One-step self-assembly of TiO₂/MXene heterostructures for improving the hydrogen storage performance of magnesium hydride

Self-assembly of TiO₂ nanoparticles (M-TiO₂, 15–20 nm in size) on few layer Ti₃C₂T_x (FL-Ti₃C₂T_x) are conducted via simple one-step ultrasound method at room temperature, in which van der Waals interactions act as the driving force. After introduced into MgH₂ system, M-TiO₂/FL-Ti₃C₂T_x heterostructure with mass ratio of 60: 40 (6 M-TiO₂/FL-Ti₃C₂T_x) shows the best catalytic activity. The one-step self-assembly preparation can alleviate the restacking of FL-Ti₃C₂T_x and the agglomeration of M-TiO₂ nanoparticles to a certain extent, which can generate lots of interfaces between M-TiO₂ and FL-Ti₃C₂T_x. The rich interfaces can not only act as hydrogen diffusion channels, but also the electron transfer on the interfaces can enhance the catalytic activity of the whole heterostructure. Besides, abundant electrons from multiple valence Ti (Ti⁴⁺, Ti³⁺, Ti²⁺, Ti⁰) can effectively promote the reversible reaction between MgH₂ and Mg, H₂. The facile preparation method facilitates the understanding of MXene heterostructure catalysts, without the influence of particle growth and impurities. These findings provide new insights to design heterostructure with high catalytic activity and guide the understanding of its catalytic mechanism.