Stability of the LiBH4/CeH2 Composite System Determined by Dynamic pcT Measurements

We determined the stability of the LiBH 4 /CeH 2 composite system by dynamic pcT (pressure, composition, temperature) measurements by using different constant hydrogen flows and by extrapolating ln( p des / p 0 ) linearly to equilibrium at zero flow. During desorption, the reaction 6LiBH 4 + CeH 2 → 6LiH + CeB 6 + 10H 2 occurs, leading to a theoretical hydrogen capacity of the destabilized system of 7.4 mass %. Within the model used and by applying the Van ˈt Hoff equation, the following thermodynamic parameters were determined for the desorption: enthalpy of reaction Δ r H = (58 ± 3) kJ mol −1 H 2 and entropy of reaction Δ r S = (113 ± 4) J K −1 mol −1 H 2, leading to a decomposition temperature T dec = (240 ± 32) °C at a hydrogen pressure of p 0 = 1.01325 bar, compared with Δ r H = 74 kJ mol −1 H 2 and Δ r S = 115 J K −1 mol −1 H 2 ( T dec = 370 °C) for pure LiBH 4 . 1