A sulfur-assisted strategy to decorate MWCNTs with highly dispersed Pt nanoparticles for counter electrode in dye-sensitized solar cells

A novel strategy was introduced to prepare hybrid nanomaterials of platinum nanoparticles and multi-walled carbon nanotubes (Pt-MWCNTs). A thin layer of sulfur on MWCNTs could absorb and bind the Pt precursors from solution on the MWCNTs' surface and also restrict their particle growth during reduction which resulted in ultrafine dispersions of metal nanocrystallites due to the strong affinity of sulfur for noble metals. The composite material was applied as the counter electrode (Pt-MWCNTs CE) for dye-sensitized solar cells (DSCs) and the fill factor (FF) and power-conversion efficiency (eta) of the DSC with Pt-MWCNTs CE were 0.63 and 7.69%, respectively. The corresponding values of the DSC with bare Pt CE were 0.55 and 6.31%. The morphology and elemental composition of Pt-MWCNTs were characterized by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The dispersion and attachment of Pt nanoparticles on the surface of MWCNTs were observed by transmission electron microscopy (TEM). Electrochemical impedance spectra (EIS), Tafel polarization measurement and cyclic voltammetry (CV) were performed to characterize the catalytic activities of this hybrid CE.