Graphitic carbon nitride/multiwalled carbon nanotubes composite as Pt-free counter electrode for high-efficiency dye-sensitized solar cells

A graphitic carbon nitride (g-C3N4)/multiwalled carbon nanotubes (MWCNT) composite is prepared by a combination of refluxing process and heating polymerization and investigated as the counter electrode in dye-sensitized solar cells. SEM and TEM studies indicate that MWCNT is very well incorporated and attached to g-C3N4. Electrochemical impedance spectroscopy demonstrates that the charge-transfer resistance of g-C3N4/MWCNT composite electrode is 2.1 Omega cm(2), which is much lower than those of the individual g-C3N4 and MWCNT electrodes. This enhanced electrocatalytic activity is beneficial for improving the photovoltaic performance of dye-sensitized solar cells. Under illumination of 100 mW cm(-2), the dye-sensitized solar cell based on g-C3N4/MWCNT counter electrode achieves a conversion efficiency of 6.34%, which is comparable to that of the cell based on Pt counter electrode. (C) 2015 Elsevier Ltd. All rights reserved.