Effective synthesis of carbon nanotubes of high purity over Cr–Ni–SBA-15 and its application in high performance dye-sensitized solar cells

Abstract

The synthesis of carbon nanotubes (CNTs) by chemical vapour deposition (CVD) using 2D hexagonal ordered mesoporous SBA-15 supported mono and bimetallic catalysts using chromium (Cr) and nickel (Ni) were prepared by a post-synthesis grafting process. The structure of the synthesized well graphitized CNTs with a uniform diameter was investigated by transmission electron microscopy, X-ray diffraction, thermogravimetry and Raman spectroscopy. Studies performed to evaluate the quality and quantity of the synthesized CNTs provide evidence in support of the superior catalytic nature of the bimetallic (Cr–Ni) catalyst over the mono metallic (Cr/Ni) catalysts. The CNTs synthesized using Cr–Ni–SBA-15 catalysts were coated on fluorine doped tin oxide conductive glass by spin-coating and evaluated as a counter electrode for dye-sensitized solar cells (DSSCs). It was observed that the counter electrode based on CNTs exhibited a photo conversion efficiency of 9.34%, which was slightly higher than that observed with a conventional Pt counter electrode (9.09%). The lower charge transfer resistance and higher electrocatalytic activity of the CNT counter electrode over the Pt counter electrode was confirmed by electrochemical impedance spectroscopy and cyclic voltammetry, respectively. The studies showed that the CNTs synthesized over Cr–Ni–SBA-15 could be employed as a counter electrode in DSSCs as a replacement for Pt.