Hollow nanostructures of metal oxides as emerging electrode materials for high performance supercapacitors
A targeted strategy of stabilizing hollow nanostructures of metal oxides is proposed for developing the next-generation supercapacitors. The nucleation and growth driven mechanism, for obtaining hollow structures, can be utilized to fabricate simple binary to complex ternary oxides. Much superior properties of hollow particles, in comparison to solid or other hierarchical nanostructures counterparts, is proven by reporting the studies on Co3O4, Fe2O3, SnO2, Mn3O4, Cu2O, NaFePO4, etc. based electrodes. X-ray diffraction studies show that the unit cells parameters donot change much in both solid and hollow type particles. This proves that, during synthesis, the reaction kinetics is leading to the opening or collapsing of cavity. The redox sites also remain similar in both morphologies, as confirmed by the XPS analysis. Therefore, the improved electrochemical response can be predominantly attributed to the enhanced active surface area, directed ion transport channels and structural stability. The results are compared with the published literature. It is observed that the hollow nanostructures even have the capacity to compete and beat these trasition metal oxide (TMO) based high performing composites based on trendy systems like graphene, rGO or conducting polymers. Therefore, the proposed hollow nanostructures can become useful for large scale industrial applications, owing to their lower weight and density, reduced cost and well understood synthesis protocols.