Insight into the energy conversion and structural evolution of magnesium hydride during high-energy ball milling for its controllable synthesis

Unlike temperature-controlled hydrogenation for synthesizing hydrogen storage materials, reactive milling of Mg crystal under hydrogen atmosphere for MgH2 synthesis is often uncontrollable. For the first time, we try to understand the preparation of MgH2 during the reactive ball milling in the perspective of energy conversion and structural evolution. High-energy ball milling can lead to basal slip of Mg crystal, which is controlled to disclose Mg(0001), thus further to enhance its hydriding reaction activity. To trigger the reaction of Mg hydriding without catalyst, the energy transferred by collisions in unit time should be over 148.1 kJ mol(-1) according to DFT calculations. Due to structural modulation of Mg crystal, the synthesis of MgH2 from Mg crystal under hydrogen atmosphere by high-energy ball milling can be divided into three periods, and can be optimized for the fine synthesis of MgH2. This work is helpful for the controllable synthesis of MgH2 during high-energy ball milling, and should also inspire how to select conditions to synthesize other functional materials. (C) 2020 Elsevier B.V. All rights reserved.