Effect of Mg–Nb oxides on hydrogen sorption kinetics of ball-milled MgH₂

Addition of Mg–Nb oxides (e.g. MgNb₂O₆, Mg₄Nb₂O₉, and Mg₃Nb₆O₁₁) ameliorates H₂ absorption/desorption kinetics of MgH₂ as demonstrated in the current article. H₂ desorption and absorption rates of the ball-milled MgH₂ are evidently temperature-dependent, which points out that the prior rate increases with increasing temperature (593–673 K) and vice versa. Among the tested samples, MgH₂ with Mg₃Nb₆O₁₁ nanoparticles showed superior performance. The Johnson–Mehl–Avrami equation was employed to construct H₂ desorption curves as well as find out reaction rate constants at different temperatures. The Arrhenius equation was fitted in the context to estimate the activation energy of the ball-milled MgH₂ and MgH₂/Mg₃Nb₆O₁₁ mixtures; for example, the values obtained were 127 and 88 kJ·mol⁻¹, respectively. In addition, a novel experimental setup combining a hydrogen detector with a differential scanning calorimeter was used to confirm the H₂ desorption properties of the ball-milled nanoparticles discussed based on the kinetic argument.