TEOS-assisted synthesis of porous MoS_2 with ultra-small exfoliated sheets and applications in dye-sensitized solar cells

摘要

Exfoliated MoS_2 of ultra-small sheets were for the first time synthesized by embedding the precursors ((NH_4)_6Mo_7O_(24)·4H_2O and thiourea) inside the hydrogel of the activated silicic acid (calculated as SiO_2) which was obtained from hydrolysis of tetraethylorthosilicate (TEOS). It was found that the added molar ratio of SiO_2/MoS_2 =10.0 can effectively be used as templates to prohibit the growth of MoS_2. Analysis of TEM, Raman spectra, XRD and BET reveals that the added TEOS plays a vital role in forming of exfoliated sheets and obtaining high specific surface area (101.6 m~2 /g) in the resultant products. The prepared exfoliated sheets of MoS_2 were employed as counter electrodes (CEs) materials for dye-sensitized solar cells (DSSCs). The electrochemical analysis (cyclic voltammograms, electrochemical impedance spectroscopy) indicates that the porous MoS_2 sheets CEs possess lower charge transfer resistance and a higher electro-catalytic activity in reducing I_3~- to I~- compared to the flower-shaped MoS_2 synthesized with less amount of the added TEOS. The DSSCs based on the porous MoS_2 sheets CEs was demonstrated to achieve a high power conversion efficiency of 6.35% which is comparable to that of Pt CEs (6.19%).