Strong Interactions between Flash Subnanometer Carbide Nanowires and Single-Walled Carbon Nanotubes for Catalysis

The synthesis of transition metal carbides with precise control over their dimension, morphology, and crystallinity at a subnanometer scale presents a significant challenge. Addressing this, a kinetics-controlled confined flash Joule heating method has been developed, characterized by superfast heating (>2000 K ms^-1) and cooling (>30 K ms^-1) rates, enabling the millisecond-scale production of subnanometer molybdenum carbide nanowires. These one-dimensional structures are synthesized through a carbothermic reduction of encapsulated polymolybdate cluster arrays, a process that eschews the need for solvents, catalysts, or special gases, utilizing single-walled carbon nanotubes (SWNTs) as both thermal conductors and structural templates. The resulting carbide-encapsulated SWNTs feature a delocalized, electron-rich surface that is ideal for the stable immobilization of iron phthalocyanine (FePc) molecules. The MoC_<i>x</i>@SWNT-FePc complex demonstrates enhanced electrocatalytic activity in the alkaline oxygen reduction reaction, boasting a high half-wave potential of 0.91 V and long-term durability in zinc-air batteries, exceeding 450 h. Further, a type of Pt₁/MoC_<i>x</i>@SWNT chainmail catalyst has been achieved and showcases exceptional catalytic efficiency in the acidic hydrogen evolution reaction. It exhibits a high mass activity of 4.84 A mg_Pt^-1, a low Tafel slope of 37.4 mV dec^-1, and sustained durability over 350 h.