Operando exploration of tribochemical decomposition of FeS2 thin films and mineral iron pyrite

Tribochemical decomposition of thin-film synthetic iron disulfide and mineral iron pyrite was studied using a combination of operando mass-spectrometry coupled to ultrahigh vacuum tribochemical cell and these gas expansion system. The composition and kinetics of gas emission were analyzed using an original methodology. It was found that carbon-containing gases were dominating. The sulfur-containing gases comprised H2S, COS and CS2. The latter two were unexpected. The emission of the gases was traced back to solid-state chemical reactions kinetically controlled by the precursor concentrations and driven through non-thermal mechanisms, which we tentatively assigned to formation of sulfur radicals.