A fuel cell system includes a fuel cell stack, an ejector in fluid communication with the fuel cell stack and having a converging-diverging (CD) nozzle with a hydrogen feed nozzle and a recirculation conduit upstream of a throat of the CD nozzle, and a thermal source configured to heat the ejector. A hydrogen supply assembly for a fuel cell system includes an ejector having a converging-diverging (CD) nozzle and a mixing chamber upstream of the CD nozzle. The mixing chamber has a recirculation conduit and a hydrogen feed nozzle. A thermal source is configured to heat the ejector. A method of controlling a hydrogen supply device for a fuel cell includes, in response to detecting a heating condition at fuel cell start up, controlling a thermal source to heat an ejector upstream of an anode stack to prevent ice formation in the ejector.