Exploring new catalytic solids is of great demand to degrade recalcitrants in an efficient/sustainable manner, yet, finds it cumbersome to do so due to low mechano-chemical stabilities of the solids in the presence of strong oxidants. This presentation highlights the use of iron sulfides as novel, cheap catalysts to produce ·OH through homolytic H₂O₂ scission. While employing phenol as a model compound for the recalcitrants, catalytic consequences of the iron sulfides were rigorously assessed via kinetic investigation and compared with iron oxide analogues. This study also showcases a benefit of the iron sulfide catalysts to dissociate H₂O₂ species via heterogeneous catalysis, as corroborated by controls including recycle runs and H₂O₂ decomposition experiments. This study therefore justifies S-modified Fe²⁺ species innate to iron sulfides should be sought after as alternatives of iron oxide catalysts that are currently in use for recalcitrants' degradation via homogeneous catalysis.