High Electrocatalytic and Wettable Nitrogen-Doped Microwave-Exfoliated Graphene Nanosheets as Counter Electrode for Dye-Sensitized Solar Cells

Abstract

We present a cost-effective and solution-based method to prepare N-MEG used as Pt-free CE to achieve high-performance dye sensitized solar cells (DSSCs). The use of cyanamide solution as N-doping source at normal pressure and room temperature is suitable for mass production. A large area of N-MEG free of structural defects using this synthesis can be observed in TEM. XPS provides evidence that the pyrrolic-N and pyridinic-N in the carbon conjugated lattice are two main structures. High electrocatalytic activities can be reached based on electrochemical characterization. The curved structure of N-MEG creates a large porosity to facilitate electrolyte diffusion, leading to an improved Nernst diffusion resistance within the electrode pores. We also found that the air exposure time after completing N-MEG film has a significant effect on the degradation of active sites and surface wettability so that influence charge transfer process and electrolyte diffusion. FF can be effectively improved because of good electrolyte permeation within the pores resulting from N-doping effect and the control of air exposure time. Therefore, measurement of DSSC with N-MEG CE demonstrates a nearly comparable performance to that with Pt CE, which presents a great potential for the preparation of cost-effective and noble metal-free DSSCs. In addition, N-MEG can be employed as CE for Co(?/?) mediated YD2-o-C8 DSSCs, showing a significant improved long-term electrocatalytic reliability as compared with Pt CE.