Hybridized heterostructure of CoS and MoS₂ nanoparticles for highly-efficient and robust bifunctional water electrolysis

For industrial hydrogen production, it is beneficial to develop highly-efficient, earth-abundant, and bifunctional electrocatalysts which exhibit compatibility between oxygen evolution reaction (OER) or hydrogen evolution reaction (HER) activity and stability in the same electrolyte. Herein, we report a bifunctional hybrid CoS/MoS₂ nanoparticle electrocatalyst in 1 M KOH, fulfilling desirable industrial criteria for water electrolysis. The CoS/MoS₂ catalyst exhibits excellent OER and HER activities with very low overpotentials as well as outstanding stability for more than 100 h, even at a high current density of 250 mA cm⁻². The bifunctional CoS/MoS₂ catalyst-based water-electrolyzer exhibits a low cell voltage of 1.52 V at 10 mA cm⁻² (1.714 V at 100 mA cm⁻²) with long–term stability. Density functional theory calculations reveal that the hybrid CoS/MoS₂ electrocatalyst shows one–way electron transfer that can activate both oxidative/reductive reactions. Therefore, it exhibits superior OER and HER activities, outperforming the state-of-the-art noble-metal-free catalysts.