Electrosynthesis and catalytic properties of magnesium oxide nanocrystals with porous structures

The modified electrochemical route, with aqueous NaNO3 as electrolyte and Mg as the sacrificial anode, has been applied to synthesize the precursor Mg(OH)2 nanocrystals (nanopowders) with different shapes at room temperature. Mg2+ and OH− ions are electrogenerated in situ so that the formation and growth rate of Mg(OH)2 could be easily controlled via adjusting current density. In the low current density (3 mA cm−2) case, Mg(OH)2 nanocrystals with porous flower-like structures could be obtained via a self-assembly process, while the electrodeposition with high current density (20 mA cm−2) could afford Mg(OH)2 nanosheets. Through the calcination at 450 °C, the precursors Mg(OH)2 crystals could be easily transformed into MgO crystals, which could reserve well-defined shapes of the precursors (nanoflowers and nanosheets). Furthermore, the obtained MgO nanocrystals, especially porous nanoflowers, exhibit high catalytic activities for the reaction of CO2 with propylene oxide in the absence of any organic solvents or assisted additives.