NiO nanofibers clad nickel foam as binder-free electrode with ultrahigh mass loading: boosting performance of hybrid supercapacitor and overall water-splitting

Abstract

Although NiO has attracted intensive attention as promising active materials for hybrid supercapacitor (HSC) and HER/OER electrocatalysts, efficiently utilizing the NiO-based electrodes with high mass loading is still a challenge. Herein, we design a battery-type electrode, i.e., NiO nanofibers clad nickel foam (NiO/NF), by facile, low-cost, and eco-friendly etching and oxidation under ambient conditions. Thanks to the in-situ growth of NiO nanofibers on NF and its ultrahigh mass loading of 17.4 mg cm−2, the binder-free NiO/NF electrode shows excellent performance in HSC and overall water-splitting. An ultrahigh areal capacity (CA) of 3.84 mAh cm−2 (gravimetric capacity of 220.7 mAh g−1) is obtained at 2 mA cm−2, which is 1255 times more than pristine NF (0.00306 mAh cm−2). Even at 100 mA cm−2, CA can reach 1.38 mAh cm−2. Hybrid supercapacitor assembling with graphene oxide (GO) delivers a peak energy density of 2572.2 Wh m−3 and possesses good cycling stability of 110% retention after 6000 cycles. Moreover, NiO/NF electrode displays low overpotentials of 69.9 mV and 262 mV at 10 mA cm−2 for HER and OER, respectively. NiO/NF||NiO/NF electrolyzer outputs 10 mA cm−2 at only 1.57 V with long-term durability for 50 h.