Tunable electronic coupling of Fe-doped CoS₂/reduced graphene oxide composites for boosting bifunctional water splitting activity

The electrochemical water splitting process is always restrained for its sluggish kinetics and high reaction energy barrier. Therefore, developing outstanding bifunctional catalysts to enhance the reaction kinetics and electron transfer efficiency of water splitting is crucial. In this work, we reported a bifunctional nanohybrid electrocatalyst consisting of Fe-doped CoS₂ nanocage-decorated reduced graphene oxide (FCSRGO) with superior water splitting activity. The Fe doping adjusts the density of state (DOS) to increase the conductivity and decreases the adsorption free energy of intermediates, contributing to optimized catalytic activity. Furthermore, the incorporation of RGO reduces the agglomeration of CoS₂ and improves the conductivity, thereby amplifying the charge/species transfer efficiency. By optimizing the amount of RGO, FCSRGO shows exceptional electrocatalytic performance, achieving a benchmark current density of 10 mA·cm⁻² at remarkably low overpotentials (ƞ₁₀) of 107 mV and 239 mV in 1 M KOH solution for HER and OER, respectively. Moreover, the nanohybrid exhibits remarkable stability with the current density retention of 89.8% for HER and 85.8% for OER after 36000 s test. This work highlights the creating of high-performance electrocatalysts for efficient and sustainable hydrogen and oxygen evolution through heteroatom doping and carbon incorporation.