A novel three-step method for preparation of a TiB2-promoted LiBH4–MgH2 composite for reversible hydrogen storage

Abstract

The reversible dehydrogenation properties of the 2LiBH(4)-MgH(2) composite can be effectively improved by incorporating heterogeneous nucleation agents, typically transition metal borides. A careful study of the 2LiBH(4)-MgH(2) composite with a titanium trifluoride (TiF(3)) additive finds that using the conventional one-step milling method renders only a partial conversion from TiF(3) to titanium boride (TiB(2)) through an intermediate of titanium hydride (TiH(2)). Based on a fundamental understanding of the reaction processes of the system, we developed a three-step preparation method, which involves pre-milling the LiBH(4)-TiF(3) mixture, isothermal treatment and milling together with MgH(2). A combination of phase/chemical state/microstructural analyses using X-ray diffraction, X-ray photoelectron spectroscopy and transmission electron microscopy techniques shows that the newly developed method can effectively promote the formation of TiB(2) and meanwhile, ensure a homogeneous dispersion of TiB(2) nanoparticles in the composite matrix. As a consequence, the composite sample prepared by the new method exhibits a favorable combination of high hydrogen capacity, fast reaction kinetics and satisfactory cyclic stability.

Superior Catalytic Effects of Transition Metal Boride Nanoparticles on the Reversible Hydrogen Storage Properties of Li‐Mg‐B‐H System

“…First, it should be pointed out that all of the components have been counted to calculate the hydrogen capacity. It can be seen that the undoped 2LiBH 4 /MgH 2 composite exhibits a poor kinetics and releases only 4.1 wt% hydrogen at 400 °C in 300 min, indicating that the incubation period for the second dehydrogenation step largely surpasses 300 min, which is consistent with the previous reports . Notably, the nano‐TMB impressively improves hydrogen storage properties of 2LiBH 4 /MgH 2 composite.…”

“…However, the real kinetics of the undoped Li‐Mg‐B‐H system is sluggish and high temperature is needed to give an acceptable dehydrogenation rate. Thereby, great efforts have been devoted to exploring efficient additives, which can be classified as chlorides, fluorides, and oxides . Undoubtedly, these additives improved the kinetics of RHC systems.…”

“…Yet, almost all of these dopants will generate some by‐products, which will take up some weight in the system, causing a decrease of reversible hydrogen storage capacity . Besides, to get an improved kinetics, activation process is needed . Moreover, the kinetics and cycling stability should be further improved for its practical application.…”

Fundamental Material Properties of the 2LiBH4-MgH2 Reactive Hydride Composite for Hydrogen Storage: (II) Kinetic Properties

“…However, it has been already reported that the presence of H2 overpressure suppresses the further formation of volatile species [46][47][48]. Moreover, Kang et al and Karimi et al have found that the interaction between titanium fluorides (TiF3 and TiF4) and Li-RHC promotes the formation of nanosized TiB2 during milling [49,50]. Moreover, the release of H2 during the processing in the planetary mill has already been verified for several other complex The results obtained from the phase composition equilibrium calculation can be seen in Table 1.…”

Progress on light metal borohydrides for reversible hydrogen storage

“…如何 高效、 弥散的将过渡金属硼化物纳米粒子引入复合体 系是当前的研究重点. 本研究组采用三步制备新方 法, 显著提高了过渡金属硼化物的生成效率及其在 两基体相界面处的分散度, 从而大幅提高了体系的 循环放氢动力学及容量稳定性 [56,57] , 见图 2. 浙大 Chen 研究组 [58] 将预先制备的无定形过渡金属硼化物 纳米颗粒球磨引入基体相, 所制备样品也具有优异 的放氢动力学和循环稳定性, 放氢反应活化能降低 约 40 kJ/mol.…”