Mechanochemical modification of LiAlH4 with Fe2O3 - A combined DFT and experimental study

LiAlH4 is a promising material for hydrogen storage, having the theoretical gravimetric density of 10.6 wt% H-2. In order to decrease the temperature where hydrogen is released, we investigated the catalytic influence of Fe2O3 on LiAlH4 dehydrogenation, as a model case for understanding the effects transition oxide additives have in the catalysis process. Quick mechanochemical synthesis of LiAlH4 thorn 5 wt% Fe2O3 led to the significant decrease of the hydrogen desorption temperature, and desorption of over 7 wt%H-2 in the temperature range 143-154 degrees C. Density functional theory (DFT)-based calculations with Tran-Blaha modified Becke-Johnson functional (TBmBJ) address the electronic structure of LiAlH4 and Li3AlH6. Fe-57 Mossbauer study shows the change in the oxidational state of iron during hydrogen desorption, while the H-1 NMR study reveals the presence of paramagnetic species that affect relaxation. The electron transfer from hydrides is discussed as the proposed mechanism of destabilization of LiAlH4 + 5 wt% Fe2O3. (C) 2021 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Automated summary

LiAlH4 with 5 wt% Fe2O3 showed significantly lower dehydrogenation temperature and released over 7 wt% H-2 in the temperature range of 143-154 degrees C. Various analytical methods were used to investigate the mechanisms of catalytic influence and electron transfer in the destabilization process.