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

Tungsten ditellurium (WTe2) is one of most important layered transition metal dichalcogenides (TMDs) and exhibits various prominent physical properties. All the present methods for WTe2 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 WTe2 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 WTe2 nanoribbon crystals with 1T' Weyl semimetal phase for the first time. Highly crystalline 1T'-WTe2 nanoribbons can be obtained on a large scale through this two-step method. In addition, the electrochemical tests show that WTe2 nanoribbons exhibit smaller overpotential and much better hydrogen evolution reaction catalytic performance than other tungsten-based sulfide and selenide (WS2, WSe2) nanoribbons of same morphology and under same preparation conditions. WTe2 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-WS2 nanoribbons (135 mV/dec) and 2H-WSe2 nanoribbons (213 mV/dec), respectively. 1T'-WTe2 nanoribbons also show ultrahigh stability in 5000 cycles and 20 h at 10 mA/cm2. The better performance is attributed to high conductivity of semimetallic 1T'-phase-stable WTe2 nanoribbons with one or two order higher charge-transfer rate than normally semiconducting 2H-stable WS2 and WSe2 nanoribbons. These results open the door for electrochemical applications of Weyl semimetallic TMDs.