The Activation of Mg Powder Promoted by Chloride and Activation Mechanism

Magnesium has bright market prospects such as generating thrust for under water engines and hydrogen production. However, the passive oxide film on the surface of magnesium powder prevents the further reaction of magnesium with water at room temperature. In this paper, highly active magnesium-based materials were prepared via ball milling pure Mg with different chlorides (NiCl2, CoCl2, CuCl2, FeCl3). The activity of the as obtained powder was analyzed through Scanning Electron Microscopy (SEM), Energy dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), synchrotron X-ray tomography, Extended X-ray Absorption Fine Structure (EXAFS), etc. Among the various compositions, the Mg-6%CoCl2 composite exhibited the best hydrogen production performance with a hydrogen generation volume of 423 mL/(0.5 g) and a conversion yield of 96.6%. The related activation mechanism was thoroughly studied, showing that the addition of chloride during ball milling can effectively break the continuity of oxide films on Mg surfaces and introduces a large number of micro defects. In addition, the EXAFS and tomography data verified that metallic cobalt was generated during the ball milling process, subsequently forming a Mg-Co micro glance cell, and the Cl- in the system accelerates the corrosion of Mg. The active mechanism can be verified as synergistic effects of micro glance cell and as-generated surface microcracks.

Automated summary

This study prepared highly active magnesium-based materials through ball milling, with the addition of chlorides effectively breaking the continuity of oxide films and introducing micro defects, ultimately improving the hydrogen production performance of magnesium. The synthesized Mg-6%CoCl2 composite exhibited the best performance, with an activation mechanism involving synergistic effects of micro defects and surface metallic compounds.