Electroactive FeS2-modified MoS2 nanosheet for high-performance supercapacitor.

Electroactive FeS 2 -modified MoS 2 (FeS 2 /MoS 2) nanosheet grown on Mo foil is designed as supercapacitor electrode material. FeS 2 /MoS 2 nanosheet is crosslinked to form nanoporous microstructure. Density functional theory calculation reveals FeS 2 /MoS 2 exhibits much narrowed bandgap and high density of states at the Fermi level, suggesting highly improved conductivity. The charge transfers resistance decreases from 1.375 Ω of MoS 2 to 0.4167 Ω of FeS 2 /MoS 2. FeS 2 /MoS 2 exhibits higher specific capacity (495 and 394 mF cm−2) than MoS 2 (132 and 218.1 mF cm−2) and FeS 2 (315 and 286.5 mF cm−2) at 1.0 mA cm−2 in 3.0 M KOH and 0.5 M Na 2 SO 4. The rate capacity retention is enhanced from 57.8% of MoS 2 and 73.3% of FeS 2 to 76.14% of FeS 2 /MoS 2 in 0.5 M Na 2 SO 4 when current density increases from 1 to 10 mA cm−2, indicating its improved rate capability. The cycling capacity retention keeps 100.2% of MoS 2 and 100.7% of FeS 2 /MoS 2 for 5000 cycles at 5 mA cm−2 in 0.5 M Na 2 SO 4 , indicating the similar cycling stability. An asymmetric solid-state supercapacitor using FeS 2 /MoS 2 anode, exfoliated graphite carbon paper cathode and NaMoO 4 –Na 2 SO 4 -PVA gel electrolyte achieves specific capacity of 1.88 F cm−3 (112.8 mF cm−2) at 1.0 mA cm−2, energy density of 0.936 mWh cm−3 (56.56 mWh cm−2), capacity retention of 97.8% after 5000 cycles at 5.0 mA cm−2 and 1.9 V output voltage. • Conductive FeS 2 and stable MoS 2 are integrated to form electroactive FeS 2 /MoS 2 nanosheet. • Density functional theory calculation proves highly improved conductivity of FeS 2 /MoS 2. • FeS 2 /MoS 2 shows superior capacitance of 495 mF cm−2 at 1.0 mA cm−2 in 3.0 M KOH. • FeS 2 /MoS 2 keeps 95% capacity retention at 5 mA cm−2 for 5000 cycles in 3.0 M KOH. [ABSTRACT FROM AUTHOR]