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

•g-C3N4/MWCNT composite with enhanced electrocatalytic performance is prepared.•The combined action of g-C3N4 and MWCNT is responsible for performance enhancement.•DSC with g-C3N4/MWCNT electrode shows a conversion efficiency of 6.34%.•The performance of g-C3N4/MWCNT electrode is very close to that of Pt electrode.

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 Ω cm2, 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.