A novel iron sulfide phase with remarkable hydroxyl radical generation capability for contaminants degradation

•A novel layered iron sulfide phase has been discovered.•The new phase has a larger interlayer spacing of 8.03 Å than the conventional FeS of 5.31 Å.•The new phase exhibits a higher propensity to generate hydroxyl radicals (•OH).•The new phase exhibits significantly enhanced degradation efficiency towards typical pollutants. The hydroxyl radical (·OH) stands as one of the most potent oxidizing agents, capable of engaging in non-selective and instantaneous reactions with contaminants in water. Herein, we present a novel iron sulfide phase (S-FeS) characterized by an unprecedented structure, accompanied by its remarkable hydroxyl radical generation capability and contaminant degradation efficiency surpassing that of the conventional metastable iron sulfide phase, namely, the Mackinawite (FeS). In comparison to FeS, S-FeS exhibits enhanced degradation kinetics and higher efficacy in the removal of methylene blue, ciprofloxacin, and trivalent arsenic. Utilizing density functional theory (DFT) calculations, we postulate the mechanism for the exceptional contaminant degradation performance of S-FeS to be attributed to the increased exposure of the highly reactive (110) crystal facets. This research uncovers a new metastable phase that expands the polymorphisms within the iron sulfide family and showcases its capability for driving the oxygen reduction reaction. [Display omitted]