Microwave-power-enabled tuning of NiCo double hydroxide nanostructures

Abstract

Microwave heating has been widely used to enhance the fabricating rate of nanomaterials in the past few decades. However, the application of interaction between microwave and chemical reaction in tuning nanomaterials morphology is yet to be explored, while strategies to manipulate material nanostructures are of great importance for enhanced function. In this work, we demonstrate the potential of microwave in tuning the morphology of nanostructured NiCo DHs by accurate temperature control through the precise design of microwave reacting system. We find that 200-W microwave irradiation gives yield to unique flower-on-sheet hierarchical structure of NiCo DHs, while microspheres are derived from oil-bath heating. Microwave power is found to play a vital role in the tuning process. When microwave power decreases to 50 W, assembled nanoflakes are obtained; when microwave power increases to 300 W, microspheres are obtained. Further, fluid permittivity is monitored and field intensity in the reacting region is simulated and found to increase with time. Taken together, it is proposed that field-induced de-solvation possibly exists and is the main tuning mechanism. When tested as electrode materials in supercapacitor, products obtained from 200 W microwave treatment show enhanced storage capacities, especially at high current density.