oxides includes one or more rare earth metals as well as other metals with similar chemical properties as the rare earth metals.

Catalysts and catalytic methods are provided. The catalysts and methods are useful in a variety of catalytic reactions, for example, the oxidative coupling of methane.