Selenium enriched hybrid metal chalcogenides with enhanced redox kinetics for high-energy density supercapacitors

[Display omitted] •Selenium-enriched NiSe2@Fe3Se4 (NFS) as binder-free electrode for supercapacitor.•Pyramid-like morphology enables the sharp-tip enhancement effect.•NFS electrode demonstrated a high areal capacitance of 6.05 C cm−2 at 6 mA cm−2.•Biomass-derived O, N enriched AC shows high specific surface area of 1528 m2 g−1.•HSC device shows superior specific energy of 52 Wh kg−1 with 92% cyclic stability. Rational design and synergistic interactions between the electrode and electroactive materials have a huge impact on elevating the energy storage performance of supercapacitor devices. Herein, selenium enriched hybrid NiSe2@Fe3Se4 (NFS) nanocomposites have been facilely deposited on Ni-foam using chemical bath deposition (CBD) technique. The NiSe2@Fe3Se4 hybrid composites exhibited better electrochemical performance than that of monometallic selenides (NiSe2 and Fe3Se4), which can be attributed to the synergy effect and improved conductivity of polymetallic ions over the Ni foam substrate. The effect of NFS deposition time on Ni foam was studied and it greatly influences the morphological and electrochemical performances. Specifically, the NFS deposited for 36 h (NFS@36 h) provides a maximum areal capacity of 6.05 C cm−2 at 6 mA cm−2, which is almost four-fold higher than that of pure NiSe2 (0.168 C cm−2) and Fe3Se4 (1.46 C cm−2). Furthermore, a hybrid supercapacitor (HSC) is assembled utilizing the NFS@36 h as a positive electrode and biomass derived O, N enriched activated carbon as a negative electrode with an aqueous electrolyte. With a high-mass loading of 21.5 mg cm−2, the device demonstrates superior specific energy of 52 W h kg−1 at 398 W kg−1 specific power and even maintained 19 W h kg−1 at a maximum specific 8000 W kg−1. Furthermore, the device exhibited excellent cycling durability with ~ 92% of specific capacitance retention for 10,000 charge/discharge cycles at 5 A g−1. Besides, the HSCs have been successfully illuminated several light emitting diodes (LEDs) and portable displays demonstrating superior energy storage performance.