and confirmed the previously reported 29 thermodynamic values for the bulk material. Although thermodynamic data are available for dehydrogenation of (LiNH2+2LiH), behavior of (LiNH2+2LiH) upon cycling. The effect of nanoscaling is clearly evident in the van't Hoff plots shown in Figure . The H2 pressure at equilibrium (the "plateau pressure") for the nanoscale material is more than an order of magnitude higher than that of the bulk material at a given temperature, corresponding to an ~20 kJ/molH2 reduction in ΔH from 67.3 kJ/mole of the bulk material to 46.7 kJ/mole of the nanoconfined material (Table ). However, the plateau pressure is determined by ΔG and the values of ΔS obtained from the van't Hoff plots exhibit a corresponding 17 J/(molH2•K) decrease relative to bulk upon nanoscaling, from 126 J/moleK of the bulk material to 109 J/moleK of the nanoconfined material (Table ). This enthalpy-entropy compensation blunts the degree of destabilization that can be achieved, consistent with the higher entropy of a nanocluster within a pore compared with the same unit in a rigid crystalline lattice, an effect that is observed for other metal hydride classes. Desorption kinetics and hydrogen capacity. The total storage capacity and rate of hydrogen release from a material are required to model fuel cell performance during a simulated drive cycle. The total capacity of bulk (LiNH2+2LiH) obtained from Sieverts data is 7.1 wt% (Figure , left), corresponding to reaction R1 and consistent with the results of Chen et al. and Ichikawa. Additional desorption from the imide (Reaction R2) to reach the theoretical capacity (10.4 wt%) did not occur after more than 4 hours at 350 ºC. The minimum hydrogen pressure in the sample chamber of the Sieverts apparatus prevents the system from reaching the pressure required to approach the theoretical capacity. For the nanoscale hydride (Figure 2, right), the rapid H2 desorption to form Li3N yields a total capacity of 5.4 wt.%, (overall reaction LiNH2+2LiH@(6-nm PC) « Li3N@(6-nm PC) + 2 H2). This corresponds to full dehydrogenation of the nano-encapsulated material, after accounting for the incomplete (60%) loading and mass of the PC host.