Ultrathin hollow-structured NiCo2O4 nanorod supported on improved N-doped graphene for superior supercapacitor applications

Novel and hollow-structured bimetallic oxide (NiCo2O4) anchored on nitrogen-doped graphene (NG) has been manufactured by a hydrothermal-calcination method. The ultrafine hollow-structured NiCo2O4 nanorod can be dexterously grafted on an N-doped graphene surface (NiCo2O4/NG) by regulating the alkali sources. The obtained NiCo2O4/NG composite shows much larger specific capacitance and stability according to the cyclic voltammetry (CV) measurements and galvanostatic charge-discharge (GCD) examinations. The electrochemical measurements show that NiCo2O4/NG-H3 composite exhibited a high specific capacitance of 2147.4 F g−1 at 1 A g−1, as well as perfect cycling stability (93.7% capacitance retention after 2000 cycles), indicating a potential application in electrochemical supercapacitors. The XPS spectra of NiCo2O4/NG-H3 further reveal that the excellent performance should be attributed to the electron-donating (synergistic effect) between NiCo2O4 and NG.