Hierarchical al-doped and hydrogenated ZnO nanowire@MnO₂ ultra-thin nanosheet core/shell arrays for high-performance supercapacitor electrode

ZnO@MnO2 and Al-doped ZnO (AZO)@MnO₂ hybrid electrodes in core/shell geometries have been synthesized on stainless steel substrates by a scalable low-cost solution route. Cyclic voltammogram (CV) and galvanostatic (GV) charge-dischargemeasurements demonstrated that the AZO@MnO₂ hybrid electrode exhibited superior capacitive properties, in 1M Na₂SO₄ aqueous solution, to the ZnO@MnO₂ electrode. The specific capacitance based on total electrode mass is estimated to be 275 F/g at a current density of 2 A/g. The AZO@MnO₂ electrode also displays an excellent long-term cyclic stability at a current density of 10 A/g with less than 3% loss after 2000 charge-discharge cycles. A ~35% capacity retention was observed at 60A/g, which is over 400% specific capacitance increment compared with the ZnO@MnO₂ electrode. The superior electrochemical capacitive properties of the AZO@MnO₂ over ZnO@MnO₂ can be attributed to the enhanced electrical conductivity in the core nanowire, as a result of Al doping and hydrogenation. The low cost fabrication combined with the excellent capacitive properties indicates that the AZO@MnO₂ hybrid architecture can serve as a promising electrode material for supercapacitors as well as other electrochemical energy storage/conversion devices.