Functionalized MWCNT decorated FeCoS₂ nanorod as bifunctional electrocatalysts for efficient water splitting reactions

A hydrothermal approach was used to successfully synthesize functionalized multi-walled carbon nanotube integrated FeCoS₂ (f-MWCNTs@FeCoS₂) nanocomposites with different f-MWCNT loadings (3, 6, and 9 wt%) and evaluate as bifunctional electrocatalysts for water splitting applications. Raman and FTIR spectroscopy revealed the effective surface functionalization of MWCNTs and their strong interfacial interaction with FeCoS₂, while XRD analysis verified the formation of phase-pure crystalline FeCoS₂. FE-SEM and TEM analyses reveal that the FeCoS₂ nanorods are uniformly anchored onto the interconnected f-MWCNT conductive network, thereby facilitating enhanced electron transport pathways and improved accessibility of active sites. Furthermore, BET analysis confirms the mesoporous nature of the 6% f-MWCNTs@FeCoS₂ nanocomposite, which promotes rapid electrolyte diffusion and provides a large number of electrochemically active sites. Electrochemical impedance spectroscopy revealed lower charge transfer resistance values of 19.3 Ω (OER) and 10.9 Ω (HER), indicating improved charge transfer kinetics. The optimized 6 wt% f-MWCNTs@FeCoS₂ catalyst achieved low overpotentials of 203 mV for HER and 160 mV for OER, with Tafel slopes of 128 mV dec⁻¹ and 98.97 mV dec⁻¹, respectively with excellent 25 h of electrochemical stability over continuous operation. The synergistic interaction between mesoporous FeCoS₂ nanorods and conductive f-MWCNTs enables rapid electron transfer, enhanced active site availability, and efficient electrolyte diffusion for sustainable hydrogen production via water splitting, resulting in superior bifunctional performance.