Facile synthesis of MoS2/graphene nanocomposite with high catalytic activity toward triiodide reduction in dye-sensitized solar cells

Abstract

In the current study, a nanocomposite of molybdenum disulfide and graphene (MoS₂/RGO) was proposed for the first time as the counter electrode (CE) catalyst in dye-sensitized solar cells (DSSCs) to speed up the reduction of triiodide (I₃⁻) to iodide (I⁻). This novel catalyst was synthesized by simply mixing graphene oxide nanosheets with a solution of ammonium tetrathiomolybdate and then converting the solid intermediate into MoS₂/RGO nanocomposite in a H₂ flow at 650 °C. Atomic force microscopy, X-ray powder diffraction and X-ray photoemission spectroscopy confirmed that MoS₂ nanoparticles were deposited onto the graphene surface. The extensive cyclic voltammograms (CV) showed that the cathodic current density of the MoS₂/RGO CE was higher than those of MoS₂, RGO and sputtered Pt CEs, due to the increased active surface area of the former. Moreover, the peak current densities of the MoS₂/RGO CE showed no sign of degradation after 100 consecutive CV tests, suggesting the great electrochemical stability of the MoS₂/RGO CE. Furthermore, the MoS₂/RGO CE demonstrated an impressively low charge-transfer resistance (0.57 Ω cm²) for I₃⁻ reduction. Finally, the DSSC assembled with the MoS₂/RGO CE showed a high power conversion efficiency of 6.04%, which is comparable to the DSSC with a Pt CE (6.38%).