Double‐Transition‐Metal MXene–CoS ₂ Hybrid Electrocatalysts: A New Avenue for Alkaline Hydrogen Evolution

ABSTRACT The global demand for hydrogen (H 2 ) production via electrolysis is rapidly increasing, necessitating the development of low‐cost and high‐performance electrocatalysts. Herein, we report the synthesis of a double‐transition‐metal (DTM) MXene, molybdenum titanium carbide (Mo 2 Ti 2 C 3 T x ), using a non‐hydrofluoric (HF) acid‐based etchant, followed by the incorporation of cobalt sulfide (CoS 2 ) nanoparticles through a hydrothermal process. The optimized Mo 2 Ti 2 C 3 T x @CoS 2 composite demonstrated excellent electrocatalytic activity for the hydrogen evolution reaction (HER) in alkaline media, achieving a low overpotential of 281 mV at 10 mA/cm 2 , a Tafel slope of 79 mV/dec, and a high electrochemical active surface area (ECSA) of 375 cm 2 . Theoretical calculations further validated the efficiency of the material, and its application in a real‐time anion exchange membrane (AEM) electrolyzer confirmed its stability and high H 2 production rate. These findings highlight Mo 2 Ti 2 C 3 T x @CoS 2 as a promising noble‐metal‐free electrocatalyst for sustainable H 2 production and electrochemical energy conversion.