Manganese oxide nanoflakes grown around cobalt oxide nanobundles with improved charge-storage performance for supercapacitors

Cobalt oxide nanobundle arrays (denoted as CoO) consisting of nanorods were homogeneously grown around the stainless steel wire mesh (SSWM) through a simple hydrothermal synthesis and subsequent heat treatment. The highly dispersed CoO can act as a supporting platform for the deposition of manganese oxide (MnO2) nanoflakes to engineer a CoO@MnO2 core-shell array structure. Without the CoO supports, the MnO2 was found to be prone to form aggregated nanoflakes on the SSWM substrate. CoO arrays with a one-dimensional nanorod skeleton can mitigate the aggregation of two-dimensional MnO2 nanoflakes. The CoO@MnO2 core-shell arrays integrate the advantages of abundant active edge sites, conductive networks for charge transfer, and pore channels for easy transport of electrolyte. The CoO@MnO2 electrode realizes a larger charge-storage capacity than the pristine MnO2 electrode in an aqueous sodium sulfate solution (1 M). The specific capacitances of CoO@MnO2 under 0.15 mA cm(-2) and 7.50 mA cm(-2) reach 79 mF cm(-2) and 53 mF cm(-2), respectively, much more than that of MnO2 (31 mF cm(-2) and 20 mF cm(-2)). The CoO@MnO2 core-shell electrode shows a definite improvement in supercapacitive behavior compared to the pristine MnO2 electrode, resulting from reduced charge- and mass-transfer resistance during charge-storage process.

Automated summary

Cobalt oxide nanobundle arrays were grown on a stainless steel wire mesh through hydrothermal synthesis and heat treatment to form a supporting platform for manganese oxide deposition, resulting in a CoO@MnO2 core-shell electrode. This electrode showed improved supercapacitive behavior compared to pristine MnO2, with higher charge-storage capacity and reduced transfer resistance.