The chemisorption of H2 on the ternary hydride active surface has unique fingerprints (Figure ). The chemisorption of H2 happens through a physisorbed transition state TS0-I, with a negligible barrier of 0.07 eV (Figure ). The H from the chemisorbed H2 participates in on-site scrambling with the lattice H on the [RuH6] active center. The on-site scrambling of the hydrogen has an insignificant activation energy of 0.04 eV (Figure ). Experimentally, we observe a minor reversible adsorption/desorption of H2 in the temperature range of 373 K to 473 K in the temperature programmed desorption (TPD) profile with no trace of net LiH, Ru powder, or a mixture of LiH and Ru (Figure ), which reinforces the observation of the chemisorbed nature of the H2 adsorption on the Li4RuH6 active surface. After charging with D2, the detection of the mixed HD signal in the TPD profile strengthens the conclusion of the on-site scrambling of D from chemisorbed D2 with lattice H (inserted plot of Figure ). A more robust signal of H2/HD than D2 in the TPD profile points out the magnitude of the on-site scrambling of the chemisorbed D2 with the lattice H.