Stoichiometry-controlled synthesis of pyrite and greigite particles for photo-Fenton degradation catalysis

Abstract

Two types of iron sulfide, namely highly crystalline pyrite (FeS₂) and greigite (Fe₃S₄), were synthesized via a hot-injection method by changing the precursor ratios of iron to sulfur (Fe : S) from 1 : 6 to 1 : 12, and were employed in photo-Fenton catalytic reactions to degrade the organic dye Rhodamine B (RhB). The degradation efficiency of 10 mg L⁻¹ RhB by Fe₃S₄ reached 99.0% in 22 minutes under sunlight irradiation, while a similar removal efficiency was realized by FeS₂ in 35 minutes in photo-Fenton catalysis. By studying the stability and structural differences, we found that the surface states of iron sulfides were the main factors affecting the catalytic efficiency in the photo-Fenton reaction, and sunlight illumination was an auxiliary factor; both of them worked together to determine the degradation efficiency. This research on the factors affecting iron sulfide photocatalytic degradation provides new insights for finding better photo-Fenton catalysts.