Phase-Engineered Weyl Semi-Metallic Mox W1-x Te2 Nanosheets as a Highly Efficient Electrocatalyst for Dye-Sensitized Solar Cells

The emerging Weyl semi-metals with robust topological surface states are very promising candidates to rationally develop new-generation electrocatalysts for dye-sensitized solar cells (DSSCs). In this study, a chemical vapor deposition (CVD) method to synthesize highly crystalline Weyl semi-metallic MoxW1-xTe2 nanocrystals, which are applied for the counter electrode (CE) of DSSCs for the first time, are employed. By controlling the temperaturedependent phase-engineered synthesis, the nanocrystal grown at 760 C exhibits the mixed phases of semiconducting Td& 2H-Mo0.32W0.67Te2.01 with charge carrier density of (1.20 0.02) 10 cm ; whereas, the nanocrystal synthesized at 820 C shows a single phase of semi-metallic TdMo0.29W0.72Te1.99 with much higher carrier density of (1.59 0.04) 10 cm . In the cyclic voltammetry (CV) analysis over 200 cycles, the MoxW1xTe2-based electrodes show better stability in the I /I3 electrolyte than a Pt electrode. In DSSC tests, a Td-Mo0.29W0.72Te1.99-decorated CE achieves the efficiency (η) of 8.85%, better than those CEs fabricated with Td& 2HMo0.32W0.67Te2.01 (7.81%) and sputtered Pt (8.01%). The electrochemical impedance spectra reveal that the Td-Mo0.29W0.72Te1.99 electrode possesses low charge-transfer resistance in electrocatalytic reactions. These exceptional properties make Weyl semi-metallic Td-MoxW1-xTe2 a potential electrode material for a wide variety of electrocatalytic applications.

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