The first 8-electron Pd/Ag superatomic alloys with an interstitial hydride [PdHAg19(dtp)12] (dtp = S2P(O i Pr)2-) 1 and [PdHAg20(dtp)12]+2 are reported. The targeted addition of a single Ag atom to 1 is achieved by the reaction of one equivalent of trifluoroacetic acid, resulting in the formation of 2 in 55% yield. Further modification of the shell results in the formation of [PdAg21(dtp)12]+3 via an internal redox reaction, with the system retaining an 8-electron superatomic configuration. The interstitial hydride in 1 and 2, contributes its 1s1 electron to the superatomic electron count, and occupies a PdAg3 tetrahedron. The distributions of isomers corresponding to different dispositions of the outer capping Ag atoms are investigated by multinuclear VT-NMR spectroscopy. The emissive state of 3 has a lifetime of 200 μs (λex =448; λem =842), while 1 and 2 are non-emissive. The catalytic reduction of 4-nitrophenol is demonstrated with 1-3 at room temperature.