Hydrogen Release and Uptake of MgH 2 Modified by Ti 3 CN MXene.

MgH₂ has a high hydrogen content of 7.6 wt% and possesses good reversibility under normal conditions. However, pristine MgH₂ requires a high temperature above 300 °C to release hydrogen, with very slow kinetics. In this work, we utilized Ti₃CN MXene to reduce the operating temperature and enhance the kinetics of MgH₂. The initial temperature of MgH₂ decomposition can be lowered from 322 °C for pristine MgH₂ to 214 °C through the employment of Ti₃CN. The desorbed MgH₂ + 7.5 wt% Ti₃CN can start absorption at room temperature, while the desorbed pristine MgH₂ can only start absorption at 120 °C. The employment of Ti₃CN can significantly improve the hydrogen release kinetics of MgH₂, with the desorption activation energy decreasing from 121 to 80 kJ mol⁻¹. Regarding thermodynamics, the desorption enthalpy changes of MgH₂ and MgH₂ + 7.5 wt% Ti₃CN were 79.3 and 78.8 kJ mol⁻¹, respectively. This indicates that the employment of Ti₃CN does not alter the thermal stability of MgH₂. Phase evolution studies through the use of X-ray diffraction and electron diffraction both confirm that Ti₃CN remains stable during the hydrogen release and uptake process of the composite. This work will help understand the impact of a transition metal carbonitride on the hydrogen storage of MgH₂. [ABSTRACT FROM AUTHOR]