A fuel cell, having improved sealing against leakage, includes a fuel cell component having a cured sealant, wherein the cured sealant includes a telechelic-functional polyisobutylene, an organhydrogenosilane crosslinker, a platinum catalyst and a photoinitiator. The fuel cell component may be a cathode flow field plate, an anode flow field plate, a resin frame, a gas diffusion layer, an anode catalyst layer, a cathode catalyst layer, a membrane electrolyte, a membrane-electrode-assembly frame, and combinations thereof. A method for forming such a fuel cell includes the steps of providing a fuel cell component including a substrate; providing a mold having a cavity; positioning the mold so that the cavity is in fluid communication with the substrate; applying a curable liquid sealant composition into the cavity, wherein the curable sealant composition includes a telechelic-functional polyisobutylene, an organhydrogenosilane crosslinker, a platinum catalyst and a photoinitiator; and curing the composition with
