Selective morphologies of MgO via nanoconfinement on gamma -Al sub(2)O sub(3) and reduced graphite oxide (rGO): improved CO sub(2) capture capacity at elevated temperatures

Two substrates, gamma -alumina ( gamma -Al sub(2)O sub(3)) and reduced graphene oxide (rGO), have been used to confine the formation of magnesium oxide (MgO) crystals so as to control the crystal growth, reduce the crystal size, and enlarge the surface area and thus increase the CO sub(2) capture capacity at elevated temperatures. Typically, MgO/ gamma -Al sub(2)O sub(3) was synthesized by a facile sol-gel route, and MgO/rGO was obtained by calcining the hydrothermally grown magnesium hydroxide (Mg(OH) sub(2)) on rGO sheets. Distinct morphologies of MgO were observed through the above two synthesis routes: spherical particles were formed when using gamma -Al sub(2)O sub(3) as the substrate while MgO nanowhiskers appeared when the loading ratio of the precursor was high in rGO-supported samples. The effects of the substrate on the morphology of the confined MgO and the corresponding CO sub(2) uptake are discussed in detail for the first time.