LAUSR

Abstract Herein, greatly enhanced oxygen evolution reaction (OER) performances are obtained under the cooperation of small-sized morphological effect and heteroatomic doping activation. Firstly, three dimensional nickel cobaltite nanoneedle arrays with smaller diameters were directly grown on the thinner carbon filaments (CF) surface. Its derivative, the flexible NiCo2O4/CF-P is successfully fabricated by phosphating of NiCo2O4/CF. Promoted by the cooperation of small-sized effect and heteroatomic doping, the as-derived flexible NiCo2O4/CF-P exhibits the excellent electrocatalytic behaviors. When assessed as an electrode for the OER, the NiCo2O4/CF-P electrode illustrates a low overpotential of 191 mV at 10 mA cm−2 in 1.0 M KOH aqueous solution, and a rapid kinetic speed with the Tafel curve slope of 83 mV decade−1 slightly worse than IrO2, but much better than NiCo2O4/CF (108 mV decade−1) and CF (142 mV decade−1). In addition, the as-prepared NiCo2O4/CF-P electrode displays an excellent long-term electrochemical durability during a 30 h test. It is also found that the hydrogen evolution reaction (HER) activities of NiCo2O4/CF-P electrode are superior to those of NiCo2O4/CF electrodes, demonstrating that the nanoneedle arrays morphology and phosphorous doping are both beneficial to improve the active sites, enhance conductivity and facilitate electron transfer in the process of water splitting.