Electrodeposited Ni-based MXene and carbide composites for hydrogen evolution: Mechanistic exploration by DEMS

• Scalable electrodeposition yields Ni/MXene and Ni/Mo₂C composites with enhanced HER performance. • Carbides and MXenes reshape Ni into high-area, high-activity interfaces for alkaline electrolysis. • DEMS enable reliable HER onset detection and clarify the rate-determining step. • Composites outperform Ni cathodes in activity, charge transfer, and stability for low-cost alkaline electrolyzers. • Ni/Mo₂C shows the fastest charge-transfer kinetics (lowest R ct ), while Ni/Mo₂TiC₂ offers the best activity–stability balance. Nickel-based catalysts are promising alternatives to noble metals for hydrogen evolution in alkaline media; however, their long-term stability and scalability remain a challenge. In this paper, we report the synthesis of nickel composites with laboratory-synthesized molybdenum carbide (Mo₂C) and MXenes (Ti₃C₂ and Mo₂TiC₂) via electrodeposition, a cost-effective and industrially scalable method compatible with the fabrication of alkaline water electrolysis (AWE) electrodes. The catalysts were systematically characterized by SEM/EDX, DRX, EIS, cyclic voltammetry, chronoamperometry, and, notably, differential electrochemical mass spectrometry (DEMS). DEMS enabled real-time quantification of hydrogen evolution, providing mechanistic insights beyond conventional electrochemical techniques. The Ni/Mo₂C composite exhibited the lowest charge-transfer resistance and superior intrinsic activity, whereas Ni/MXene electrodes demonstrated higher electrochemically accessible surface areas and improved stability. Overall, this work highlights electrodeposition as a versatile strategy for preparing advanced Ni-based composites and underscores the value of DEMS in elucidating the hydrogen evolution mechanism in noble-metal-free systems