LiAlH4 supported on TiO2/hierarchically porous carbon nanocomposites with enhanced hydrogen storage properties

Abstract

We report the synthesis of LiAlH₄ supported on TiO₂/hierarchically porous carbon (LAH–TiO₂/HPC) nanocomposites using a one-step solvent method and their enhanced catalytic dehydrogenation performance. The as-prepared TiO₂/HPC nanocomposites show that TiO₂ nanoparticles (∼10 nm) are homogeneously distributed on the surface of hierarchically porous carbon (HPC). The results show that TiO₂/HPC nanocomposites exhibit better catalytic performance for the dehydrogenation of LiAlH₄ and rehydrogenation of the dehydrided sample than that of TiO₂ nanoparticles and HPC. The dehydrogenation temperature of 37LAH–25TiO₂/38HPC with 37 wt% LiAlH₄, 25 wt% TiO₂ and 38 wt% HPC is the lowest. Hydrogen started to be released at 64 °C, which is about 100 °C lower than that of pure LiAlH₄. In addition, 4.3 wt% of hydrogen could be released from 37LAH–25TiO₂/38HPC within 40 min at 130 °C, indicating fast kinetics with an activation energy of 47.1 ± 3.5 kJ mol⁻¹. Furthermore, it can re-adsorb H₂ at 300 °C under a hydrogen pressure of 4 MPa. The nanoconfinement of LiAlH₄ into hierarchically porous carbon with high surface areas and the high distribution of TiO₂ nanoparticles with a Ti(4+)/Ti(3+)/Ti(2+) defect site play a synergistic role in improving the hydrogen storage properties of LiAlH₄.