Roles of carbon aerogels and catalysts on the hydrogen desorption behaviors of LiAlH₄

Abstract

LiAlH4 was modified with carbon aerogels (CAs) and catalysts to improve their desorption behaviors and desorption temperatures. The mechanical ball milling was used to mix LiAlH4 with the CAs and catalysts. TPD and Thermo-volumetric apparatus were used to measure the desorption temperature and the amount of desorbed hydrogen. The amounts of CAs were varied from 5 to 15 wt%, while that of a catalyst including TiCl3, TiO2, Ti, and Ni was 5 wt%. The desorption processes were operated with a heating rate of 2 ℃/min from room temperature to 250 ℃. Mixing 15 wt% CAs with LiAlH4 decreased the desorption temperature to 115 ℃ from 145 ℃. while with 5 wt% CAs, the desorption temperature was still at 145 ℃. In contrast, the desorption behaviors of the hydride mixed with 15 wt% CAs did not improve, but adding 5 wt% CAs resulted in an improvement in the desorption behaviors. In addition, mixing with a catalyst decreased the desorption temperature and decreased the desorption behaviors of LiAlH4. The desorption temperatures of LiAlH4 co-mixed with 5 wt% CAs and 5 wt% catalysts also were improved in the second desorption step and their desorption behaviors were better than the sample with the catalysts. However, desorbed LiAlH4 cannot absorb hydrogen at 180 ℃ and 11 MPa hydrogen pressure.