Researchers have synthesised highly crystalline pyrite FeS2 at low temperatures and utilised them for fabricating electrochemical energy storage devices such as batteries and high energy density supercapacitors, says a press release from the Department of Science and Technology (DST).

Transition metal sulfides (TMS) are an important class of inorganic materials and find applications in diverse fields including electrochemical energy storage devices such as batteries and supercapacitors. Solid-state synthetic methods are used to generate metal sulfides from the corresponding metal salts or their equivalent oxides usually by annealing at high temperatures.

However, the experiments were carried out by Savithri Vishwanathan, under the supervision of Dr HSS Ramakrishna Matte at the Centre for Nano and Soft Matter Sciences, Bengaluru, an autonomous institute under DST, demonstrated the low-temperature synthesis of crystalline pyrite FeS2 through a solid-state synthesis route. They have utilised a metastable oxyhydroxide (FeOOH) precursor for this process.

The team reported stabilising this intermediate oxyhydroxide and utilising it as a precursor for sulfidation, in the presence of H2S gas, for the first time in their paper published in the journal Chemical Communications.

Using a metastable precursor helped in lowering the annealing temperature, as FeOOH converted into pyrite FeS2 with fairly good crystallinity at a low temperature. This synthetic route of obtaining sulfides from their corresponding metastable oxyhydroxides can be extended to other transition metals to obtain crystalline materials in an energy intensive way.