Two-step electrodeposition synthesis of iron cobalt selenide and nickel cobalt phosphate heterostructure for hybrid supercapacitors.

Exploring novel heterostructure with multiscale nanoarchitectures and modulated electronic structure is crucial to improve the electrochemical properties of electrode materials for supercapacitors (SCs). In this study, a two-step electrodeposition approach which involves suitable efficient procedures, is leading to in-situ preparation of iron cobalt selenide (FeCoSe) @ nickel cobalt phosphate (NiCo(HPO)·3HO, denoted as NiCo-P) hybrid nanostructure on carbon cloth (CC) substrate. Particularly, depositing two-dimensional (2D) NiCo-P nanosheets on the surface of FeCoSe nanobelts results in formation of well-organized FeCoSe@NiCo-P nanocomposite with large surface area, hierarchical porous nanoarchitecture as well as numerous electroactive sites, leading to enhanced electroactivity and accelerated mass/electron transfer. Benefiting from its unique nanoarchitecture and synergistic effect of two components, the obtained free-standing FeCoSe@NiCo-P electrode demonstrates gravimetric capacity (C)/volumetric capacity (C) of 202.3 mAh/g/319.6 mAh cm at 1 A g and good cyclic stability (83.9% capacity retention over 5000 cycles), which are superior to those of pure FeCoSe and NiCo-P electrodes. Impressively, it was established that an aqueous hybrid supercapacitor (HSC) based on FeCoSe@NiCo-P and rape pollen derived hierarchical porous carbon (RPHPC) achieves gravimetric energy density (E)/volumetric energy density (E) of 64.4 Wh kg/10.7 mWh cm and a long cycle life with 90.3% capacity retention over 10,000 cycles. This report offers a perspective to design selenide/phosphate heterostructure on conducting substrate for electrochemical energy storage applications.