To overcome the low-energy-density
limitation of supercapacitors,
we aimed to achieve a material with a high specific capacitance by
manipulating the nanostructure of FeS2, which comprises
the most abundant and affordable elements. In this study, nanosheet-assembled
FeS2 (NSA-FeS2) was fabricated using a novel
method. Sub-micron droplets of sulfur particles stabilized with polyvinylpyrrolidone
were formed in silicone oil medium, and Fe(CO)5 was absorbed
and reacted on the surface to form core-shell particles, ES/[Fe],
with a sulfur core and an iron-containing outer shell. The high temperature
treatment of ES/[Fe] produced NSA-FeS2, in which pyrite
FeS2 nanosheets grew and were partially interconnected.
In a three-electrode system, the as-prepared NSA-FeS2 and
NSA-FeS2/polyaniline (PANI) composites exhibited specific
capacitances of 763 and 976 Fg–1, respectively,
at a current density of 0.5 Ag–1, with corresponding
capacitance retentions of 93 and 96% after 3000 charge–discharge
cycles. The capacitance retention of the NSA-FeS2/PANI
composites was 49% when the current density was increased from 0.5
to 5 Ag–1. Notably, the obtained specific capacitances
exhibited the highest values in pure FeS2 and FeS2-based composites, indicating the significant potential for the utilization
of iron sulfide in pseudocapacitive electrode materials.