Enhanced Electrocatalytic Hydrogen Evolution from Large-Scale, Facile-Prepared, Highly Crystalline WTe₂ Nanoribbons with Weyl Semimetallic Phase

Tungsten ditellurium (WTe 2 ) is one of most important layered transition metal dichalcogenides (TMDs) and exhibits various prominent physical properties. All the present methods for WTe 2 preparation need strict conditions such as high temperature or cannot be applied in large scale, which limits its practical applications. In addition, most studies on WTe 2 focus on its physical properties, whereas its electrochemical properties are still illusive with little investigation. Here, we develop a facile and scalable two-step method to synthesize high-quality WTe 2 nanoribbon crystals with 1T′ Weyl semimetal phase for the first time. Highly crystalline 1T′-WTe 2 nanoribbons can be obtained on a large scale through this two-step method. In addition, the electrochemical tests show that WTe 2 nanoribbons exhibit smaller overpotential and much better hydrogen evolution reaction catalytic performance than other tungsten-based sulfide and selenide (WS 2, WSe 2 ) nanoribbons of same morphology and under same preparation conditions. WTe 2 nanoribbons show a Tafel slope of 57 mV/dec, which is one of best values for TMD catalysts and about 2 and 4 times smaller than that for 2H-WS 2 nanoribbons (135 mV/dec) and 2H-WSe 2 nanoribbons (213 mV/dec), respectively. 1T′-WTe 2 nanoribbons also show ultrahigh stability in 5000 cycles and 20 h at 10 mA/cm 2 . The better performance is attributed to high conductivity of semimetallic 1T′-phase-stable WTe 2 nanoribbons with one or two order higher charge-transfer rate than normally semiconducting 2H-stable WS 2 and WSe 2 nanoribbons. These results open the door for electrochemical applications of Weyl semimetallic TMDs.