Nickel impregnated multi-walled carbon nanotubes (Ni/MWCNT) as active catalyst materials for efficient and platinum-free dye-sensitized solar cells (DSSCs)

The main purpose of this work is to improve the efficiency of dye-sensitized solar cells (DSSCs) by replacing the expensive platinum counter electrode material with nickel impregnated Multi-Walled Carbon Nanotubes (Ni/MWCNTs or Ni/CNTs). Catalyst materials for the counter electrode of DSSCs have been synthesized by impregnating different concentrations of nickel (Ni) into CNTs. According to Brunauer-Emmett-Teller (BET) analysis, the maximum surface area of Ni/CNT catalysts has been obtained at 3% loading of Ni. The surface morphology and presence of the Ni catalyst over the CNT support have been examined with the help of field emission scanning electron microscopy (FESEM) and energy-dispersive X-ray spectroscopy (EDX) mapping of reduced Ni/CNT catalysts. The presence of different phases and crystal structures of reduced Ni/CNT catalysts has been investigated through X-ray powder diffraction (XRD) analysis. The catalytic activity of Ni/CNT catalysts has been investigated by Cyclic Voltammetry (CV) and Tafel polarization analyses. The CV results demonstrate that Ni/CNT materials exhibit an outstanding electrochemical activity in DSSCs. The DSSC fabricated under optimal conditions exhibits a power-conversion-efficiency (PCE) of 9.72%, which is greater than that of a Pt-based DSSC (8.85%). These results demonstrate that the Ni/CNT material is a promising substitute for the costly Pt CE for low-cost DSSCs.