Purge systems and methods are disclosed for flushing unreacted materials and byproducts from a reactor. In one embodiment, the reactor houses a hydrogen generation catalyst and the system comprises a hydrogen generation fuel cartridge containing a reservoir that stores water which may be recovered from the exhaust of a fuel cell. The reservoir may comprise a flexible bladder or a piston-type configuration. Water is delivered from the reservoir to flush the reactor of any residual fuel and/or byproducts.