Mg-Mg2X (X=Cu, Sn) eutectic alloy for the Mg2X nano-lamellar compounds to catalyze hydrolysis reaction for H2 generation and the recycling of pure X metals from the reaction wastes

The hydrogen generating characteristics of typical Mg-Mg2X (Cu, Sn) eutectic alloys in the hydrolysis of seawater were investigated. Cu and Sn are cheaper than Nd, Ni, Co, and rare earth elements, and these were used as catalysts in the rapid (30 min) formation of Mg-Mg2X (Cu, Sn) eutectic alloy in an induction furnace. Hydrogen was evolved in 3.5 wt % NaCl solution (to mimic seawater). Both bulk Mg-Mg2Cu and Mg-Mg2Sn eutectic alloys reacted until the Mg ran out. This typical process involves the unique eutectic lamellar structure of multi-layered Mg2X (as the cathode) stock with Mg (as the anode). This eutectic structure creates numerous nano galvanic-cells in the alloy matrix that accelerates the hydrolysis reaction. The better hydrogen evolution performance was achieved using Mg-Mg2Cu eutectic alloy because it has the highest electrochemical potential difference (Mg vs. Mg2Cu:0.32 V > Mg vs. Mg2Sn:0.17 V). The by-product of hydrolysis was not wasted: an extraction method for recycling the valuable metals (Cu and Sn) at room temperature was developed.