Synthesis of 1T/2H-MoS₂ nanosheets on dome-shaped CoS₂ particles embedded in carbon nanofibers as free-standing electrodes for alkaline water splitting

Background: The development of cost-effective and earth-abundant non-noble metal electrocatalysts is crucial for advancing water electrolysis. Transition metal sulfides (TMSs) are promising candidates due to their low cost and abundant active sites. However, individual TMSs often exhibit limited efficiency in alkaline media. Constructing binder-free heterostructures based on TMSs has emerged as an effective strategy to overcome these limitations. Methods: A bifunctional electrocatalyst was synthesized by uniformly depositing 1T/2H-MoS₂/CoS₂ heterostructure nanoparticles on nitrogen-doped carbon nanofibers (NCNFs) through electrospinning, carbonization, and low-temperature hydrothermal synthesis, yielding 1T/2H-MoS₂/CoS₂@NCNF. Significant findings: The dome-shaped CoS₂ nanoparticles covered with flower-like MoS₂ nanosheets on interconnected NCNFs significantly enhanced HER and OER activity in an alkaline electrolyte. The improved performance is attributed to the increased number of active sites, synergistic catalytic effects of the heterostructure, and superior electrical conductivity. The optimized catalyst exhibited low overpotentials of 144 mV (HER) and 322 mV (OER) at 10 mA cm^–2 in 1.0 M KOH. As a bifunctional electrode, it delivered a low water splitting voltage of 1.68 V at 10 mA cm^–2. This work demonstrates a viable approach for designing free-standing, bifunctional electrodes using heterogeneous TMSs on carbon nanofibers for efficient overall water splitting.