Synergistic regulation of sulfides and carbon in Fe-doped CoS2@MOF-based nanocomposites for enhanced catalytic performance

Abstract

Multimetal doping CoS₂ offers a promising strategy for developing high-performance electrocatalysts for the oxygen evolution reaction (OER). The performance of such catalysts is often limited by insufficient active sites exposure and low electrical conductivity. While previous literatures have focused on high-temperature complete carbonization of metal-organic frameworks (MOFs) into nanotubes, research on partial carbonization of MOFs remains limited. In this study, we successfully prepared porous Co₉Fe₁-MOF/S composites with enhanced OER performance by optimizing Co:Fe doping ratios, sulfidation temperature, and sulfur content. The results show that Fe doping significantly improved the electrical conductivity and increased the exposure of active sites, attributed to electronic structure modifications and the formation of nanosheet-like morphologies. After optimized sulfidation treatment, the samples achieved effective Fe incorporation and amorphous carbon formation while maintaining the porous structure of the MOF, further enhancing the catalytic activity. The prepared Co₉Fe₁-MOF/S samples exhibited excellent performance with a low overpotential of 308 mV and a small Tafel slope of 55.4 mV dec^-¹ in 1.0 M KOH solution, along with outstanding durability. Density functional theory (DFT) calculations confirmed the significant improvement in electrical conductivity resulting from Fe doping. This study provides important theoretical and experimental insight for designing high-performance bimetallic sulfide-based OER electrocatalysts.