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.