Next-generation CoMoS3/carbon sphere nanoflower catalyst for sustainable hydrogen production through urea oxidation-assisted water electrolysis

Development of effective and economical electrocatalysts for hydrogen production is of particular importance in sustainable energy policies. In this study, we present a novel cobalt molybdenum sulphide/carbon sphere (CoMoS 3 /CS) nanoflower synthesized by a facile hydrothermal process that has a high electrochemically active surface area and dense catalytic sites. The CoMoS 3 /CS rose-like nanoflower catalyst has excellent trifunctional activity towards the hydrogen evolution reaction (HER), oxygen evolution reaction (OER) and urea oxidation reaction (UOR). It shows a low HER overpotential of 93 mV at 10 mA cm 2 , superior to that of CoS/CS (143 mV) and CS (242 mV). For UOR, the oxidation potential is 1.33 V vs. RHE with a Tafel slope of 49 mV dec 1 and an OER oxidation potential of 1.67 V with a Tafel slope of 64 mV dec 1 . Both HER and UOR long-term electrochemical stability was established through chronoamperometry and voltammetry tests with little performance loss. In a hybrid water electrolysis configuration (HER ||UOR), the catalyst facilitated effective hydrogen production with significantly lower cell voltage of 1.46 V compared to conventional HER ||OER system. The incorporation of carbon spheres in this nanostructured catalyst improved the active surface area and facilitated synergistic interactions resulting in high catalytic activity, and durability. This study emphasizes the design of next generation electrocatalysts for hybrid water electrolysis to produce sustainable hydrogen. • CoMoS 3 /CS with rose petal morphology synthesized via hydrothermal strategy. • Exhibits superior HER, OER, and UOR activity in alkaline and urea media. • Urea-assisted water electrolysis reduces energy input for H 2 production.