TiO2 decorated porous carbonaceous network structures offer confinement, catalysis and thermal conductivity for effective hydrogen storage of LiBH4

Abstract

Lithium borohydride (LiBH4), with a high theoretical capacity of 18.4 wt%, is one of the most promising materials for solid–state hydrogen storage. However, it suffers from too high an operation temperature and poor reversibility. Here, a synergetic approach is developed to improve the properties. An active porous core–shell network structure is constructed as a scaffold for LiBH4–with carbon nanotube (CNT) as the core and nano–TiO2 decorated porous amorphous carbon as the shell (CNT@PC@TiO2) with an optimized fraction of TiO2. The hybrid scaffold possesses high porosity, large specific surface area and small pore sizes, for effective confinement of LiBH4 by a melt infiltration method and high loadings of LiBH4 up to 50–70 wt%, with enhanced interface diffusion and reaction without agglomeration; TiO2 reacts with LiBH4 during the infiltration process, to form LiTiO2 and TiB2 as the catalysts for LiBH4, and the CNTs facilitate heat management. The confined LiBH4 system shows considerable improvement of hydrogen sorption properties. At a LiBH4 loading of 60 wt%, the system releases 7.3 wt% H2 within 60 min at 320 °C, and a reversible capacity of 5.1 wt% is maintained even after 20 cycles. The present study provides further insight into the rational design and utilization of the synergetic effects of nanoconfinement, catalysis, surface interaction and thermal transfer to improve the overall hydrogen storage performance of LiBH4.