Molybdenum disulfide/reduced graphene oxide hybrids with enhanced electrocatalytic activity: An efficient counter electrode for dye-sensitized solar cells

Development of low cost, metal-free electrodes for photovoltaic applications is critical to meet future energy demands. In this work, the one-step hydrothermal synthesis and electrocatalytic activity of molybdenum disulfide/reduced graphene oxide (MoS2-rGO) hybrids are investigated as high-performance counter electrode materials for dye-sensitized solar cells (DSSCs). The crystal structure and morphology analyses of as-prepared MoS2-rGO hybrids indicated the presence of MoS2 nanostructures having a petal-like morphology on rGO sheets. Raman spectroscopy provided evidence for weak Van der Waals interactions between MoS2 and rGO layers along with a low defect density. DSSCs made with counter electrodes (CEs) of MoS2-rGO hybrids, showed an impressive power conversion efficiency of 7.83% surpassing the DSSCs with CEs of pristine MoS2 (5.97%) and the conventional Pt (7.57%). The cyclic voltammetry and electrochemical impedance studies have shown that the incorporation of reduced graphene oxide in the MoS2 nanostructures significantly decreased the charge transfer resistance and improved the electrocatalytic activity of their CEs. This is partly attributed to the morphology of the hybrid in which the petal-like MoS2 nanostructures on the rGO sheets provided numerous catalytic sites, which, in turn, enhanced the charge transfer across the CE providing a synergistically high performance. These results have indicated that the MoS2-rGO hybrids are promising alternatives to the conventional Pt-based CEs in DSSCs.