One step laser-induced synthesis of a bimetallic iron–cobalt sulfide for efficient solar light driven, Fenton-like and electrochemical catalysis

Pulsed laser irradiation of an equimolar mixture of FeS₂ and CoS₂ onto a Ta substrate results in the one-step formation of bimetallic iron cobalt sulfide. The use of complementary analytical techniques, such as scanning electron microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction, high-resolution electron microscopy, and electron diffraction, confirmed the presence of nanocrystalline cobaltpentlandite [FeCo₈S₈] and maghemite [γ-Fe₂O₃]. The mechanism by which this occurs involves the reactive interaction of laser-ionized Fe, Co, and S species, which subsequently undergo rapid non-equilibrium cooling and deposition. The higher deposition tendency of CoS₂ along with iron ions/atoms leads to the formation of FeCo₈S₈. This proposed mechanism is supported by density functional theory (DFT), which provides a deeper understanding of the higher thermodynamic stability of Fe in Co_1-<i>x</i> Fe _<i>x</i> S₂ compared with Co in Fe_1-<i>x</i> Co _<i>x</i> S₂. The FeCo₈S₈-based deposit exhibited enhanced catalytic efficiency for methylene blue daylight-driven and Fenton-like degradation. In contrast, for solar light-driven degradation of sulfamethoxazole and trimethoprim, the FeCo₈S₈-based deposit does not show enhanced catalytic activity compared to FeS₂ and CoS₂. Additionally, electrochemical testing of the oxygen evolution reaction (OER) revealed significantly improved performance for the FeCo₈S₈-based deposit compared to FeS₂ and CoS₂ individually.