Rangasamy Thangamuthu

Growth of carbon nanotubes over transition metal loaded on Co-SBA-15 and its application for high performance dye-sensitized solar cells

High quality MWCNT material based counter electrodes for dye-sensitized solar cells (DSSCs) were fabricated using a novel route and their power-conversion efficiency was studied. Transition metals such as Fe, Ni, V, Mn, Cr, Mo, Ru and Pd loaded on Co-SBA-15 molecular sieves were synthesized and tested for the formation of MWCNTs at different temperatures (700–1000 °C) using a chemical vapour deposition (CVD) method. This result showed that Fe/Co-SBA-15 and Ru/Co-SBA-15 systems are highly suitable sources as catalysts for the growth of MWCNTs compared to other bimetallic systems. TEM and Raman spectroscopy revealed that the synthesized MWCNTs were of high quality and well-graphitized. The MWCNTs were applied to the counter electrode of dye-sensitized solar cells (DSSCs). Cyclic voltammetry measurements proved that the catalytic activity of the MWCNT coated electrode towards I3− reduction was significantly higher than that of the Pt coated electrode. Electrochemical impedance measurement of the symmetric cell revealed that the charge transfer resistance of the MWCNT coated electrode was less than that of the Pt coated electrode. Due to the low charge transfer resistance of the synthesized MWCNTs, the DSSCs with MWCNTs as counter electrode gave better photoelectric performance compared to DSSCs equipped with a conventional Pt counter electrode.

Anchoring of ultrafine Co3O4 nanoparticles on MWCNTs using supercritical fluid processing and its performance evaluation towards electrocatalytic oxygen reduction reaction

Developing an efficient electrocatalyst for improving oxygen reduction reaction (ORR) kinetics is essential for various renewable energy appliances and energy-intensive technologies. The design of a low cost and robust ORR catalyst with desired durability still remains a challenging task. Here we demonstrated a facile and environmentally friendly supercritical fluid-assisted decoration of Co3O4 on multi-walled carbon nanotubes (MWCNTs) to generate a hybrid nanostructure electrocatalyst for ORR. The mildly oxidized MWCNTs provided functional groups on the outer walls to seed and anchor nanocrystals, while keeping the inner walls intact for a highly conducting network. In particular, the 11 wt% Co3O4-MWCNTs hybrid exhibited improved half wave potential by 240 mV compared to Co3O4 and 125 mV with respect to MWCNTs based on the rotating ring disc voltammetry results. Similarly, the observed ORR current density was superior to those of both bulk Co3O4 and bare MWCNTs at medium overpotential, proceeding dominantly through a 4-electron reduction pathway. Such enhancement may be attributed to the synergetic effect of the specific heterogeneous architecture, which results in improved conductivity, accessible active centres and enhanced reaction rate at Co3O4 decorated on the MWCNT surface.

Synthesis of carbazole-based copolymers containing carbazole-thiazolo[5,4-d]thiazole groups with different dopants and their fluorescence and electrical conductivity applications

To improve the electrical conductivity of poly(carbazole-thiazolo[5,4-d]thiazole) (p-CzTT), five different dopants, such as HCl, Fe(III), Cu(II), H3BO3, and I2, were introduced into its framework through protonation of a nitrogen atom or by complex formation. Carbazole-thiazolo[5,4-d]thiazole (CzTT) and poly(carbazole-thiazolo[5,4-d]thiazole) (p-CzTT) were synthesized by the reactions of carbazole aldehydes and dithiooxamide. The synthesized monomer and polymer were confirmed by FT-IR, UV-vis, 1H, 13C-NMR, and GPC studies. The doped polymers were examined by FT-IR spectroscopy, UV-visible absorption, fluorescence, thermogravimetric analysis (TGA), cyclic voltammetry (CV), and electrical conductivity. The optical band gap (Eoptg) of CzTT and p-CzTT were found to be 2.74 eV and 1.95 eV, respectively. The thermal stability of the polymer showed 5% weight loss at 358 °C. Based on CV analysis, the HOMO and LUMO energy levels and the electrochemical band gap (Ecvg) of p-CzTT were obtained as −5.86 eV, −3.19 eV, and 2.67 eV, respectively. The CzTT and p-CzTT exhibited fluorescence emission at 461 nm and 448 nm, respectively. Among the dopants introduced, Fe(III)- and I2-doped polymer showed excellent electrical conductivities of 6.8 × 10−5 S cm−1 and 5.9 × 10−5 S cm−1, respectively.

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

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.

Synthesis and Characterization of Bay Substituted Perylene Diimide Small Molecule for Organic Solar Cell Application

We report the synthesis of N,N′-Bis(hexyl)-1,7-di(thiophenyl)perylene -3,4:9,10-tetracarboxylic acid diimide (T-PDI-H) based small molecule by Suzuki coupling method for organic photovoltaic (OPV) application. The synthesized small molecule was confirmed by FT-IR and NMR techniques. The T-PDI-H showed broad and strong absorption in the UV-Visible region. From UV-Visible spectra we observed a low optical band gap (E g opt ) of 1.96 eV for T-PDI-H. From the cyclic voltammetry, the calculated HOMO, LUMO and electrochemical band gap (E g ele ) for the small molecule was −5.77, −3.44 and 2.33 eV respectively. Thermogravimetric analysis was employed to elucidate the thermal stability of T-PDI-H small molecule, it showed good thermal stability up to 400 °C. The preferred property for the high power conversion efficiency (PCE) OPV device, molecule must possess broad and strong absorption in the UV-Vis region, low band gap , and high thermal and environmental stability. T-PDI-H small molecule might satisfy the above standards with the chance to give maximum power conversion efficiency (PCE).