Low temperature synthesis of crystalline pyrite FeS₂ for high energy density supercapacitors

Herein, we report a low-temperature synthesis of crystalline pyrite-FeS2 through a solid-state annealing route, which was achieved using FeOOH, a metastable precursor, in the presence of H2S gas. The as-synthesized pyrite FeS2 was employed as an electrode for fabricating high energy density supercapacitors. The device delivered a high specific capacitance of 51 mF cm-2 at 20 mV s-1 and showed a superior energy density of 30 μW h cm-2 at a power density of 1.5 mW cm-2.