Stoichiometry-Controlled MoxW1-xTe2 Nanowhiskers: A Novel Electrocatalyst for Pt-Free Dye-Sensitized Solar Cells.

Abstract

Novel polymorphic MoxW1-xTe2-based counter electrodes possess high carrier mobility, phase-dependent lattice distortion, and surface charge density wave to boost the charge-transfer kinetics and electrocatalytic activity in dye-sensitized solar cells (DSSCs). Here, we report the syntheses of stoichiometry-controlled binary and ternary MoxW1-xTe2 nanowhiskers directly on carbon cloth (CC), denoted by MoxW1-xTe2/CC, with an atmospheric chemical vapor deposition technique. The synthesized MoxW1-xTe2/CC samples, including 1T'-MoTe2/CC, Td-WTe2/CC, Td-Mo0.26W0.73Te2.01/CC, and 1T'- & Td-Mo0.66W0.32Te2.02/CC, were then employed as different counter electrodes to study their electrochemical activities and efficiencies in DSSCs. The photovoltaic parameter analysis manifests that MoxW1-xTe2/CCs are more stable than a standard Pt/CC in the I-/I3- electrolyte examined by cyclic voltammetry over 100 cycles. A 1T'- & Td-Mo0.66W0.32Te2.02/CC-based DSSC can achieve a photocurrent density of 16.29 mA cm-2, a maximum incident photon-to-electron conversion efficiency of 90% at 550 nm excitation, and an efficiency of 9.40%, as compared with 8.93% of the Pt/CC counterpart. Moreover, the 1T'- & Td-Mo0.66W0.32Te2.02/CC shows lower charge-transfer resistance (0.62 Ω cm2) than a standard Pt/CC (1.19 Ω cm2) in electrocatalytic reactions. Notably, MoxW1-xTe2 nanowhiskers act as an electron expressway by shortening the path of carrier transportation in the axial direction from a counter electrode to electrolytic ions to enhance the reaction kinetics in DSSCs. This work demonstrates that the nanowhisker-structured 1T'- & Td-Mo0.66W0.32Te2.02/CC with high carrier mobility and robust surface states can serve as a highly efficient counter electrode in DSSCs to replace the conventional Pt counter electrode for electrocatalytic applications.