In situ formation of FeSx layer on Fe-based amorphous alloys: Improvement of catalytic activity and mechanism of sulfide layer formation

Sulfidated zero-valent iron (S-ZVI) has been demonstrated as a reliable approach for improving the surface passivation and accelerating electron transfer of ZVI. However, consumption of the iron sulfide layer resulted in a short lifespan. In this study, sulfidated FeBCCr₁ amorphous ribbons were successfully fabricated to effectively activate the persulfate (PS) for RhB degradation over a wide initial pH range (2.0–10.0), with a result of nearly 100 % of the color and 66.3 % of the total organic carbon removal efficiency. Based on the experiment results and adsorption phenomena, a surface-mediated heterogeneous activation mechanism was proposed. The in situ “self-reconstruction” iron sulfide layer (FeS_x) generated on the surface of the amorphous ribbon acted as a cocatalyst to promote electron transfer from the matrix Fe⁰ and continually accelerated the circulation of Fe³⁺/Fe²⁺. The continuous generation of FeS_x during degradation prevented the layer aging and ensured the catalytic activity of the FeBCCr₁ amorphous ribbons. More importantly, the co-existence of Fe³⁺ dramatically improved the stability of sulfide layer, electron utilization efficiency and material reusability, which was attributed to the improved conversion of Fe³⁺ to Fe²⁺ through charge transfer and the low consumption of Fe⁰ in FeBCCr₁/PS/Fe³⁺ system. This work provides a new strategy for designing FeS_x co-catalyst layer in FeBCCr₁/PS system and provides an effective approach for macroscopic preparation of sulfidated Fe-based amorphous ribbons, establishing a solid foundation for the application of zero valent iron in the environmental field.