Catalysts In Dye-sensitized Solar Cells Research Articles

W-based carbide derived from PW12@ZIF-8 as Pt-free catalyst on counter electrode of dye-sensitized solar cells for triiodide reduction

The preparation of counter electrodes (CEs) catalysts at different pyrolysis temperatures will directly affect the composition, morphology, and performance of the catalysts in dye-sensitized solar cells (DSSCs) applications. Herein, four W-based carbides catalysts were derived from H3PW12O40-based ZIF-8 metal–organic frameworks (PW12@ZIF-8) by in-situ pyrolysis at 600, 700, 800, and 900 ℃ under N2 atmosphere. The pyrolysis mechanism and structure characteristics of the prepared W-based carbides with temperature variation were confirmed by TG-DTG-DSC simultaneous, XRD, XPS, TEM, SEM and N2 adsorption/desorption, which exhibits the gradual transformation of PW12@ZIF–8 → WC-C→WC→W1-xC→W2C. Furthermore, the photovoltaic performance of four different W-based carbides as CEs catalysts for regenerating I3−/I− shuttles in DSSCs were identified by photocurrent-voltage (J-V) measurement, which achieved PCEs of 4.63, 4.91, 5.05 and 5.78 %, respectively. As a result, W2C (900 ℃) provide more vacancies and defects on the catalyst surface as abundant catalytic active sites, as well as promote the appearance of more pores and voids in the morphology to diffuse and permeate electrolyte due to the highest specific surface area, and the PCE value of 5.78 % was also superior to 5.51 % of Pt CE.

MWCNT supported CuS/ZrS3 composite: A versatile multifunctional catalyst for Dye-sensitized solar cells, water splitting, and supercapacitors

This study focuses on developing cost-effective energy conversion and storage catalysts critical for a fossil-fuel-free society. The effect of MWCNT-supported CuS/ZrS3 on the catalytic performance for dye-sensitized solar cells (DSSCs), overall water splitting, and supercapacitors had been investigated in comparison with the bare CuS/ZrS3, CuS, and ZrS3. The structure, porosity, morphology, and valence states of the composites are analyzed. Optimally, DSSCs with CuS/ZrS3/MWCNT as the counter electrode achieve 5.15 % efficiency, surpassing pristine CuS/ZrS3 at 4.21 %. The catalyst's energy storage properties reveal exceptional capacitive performance of 1214 F g−1 @ 2 A g−1 and an asymmetric supercapacitor (CuS/ZrS3/MWCNT//MWCNT) exhibiting 91 % capacitance retention after 2100 cycles, yielding an outstanding energy density of 85.1 Wh kg−1 at 3840 W kg−1 power density. The optimized CuS/ZrS3/MWCNT composite demonstrates superior bifunctional activity for hydrogen and oxygen evolution with an overpotential of 358 mV and 301 mV, respectively, at 10 mA cm−2. This enhanced performance is attributed to the combined effects of metal sulfides and MWCNT, like rich active sites, large surface area for enhanced diffusion, high conductivity, and catalytic ability. These findings propose CuS/ZrS3/MWCNT as an efficient tetrafunctional catalyst with multiple applications for future energy devices.

Phase-Selective Synthesis of Cobalt Sulfide Heterostructure Catalysts as Efficient Counter electrodes in Dye-Sensitized Solar Cells.

Developing a cost-saving, high-efficiency, and simple synthesis of counter electrode (CE) material to replace pricy Pt for dye-sensitized solar cells (DSSCs) has become a research hotspot. Owing to the electronic coupling effects between various components, semiconductor heterostructures can significantly enhance the catalytic performance and endurance of counter electrodes. However, the strategy to controllably synthesize the same element in several phase heterostructures used as the CE in DSSCs is still absent. Here, we fabricate well-defined CoS2/CoS heterostructures and use them as CE catalysts in DSSCs. The as-designed CoS2/CoS heterostructures display high catalytic performance and endurance for the triiodide reduction in DSSCs thanks to the combined and synergistic effects. As a result, a DSSC with CoS2/CoS achieves a high power conversion efficiency of 9.47% under illumination, surpassing that of pristine Pt-based CE (9.20%). Besides, the CoS2/CoS heterostructures possess a quick activity initiation process and extended stability, broadening their potential applications in various areas. Therefore, our proposed synthetic approach could offer new insights for synthesizing functional heterostructure materials with improved catalytic activities in 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.

Electrodeposited PPy@TiO2 and PEDOT@TiO2 Counter Electrodes for [Co(bpy)3]2+/3+ Redox Mediator-Based Dye-Sensitized Solar Cells

The main goal of this work is to enhance the catalytic performance of PPy and PEDOT films toward the Co2+/Co3+ redox couple. PPy and PEDOT films were electrodeposited separately on a porous TiO2 template to assess their suitability as alternative catalysts in dye-sensitized solar cells (DSSC) based on the [Co(bpy)3]2+/3+ redox shuttle. The obtained PPy@TiO2 and PEDOT@TiO2 counter electrodes displayed much rougher surfaces. Electrochemical studies indicate the superior catalytic activity of both the electrodeposited electrodes toward Co3+ reduction, as indicated by lower charge transfer resistance than that of pristine films and even that of Pt electrodes. Therefore, the fabricated DSSC devices with these counter electrodes achieved higher power conversion efficiencies compared to cells with pristine PPy and PEDOT counter electrodes, or even with a Pt counter electrode. Interestingly, the assembled DSSC device with a PEDOT@TiO2 counter electrode displayed the highest performance among all with a power conversion efficiency of 6.62%, which is better than that obtained by the device with a Pt electrode (6.07%).

Manipulation of flexible carbon cloths for stable and efficient catalysts in dye-sensitized solar cells

• The CC with preferred characteristics can be facilely manipulated. • The catalytic activity and stability of CE can be improved via underlying supports. • The simultaneously improved PCE and stability are achieved by using an optimal CE. The highly stable and efficient dye-sensitized solar cell (DSC) strongly relies on the catalytic activity and stability of the counter electrode (CE) in the electrolyte. Herein, we explore an effective and eco-friendly method of making a high catalytic activity of CE with the improved stability by utilizing the high-conductivity carbon cloth (CC) with great corrosive resistance as flexible carbon-based supports for nanoparticle-based catalysts and using Pt as an example. A variety of CCs with different characteristics are facilely manipulated by the hybrid solution-based surface treatments, enabling to systemically investigate the influence of different CCs on the performance of Pt catalysts. The result shows that the surface activated CC with properly porous structure and wetting surface facilitates the accommodation of catalysts and the diffusion of redox couple within the carbon fiber network. The existence of active sites such as defective structures and oxygen-containing groups on CCs effectively serve as the nucleation or adsorbed sites of Pt catalysts, which simultaneously improve the catalytic and stable performance of CE. Multi-scan cyclic voltammetry indicates that a preferred surface activated CC as Pt catalyst support retains 95.9% of its initial catalytic ability in comparison with the typical platinized fluorine-doped tin oxide (76%). The DSC using the desirable Pt-decorated CC displays an improvement of 49% in conversion efficiency as compared with that using the nonoptimal counterpart. Such improvements highlight the feasibility of simply manipulating the characteristics of underlying flexible carbon-based supports in pursuit of the high catalytic activity and stability of CEs in DSCs.

N-doped W2C derived from polyoxotungstate precursors by pyrolysis along the temperature gradient as Pt-free counter electrode in dye-sensitized solar cells

The counter electrodes (CEs) as the basic components of dye-sensitized solar cells (DSSCs) mainly use Pt-based catalysts. It is still an urgent need to decrease the assembled cost of DSSCs by designing high-performance and low-cost Pt-free materials to replace the scarce and expensive Pt as CEs catalyst. How particularly striking are that specific precursors were prepared by ball-grinding with polyoxotungstate (H 3 PW 12 O 40 ) as metal source and melamine (C 3 N 3 (NH 2 ) 3 ) as carbon source and nitrogen source, and then the pyrolysis process of precursors were dynamically controlled along the temperature gradient to make the auxiliary groups leave, so as to obtain the expected N-doped W 2 C catalytic materials. Herein, four kinds of N-doped W 2 C materials have derived from polyoxotungstate precursors at the pyrolysis temperatures of 700, 800, 900 and 1000 °C, and further applied to assemble CEs catalysts in DSSCs. The high power conversion efficiencies (PCE) of 6.10, 7.01, 5.95 and 5.34% were obtained for the regeneration of traditional iodide/triiodide (I 3 − /I − ), respectively. The enhanced performance of N-doped W 2 C materials can be attributed to the larger number of catalytic active sites, which was due to the higher specific surface area provided by pyrolysis and carbonization of organic complex precursor, and the activation and modification of materials by the N-doped and the high temperature. • N-Doped W 2 C derived from the pyrolyzed precursors of H 3 PW 12 O 40 with C 3 N 3 (NH 2 ) 3 . • There is the highest PCE of 7.01% of N-Doped W 2 C (obtained at 800 °C) as CEs in DSSC. •N-Doped W 2 C materials are a prospective alternative of Pt-free CEs in DSSCs.

Strategic Design of a Bifunctional NiFeCoW@NC Hybrid to Replace the Noble Platinum for Dye-Sensitized Solar Cells and Hydrogen Evolution Reactions.

High-performance triiodide reduction reaction (IRR) catalysts in dye-sensitized solar cells (DSSCs) and hydrogen evolution reaction (HER) catalysts in electrochemical water splitting are extremely compelling for renewable energy conversion and storage. The best IRR and HER catalysts generally rely on the use of noble metal platinum (Pt), which suffers obstacles in real-world implementation. The rational design of efficient bifunctional IRR and HER catalysts based on inexpensive and earth-abundant elements to replace scarce Pt could enable low-cost photoelectric conversion and hydrogen production but is challenging and rarely reported. Herein, we present a bifunctional NiFeCoW@NC hybrid with the unique architecture of WC loaded on the in situ formed carbon nanotubes embedded with Co-doped FeNi3 nanoparticles based on the anisotropic integration design principle, which operates efficiently for DSSCs and hydrogen evolution. The assembled DSSCs using the designed multimetal-based NiFeCoW@NC counter electrode delivered a high power conversion efficiency of 6.92% and long-term stability superior to bimetal-based NiFe@NC, CoW@NC, and Pt counterparts. It also exhibited eminent hydrogen evolution performance with a low overpotential of 127.8 mV to drive a 10 mA cm-2 current density, a Tafel slope of 60.4 mV dec-1, and satisfactory durable stability in 0.5 M H2SO4. This work provides a design principle for low-cost and highly active bifunctional catalysts to replace Pt for DSSCs and hydrogen evolution.

Biomass-derived carbon boosted catalytic properties of tungsten-based nanohybrids for accelerating the triiodide reduction in dye-sensitized solar cells

Manganese tungstate (MnWO4), zinc tungstate (ZnWO4), and copper tungstate (CuWO4) embedded biomass-derived carbon (MWO-C, ZWO-C, CWO-C) was synthesized by hydrothermal treatment and investigated as counter electrode (CE) catalysts to test electrochemical activity. Biomass-derived carbon was used as the shape controlling agent, which changed the morphology of MWO from spherical to spindle-like. Owing to the synergistic effect between tungsten-based bimetal oxides and biomass-derived carbon, the MWO-C, ZWO-C, and CWO-C catalysts exhibited enhanced electrochemical performance in dye-sensitized solar cells (DSSCs) system. The MWO-C, ZWO-C and CWO-C catalysts in DSSCs showed outstanding power conversion efficiency (PCE) of 7.33%, 7.61%, and 6.52%, respectively, as compared with 7.04% for Pt based devices. Biomass-derived carbon improves the catalytic properties of tungsten-based nanohybrids. The results showed that biomass-derived carbon-enhanced inorganic compound as CE catalysts are promising alternatives to Pt-based CE catalysts for energy conversion devices.

Dye-sensitized solar cell based on poly(ε-caprolactone) gel polymer electrolyte and cobalt selenide counter electrode

In this work, gel-like polymer electrolytes were prepared by incorporating poly(e-caprolactone) (PCL) into dimethylformamide (DMF)-potassium iodide (KI) liquid electrolytes. The optimized gel polymer electrolyte has the composition of 40 wt.% of PCL, 45 wt.% of DMF and 15 wt.% of KI with a conductivity of 2.72 × 10−3 S cm−1 at room temperature. Increase in conductivity with temperature is attributed to the increase in diffusion coefficient, D, number, n and mobility, μ of ions as determined from Nyquist plots fitting. Cobalt selenide (CoSe) was prepared by hydrothermal method and used as counter electrode catalysts in dye-sensitized solar cells (DSSCs). X-ray diffraction (XRD) studies show the formation of the as-prepared CoSe. The morphology and stoichiometric composition of CoSe were studied by field-emission scanning electron microscopy (FESEM) and energy dispersive X-ray spectroscopy (EDX). The PCL-DMF-KI gel polymer electrolytes were assembled into DSSCs with CoSe or platinum (Pt) as the counter electrodes. DSSC with CoSe counter electrode shows an efficiency of 6.74% while DSSC with Pt counter electrode yields an efficiency of 6.99%. Impedance studies of DSSCs suggest that the electrocatalytic reduction of triiodide, I3− by the CoSe is as good as Pt.

Catalytic mechanism and design principles for heteroatom-doped graphene catalysts in dye-sensitized solar cells

Doped carbon nanomaterials are promising candidates to replace expensive Pt counter electrode for catalyzing triiodide reduction reaction (IRR) in dye-sensitized solar cells (DSSCs), but trial-and-error approaches have been used to develop better catalysts. Here, design principles are developed for p-block heteroatom-doped graphene as efficient IRR catalysts through density functional theory (DFT) calculations. The descriptors based on the intrinsic properties of dopant elements are identified to establish a quantitative relationship that correlates the doped structures to catalytic activities. Moreover, a quantitative relationship is also established between the catalytic performance and the extrinsic factors such as the number of exposed active sites for a particular mass loading. It is predicted that most p-block element doped graphene catalysts have better performance than Pt, and that doping at graphene edges enhances catalytic activities. These predictions are consistent with experimental results. The proposed design principles enable us to rationally design and search for highly active catalysts based on earth-abundant, cost-effective materials.

Synergistically Enhanced Electrochemical Performance of Ni3S4-PtX (X = Fe, Ni) Heteronanorods as Heterogeneous Catalysts in Dye-Sensitized Solar Cells.

Platinum (Pt)-based alloys are considerably promising electrocatalysts for the reduction of I-/I3- and Co2+/Co3+ redox couples in dye-sensitized solar cells (DSSCs). However, it is still challenging to minimize the dosage of Pt to achieve comparable or even higher catalytic efficiency. Here, by taking full advantages of the Mott-Schottky (M-S) effect at the metal-semiconductor interface, we successfully strategize a low-Pt-based M-S catalyst with enhanced electrocatalytic performance and stability for the large-scale application of DSSCs. The optimized M-S electrocatalyst of Ni3S4-Pt2X1 (X = Fe, Ni) heteronanorods is constructed by rationally controlling the ratio of Pt to transition metal in the hybrids. It was found that the electrons transferred from Ni3S4 to Pt2X1 at their interface under the Mott-Schottky effect result in the concentration of electrons onto Pt2X1 domains, which subsequently accelerates the regeneration of both I-/I3- and Co2+/Co3+ redox shuttles in DSSCs. As a result, the DSSC with Ni3S4-Pt2Fe1 manifests an impressive power conversion efficiency (PCE) of 8.79% and 5.56% for iodine and cobalt-based electrolyte under AM1.5G illumination, respectively. These PCEs are obviously superior over those with Ni3S4-Pt, PtFe, Ni3S4, and pristine Pt electrodes. The strategy reported here is able to be further expanded to fabricate other low-Pt-alloyed M-S catalysts for wider applications in the fields of photocatalysis, water splitting, and heterojunction solar cells.

Intrinsic Origin of Superior Catalytic Properties of Tungsten-based Catalysts in Dye-sensitized Solar Cells

To clarify the intrinsic factor of the superior catalytic activity of tungsten (W)-based catalysts in DSSCs, W-based compounds, including W18O49, W2N, WC, and WO3, were prepared as CEs and tested in I−/I3− redox shuttle. A systematic investigation of the catalytic properties and stability, as well as first-principle density functional theory (DFT) calculations, was performed for these W-based catalysts in DSSCs. The DSSCs assembled with the I−/I3− redox shuttle, based on W18O49, W2N, WC, and WO3 CEs, exhibited power conversion efficiencies (PCEs) of 6.69%, 5.97% 5.20%, and 4.69%, respectively; these values were equal to or better than those of DSSCs with Pt CEs (6.52%) under the same conditions. The superior electrocatalytic activities of W-based compounds are determined by their electronic structure. Electronic density of states (DOS) revealed that the band gaps of W18O49, W2N, WC, and Pt were zero, whereas that of WO3 was 1.7eV. Wider band gaps do not facilitate electron conduction as easily as Pt. In addition, the W/O ratio (1:2.72) in W18O49 was greater than that in WO3 (1:3), and the W/N ratio (2:1) in W2N was greater than that in WC (1:1). Higher ratios of W/(O or N) favored the electrocatalytic activity of the CE materials in the reduction of I3− in DSSCs. This is the intrinsic reason why W-based compounds exhibit different catalytic properties in DSSCs under the same conditions. This work sheds light on the origin of W-based catalysts, and explains the differences in the catalytic performances of W-based compounds for this work and several published works.

Synthesis of bimodal mesoporous carbon with embedded nickel nanoparticles through pyrolysis of nickel-organic framework as a counter-electrode catalyst for dye-sensitized solar cells

Bimodal mesoporous carbon with embedded Ni nanoparticles (BMCNi) was prepared by thermal pyrolysis of nickel-organic framework (NiOF) in nitrogen environment followed by acid treatment. The coordination complex of NiOF enabled the formation of small mesopores (3.6nm) during pyrolysis. The thermal decomposition and acid treatment generated large mesopores (23.6nm). The small mesopores contributed to high surface area and the large mesopores speeded up the transport of electrolyte species. Fluorine-doped tin oxide electrode with attached BMCNi catalyst possessed good electrocatalytic performance for I−/I3− couple compared with bimodal mesoporous carbon (BMC) only, owing to its high current peak and small voltage separation between anodic and cathodic peaks in cyclic voltammetry test. Ni nanoparticles embedded in BMC could provide electrical conductivity and extra active sites for facilitating the redox reaction. BMC with high surface area acted as not only a catalyst, but also a protective matrix to lessen the corrosion of Ni nanoparticles in I−/I3− electrolyte, leading to an improved electrochemical stability. Consequently, the dye-sensitized solar cell employing BMCNi counter electrode could reach a cell efficiency of 8.6%, which is higher than that using Pt (8.4%).

ZIF-67 Derived Nanostructures of Co/CoO and Co@N-doped Graphitic Carbon as Counter Electrode for Highly Efficient Dye-sensitized Solar Cells

In this work, a facile one-step approach is reported for using ZIF-67 as a sacrificial template in the synthesis of a counter electrode (CE) catalyst for dye-sensitized solar cells (DSCs). Porous nanocomposites of Co, CoO and N-doped graphitic carbon were synthesized by controlling the carbonization temperature of the templates in a N2 atmosphere. The characterization of the structure of the products indicated that cobalt nanoparticles were embedded in an N-doped graphitic carbon matrix, (a core-shell structure termed Co@NGC) while cobalt and cobalt oxide nanoparticles were exposed on the external surface of the carbon (termed Co/CoO). In particular, the chemical stability of the nanostructure of the Co@NGC was superior to Co/CoO with respect to etching by strong acids such as hydrochloric acid (HCl, 0.1M). The DSC performance of ZIF-67-850 (pyrolyzed at 850°C) employed as a CE resulted in a photoelectric conversion efficiency (PCE) of 7.92%, which was close to a Pt CE (8.18%) in the liquid I3−/I− redox couple electrolyte. The excellent performance of ZIF-67-850 can be attributed to the synergetic effects between the Co and CoO coupled with the nitrogen doped graphitic carbon. The cost-effective porous Co/CoO and Co@NGC nanocomposites exhibit great potential for application as high performance CE in solar cells.

Hollow spherical NiS/NiS2 composite as effective counter electrode catalyst for dye-sensitized solar cells

In this study, NiS/NiS2 composite hollow spheres were synthesized by a one-step solvothermal route without the help of template or surfactant. Electrochemical behavior of NiS/NiS2 composite was investigated through the cyclic voltammetry, electrochemical impedance spectroscopy and Tafel polarization tests. The results exhibit that the NiS/NiS2 composite possess excellent electrocatalytic activity toward the reduction of I3−, superior electrochemical stability and low charge transfer resistance (0.34 Ω cm−2) at the electrode/electrolyte interface. When used as counter electrode (CE) catalyst for dye-sensitized solar cells, hollow spherical NiS/NiS2 composite achieved a satisfactory power conversion efficiency of 7.66 %, which outperformed that of using Pt CE (7.01 %).

Tuning shape of three dimensional graphene sheets

3D graphene has been explored as an important material and catalyst for many applications. However, it is still a challenge to tune the shape of 3D graphene sheets. Herein, it is demonstrated that the shapes of 3D graphene sheets, which were synthesized from the reaction between Li2O and CO, are strongly dependent on the particle size of Li2O. When Li2O particle size was very small (about 400nm), the formed graphene sheets possessed a granulated shape. However, as Li2O particle size increased, the shape of the synthesized graphene sheets changed to flower-structure and then to honeycomb-structure. Furthermore, the shape change of graphene from the granulated to the honeycomb-structured can increase its electro-catalytic efficiency as a counter electrode catalyst for dye-sensitized solar cells (DSSCs).

Dual-template synthesis of N-doped macro/mesoporous carbon with an open-pore structure as a metal-free catalyst for dye-sensitized solar cells

Dye-sensitized solar cells (DSSCs) have attracted world-wide attention due to their low cost, high conversion efficiency, and environmental friendliness. Pt catalyst is usually used as the catalyst in the counter electrode of DSSCs due to its high electrochemical catalytic activity toward tri-iodide reduction. However, the high cost and scarcity of Pt prevent its large-scale application in DSSCs. It is highly desirable to replace Pt with low-cost catalysts made from earth-abundant elements. Here, we report a dual-template synthesis of N-doped macro/mesoporous carbon (macro/meso-NC) with an open-pore structure as the catalyst in the counter electrode of DSSCs. The catalytic activity of macro/meso-NC toward tri-iodide reduction has been tested by cyclic voltammetry (CV) and photocurrent-voltage (J–V) curves. It is found that the macro/meso-NC possesses excellent electrochemical catalytic activity with higher open-circuit voltage and cell efficiency than Pt. A high energy conversion efficiency of 7.27% has been achieved based on the metal-free macro/meso-NC, demonstrating as a promising catalyst for low-cost DSSCs.

Synthesis of highly effective Pt/carbon fiber composite counter electrode catalyst for dye-sensitized solar cells

Pt/carbon fiber composite (Pt/Cf) with a low Pt loading of 1.0wt% is introduced into dye-sensitized solar cells as counter electrode (CE) catalyst. The cobalt-electrolyte based device using this composite CE achieves power conversion efficiency of 8.97%, a great improvement of 40.4% as compared to the Cf CE based device. This research provides a feasible route to reduce the dosage of Pt in DSCs system, benefiting for the commercial application of DSCs.

Investigation of carbon nanotubes decorated with cobalt sulfides of different phases as nanocomposite catalysts in dye-sensitized solar cells

In this study, nanocomposites of cobalt sulfide and carbon nanotube (CNT) in the forms of CNT@CoS1.097 and CNT@Co9S8 were deposited on fluorine-doped SnO2 (FTO)-coated glasses by using a facile spray-coating approach, followed by annealing under N2 atmosphere at 400 and 600°C, respectively; and employed as counter electrodes (CEs) for dye-sensitized solar cells (DSCs). According to the electrochemical properties of CEs quantified by cyclic voltammetry, electrochemical impedance spectroscopy, and Tafel polarization measurements, the CNT@Co9S8 CE showed a superior electrocatalytic activity towards triiodide (I3) reduction to that of the CNT@CoS1.097 CE. As a result, the DSC based on the CNT@Co9S8 CE achieved an impressive photovoltaic conversion efficiency of 7.78%, which was even higher than those of the DSCs assembled with the CNT@CoS1.097 CE (7.29%) and Pt CE (7.46%). This signifies that the CNT@Co9S8 was indeed an efficient and cost-effective Pt-like alternative CE for I3 reduction reaction in DSCs.