Low temperature synthesis of crystalline pyrite FeS 2 for high energy density supercapacitors.

Herein, we report a low-temperature synthesis of crystalline pyrite-FeS 2 through a solid-state annealing route, which was achieved using FeOOH, a metastable precursor, in the presence of H 2 S gas. The as-synthesized pyrite FeS 2 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 .