Research progress of hydrogen energy and metal hydrogen storage materials

•The solid storage of hydrogen is summarized, including metal, carbon, metal-organic framework, et al.•The advantages and disadvantages of TiFe alloy in hydrogen storage are described.•Element substitution and milling are advanced methods to improve the performance of TiFe alloy.•Rare earth elements are introduced to improve the activation performance of TiFe alloy. Hydrogen energy has become one of the most ideal energy sources due to zero pollution, but the difficulty of storage and transportation greatly limits the development of hydrogen energy. In this paper, the metal hydrogen storage materials are summarized, including metal alloys and metal-organic framework. TiFe-based hydrogen storage alloys have become one of the most promising materials because of their reversible hydrogen absorption and desorption at room temperature and low hydrogen pressure. However, the first hydrogenation requires activation at high pressure and high temperature, which is not conducive to practical application. This paper reviews the methods to improve the hydrogen storage performance of TiFe-based alloys: (1) High energy ball milling leads to the formation of microcrystalline, nanocrystalline boundaries and a large number of structural defects in the alloy, resulting in a significant increase in hydrogen diffusion channels. Meanwhile, the high surface activity of the ball-milled alloy weakens the bond energy of the Ti–H bond, thus promoting the improvement of the activation performance, hydrogen storage capacity and subsequent hydrogen absorption and desorption kinetics of the TiFe-based alloy. (2) Transition metals and rare earth elements with high valence and high affinity for hydrogen are also introduced to improve the activation performance.