Tuning the Thermodynamic Properties of MgH 2 at the Nanoscale via a Catalyst or Destabilizing Element Coating Strategy

Magnesium nanoparticles as small as 7 nm have been synthesized by reducing di- n -buytlmagnesium with lithium and individually coated with elements including Co, Fe, Ni, Si, or Ti for further tuning of their thermodynamic and kinetic properties. Coating was achieved via a transmetalation process whereby precursors were directly deposited at the surface of the magnesium nanoparticles acting as a reducing agent. Studies of hydrogen storage properties showed that these coated magnesium nanoparticles were capable of absorbing hydrogen at low temperatures <140 °C and partially formed transition metal complex hydrides at temperatures above 350 °C. These complex hydrides, assumed to form a shell around the magnesium core, were found to control hydrogen desorption kinetics to some extent. More remarkably, thermodynamics of nanosize magnesium were significantly altered through this coating process. In particular, upon Ni coating a significant decrease of the plateau pressure occurred while achieving fast kinetics. This demonstrates the possibility of tuning both the thermodynamic and kinetic properties of magnesium at the nanoscale and provides a new tool for achieving enhanced hydrogen storage properties for nanosize magnesium.