Surface-Tuned Ti₃C₂T_x MXene Nanofiber Catalyst Decorated with Electrodeposited Nickel for High-Performance Hydrogen...

The development of earth-abundant, high-performance electrocatalysts is critical for enabling scalable and sustainable hydrogen production via alkaline water electrolysis. Herein, we report a combined dimensional and surface-engineering strategy to transform two-dimensional Ti₃C₂T_x MXene nanosheets into one-dimensional MXene nanofibers (MXnf) through controlled alkaline reconstruction, followed by the rational electrodeposition of metallic Ni to create a highly efficient hydrogen evolution reaction (HER) electrocatalyst. Although alkaline-induced replacement of -F terminations with -O/-OH has been recognized as an effective strategy for improving MXene stability and tuning surface chemistry, this approach has rarely been integrated with dimensional reconstruction to systematically optimize HER activity in metal-MXene nanofiber systems for alkaline media. In this work, alkaline surface termination tuning is intentionally coupled with one-dimensional MXene nanofiber formation to promote intimate structural integration between Ni and the MXene nanofiber scaffold and accelerate HER kinetics. The optimized Ni-decorated MXene nanofiber catalyst (NiMXnf-30) exhibits outstanding HER activity in 1 M KOH, delivering a low overpotential of 87 mV at 10 mA cm^-2, a small Tafel slope of 79 mV dec^-1, and an ultralow charge-transfer resistance of 0.05 Ω. Moreover, the catalyst demonstrates a substantially enlarged electrochemically active surface area and excellent operational durability, maintaining stable performance at 100 mA cm^-2 over 30 h. This work provides a scalable and versatile platform for MXene-based catalyst design and highlights the critical role of simultaneous dimensional and surface termination engineering in advancing non-noble metal electrocatalysts for efficient green hydrogen production.