Improved overall hydrogen storage properties of a CsH and KH co-doped Mg(NH2)2/2LiH system by forming mixed amides of Li–K and Cs–Mg

Abstract

A CsH and KH co-doped Mg(NH₂)₂/2LiH composite was prepared with a composition of Mg(NH₂)₂/2LiH–(0.08 − x)CsH–xKH, and the hydrogen storage characteristics was systematically investigated. The results showed that the presence of KH further improved the reaction thermodynamics and kinetics of hydrogen storage in a CsH-containing Mg(NH₂)₂/2LiH system. A sample with 0.04 mol CsH and 0.04 mol KH had optimal hydrogen storage performance; its dehydrogenation could proceed at 130 °C and hydrogenation at 120 °C with 4.89 wt% of hydrogen storage capacity. At 130 °C, a 25-fold increase in the dehydrogenation rate was achieved for the CsH and KH co-doped sample. More importantly, the CsH and KH co-doped sample also had good cycling stability because more than 97% of the hydrogen storage capacity (4.34 wt%) remained for the Mg(NH₂)₂/2LiH–0.04CsH–0.04KH sample after 30 cycles. A structural characterization revealed that added CsH and KH participated in the dehydrogenation and hydrogenation reactions by reversibly forming mixed amides of Li–K and Cs–Mg, which caused the improved hydrogen storage thermodynamics and kinetics.