Active Sites-Enriched Hierarchical Weyl Semimetal WTe2 Nanowire Arrays for Highly Efficient Hydrogen Evolution Reaction

Abstract

Weyl semimetal tungsten ditelluride (WTe₂), characterized by its high conductivity and robust topological surface state, possesses promising catalytic properties for electrochemical reactions. However, the synthesis of well-defined WTe₂ nanostructures has faced challenges, hindering their practical applications. This study introduces a new method for synthesizing Weyl semimetal WTe₂ nanowire arrays grown vertically on conductive carbon cloth. Through a selective synthesis process, WTe₂ and core-shell semiconductor-semimetal WO_{3- x}-WTe₂ nanowires are successfully fabricated via tellurization of WO_2.9 nanowires. To gain a comprehensive understanding of the structural, chemical, and catalytic properties of these nanowires, WO_2.9 nanowires are gradually converted to WO_{3- x}-WTe₂ and WTe₂ nanowires. The hierarchical structure of the WTe₂ nanowires greatly increases the number of active sites and promotes efficient charge transfer, resulting in exceptional electrochemical catalytic performance. In the hydrogen evolution reaction, WTe₂ nanowire arrays exhibit an exceptionally low Tafel slope of 49 mV dec^-1, as well as remarkable stability under both high and low current densities. These exceptional properties highlight the potential of WTe₂ nanowire arrays as highly effective electrochemical catalysts. It is expected that this facile synthesis approach will pave the way for the fabrication of well-structured Weyl semimetal nanowires, enabling further exploration of their intriguing properties and promising applications.

Keywords: catalysis; core–shell; transition metal dichalcogenide; transition metal oxide; tungsten ditelluride; tungsten oxide; water splitting.

Figure 1

a) Schematic of the experimental setup for synthesizing WTe₂ NW arrays and core–shell WO_{3− x} –WTe₂ NW arrays via a two‐step synthesis process. b) Growth pathways of WO_{3− x} –WTe₂ NWs and WTe₂ NWs on CC.

Figure 2

a) Optical image of the Au‐deposited CC, WO_2.9 NWs/CC, and WTe₂ NWs/CC. b,c) Low‐magnification SEM images of WO_2.9 NW arrays. d) High‐magnification SEM image of the white square region indicated in (c). e,f) Low‐magnification SEM images of WTe₂ NW arrays. g) High‐magnification SEM image of the white square region indicated in (f).

Figure 3

a) XRD patterns and b) Raman spectra of WO_2.9 NWs, core–shell WO_{3− x} –WTe₂ NWs, and WTe₂ NWs. XPS spectra for c) W 4f and d) Te 3d regions of the as‐synthesized NWs.

Figure 4

TEM images, STEM images, and EDS element maps of a,b) WO_2.9 NWs, c,d) core–shell WO_{3− x} –WTe₂ NWs (tellurization for 30 min), and e,f) WTe₂ NWs, respectively. The structures of tungsten oxide compounds. The W─W distances g) between two corner‐sharing [WO₆]‐octahedra, h) between two edge‐sharing [WO₆]‐octahedra, and i) between a [WO₆]‐octahedra and a bipyramidal pentagonal column. j–l) The structures of monoclinic WO₃, WO_2.9, and WO_2.72. W is shown in blue, O in red.

Figure 5

Electrochemical performance of WTe₂ NWs and core–shell WO_{3− x} –WTe₂ NWs at different tellurization times. a) LSV polarization curves, b) Tafel plots, c) Nyquist plots, and d) correlation between current density and scan rate for the catalysts. e) LSV polarization curves of WTe₂ NWs before and after 1500 HER cycles, with the inset showing an SEM image of WTe₂ NWs post‐HER. f) Stability test of WTe₂ NWs at a current density of 500 mA cm⁻².