Eco-Friendly Synthesis of Nanoporous Magnesium By Air-Free Electrolytic Dealloying of Magnesium-Lithium Alloy with Recovery of Sacrificial Lithium

Abstract

In recent years, air- and water-sensitive nanostructured materials with minimal surface oxide coverage have received increased attention for their potential role in various applications, such as catalysts for combustion fuels, active ingredients in solid-propellant rockets, and reactants for onboard and on-demand hydrogen generation to feed fuel cells. However, the fabrication of this class of materials has been hindered by their inherently high chemical reactivity. Magnesium, with its standard reduction potential of -2.37 V vs. SHE, is highly water-reactive in its nanostructured form, thus the synthesis of nanostructured magnesium with minimal surface oxide coverage poses a challenge. In this talk, I will introduce a novel eco-friendly air-free selective electrolytic leaching route to fabricate three-dimensional (3D) bicontinuous nanoporous magnesium (NP-Mg) with minimal surface oxide coverage. The starting material consists of a Mg-Li parent alloy, with lithium as the sacrificial component. During selective electrolytic leaching in an anhydrous lithium-conducting organic electrolyte solvent, the sacrificial lithium is stripped from the Mg-Li parent alloy used as the working electrode and plated on a pure lithium foil used as the counter electrode. This process enables sacrificial element recovery, making it eco-friendly. The dealloyed NP-Mg exhibits a characteristic ligament and pore size in the range of 20-30 nm, and its morphology was thoroughly investigated using electron microscopy, inductively coupled plasma (ICP) spectroscopy, small-angle X-ray scattering (SAXS), and X-ray diffraction, as will be shown during my talk. NP-Mg with such ultra-small feature size could be attractive for several applications including hydrogen storage in the form of magnesium hydride, and on-demand hydrogen generation by hydrolysis with pure water.