Abstract: Disclosed herein are various embodiments of systems (including vehicle systems and fuel cell systems), as well as reformers and methods for operating the systems. In one embodiment, the reformer comprises: a support comprising a reforming catalyst and a hexaaluminate comprising a crystal stabilizer disposed in a hexaaluminate crystal structure. Meanwhile, one embodiment of the system comprises: a device selected from the group consisting of an engine, a fuel cell, and combinations thereof, and the reformer.