Triiodide Reduction Research Articles

Multi-synergy enabling Ni-doped MoS2@N-doped carbon composite as versatile catalysts toward hydrogen production and photovoltaics

Construction of efficient non-precious catalyst with desired chemical composition and well-defined nanostructure is of great essential to enhance the kinetics of hydrogen evolution reaction (HER) and triiodide (I3−) reduction reaction (IRR), which is conducive to promote the development of green hydrogen production and obtain impressive photovoltaic performance of dye-sensitized solar cells (DSSCs). Herein, ZIF-8 derived N-doped carbon (NC) wrapped with two-dimensional Ni-doped MoS2 nanosheets (Ni–MoS2@NC) are elaborately designed. The catalytic activity of Ni–MoS2@NC for HER and IRR are significantly improved by modifying electronic structure through heteroatom doping. The optimized Ni–MoS2@NC has lower overpotential of 122 mV at 10 mA cm−2 in comparison with counterpart. Meanwhile, the power conversion efficiency (PCE) of DSSCs based on Ni–MoS2@NC CE catalyst is comparable to that of Pt. Density functional theory (DFT) calculation is used to unveil the mechanism of Ni–MoS2@NC for alkaline HER and IRR, namely, the multi-synergy of various sites endows Ni–MoS2@NC with appropriate Gibbs free energy for H∗ adsorption and water dissociation energy, while the top and interfacial S sites of Ni–MoS2@NC are responsible for the adsorption and activation of I3−. Our work provides a feasible route to design efficient catalysts in the field of energy conversion and understand mechanism.

Flower-like SnS2/rGO composites with efficient iodide-triiodide redox performance for counter electrodes in Pt-free dye-sensitized solar cells

The work function (WF) of the counter electrode (CE) predominantly determines the device performance of dye sensitized solar cells (DSSCs) as it controls the electron transfer rate for dye regeneration. Hence in this work, tin disulphide/reduced graphene oxide (SnS2/rGO) composites were synthesized with different wt.% of rGO (3, 5, 7, 10 %) and investigated their performance in DSSCs applications. At the outset, the formation of pristine SnS2 and SnS2/rGO composites were confirmed through X-ray diffraction and Raman spectral analysis. The morphological imaging revealed the micro flower-like structure of SnS2 with cross-sectional width of 5 ± 0.2 μm, and petal thickness ranges from 30.7 nm to 46.4 nm. The binding energy spectra confirms the 4+ oxidation state of Sn in both SnS2 and 7 wt% SnS2/rGO, suggesting that the rGO does not alter the chemical states of SnS2. Further, the peak-to-peak separation values obtained from Cylic-Voltammetry analysis were found to be 0.37 and 0.57 V for S7 and Pt CE respectively, indicating the rapid electrolyte reduction of 7 wt% SnS2/rGO. Finally, a photo conversion efficiency (PCE) of 7.3 % has been achieved with 7 wt% SnS2/rGO CE which is greater than that of the PCE with Pt CE (6.5 %) and also higher than that of pristine SnS2 with 4.7 %. The improved PCE is attributed to the reduced WF of the 7 wt% SnS2/rGO composite as measured from the Kelvin probe force microscopy analysis, enabling the rapid redox reaction towards triiodide reduction.

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.

Enhanced efficiency and stability of dye-sensitized solar cells utilizing FeCo2S4 nanowires as Pt-free counter electrodes

Replacing traditional Pt-based counter electrodes with low-cost and highly stable materials is crucial for the development of commercially viable dye-sensitized solar cells (DSSCs). In this study, we synthesized a ternary Pt-free FeCo2S4 nanowire (NW)-based sulfide electrocatalyst by a three-step solvothermal method. This material was then used as a counter electrode in DSSCs to facilitate the reduction of triiodide species. The formation of FeCo2S4 NW was confirmed by various characterization techniques such as X-ray diffraction, energy dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy. Scanning electron microscopy analysis revealed the structure of the nanowires. Electrochemical studies, which included cyclic voltammetry, electrochemical impedance spectroscopy and Tafel polarization methods, revealed the excellent stability, superior electrocatalytic activity and remarkable kinetics of FeCo2S4 NW in the reduction of triiodide to iodide. Photovoltaic measurements of the fabricated DSSCs yielded a power conversion efficiency (PCE) of 7.88 % for the FeCo2S4-based devices, outperforming the control device made of Pt (PCE=7.45 %). This improvement was primarily due to the increase in short-circuit current density (JSC), thanks to the lower charge transfer resistance (RCT) of FeCo2S4 NW (JSC=15.23 mA/cm2; RCT=5.54 Ω cm2) compared to Pt (JSC=14.12 mA/cm2; RCT=7.07 Ω cm2). In addition, the FeCo2S4 NW-based solar cells exhibited excellent stability and maintained their high PCE value even after 10 days of aging under ambient conditions, while Pt-based DSSCs showed a 3 % decrease from their initial PCE value. This FeCo2S4 NW counter electrode proves to be an excellent alternative to Pt, and the presented results provide valuable insights for the development of cost-effective and highly stable DSSCs.

MOF derived M/Sn/N (M= Mg, Mn) based carbon nanospheres as highly efficient multicomponent electrocatalysts towards hydrogen evolution and photovoltaics

Constructing multicomponent electrocatalysts towards efficient energy conversion is widely adopted strategy, in this regard, high performance metal/nonmetal codoped carbon electrode materials have attained great consideration. Still, the electroacatalytic susceptibility, abundant intrinsic active sites, and stable electrochemical performance in different electrolytes are considered as underline challenges, which can be addressed by rational structural modifications to build a hybrid electroactive material. In this work, unique Sn based multicomponent carbon nanospheres are firstly developed as highly efficient bi-functional electrocatalysts in solar cells and hydrogen evolution. The designed electrocatalysts feature the combined effect of dispersed bimetal active sites and sufficient nitrogen components within spherical carbon framework, which readily enhanced the charge transfer rate via multiple channels, boosting the triiodide reduction reaction (IRR) and hydrogen evolution reaction (HER). As a result, solar cell with Mn/Sn-NC based counter electrodes (CEs) exhibited an excellent power conversion efficiency (PCE) of 8.39 %, outperforming Pt (7.67 %). Moreover, superior HER kinetics are also demonstrated by Mn/Sn-NC with a small overpotential of 127.8 mV at 10 mA cm−2 and tafel slope of 77 mV dec−1. The rational design of the carbon nanospheres with MnSn2 bimetal nanoparticles and N doping promotes a high electrochemically active surface area, low charge-transfer resistance, excellent electrochemical stability, and superior electrocatalytic activity, providing a promising route to construct highly efficient materials towards multiple energy conversion applications.

Electrodeposited polyaniline modified CNT fiber as efficient counter electrode in flexible dye-sensitized solar cells

Carbon-based electrodes played a significant role toward the development of wearable and flexible photovoltaic energy devices in an efficient and affordable manners. Here, all-carbon-based electrodes composed of carbon nanotubes fiber (CNTF) have been used to fabricate a flexible wire shaped dye-sensitized solar cell (DSSC). A facile electrodeposited approach has been adopted to modify a CNTF with polyaniline (PANI) under acidic conditions. Both photoanode (TiO2@CNTs) and counter electrode (PANI@CNTs) twisted around each other, acted as electrons and hole collectors in the presence of redox couple (iodide/triiodide) as electrolyte. Scanning electron microscopy (SEM) images demonstrated the successful growth of TiO2 nanoparticles and conducting polyaniline (PANI) over the surface of CNTs fibers, as photoanode and counter electrode, respectively. Cyclic voltammetric (CV) measurements and electrochemical impedance spectroscopy (EIS), examined the reduction of triiodide and resistance of charge transfer. While the current-voltage measurements were carried out to check the performance of fabricated device when illuminated under simulated light source. With APNI modified counter electrode, device exhibited higher photoelectric conversion efficiency (3.57 %) under optimal conditions as compared to pristine CNTs fiber-based device with lower efficiency (2.26 %). The improved performance of modified counter electrode further confirmed by the lower peak separation (ΔEp= 0.42 V) and charge transfer resistance (RCE =19.28 Ω) in cyclic voltammetry and impedance spectroscopy, respectively. These fabricated electrodes could be promising alternate for metal-based electrodes in dye-sensitized solar cells due to its facile fabrication process, low cost, and higher chemical stability.

Boosting the performance of dye-sensitized solar cells by employing Li-substituted NiO nanosheets as highly efficient electrocatalysts for reduction of triiodide

Dye-sensitized solar cells (DSSCs) exhibit considerable potential as a promising technology, particularly when addressing the challenge of replacing the costly Platinum (Pt) counter electrode (CE) with economically viable and chemically stable CE materials. This study examines the use of two-dimensional hexagonal-shaped nickel oxide nanosheets substituted with varying mol% of lithium (1, 3, and 5 %) (Li (1–5%)-NiO NSs) as the counter electrodes (CEs) for DSSCs. The facile hydrothermal method was employed for the preparation of NiO and Li (1–5 mol%)-NiO samples. The BET analysis of NiO and Li (1–5%)-NiO indicates that higher concentrations of Li1+ ions in Ni2+ ions sites lead to an increase in the overall surface area of NiO. This leads to an elevated number of exposed electrocatalytic active sites which resulted in enhancing the rate of reduction of I3− ions. The cyclic voltammetry (CV) result of 5 mol% of Li substituted NiO (5-LNO) shows outstanding electrocatalytic activity towards the redox reaction of I3−/I− redox mediator among the as-prepared CEs. The DSSCs assembled with 5-LNO CE show an excellent power conversion efficiency (η) of 5.84 % with short-circuit current (Jsc) of 18.76 mAcm−2, and open-circuit voltage (Voc) of 0.80 V which is higher than Pt-based CE (η of 4.05 % with Jsc of 10.16 mAcm−2, and Voc of 0.69 V). The DSSCs fabricated with 5-LNO CE exhibit excellent photovoltaic performance because of their high active surface area and enhanced electrical conductivity. The 5-LNO CE has low cost, significant electrocatalytic activity, less toxicity, and superior device efficiency than NiO, other Li (1–3%)-NiO, and Pt CEs, making it a suitable candidate for Pt-free DSSCs application.

Laser-induced nitrogen and boron co-doped graphene film for dye-sensitized solar cell applications

Heteroatom-doped graphenes play a crucial role in developing metal-free electrocatalysts for dye-sensitized solar cells (DSSCs). This work demonstrates an approach to synthesizing nitrogen and boron dual-doped porous graphene as an efficient DSSC counter electrode (CE) by one-step laser induction technology. The morphologies, crystal structure, and chemical composition of N and/or B-doped laser-induced graphene were characterized and confirmed by SEM, XRD, and XPS measurements. Electrochemical results indicate that the conductivity and electrocalalytic activity of the nitrogen and boron co-doped graphene (BN-LIG) for triiodide reduction were enhanced after B-doping. Hence, the DSSC based on BN-LIG CE achieved a power conversion efficiency of 4.99%, which is 90.9% of a DSSC with Pt CE.

Intrinsic pentagon defect engineering in multiple spatial-scale carbon frameworks for efficient triiodide reduction

Intrinsic topological defect engineering has been proven as a promising strategy to elevate the electrocatalytic activity of carbon materials. However, the controllable construction of high-density and specific topological defects in carbon frameworks to reveal the relationship between reactivity and defect structure remains a challenging task. Herein, the intrinsic pentagon carbon sites that can favor electron overflow and enhance their binding affinity towards the intermediates of catalytic reaction are firstly presented by the work function and the p-band center calculations. To experimentally verify this, the cage-opening reaction of fullerene is proposed and utilized for synthesizing carbon quantum dots with specific pentagon configuration (CQDs-P), subsequently utilizing CQDs-P to modulate the micro-scale defect density of three-dimensional reduced graphene oxide (rGO) via π-π interactions. The multiple spatial-scale rGO-conjugated CQDs-P structure simultaneously possesses abundant pentagon and edge defects as catalytic active sites and long-range-ordered π electron delocalization system as conductive network. The defects-rich CQDs-P/rGO-4 all-carbon-based catalyst exhibits superb catalytic activity for triiodide reduction reaction with a high photoelectric conversion efficiency of 8.40%, superior to the Pt reference (7.97%). Theoretical calculations suggest that pentagon defects in the carbon frameworks can promote charge transfer and modulate the adsorption/dissociation behavior of the reaction intermediates, thus enhancing the electrocatalytic activity of the catalyst. This work confirms the role of intrinsic pentagon defects in catalytic reactions and provides a new insight into the synthesis of defects-rich carbon catalysts.

Facile Fabrication of an SnSx‐SnO2‐Decorated Cobalt Sulfide Film as an Effective Counter Electrode for Dye‐Sensitized Solar Cells

AbstractMetal sulfide stands out as one of the novel and promising platinum‐free counter electrode (CE) materials for dye‐sensitized solar cells (DSSCs). In this work, SnSx‐SnO2‐decorated CoSx films were designed and synthesized by a low‐temperature fabrication process. The small clusters of nanoparticles create a large amount of catalytic active sites, resulting in superior electrocatalytic activity for triiodide reduction. The DSSC with SnSx‐SnO2‐decorated CoSx film has achieved an impressive power conversion efficiency of 4.57 %, which is close to the efficiency of the DSSC with platinum CE (4.82 %). Furthermore, regarding the attenuation of the photovoltaic performance for the DSSC with SnSx‐SnO2‐decorated CoSx film, negligible change was observed after a prolonged storage under ambient condition for five days. Therefore, it is worthwhile to expect the explorations of novel fabricate technique for synthesizing cost‐effective metal sulfide films with long‐term stability in DSSCs.

Metal-organic framework-derived nitrogen-coordinated cobalt single-atom catalysts for triiodide reduction reaction in solar cells

The counter electrode (CE) is a critical component of a dye-sensitized solar cell (DSSC), and developing Pt-free CEs with high catalytic activities and superior stabilities is urgent. Herein, N-doped carbon-supported Cobalt (Co-NC) single-atom catalysts (SACs) were prepared via in-situ pyrolysis. The DSSCs assembled using the Co-NC SACs CEs exhibited superior power conversion efficiencies (9.25%) compared with those of the DSSCs with the N-doped carbon substrate (6.32%), related Cobalt nanoparticles (7.01%), and Pt (8.05%) CEs. This was attributed to the synergistic effects of the N-doped C matrix and single dispersed Co species, which could provide high active Co–Nx as well as a porous structure that offered unobstructed access to the electroactive sites. The catalytic mechanism was elucidated from I3- and I adsorption, I2 and I- dissociation and charge transfer process by DFT calculations. This study expands the range of non-noble metal CE materials for the commercialization of DSSCs.

Size-dependent activity of FeSe2 nanosheets for efficient tri-iodide reduction reaction in photovoltaics

Constructing two-dimensional (2D) transition metal selenide with tunable size is of utmost importance to replace traditional noble metal counter electrode (CE) catalyst and display their size-dependent activity for tri-iodide (I3-) reduction reaction (IRR) in dye-sensitized solar cells (DSSCs), yet it remains challenge. Herein, the theoretical calculation is firstly calculated to uncover the feasibility of FeSe2 as CE catalysts, where the abundant Fe sites at surface acted as the mainly catalytic center for IRR and reinforced interaction between Fe 3d and I 5p endow FeSe2 (111) with excellent catalytic activity for IRR. Inspired by the mentioned inherent merits of FeSe2 and facilitated charge-transfer capability of 2D nanomaterials, the well-defined 2D FeSe2 nanosheets with different size has been precisely synthesized by optimizing reaction temperature via the hot-injection method. As expected, the FeSe2 nanosheets with ca. 210 nm (FeSe2-M) shows higher photovoltaic performance than that of FeSe2-S (ca. 140 nm) and FeSe2-L (ca. 450 nm), proving the size-dependent activity of FeSe2 nanosheets, which can be attributed to the differences in the number of exposed Fe atoms and charge-transfer capability on surface that affected by the size. More importantly, the photovoltaic performance of FeSe2-M is also superior to that of Pt, demonstrating its potential to be used as Pt-free CE catalysts in low-cost DSSCs.

Fabrication of a free-standing Ti3C2T x -PTh counter electrode via interfacial polymerization for dye-sensitized solar cells.

The current work involves the fabrication of a MXene-Polythiophene (Ti3C2T x -PTh) composite via interfacial polymerization, alongside its deployment as a counter electrode (CE) or photocathode in dye-sensitized solar cells (DSSCs). The structural properties of the synthesized materials were investigated through a comprehensive array of techniques, including X-ray diffraction (XRD), fourier-transform infrared (FT-IR) spectroscopy, high resolution scanning electron microscopy (HRSEM), energy-dispersive X-ray analysis (EDAX), and X-ray photoelectron spectroscopy (XPS). The electrochemical performance, assessed via cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), revealed that the Ti3C2T x -PTh CE exhibits superior electro-catalytic activity, and reduction in charge transfer resistance compared to other individual CEs. These observations are in concordance with the data obtained from Tafel analysis. The incorporation of Ti3C2T x sheets into the composite significantly augmented its catalytic efficacy for triiodide reduction, manifesting in elevated short-circuit photocurrent density and enhanced fill factor metrics. A DSSC utilizing the Ti3C2T x -PTh CE exhibited a power conversion efficiency (PCE) of 5.83%, which stands on par with that of traditional Pt CEs. Thus, the Ti3C2T x -PTh CE material is posited as a viable, cost-efficient alternative to Pt, heralding a new era in the engineering of counter electrodes for the next generation of DSSCs.

Constructing NiSe2/MoSe2 Mott–Schottky Heterojunctions Onto N‐doped Brain Coral‐Carbon Spheres by Phase Separation Strategies for Advanced Energy Conversion Applications

AbstractConstructing Mott–Schottky heterojunctions in nanohybrids is an effective strategy for facilitating electron transfer and optimizing the electronic structure of active sites; however, challenges remain. Herein, a selenium‐induced phase separation strategy is proposed and successfully construct NiSe2/MoSe2 Mott–Schottky heterojunctions on N‐doped brain coral carbon nanospheres (N‐BCCSs). Owing to built‐in electric fields, optimized electronic density, and unique nanoflake/sphere structures, the designed NiSe2/MoSe2@N‐BCCSs carbon‐based Mott–Schottky catalysts achieved satisfactory electrocatalytic performance. When serving as a counter electrode for the triiodide reduction reaction (IRR), a power conversion efficiency of 8.49% is obtained, which outperformed that of conventional Pt electrodes (7.80%). When the NiSe2/MoSe2@N‐BCCSs are used as electrocatalysts for the hydrogen evolution reaction (HER), their overpotential (η10) is as low as 119 mV, which is significantly better than that of other transition‐metal selenides. This research demonstrates a new concept for constructing Mott–Schottky heterojunctions and provides a new direction for investigating multifunctional carbon‐based composites.

NiSe2-CoSe2 hollow polyhedron as counter electrode catalyst for high-efficiency dye-sensitized solar cells

The design of efficient counter electrode (CE) materials for dye sensitized solar cells (DSSCs) strongly depend on the microstructure construction and the effective combination of different active components. In this study, a hollow polyhedral structured NiSe2-CoSe2 composite electrode was synthesized through the direct selenization of the hollow nanocage morphology nickel-cobalt layered double hydroxide (NiCo-LDH) ultrathin nanosheets, which was derived from ZIF-67 nanocrystals. Notably, owing to the unique hollow structure and synergistic effect of the Ni-Co bimetallic selenides, the hollow polyhedral NiSe2-CoSe2 CE exhibited the expected electrochemical catalytic activity in the reduction of triiodide, as revealed by electrochemical impedance spectroscopy, cyclic voltammetry and Tafel polarization measurements. The photovoltaic results revealed that the PCE of the NiSe2-CoSe2 CE reached 8.21 %, which was higher than those of the Pt and CoSe2 CEs (7.62 % and 6.78 %, respectively). Moreover, the hollow NiSe2-CoSe2 CE exhibited a favourable photocurrent response upon light on-and-off cycling and improved stability over multiple start. This study provides a meaningful reference for the construction of hollow polymetallic transition-metal selenides for DSSC devices.

Enhancing surface area, morphology, and electrocatalytic activity favouring triiodide reduction via surface sulfurization of metal oxide

Herein, a direct anionic exchange method was employed using Thioacetamide (TAA) and Phosphorous Pentasulfide (P2S5) by facile hydrothermal method. The preliminary results confirm that the sulfurization leads to amorphization and formation of MoS2. BET analysis demonstrates the substantial improvement in the surface area from 72.046 m²/g for pristine MoO3 to 104.402 m²/g, and 140.802 m²/g, for TAA and P2S5 treated MoO3 respectively, was achieved upon sulfurization. Cyclic Voltammetry (CV) studies show an excellent triiodide reduction ability in LiI/I redox system which is due to the improvement in electrocatalytically active sites and stability across the CE/electrolyte interface. The lower charge transfer resistance (Rct) values obtained from Electrochemical impedance spectroscopy (EIS) confirm the effective charge carrier transport that improved the conductivity across electrode/electrolyte interface. The power conversion efficiency (PCE) measured under our lab conditions found an improvement for pristine MoO3 i.e. 0.78% to a maximum PCE of 5.48% and 4.12% for the P2S5 and TAA sulfurized MoO3 respectively. In general, this work highlights the use of phosphorous pentasulfide which can also be utilized for direct anionic exchange with the advantage of phosphorous content in resultant products which could greatly improve various physio-chemical properties of the material.

Laminated 2D-Ti3C2-MXenes as high-performance counter electrode for triiodide reduction in dye-sensitized solar cells

The different surface terminals, sizes, and sheet quality of laminated 2D-Ti3C2-MXenes were prepared by selective etching intermediate Al atoms layer form the strongly bonded compound Ti3AlC2 as precursor at low temperature using different etchants of HF, HF + HCl, LiF + HCl, and NH4HF2 for 24 h, respectively. Then, 2D-Ti3C2-MXenes were further instead of traditional Pt as counter electrodes (CEs) in triiodide reduction for dye-sensitized solar cells (DSSCs). The selection of different etchant directly affects the properties and performance of the laminated 2D-Ti3C2-MXenes catalyst. Herein, the DSSCs with 2D-Ti3C2-MXenes CEs yielded power conversion efficiencies (PCE) of 7.15 % (HF-), 6.06 % (HF + HCl-), 6.38 % (LiF + HCl-), and 6.05 % (NH4HF2-) for regenerate traditional I3−/I− shuttles via the photocurrent-voltage (J-V) test, respectively. The outstanding electrocatalytic performances of laminated 2D-Ti3C2-MXenes can be attributed to the formation of regular inter-stratification structures by etching to expose larger specific surface areas and further generate more catalytic reaction sites, as well as the acceleration of I3−/I− shuttle diffusion channels by adjusting the interlayer d-spacing, implying a potentially candidate of Pt catalyst for applications in the encapsulated DSSCs as Pt-free CEs.

Experimental and computational investigation of multi-walled carbon nanotubes decorated by Co–Ni–Se@MoSe2 core–shell as a sustainable counter electrode for dye-sensitized solar cells

The development of a highly active, long-lasting, and cost-effective electrocatalyst as an alternative to platinum (Pt) is a vital issue for the commercialization of dye-sensitized solar cells (DSSCs). Herein, Co–Ni–Se@MoSe2 core–shell structures decorated on multi-walled carbon nanotubes (MWCNTs) were synthesized for the first time by the hydrothermal and probe-sonication methods. The electrochemical performance of this composite was examined using electrochemical measurement techniques. The results showed improved properties and better electrochemical activities of the Co–Ni–Se@MoSe2@MWCNTs than Pt and other counter electrodes (CEs) for the triiodide reduction and exhibit good electrochemical stability in iodine-based electrolytes. The power conversion efficiency of DSSCs based on Co–Ni–Se@MoSe2@MWCNTs CE reaches 9.43%, significantly superior to that with Co–Ni–Se@MoSe2 core–shell (8.13%), Pt CE (7.44%), and other CEs. The notable performance is attributed to the synergistic effect between Co–Ni–Se@MoSe2 and MWCNTs. As a result, the transfer of electrons to the active site is promoted, the agglomeration of Co–Ni–Se@MoSe2 is hampered, and more active sites are available. Density functional theory calculations revealed that I2 adsorption on MoSe2 surfaces facilitated the generation of I− ions, which played a critical role in enhancing the reaction efficiency. Therefore, the Co–Ni–Se@MoSe2@MWCNTs composite is a promising candidate for use in high-performance DSSCs.

Unveiling the Potential of MnxCo3–xS4 Electrocatalyst in Triiodide Reduction for Dye-sensitized Solar Cells

The development of a low-cost and high-efficiency Pt-free counter electrode is an important goal to improve the performance of dye-sensitized solar cells. In this study, we successfully synthesized a MnxCo3-xS4-based counter electrode by a facile solvothermal synthesis technique. The electrocatalyst was directly deposited on a fluorine doped titanium oxide (FTO) coated glass substrate. Various characterization techniques such as Xray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy were employed to analyze the obtained MnxCo3-xS4 counter electrode material. The photovoltaic measurements performed on the dye-sensitized solar cells showed a remarkable improvement in energy conversion efficiency with the MnxCo3-xS4 counter electrode (8.60 %) compared to the conventional Pt (8.11 %). Moreover, the MnxCo3-xS4counter electrode exhibited excellent stability, further highlighting its potential as an efficient and durable alternative to Pt in dye-sensitized solar cells. Overall, our results contribute to the further development of Pt-free counter electrode materials for sustainable solar energy applications.

Nitrogen-doped reduced graphene oxide enfolded zinc cobaltite micro flowers as efficient triiodide reduction for a platinum-free counter electrode in dye-sensitized solar cell applications

Diverse varieties of organic and inorganic materials have been employed as counter electrodes (CEs) in dye-sensitized solar cell applications (DSSCs) to replace platinum (Pt). Interestingly, the influence of N-doped reduced graphene oxide on ZnCo2O4 with high surface area, superior electrical activity, and chemical stability has been addressed in this work. Pure ZnCo2O4 (ZCO), ZnCo2O4/reduced graphene oxide (rGO) (ZCOG), and ZnCo2O4/nitrogen-doped reduced graphene oxide (N-rGO) (ZCONG) had synthesized using a facile hydrothermal technique, and their performance as a CE material in DSSC application was further investigated. The formation of the material free of impurities is depicted by X-Ray Diffraction (XRD) and Raman analysis. The analysis utilizing Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) confirmed the existence of ZnCo2O4 micro flowers made of rods and sheets as well as the thin sheet-like shape of graphene oxide (GO) and N-rGO. The X-ray photoelectron spectroscopy (XPS) analysis technique was employed to determine the chemical composition and purity of the prepared samples. Further, the BET analysis confirms the higher specific surface area (1198.431 m2/g) of the ZCONG sample. The electrochemical property of the coated CEs was investigated using cyclic voltammetry (CV) analysis with the iodine-based electrolyte in a three-electrode system showing superior catalytic properties of the ZCONG CE than the other ZCO and ZCOG CEs. The as-fabricated CEs were utilized to assemble the DSSC device, and the ZCONG CE reached a photovoltaic power conversion efficiency (PCE) of 5.84 ± 0.06%, surpassing ZCO (3.51 ± 0.15 %) and ZCOG (4.81 ± 0.08 %) CEs.