Controlled growth of NiMoO₄ nanosheet and nanorod arrays on various conductive substrates as advanced electrodes for asymmetric supercapacitors

Hierarchical NiMoO₄ architectures assembled from well-aligned uniform nanosheets or nanorods are successfully grown on various conductive substrates using a facile and effective general approach. Importantly, the nanostructures of NiMoO₄ can be easily controlled to be nanosheets or nanorods by using different solvents. By virtue of their intriguing structure features, NiMoO₄ nanosheets as integrated additive-free electrodes for supercapacitors manifest higher Faradaic capacitance than NiMoO₄ nanorods. Moreover, an asymmetric supercapacitor (ASC) is constructed using the as-prepared NiMoO₄ nanosheets as the positive electrode and activated carbon (AC) as the negative electrode. The optimized ASC with an extended operating voltage range of 0-1.7 V displays excellent electrochemical performance with a high energy density of 60.9 Wh kg^-1 at a power density of 850 W kg^-1 in addition to superior rate capability. Furthermore, the NiMoO₄//AC ASC device exhibits remarkable cycling stability with 85.7% specifi c capacitance retention after 10 000 cycles. The results show that these NiMoO₄-based nanostructures are promising for high-energy supercapacitors. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA.