Design of hierarchical nanostructures towards a specific morphology is an important research area due to their shape dependent properties. Here, 3D hierarchically assembled lotus shaped porous MnO 2 is synthesized using a simple aqueous solution based chelating agent (citric acid) mediated growth of MnCO 3 followed by calcination at 350 C. MnCO 3 in other shapes, such as rods, spheres and nanoaggregates, is also synthesized just by varying the chelating agents. It is observed that the geometry and strength of the chelating ligands has a crucial role in the controlled shape selective synthesis and based on this a probable chelating agent driven formation mechanism is discussed. The synthesized porous MnO 2 shapes exhibit excellent shape dependent catalytic oxidation of a-pinene to verbenone using molecular oxygen as the oxidant. The lotus shaped porous MnO 2 shows superior activity, with 94% conversion of a-pinene and 87% selectivity of verbenone, to that of other MnO 2 shapes. The activity is reasonably high compared to heterogeneous as well as homogeneous catalysts reported in the literature and bulk MnO 2 with respect to both their conversion and selectivity. The synthesized lotus shaped MnO 2 also showed good catalytic activity towards oxidation of allylic compounds to corresponding ene-ones using molecular oxygen as oxidant and is reusable.
Three dimensional (3D) hierarchically
assembled porous transition
metal oxide nanostructures are promising materials for next generation
rechargeable Li-ion batteries (LIBs). Here, the controlled synthesis
of 3D hierarchically porous ZnCo2O4 “wrinkled-paper-like”
structure constructed from two-dimensional (2D) nanosheets (∼20
nm thick) through calcination of corresponding mixed metal carbonate
intermediate is presented. The mixed metal hydroxy-carbonate intermediate
with wrinkled-paper-like structure has been synthesized by a novel
organic surfactant and organic solvent free protocol at reflux condition
using an aqueous solution of corresponding metal salt and ammonium
carbonate. Active-inactive nanocomposites of Co-ZnO@C with similar
wrinkled-paper-like morphology with varying carbon content, have also
been synthesized through carbonation of hydroxyl-carbonate intermediate
followed by calcination (under reducing environment). Calcination
of the carbon coated mixed metal carbonate results in phase separated
uniform Co metal and ZnO particles embedded on carbon matrix. The
results demonstrate that incorporation of ∼23% carbon in the
matrix significantly improves the performance as anode material in
LIB by exhibiting high specific capacity and enhanced cycling performance.
At a current density of 100 mAg–1, it shows an excellent
initial specific capacity of 527 mAhg–1, which is
maintained up to 50 cycles. In fact, a slight gradual increase in
capacity with cycling has been observed.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.