Se-doped FeS₂/CoS nanosphere catalysts bifunctional electrocatalyst for superior OER and HER activity

In this study, we synthesized FeS₂₋ₓSeₓ/CoS@CC catalysts and investigated their electrocatalytic performance for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). The introduction of Se into the FeS₂ structure enhanced its electronic properties, while the CoS layer, forming a heterojunction with FeS₂₋ₓSeₓ@CC, optimized charge separation and electron transfer. The FeS₂₋ₓSeₓ/CoS@CC catalysts featured a three-dimensional porous array structure that provided a large surface area for efficient reactant adsorption and improved electron distribution. XRD and XPS analyses confirmed the successful Se doping and the preservation of the FeS₂ crystal structure. Electrochemical tests revealed that FeS₂₋ₓSeₓ/CoS@CC exhibited lower overpotentials for both OER and HER, with enhanced reaction kinetics indicated by low Tafel slopes (68.5 mV dec⁻¹ for OER and 135.1 mV dec⁻¹ for HER). The catalyst also demonstrated excellent charge transport characteristics and stability during prolonged cycling. These results highlight the significant role of Se doping and CoS heterojunctions in boosting the electrocatalytic performance and stability, making FeS₂₋ₓSeₓ/CoS@CC a promising candidate for renewable energy applications.