Dual functionalized Fe2O3 nanosheets and Co9S8 nanoflowers with phosphate and nitrogen-doped carbon dots for advanced hybrid supercapacitors

The development of novel electrode materials with admirable electrochemical behaviors is a new opportunity to meet the current demand for the high energy density of supercapacitors. Herein, a facile molecular precursor route is used to synthesize dual functionalized Fe2O3 two-dimensional nanosheets with phosphate and nitrogen-doped carbon dots (P-Fe2O3/NCDs) modifications. Taking full use of the excellent characteristics of each component, the optimized P-Fe2O3/NCDs anode material achieves superior electrochemical features with an outstanding specific capacitance of 453 F g−1 at 1 A g−1. The cycling stability of P-Fe2O3/NCDs nanosheets is as high as 91.0 % after 10,000 cycles at 15 A g−1. Subsequently, phosphate and NCDs modified Co9S8 (P-Co9S8/NCDs) nanoflowers with convenient ion transport properties are fabricated, which possess a satisfied electrochemical capacity of 569 C g−1 at 1 A g−1 with desirable cycling stability at 15 A g−1. Impressively, the designed P-Co9S8/NCDs//P-Fe2O3/NCDs hybrid supercapacitor can achieve an excellent energy density of 85.1 Wh kg−1 at 937.5 W kg−1 and can retain 93.9 % capacitance efficiency after 20,000 cycles at 10 A g−1. The superior properties of the dual functionalized electrode materials provide a new choice for constructing advanced hybrid supercapacitors.