Effects of Ti- and Nb-based transition element from single to multiple compound oxides and carbon-based composite additives on Mg-MgH₂ hydrogen storage material

MgH₂ is considered as a promising hydrogen storage material for its high hydrogen storage capacity, low cost and abundant resource advantages. However, the low kinetics and high enthalpy formation of MgH₂ limit its wide application. From the perspective of adding catalysts to enhance the hydrogen storage properties of Mg-MgH₂, this article elaborated the main catalysts based on Ti and Nb transition elements, including single oxide catalysts, binary oxides catalysts (combined with Ni, Na, Sr, V, etc.), multiple catalysts bound to carbon, and composite catalysts with Ti and Nb elements combined with MXene phase. Moreover, the main pathways of various catalysts to reduce the reaction activity and broaden the hydrogen desorption channel were also analyzed. The Ti-based catalysts can enhance the reactive sites of the matrix by forming multivalent states, while Nb-based catalysts broaden the hydrogen reaction channels by forming tiny Nb. By improving the size structure and enhancing the grain size stability, combined with carbon materials should be the future considerations.