Improvement of hydrogen storage characteristics of catalyst free magnesium nanoparticles prepared by wet milling
Seemita Banrejee, Asheesh Kumar, Priyanka Ruz, V. Sudarsan
Abstract
Summary Magnesium is one of the potential candidates for on‐board hydrogen storage, but slow hydrogenation kinetics and unfavourable thermodynamics limits its practical implementation. To improve the hydrogenation characteristics, nanocrystalline magnesium was prepared by a simple wet milling method without addition of heavy metal catalyst. Compared to micro‐crystalline Mg, developed nanocrystalline Mg exhibits improved hydrogen storage properties showing extended plateau region in the pressure‐composition‐temperature curves with higher hydrogen storage capacity (6.24 wt% at 300°C). Hydrogenation and dehydrogenation kinetics is found to follow Kolmogorov−Johnson−Mehl−Avrami activation energy model confirming the involvement of nucleation‐growth‐impingement mechanism. Prolonged ball milling leads to quite fast hydrogenation kinetics (upto 90% of the saturation value in 15.5 minutes at 250°C) and leads to substantial decrease in the activation barrier. The activation energy for hydrogenation is found to be 68.88 kJ mol −1 for 8 hours ball milled sample. Present study established a simple and scalable method for nanocrystalline Mg, which can undergo reversible hydrogen absorption and desorption with improved performance without using any additional catalyst.