3LiBH4 + TiF3 releases H2 with an exceptionally low onset temperature below 100°C (giving a 9 wt% loss below 150°C). The mechanism isn¿t fully understood, with the possibility of anion substitution in the complex hydride reagent as well as the crystalline LiF product (forming LiBH4-xFx and LiF1-yHy, respectively). Due to the inability of PXD to accurately detect light elements such as H and Li (and F), we propose the use of PND to determine the composition, stoichiometry and defect structure of these substituted phases, and to follow the reaction in-situ, to elucidate the reaction mechanism for the first time. This will be achieved through 2 ex-situ experiments looking at both the hydrogenated and dehydrogenated samples under ambient conditions, and 2 in-situ experiments following the dehydrogenation whilst heating to 200°C, collecting diffraction data at set isothermal points.