Fabrication of ZnO@MWCNT@Nafion composite counter electrode for enhanced electrocatalytic performance in dye-sensitized solar cells

Abstract

The development of low-cost and efficient counter electrodes (CEs) is crucial for improving the performance and large-scale commercialization of dye-sensitized solar cells (DSSCs). In this work, ZnO-decorated multi-walled carbon nanotube (ZnO@MWCNT@Nafion) composite counter electrodes were fabricated through a facile solution-based approach with different ZnO loadings (1%–4%). Structural and morphological analyses using x-ray diffraction, Raman spectroscopy, scanning electron microscopy, and transmission electron microscopy (TEM) confirmed the successful anchoring of crystalline ZnO nanoparticles onto the MWCNT network. Nitrogen adsorption–desorption measurements revealed enhanced mesoporosity and increased specific surface area for the composites, particularly for ZnO(2%)@MWCNT@Nafion. Electrochemical studies, including cyclic voltammetry (CV), Tafel polarization, and electrochemical impedance spectroscopy, demonstrated significantly improved electrocatalytic activity toward the I3−/I− redox couple compared with pristine MWCNT electrodes. Among the prepared composites, ZnO(2%)@MWCNT@Nafion exhibited the lowest charge-transfer resistance and the highest catalytic activity. DSSCs assembled with this electrode delivered a short-circuit current density of 15.1 mA cm−2, an open-circuit voltage of 0.661 V, a fill factor of 73%, and a power conversion efficiency of 7.3%, approaching that of the Pt-based device (8.1%). The enhanced performance arises from the synergistic interaction between ZnO nanoparticles and the conductive MWCNT framework, which increases active catalytic sites and facilitates rapid charge transfer.