Sodium dodecyl sulfate-assisted fabrication of NiO nanowalls grown on nickel foam as supercapacitor electrode materials

The NiO nanowalls which are directly grown on nickel foam (NiO NWs/NF) have been successfully synthesized via a facile sodium dodecyl sulfate-assisted hydrothermal process and subsequent annealing process. With the assistance of sodium dodecyl sulfate (SDS), ordered NiO nanowalls are formed by the NiO nanorods through a partial dissolution-redeposition process, which is proposed and verified by scan electron microscopy and high-resolution transmission electron microscopy. The addition amount of SDS highly affects both the microstructure and electrochemical performances of the NiO samples. The optimized NiO NWs/NF exhibits higher specific capacitance of 1799.8 F g −1 at 1 A g −1 , excellent rate performance and superior cycle stability. The enhanced electrochemical performances benefit from the vertical growth of uniform nanowalls on the substrate, which provides open access and promotes ion/electron transport. In addition, an asymmetric supercapacitor was assembled and high energy density of 30.4 Wh kg −1 at the power density of 752.3 W kg −1 with capacitance retention of 83.7% after 5000 cycles was achieved. The results indicate that the as-prepared NiO NWs/NF material can be used as a potential binder-free electrode for supercapacitors.