Operando exploration of tribochemical decomposition in synthetic FeS2 thin film 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 the 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 these 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.