DMSO-assisted sulfur incorporation in a trimetallic composite electrocatalyst for hydrogen generation by alkaline water splitting

Sustainable hydrogen generation via alkaline water electrolysis necessitates the development of efficient and durable noble-metal-free electrocatalysts. Herein, we report a solvent-engineered solvothermal synthesis of a trimetallic Co₉S₈-MnCO₃-TiO_x composite over nickel foam. The H₂O:DMSO solvent (HD) ratio governed the phase evolution and morphology of the electrocatalyst. The optimized solvent ratio modulated the coprecipitation and nucleation kinetics of Co and Mn ions to form cobalt sulfide and manganese carbonate phases as evidenced by the structural analysis. The morphological studies revealed a nanoneedle architecture with anisotropic growth, forming a porous network throughout the catalyst surface. The HD-1:1 electrocatalyst exhibited electrochemical HER and OER overpotentials of −286 mV and 374 mV, respectively, to achieve a current density of 100 mA·cm⁻², which could be attributed to favorable reaction kinetics and accelerated electron transfer governed by optimized sulfur incorporation. This bifunctional nature facilitated the HD-1:1 electrocatalyst to exhibit overall water splitting (OWS), sustaining a durability of 12 h at 100 mA·cm⁻². Post-durability morphological analysis revealed a preserved three-dimensional morphology and elemental composition. This work highlights that solvent engineering can be an effective strategy for the incorporation of sulfur into multimetallic composite electrocatalysts to facilitate prolonged alkaline water electrolysis. Also, this work helps researchers working on responsible consumption and production energy pathways for climate action.