In-situ introduction of highly active TiO for enhancing hydrogen storage performance of LiBH4

Abstract

• A valid strategy to in-situ introduce highly active additive to LiBH 4 is employed. • TiO is in-situ introduced into LiBH 4 and the LiBH 4 -0.06TiO system is obtained. • Enhanced kinetics and favorable cycling stability are achieved for the system. • Li 3 BO 3 and TiH 2 are generated and act as catalysts for LiBH 4 . • Dehydrogenation energy barrier is reduced and formation of Li 2 B 12 H 12 is inhibited. LiBH 4 is a promising candidate for solid state hydrogen storage, however, it still suffers from high hydrogen desorption temperature, harsh hydrogen absorption conditions, and poor reversibility, which hinder its practical development. In this paper, a novel synthetic strategy of heat treating a LiBH 4 and Ti(OEt) 4 mixture is employed to prepare LiBH 4 system with TiO in-situ introduced. With an optimized TiO content of 0.06 in molar fraction, the LiBH 4 -0.06TiO system shows onset and peak dehydrogenation temperatures of 240 °C and 340 °C, respectively, which are 140 °C and 90 °C lower than those of the pure LiBH 4 . The LiBH 4 -0.06TiO system can rapidly release 9 wt% H 2 after dwelling at 400 °C for 10 min. The hydrogenation of the dehydrogenation product initiates at 150 °C, and a capacity of 9 wt% is reached after isothermal dwelling at 500 °C under 50 bar of H 2 for 100 min. The capacity retention of the system can reach 74.4% after 10 cycles, indicating a favorable reversibility. With the introduction of TiO, the apparent dehydrogenation activation energy of the system is evidently reduced, and the formation of Li 2 B 12 H 12 , a highly thermal stable intermediate phase, is greatly suppressed. In addition, the aggregation is evidently alleviated. All of these contribute to the enhanced dehydrogenation kinetics and reversibility. TiO reacts with LiBH 4 , forming Li 3 BO 3 and TiH 2 after the initial dehydrogenation, which play significant catalytic effect to LiBH 4 .