Atomic-Scale Confined Synthesis of Ultrathin W<sub>2</sub>C Nanowires in Single-Wall Carbon Nanotubes for the High-Performance Hydrogen Evolution Reaction.

Zhang, Zichu; Xie, Rui-Hong; Liang, Xuefeng; Zhang, Feng; Yang, Hao; Zou, Meng-Ke; Zhang, Lili; Shi, Chao et al. · Nano Lett · 2025

basic_science · Level V

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Abstract

Phase-pure ultrafine W<sub>2</sub>C nanostructures are promising electrocatalysts but face synthesis challenges due to unclear formation mechanisms and harsh thermodynamics. Here, we reveal the formation mechanism of ultrathin W<sub>2</sub>C nanowires (NWs) confined in the cavity of single-wall carbon nanotubes (SWCNTs) at the atomic scale by combined <i>in situ</i> transmission electron microscopy and density functional theory calculations. It was found that the hollow core of SWCNTs can control the phase, axial orientation, and diameter of W<sub>2</sub>C NWs. Leveraging this mechanism, we synthesized SWCNT-encapsulated W<sub>2</sub>C NWs, WS<sub>2</sub>-W<sub>2</sub>C heterostructures, and WS<sub>2</sub> NWs (1D@1D), which assembled into free-standing hybrid films. The integrated W<sub>2</sub>C NWs@SWCNT membrane was primarily tested, exhibiting a low overpotential of 44 mV to reach a current density of 10 mA cm<sup>-2</sup> and outstanding durability (500 h at a high current density of 250 mA cm<sup>-2</sup> in acidic conditions).