Nitrogen-doped graphene/molybdenum disulfide composite as the electrocatalytic film for dye-sensitized solar cells

A composite thin film of nitrogen-doped graphene and molybdenum disulfide (NGr/MoS2) was prepared via a simple drop-coating method, and used as an electrocatalytic film for the counter electrode (CE) of a dye-sensitized solar cell (DSSC). The NGr was intended for increasing the conductivity and serving as the skeleton of the composite film, while the MoS2 with remarkable electrocatalytic ability increased the effective electrocatalytic sites in the composite film. The NGr acts as the architecture framework for MoS2 sheet, which could expose the active sites on its edge, as demonstrated in scanning electron microscopy (SEM). The weight percent (wt %) of the NGr in the composite film was optimized for obtaining the best performance to the pertinent DSSC. The NGr/MoS2 composite film shows much higher electrocatalytic ability for the reduction of I-/I3-, compared to the films of bare NGr and bare MoS2. Electrocatalytic abilities of the films were estimated by cyclic voltammetry (CV), rotating disc electrode (RDE), Tafel polarization plot, and electrochemical impedance spectroscopy (EIS) analyses. The DSSC with the NGr/MoS2 CE exhibits a solar-to-electricity power conversion efficiency of 7.82%, close to 8.25% of the DSSC with a platinum CE film. The low-cost NGr/MoS2 composite film is a potential alternative to replace the expensive platinum film for use as the catalytic film on the counter electrode of a DSSC. (C) 2016 Elsevier Ltd. All rights reserved.