Multi-walled Carbon Nanotubes Counter Electrode Research Articles

Multifunctional Structure-Modified Quaternary Compounds Co9Se8-CuSe2-WSe2 Mixed with MWCNT as a Counter Electrode Material for Dye-Sensitized Solar Cells.

In this study, a trimetallic selenide material with a hollow spherical structure (Co9Se8-CuSe2-WSe2) was synthesized through two consecutive solvothermal reactions. The synergistic effect between the quaternary elements, the benefits of the selenization of metals, and the unique morphology led to the prominent electrocatalytic ability of Co9Se8-CuSe2-WSe2 hollow spheres. Co9Se8-CuSe2-WSe2 hollow spheres were then mixed with oxygen plasma-treated multiwalled carbon nanotubes (MWCNT) as counter electrode (CE) material for dye-sensitized solar cells (DSSCs), achieving a photoelectric conversion efficiency (η) of 9.23% under one sun condition (AM 1.5G, 100 mW cm-2), surpassing the 8.08% of devices with platinum counter electrodes (PtCEs). For indoor conditions, a T5 light source was applied to the DSSCs with Co9Se8-CuSe2-WSe2 + MWCNT CE, and the efficiency increased to 14.14% under 3600 lx irradiance. Finally, Co9Se8-CuSe2-WSe2 + MWCNT CE demonstrated good stability with 92.23% retention after 1000 cycles of cyclic voltammetry, exceeding the 82.49% of PtCE. Therefore, Co9Se8-CuSe2-WSe2 + MWCNT shows potential as a substitute for platinum as CE material for DSSCs.

Mixed phase nanoarchitectonics of NiS@SnS@Ni3Sn2S2 as a tetrafunctional catalyst for dye-sensitized solar cells, supercapacitors, and water splitting applications

The development of low-cost, high-efficiency multifunctional electrocatalysts is an ongoing concern, and it is critical for future energy-related devices. Mixed-phase NiS@SnS@Ni3Sn2S2 nanostructures are synthesized by facile microwave approach and are used as an electrocatalyst for the reduction of tri-iodide to iodide (I3−/I−) in dye-sensitized solar cells (DSSCs), asymmetric supercapacitors, and overall water-splitting applications. Further, the performances have been improved by adding multi-walled carbon nanotubes (MWCNT). For assessing the crystalline structure, phase, size, shape, porosity, and composition, several analytical tools are employed. The electrochemical outcomes show that NiS@SnS@Ni3Sn2S2/MWCNT counter electrode assisted DSSC cell delivered the highest efficiency of 6.0 % and found to be an efficient electrode for supercapacitors, evidencing a large specific capacitance (766 F g−1 at 1 A g−1), an outstanding energy density of 85.2 W h kg−1 at an ultra-high-power density of 3600 W kg−1 and cycling stability (94 % after 10,000 cycles at 15 A g−1). Furthermore, the optimized NiS@SnS@Ni3Sn2S2/MWCNT catalyst demonstrates better oxygen and hydrogen evolution reaction. The combination of different phases and shapes in the catalysts can provide a synergistic effect as well as good surface active sites along with a carrier transfer path, resulting in efficient I3− reduction, higher specific capacitance and energy density, superior cycling stability, and low over-potential, thus making NiS@SnS@Ni3Sn2S2/MWCNT hybrid as an efficient tetrafunctional electrocatalyst for energy gadgets.

Efficient and cost-effective dye-sensitized solar cells using MWCNT-TiO2 nanocomposite as photoanode and MWCNT as Pt-free counter electrode

In the present study, a new cost-effective and efficient configuration [n-MWCNT-TiO2/N3/MWCNT] of dye-sensitized solar cell (DSSC) is proposed and fabricated, where n-MWCNT-TiO2 is the nano composite of multiwall carbon nanotube (MWCNT), and titanium dioxide (TiO2) in different mass proportions, sensitized by N3 dye used as a photo anode, and MWCNT is the material for the counter electrode. In the [n-MWCNT-TiO2/N3/MWCNT] configuration, the photo anode with four mass proportions (n = 0.03%, 0.06%, 0.09% and 0.12%) were used as a design variant, and it was found that the photovoltaic efficiency as high as 7.15% was achieved when the nano composite of 0.06%-MWCNT-TiO2 was applied as a photoanode in the proposed DSSC configuration. Besides achieving a 13% photovoltaic efficiency enhancement compared to the ubiquitous [TiO2/N3/Pt] DSSC configuration, the replacement of Pt with inexpensive MWCNT in the [n-MWCNT-TiO2/N3/MWCNT] DSSC ensures the cost effectiveness of the proposed configuration. The morphological and optical characterization of the n-MWCNT-TiO2 photoanode (nanocomposite) films, the stability and catalytic activity of MWCNT counter electrode, UV–VIS absorption spectroscopy, current-voltage characteristics, incident photon to electron conversion efficiency and the electrochemical impedance spectroscopy of the fabricated DSSCs were performed in order to elucidate the improved performance of the [n-MWCNT-TiO2/N3/MWCNT] configuration. Based on these characterization studies, it was found that the observed enhancement of light absorbance in the visible spectral region, the improved electron transportation, decreased recombination of electrons with oxidized dye and redox mediator, better catalytic activity of MWCNT counter electrode are the key contributory factors for the increased photovoltaic efficiency of the [n-MWCNT-TiO2/N3/MWCNT] DSSC configuration.

A transparent honeycomb-like poly(3,4-ethylenedioxythiophene)/multi-wall carbon nanotube counter electrode for bifacial dye-sensitized solar cells

A novel transparent honeycomb-like poly(3,4-ethylenedioxythiophene)/multi-wall carbon nanotube (PEDOT/MWCNT) electrode served as a counter electrode (CE) for the bifacial dye-sensitized solar cell (DSSC) has been fabricated on the fluorine-doped tin oxide (FTO) glass using a sacrificial template of poly(methyl methacrylate) for the first time. Cyclic voltammetry and electrochemical impedance spectroscopy measurements indicate that the honeycomb-like PEDOT/MWCNT CE has a higher electrocatalytic activity for the I3−/I− redox reaction and a smaller charge transfer resistance than those of the flat PEDOT CE. Ultraviolet–visible spectrophotometer measurement indicates that the PEDOT/MWCNT CE with honeycomb-like nanostructure demonstrates high transparency for the backside illumination. The bifacial DSSC based on this honeycomb-like PEDOT/MWCNT CE shows conversion efficiencies of 9.07% and 5.62% from front and rear side illumination, respectively, which are higher than those of the bifacial DSSC based on the flat PEDOT CE (7.51% and 3.49% respectively).

Effect of Nanotube Morphologies on Multi-Walled Carbon Nanotubes Based Counter Electrode for Dye-Sensitized Solar Cell.

Multi-walled carbon nanotubes (MWCNTs) with different morphologies were introduced into dyesensitized solar cell (DSSC) as low-cost substitutes for Pt counter electrode (CE). The effect of length and orientation of MWCNTs on the power conversion efficiency (PCE) of DSSC with MWCNTs CE were studied by measuring electrochemical impedance spectroscopy of MWCNTs and the photocurrent density–voltage (J–V ) characteristics of DSSC in this study. Results revealed that the long MWCNTs showed better electrocatalytic activity of reducing triiodide ions than short MWCNTs and yielded the power conversion efficiency of 2.42%. When the aligned multi-walled carbon nanotubes (AMWCNTs) with the same length as the long MWCNTs were used to prepare the CE, the power conversion efficiency of the DSSC reaches 2.95%. In order to further improve the performance of the DSSC, the processing of photoanode and counter electrode were adjusted. The power conversion efficiency of the cell with AMWCNTs as CE prepared by adjusted processing achieved 3.95% and the short circuit current density is superior to the DSSC with Pt as CEs, and it indicated the adjusted processing is beneficial to increase the overall performance of the dye-sensitized solar cell.

Application of non-covalent functionalized carbon nanotubes for the counter electrode of dye-sensitized solar cells

Multi-walled carbon nanotubes (MWCNTs) were functionalized noncovalently by lysozyme (LZ), cetyl pyridinium chloride (CPC), deoxycholate sodium (NaDC) and polyethylene glycol octylphenol ether (Triton X-100), respectively in this study. Four different kinds of functionalized MWCNTs were employed into dye-sensitized solar cell (DSSC) as the Pt-free counter electrode (CE). The correlation between the dispersion of MWCNTs and electrochemical active area of CE and the photovoltaic characteristic of DSSC were investigated. Among these four DSSCs, the one with Triton X-100 functionalized MWCNTs showed the best energy conversion efficiency of 2.69% which is 11.16% higher than the DSSC using pristine MWCNTs CE (2.42%), yet the efficiency is lower than the DSSC using Pt CE. While the DSSC with CPC, NaDC and LZ functionalized MWCNTs as the CE showed inferior the photovoltaic conversion efficiency than the DSSC using pristine MWCNTs CE. On analysis of the photovoltaic performance of DSSC and the dispersion of MWCNTs and electrochemical active area of CE, it is found that the high efficiency of the DSSC is associated with the good dispersion of MWCNTs and large electrochemical active area of the counter electrode material.

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 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 100mWcm−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.

Facile synthesis of high quality multi-walled carbon nanotubes on novel 3D KIT-6: application in high performance dye-sensitized solar cells.

A novel hard templating strategy for the synthesis of high quality multi-walled carbon nanotubes (MWCNTs) with a uniform diameter was developed. MWCNTs were successfully synthesized through chemical vapour deposition (CVD) using acetylene by employing 3D bicontinuous mesoporous silica (KIT-6) as a hard template and used as the counter electrode in dye-sensitized solar cells (DSSCs). Here, we report that Ni-Cr-KIT-6 and Co-Cr-KIT-6 systems are the most suitable catalysts for the growth of MWCNTs. Raman spectroscopy and TEM analysis revealed that the synthesized MWCNTs were of high quality and well graphitized. Impressively, DSSCs with a MWCNT counter electrode demonstrated high power conversion efficiencies (PCEs) of up to 10.53%, which was significantly higher than that of 9.87% obtained for a DSSC with a conventional Pt counter electrode. Moreover, MWCNTs had a charge transfer resistance (Rct) of only 0.74 Ω cm(2) towards the I3(-)/I(-) electrolyte commonly applied in DSSCs, which is several orders of magnitude lower than that of a typical Pt electrode (2.78 Ω cm(2)). These results indicate that the synthesized MWCNT counter electrodes are versatile candidates that can increase the power conversion efficiency (PCE) of DSSCs.

Growth of well graphitized MWCNTs over novel 3D cubic bimetallic KIT-6 towards the development of an efficient counter electrode for dye-sensitized solar cells

The well graphitized multi-walled carbon nanotubes (MWCNTs) have been effectively synthesized over ordered 3D cubic bimetallic Fe–Co-KIT-6. The synthesized MWCNTs have been successfully fabricated onto transparent conducting oxide glass and implemented as efficient low-cost, platinum-free counter electrode in dye-sensitized solar cells (DSSCs), attributing notably improved electrocatalytic activity towards iodide/tri-iodide (I-/I3-) redox transport over conventional Pt counter electrode. Impressively, device with MWCNTs counter electrode demonstrates a high fill factor of 0.79 and power conversion efficiency up to 9.56%, which is higher than 0.78 and 9.34% for that with a conventional Pt counter electrode. Moreover, the synthesized MWCNTs counter electrode produces a charge transfer resistance of only 2.99Ωcm2 towards aqueous I-/I3- redox electrolyte, which are several orders of magnitude lower than that of a typical Pt counter electrode (3.57Ωcm2). Therefore, the synthesized MWCNTs counter electrode is believed to be a versatile candidate for further improvement of the power conversion efficiency of iodine redox couple based DSSCs.

Dye-sensitized solar cells based on hydroquinone/benzoquinone as bio-inspired redox couple with different counter electrodes

In the present study, tetramethylammonium hydroquinone (HQ)/benzoquinone (BQ) were developed for use as a redox couple, with poly(3,4-ethylenedioxythiophene) (PEDOT) and multiwalled carbon nanotubes (MWNT) being proposed for use as counter electrode (CE) catalysts in dye-sensitized solar cells (DSSCs). Both metal-complex N719 and metal-free organic dye CM309 were employed to fabricate devices. For the devices sensitized by N719, when using PEDOT and MWNT CEs, power conversion efficiencies (PCE) of 5.2 and 4.9% were obtained, respectively, which were much higher than that of the device using the traditional Pt CE (4.7%) when HQ/BQ electrolyte was employed. However, with the HQ/BQ redox shuttle, the efficiency of the devices sensitized by N719 is much lower than that of the devices when the traditional I(-)/I3(-) based electrolyte and Pt CE were employed (7.9%). While for the CM309 sensitized solar cells, when the HQ/BQ redox shuttle was employed, PEDOT and MWNT performed much better than Pt, the DSSC using the PEDOT CE showed an efficiency of 6.2%, which was close to that of the DSSC using the traditional I(-)/I3(-) electrolyte and Pt CE (6.3%).

Photovoltaic performance of dye-sensitized solar cells with various MWCNT counter electrode structures produced by different coating methods

We report the successful application of multi-walled carbon nanotubes (MWCNTs) as electrocatalysts for triiodide reduction in dye-sensitized solar cells (DSSCs). To improve the photovoltaic performance of DSSCs, upgrade the quality of MWCNT structure and obtain an optimum deposition approach regarding a counter electrode, the present study was investigated. Three different MWCNT structures, raw, purified and purified and ground, were investigated as platinum (Pt) alternatives for counter electrodes in DSSCs. The counter electrodes were prepared on fluorine-doped tin oxide (FTO) glass substrates by two different techniques: spin coating from fluid-type MWCNTs and screen printing from paste-type MWCNTs. By utilizing a spin-coating technique, a DSSC that was fabricated with a purified and ground MWCNT counter electrode achieved an overall photovoltaic efficiency of 4.94%. This photovoltaic performance is comparable to that of a DSSC using a conventional “Pt” counter electrode fabricated under the same conditions. We found that the grinding method is powerful for increasing specific surface area and porosity. With this technique, macropores can be transformed into mesopores, thereby reducing the agglomeration of the MWCNTs, and with an additional modification, an increased DSSC photovoltaic efficiency results.

High performance dye-sensitized solar cell based on hydrothermally deposited multiwall carbon nanotube counter electrode

Conductive glass was coated with multiwall carbon nanotubes (MWCNTs) by a hydrothermal method. MWCNTs films were subsequently used as dye-sensitized solar cell (DSSC) counter electrodes. The performance of hydrothermal MWCNT DSSC was ∼2.37%. After film annealing in an Ar atmosphere, annealed-hydrothermal MWCNT (AHT-CNT) DSSC efficiency was significantly increased to ∼7.66%, in comparison to ∼8.01% for sputtered-Pt DSSC. Improvement of AHT-CNT DSSC performance is attributed to a decrease in charge-transfer resistance from 1500 Ω to 30 Ω as observed by electrochemical impedance spectroscopy.

Enhancement of the efficiency of dye-sensitized solar cell with multi-wall carbon nanotubes/polythiophene composite counter electrodes prepared by electrodeposition

For the purpose of increasing the energy conversion efficiency of dye-sensitized solar cells (DSSCs), multi-wall carbon nanotube (MWCNT)/polythiophene (PTh) composite film counter electrode has been fabricated by electrophoresis and cyclic voltammetry (CV) in sequence. The morphology and chemical structure have been characterized by transmission electron microscopy (TEM), scanning electron microscope (SEM), and Raman spectroscopy respectively. The overall energy conversion efficiency of the DSSC employing the MWCNT/PTh composite film has reached 4.72%, which is close to that of the DSSC with a platinum (Pt) counter electrode (5.68%). Compared with a standard DSSC with MWCNT counter electrode whose efficiency is 2.68%, the energy conversion efficiency has been increased by 76.12% for the DSSC with MWCNT/PTh counter electrode. These results indicate that the composite film with high conductivity, high active surface area, and good catalytic properties for I 3 − reduction can potentially be used as the counter electrode in a high-performance DSSC.

Effect of SiO2 Layer of Si Substrate on the Growth of Multiwall-Carbon Nanotubes

Multi-walled carbon nanotubes (MWNTs) were synthesized on different substrates (bare Si and /Si substrate) to investigate dye-sensitized solar cell (DSSC) applications as counter electrode materials. The synthesis of MWNTs samples used identical conditions of a Fe catalyst created by thermal chemical vapor deposition at . It was found that the diameter of the MWNTs on the Si substrate sample is approximately larger than that of a /Si substrate sample. Moreover, MWNTs on a Si substrate sample were well-crystallized in terms of their Raman spectrum. In addition, the MWNTs on Si substrate sample show an enhanced redox reaction, as observed through a smaller interface resistance and faster reaction rates in the EIS spectrum. The results show that DSSCs with a MWNT counter electrode on a bare Si substrate sample demonstrate energy conversion efficiency in excess of 1.4 %.

Spray coated multi-wall carbon nanotube counter electrode for tri-iodide [formula omitted] reduction in dye-sensitized solar cells

Spray coated multi-wall carbon nanotube (CNT) film on fluorine-doped tin oxide glass substrate has been investigated as a counter electrode for tri-iodide reduction in dye-sensitized solar cells. The photovoltaic parameters, in particular, the fill factor shows a strong dependency on the spraying time of multi-wall CNTs. Under one sun illumination (100 mW cm −2, AM 1.5 G), the device shows a maximum energy conversion efficiency of 7.59%. Electrochemical impedance spectroscopy analysis reveals a decrease in the charge transfer resistance of multi-wall CNT counter electrode with increase of spraying time; leads to an improvement in the photovoltaic parameters.