X-CoOTe (X = S, Se, and P) with Oxygen/Tellurium Dual Vacancies and Banana Stem Fiber-Derived Carbon Fiber as Battery-Type Cathode and Anode Materials for Asymmetric Supercapacitor.

In this work, we demonstrated the synthesis of anions (X = selenium (Se), sulfur (S), and phosphorus (P)) doped cobalt oxytelluride (X-CoOTe) with oxygen and tellurium dual vacancies using hydrothermal methods, followed by selenization, sulfurization, and phosphorization reactions. Especially, the Se-CoOTe-modified nickel foam (Se-CoOTe/NF) electrode delivered a higher specific capacity (752.95 C/g) and an extremely lower charge transfer resistance (0.87 Ω) than S-CoOTe/NF and P-CoOTe/NF due to the higher metallic conductivity of Se. Both oxygen and tellurium vacancies facilitate higher charge transfer conductivity, specific capacity, and stability. On the other hand, banana stem core fiber-derived activated carbon fiber (AC) with exfoliated carbon sheet, cracked surface, and corresponding high surface area boosts the excellent cycle stability up to 4000 cycles with capacitance retention of 100.29%. Thus, the asymmetric device (Se-CoOTe/NF//AC/NF) exhibited an extendable cell voltage (1.55 V), higher energy density (155.6 W h kg-1) at a power density (1356.2 W kg-1), and generous long-term stability (100% retention up to 10 000 cycles) in a liquid alkaline electrolyte. In the practicability test, the proposed asymmetric device mutually showed an increased operating voltage from 1.55 to 4.65 V for a three-series connection. In a three-series connection, a single white LED and an LED string glowed efficiently. This new finding will be very useful to develop tellurium-based chalcogenides and biowaste-derived carbon for energy storage applications.

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.

Demonstration of a Gel-Polymer Electrolyte-Based Electrochromic Device Outperforming Its Solution-Type Counterpart in All Merits: Architectural Benefits of CeO2 Quantum Dot and Nanorods.

For years, solution-type electrochromic devices (ECDs) have intrigued researchers' interest and eventually rendered themselves into commercialization. Regrettably, challenges such as electrolyte leakage, high flammability, and complicated edge-encapsulation processes limit their practical utilization, hence necessitating an efficient alternate. In this quest, although the concept of solid/gel-polymer electrolyte (SPE/GPE)-based ECDs settled some issues of solution-type ECDs, an array of problems like high operating voltage, sluggish response time, and poor cycling stability have paralyzed their commercial applicability. Herein, we demonstrate a choreographed-CeO2-nanofiller-doped GPE-based ECD outperforming its solution-type counterpart in all merits. The filler-incorporated polymer electrolyte assembly was meticulously weaved through the electrospinning method, and the resultant host was employed for immobilizing electrochromic viologen species. The filler engineering benefits conceived through the tuned shape of CeO2 nanorod and quantum dots, along with the excellent redox shuttling effect of Ce3+/Ce4+, synchronously yielded an outstanding class of GPE, which upon utilization in ECDs delivered impressive electrochromic properties. A combination of features possessed by a particular device (QD-NR/PVDF-HFP/IL/BzV-Fc ECD) such as exceptionally low driving voltage (0.9 V), high transmittance change (ΔT, ∼69%), fast response time (∼1.8 s), high coloration efficiency (∼339 cm2/C), and remarkable cycling stability (∼90% ΔT-retention after 25,000 cycles) showcased a striking potential in the yet-to-realize market of GPE-based ECDs. This study unveils the untapped potential of choreographed nanofillers that can promisingly drive GPE-based ECDs to the doorstep of commercialization.

Graphene quantum dots induced defect-rich NiFe Prussian blue analogue as an efficient electrocatalyst for oxygen evolution reaction.

High energy resource demand has led to the rapid development of hydrogen as a clean fuel through electrolytic water splitting. The exploration of high-performance and cost-effective electrocatalysts for water splitting is a challenging task to obtain renewable and clean energy. However, the sluggish kinetics of oxygen evolution reaction (OER) greatly hindered its application. Herein, a novel oxygen plasma-treated graphene quantum dots embedded Ni-Fe Prussian blue analogue (O-GQD-NiFe PBA) is proposed as a highly active electrocatalysts for OER. Furthermore, the defect induced by GQD can provide an abundant lattice mismatch in the matrix of NiFe PBA, which further facilitates faster electron transport and kinetic performance. After optimization, the as-assembled O-GQD-NiFe PBA exhibits excellent electrocatalytic performance towards OER with a low overpotential of 259 mV for reaching a current density of 10 mA cm-2 and impressive long-term stability for 100 h in an alkaline solution. This work broadens the scope of metal-organic frameworks (MOF) and high-functioning carbon composite as an active material for energy conversion systems.

Morphological Features of SiO2 Nanofillers Address Poor Stability Issue in Gel Polymer Electrolyte-Based Electrochromic Devices.

Nanofillers' applicability in gel polymer electrolyte (GPE)-based devices skyrocketed in the last decade as soon as their remarkable benefits were realized. However, their applicability in GPE-based electrochromic devices (ECDs) has hardly seen any development due to challenges such as optical inhomogeneity brought by incompetent nanofiller sizes, transmittance drop due to higher filler loading (usually required), and poor methodologies of electrolyte fabrication. To address such issues, herein, we demonstrate a reinforced polymer electrolyte tailored through poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP),1-butyl-3-methylimidazolium tetrafluoroborate (BMIMBF4), and four types of mesoporous SiO2 nanofillers, porous (distinct morphologies) and nonporous, two each. The synthesized electrochromic species 1,1'-bis(4-fluorobenzyl)-4,4'-bipyridine-1,1'-diium tetrafluoroborate (BzV, 0.05 M), counter redox species ferrocene (Fc, 0.05 M), and supporting electrolyte (TBABF4, 0.5 M) were first dissolved in propylene carbonate (PC) and then immobilized in an electrospun PVDF-HFP/BMIMBF4/SiO2 host. We distinctly observed that spherical (SPHS) and hexagonal pore (MCMS) morphologies of fillers endowed higher transmittance change (ΔT) and coloration efficiency (CE) in utilized ECDs; particularly for the MCMS-incorporated ECD (GPE-MCMS/BzV-Fc ECD), ΔT reached ∼62.5% and CE soared to 276.3 cm2/C at 603 nm. The remarkable benefit of filler's hexagonal morphology was also seen in the GPE-MCMS/BzV-Fc ECD, which not only marked an astounding ionic conductivity (σ) of ∼13.5 × 10-3 S cm-1 at 25 °C, thus imitating the solution-type ECD's behavior, but also retained ∼77% of initial ΔT after 5000 switching cycles. The enhancement in ECD's performance resulted from merits brought by filler geometries such as the proliferation of Lewis acid-base interaction sites due to the high surface-to-volume ratio, the creation of percolating tunnels, and the emergence of capillary forces triggering facile ion transportation in the electrolyte matrix.

Nanoflower-like P-doped Nickel Oxide as a Catalytic Counter Electrode for Dye-Sensitized Solar Cells.

Flower-like phosphorus-doped nickel oxide (P-NiO) is proposed as a counter electrode (CE) for dye-sensitized solar cells (DSSCs). The flower-like nickel oxide essentially serves as the matrix for the CE, which is expected to promote a two-dimensional electron transport pathway. The phosphorus is intended to improve the catalytic ability by creating more active sites in the NiO for the catalysis of triiodide ions (I3-) to iodide ions (I-) on the surface of the CE. The P-NiO is controlled by a sequencing of precursor concentration, which allows the P-NiO to possess different features. The debris aggregation occurs in the P-NiO-1, while the P-NiO-0.75 leads to the incomplete flower-like nanosheets. The complete flower-like morphology can be observed in the P-NiO-0.5, P-NiO-0.25 and P-NiO-0.1 catalytic electrodes. The DSSC with the P-NiO-0.5 CE achieves a power conversion efficiency (η) of 9.05%, which is better than that of the DSSC using a Pt CE (η = 8.51%); it also performs better than that with the Pt CE, even under rear illumination and dim light conditions. The results indicate the promising potential of the P-NiO CE to replace the expensive Pt CE.

Introducing Postmetalation Metal-Organic Framework to Control Perovskite Crystal Growth for Efficient Perovskite Solar Cells.

A novel lead-containing metal-organic framework (Pb-MOF) is synthesized through postmetalation of MOF-525. Postmetalation renders lead ions bound with the organic linker of MOF-525, which can serve as nucleation points to promote perovskite crystallization. The introduction of lead postmetalated MOF-525 (Pb-MOF) as a scaffold layer between compact TiO2 (c-TiO2) layer and perovskite layer promotes perovskite crystal growth in enlarging crystal grain size with better crystallinity, hence decreasing defect sites in the perovskite layer. Postmetalation of MOF-525 with lead ions allows MAPbI3 to form a solid crystal structure to facilitate the charge separation between electron transport layer (ETL) and light-harvesting layer so as to resolve the issue of possible vacancies present in MOFs. As a result, the champion perovskite solar cell (PSC) with the introduction of Pb-MOF exhibits a power conversion efficiency (PCE) of 20.87% and better stability (86% PCE retention after 40 days), outperforming the pristine PSC (16.85% PCE, with 52% retention after 40 days) and MOF-525-introduced PSC (18.61% PCE, with 76% retention after 40 days).

Orientation-Adjustable Metal-Organic Framework Nanorods for Efficient Oxygen Evolution Reaction.

A series of orientation-adjustable metal-organic framework (MOF) nanorods, CoFe(dobpdc)-I to CoFe(dobpdc)-III (dobpdc = 4,4'-dihydroxybiphenyl-3,3'-dicarboxylate), is developed on a 3D nickel foam (NF) template. By modulating the solvent composition for synthesis, the feature of MOF nanorods on the template can be varied from disorganized to a unidirectional orientation perpendicular to the NF. Well-aligned, vertically oriented CoFe(dobpdc)-III nanorods are hydrophilic and have more exposed active sites and interfacial charge transfer ability. Consequently, they exhibit a superior activity for oxygen evolution reaction (OER) with ultralow overpotentials of 176 and 240 mV at 10 and 300 mA cm-2 in 1.0 M KOH (aq), respectively. CoFe(dobpdc)-III also shows a record low overpotential of 204 mV at J10 mA cm-2 among the electrocatalysts based on CoFe MOF and an excellent overpotential at a high current density (100 mA cm-2) of 312 mV in 0.1 M KOH (aq). This is the first report of a convenient method to straighten up MOF nanorods on a template for highly efficient OER.

Additive Engineering by Bifunctional Guanidine Sulfamate for Highly Efficient and Stable Perovskites Solar Cells.

High efficiency and good stability are the challenges for perovskite solar cells (PSCs) toward commercialization. However, the intrinsic high defect density and internal nonradiative recombination of perovskite (PVK) limit its development. In this work, a facile additive strategy is devised by introducing bifunctional guanidine sulfamate (GuaSM; CH6 N3 + , Gua+ ; H2 N-SO3 - , SM- ) into PVK. The size of Gua+ ion is suitable with Pb(BrI)2 cavity relatively, so it can participate in the formation of low-dimensional PVK when mixed with Pb(BrI)2 . The O and N atoms of SM- can coordinate with Pb2+ . The synergistic effect of the anions and cations effectively reduces the trap density and the recombination in PVK, so that it can improve the efficiency and stability of PSCs. At an optimal concentration of GuaSM (2 mol%), the PSC presents a champion power conversion efficiency of 21.66% and a remarkably improved stability and hysteresis. The results provide a novel strategy for highly efficient and stable PSCs by bifunctional additive.

Transparent Cobalt Selenide/Graphene Counter Electrode for Efficient Dye-Sensitized Solar Cells with Co2+/3+-Based Redox Couple.

In this study, we demonstrate a facile, one-pot, and low-temperature (∼85 °C) chemical bath method for the preparation of a composite of cobalt selenide/graphene (Co0.85Se/Gr) as the electrocatalyst for the counter electrode (CE) of dye-sensitized solar cells (DSSCs) with a cobalt-based electrolyte. The Co0.85Se/Gr composite film was envisaged to have the advantages of both components, that is, the high electrochemical surface area of Co0.85Se and the straight paths for electron transfer from Gr. The DSSCs with Co0.85Se/Gr exhibited a power conversion efficiency (η) of 11.26%. According to the results of the rotating disk electrode, the film of Co0.85Se/Gr showed a high electrocatalytic surface area (Ae) and an extremely large intrinsic heterogeneous rate constant (k0). Furthermore, the composite film of Co0.85Se/Gr exhibits a high transparency in the wavelength region of 400-800 nm (>82%), which implied that the corresponding electrode shall be a potential CE in rear-side illuminated DSSCs. The photovoltaic parameters of the DSSCs with Pt, Co0.85Se, Gr, and Co0.85Se/Gr were obtained for rear-side illumination and additionally for front- and rear-side illuminations (AM 1.5, 100 mW/cm2) using different electrolytes. As the cobalt-based electrolyte of [Co(bpy)3]2+/3+ exhibited a low light absorption and low overpotential for dye regeneration, a rear-side illuminated DSSC with a cobalt-based electrolyte showed the highest efficiency of 9.43 ± 0.02%, which is greater than that of the DSSC with an I-/I3--based electrolyte (η = 7.63 ± 0.04%).

Oxygen Plasma Activation of Carbon Nanotubes-Interconnected Prussian Blue Analogue for Oxygen Evolution Reaction.

To obtain renewable and clean fuels, exploration of effective electrocatalysts is highly desirable due to the sluggish kinetics of water splitting. In this study, the oxygen plasma-activated hybrid structure of Ni-Fe Prussian blue analogue (PBA) interconnected by carbon nanotubes (O-CNT/NiFe) is reported as a highly effective electrocatalytic material for the oxygen evolution reaction (OER). The electrocatalytic performance is significantly influenced by different mass ratios of CNTs to Ni-Fe PBA. Benefiting from the conductive and oxygen plasma-activated CNTs as well as ordered and distributed metal sites in the framework, the optimized O-CNT/NiFe 1:18 exhibits a competitive overpotential of 279 mV at a current density of 10 mA cm-2 and a low Tafel slope of 42.8 mV dec-1 in 1.0 M KOH. Furthermore, the composite shows superior durability for at least 100 h. These results suggest that the O-CNT/NiFe 1:18 possesses promising potential as a highly active electrocatalyst.

Stoichiometry-Controlled MoxW1-xTe2 Nanowhiskers: A Novel Electrocatalyst for Pt-Free Dye-Sensitized Solar Cells.

Novel polymorphic MoxW1-xTe2-based counter electrodes possess high carrier mobility, phase-dependent lattice distortion, and surface charge density wave to boost the charge-transfer kinetics and electrocatalytic activity in dye-sensitized solar cells (DSSCs). Here, we report the syntheses of stoichiometry-controlled binary and ternary MoxW1-xTe2 nanowhiskers directly on carbon cloth (CC), denoted by MoxW1-xTe2/CC, with an atmospheric chemical vapor deposition technique. The synthesized MoxW1-xTe2/CC samples, including 1T'-MoTe2/CC, Td-WTe2/CC, Td-Mo0.26W0.73Te2.01/CC, and 1T'- & Td-Mo0.66W0.32Te2.02/CC, were then employed as different counter electrodes to study their electrochemical activities and efficiencies in DSSCs. The photovoltaic parameter analysis manifests that MoxW1-xTe2/CCs are more stable than a standard Pt/CC in the I-/I3- electrolyte examined by cyclic voltammetry over 100 cycles. A 1T'- & Td-Mo0.66W0.32Te2.02/CC-based DSSC can achieve a photocurrent density of 16.29 mA cm-2, a maximum incident photon-to-electron conversion efficiency of 90% at 550 nm excitation, and an efficiency of 9.40%, as compared with 8.93% of the Pt/CC counterpart. Moreover, the 1T'- & Td-Mo0.66W0.32Te2.02/CC shows lower charge-transfer resistance (0.62 Ω cm2) than a standard Pt/CC (1.19 Ω cm2) in electrocatalytic reactions. Notably, MoxW1-xTe2 nanowhiskers act as an electron expressway by shortening the path of carrier transportation in the axial direction from a counter electrode to electrolytic ions to enhance the reaction kinetics in DSSCs. This work demonstrates that the nanowhisker-structured 1T'- & Td-Mo0.66W0.32Te2.02/CC with high carrier mobility and robust surface states can serve as a highly efficient counter electrode in DSSCs to replace the conventional Pt counter electrode for electrocatalytic applications.

Cobalt-tungsten diselenide-supported nickel foam as a battery-type positive electrode for an asymmetric supercapacitor device: comparison with various MWSe2 (M = Ni, Cu, Zn, and Mn) on the structural and capacitance characteristics.

New exploration in nanomaterial research has been greatly encouraged so as to discover active electrode materials with extraordinary properties and performances. In this report, we demonstrated the synthesis of different transition metal-incorporated MWSe2 (M = Co, Ni, Cu, Zn, and Mn) and studied them using various characterization techniques. Subsequently, the proposed bimetallic chalcogenides were successfully applied as the active electrode materials for pseudocapacitor applications. The results of the electrochemical studies showed that CoWSe2 exhibited a higher specific capacitance of 3309.58 F g-1 at a constant applied current density of 1.35 A g-1, which is 1.07, 1.76, 2.04, 8.7, and 12.28-fold higher than that of NiWSe2, CuWSe2, ZnWSe2, MnWSe2, and pristine WSe2, respectively. The interconnected nanosheet structure with voids facilitates rich active sites for efficient electrolyte uptake and superior charge transfer during the faradaic redox reaction. In addition, the cycle stability of CoWSe2/NF was studied and the retention capacitance of about 82.1% was recorded, which is higher than that of NiWSe2 (60.4%), CuWSe2 (50.12%), ZnWSe2 (46.44%), MnWSe2 (40.12%), and pristine WSe2 (31.2%). Owing to the higher specific capacitance and cycle stability, CoWSe2 was proposed as a battery-type electrode material for the fabrication of an asymmetric device. The fabricated CoWSe2//AC device provided excellent energy density and power density of 182.54 W h kg-1 and 2810.81 W kg-1, respectively, at 3.51 A g-1. Based on these properties, the proposed research and studies can provide a way for the profound development of 2D-layered metal chalcogenides for energy storage applications.

Asymmetric Benzotrithiophene-Based Hole Transporting Materials Provide High-Efficiency Perovskite Solar Cells.

In this study, we synthesized a series of small-molecule benzotrithiophenes (BTTs) and used them as hole transporting materials (HTMs) in perovskite solar cells (PSCs). The asymmetric benzo[2,1-b:-3,4-b':5,6-b″]trithiophene unit was used as the central core to which were appended various donor groups, namely, carbazole (BTT-CB), thieno thiophene (BTT-FT), triphenylamine (BTT-TPA), and bithiophene (BTT-TT). The extended aromatic core in the asymmetric BTT provided full planarity, thereby favoring intermolecular π-stacking and charge transport. The physical, optical, and electrical properties of these small-molecule HTMs are reported herein. BTT-TT displayed good crystallinity and superior hole mobility, when compared with those of the other three HTMs, and formed smooth and uniform surfaces when covering the perovskite active layer. Accordingly, among the devices prepared in this study, a PSC incorporating BTT-TT as the HTM achieved the highest power conversion efficiency (18.58%). Moreover, this BTT-TT-containing device exhibited good stability after storage for more than 700 h. Thus, asymmetric BTTs are promising candidate materials for use as small-molecule HTMs in PSCs.

Thioalkyl-Functionalized Bithiophene (SBT)-Based Organic Sensitizers for High-Performance Dye-Sensitized Solar Cells.

A series of 3,3'-dithioalkyl-2,2'-bithiophene (SBT)-based organic chromophores were designed and developed for the use in dye-sensitized solar cells (DSSCs). By appropriate structural modification of the SBT π-linkers with different alkyl chains and conjugated thiophene units, chromophore aggregation and interfacial charge recombination could be suppressed to a remarkable degree. Single-crystal and optical/electrochemical data clearly show that the SBT core is nearly planar with the torsional angle <1°, likely via S(alkyl)···S(thiophene) intramolecular locks. Therefore, this highly π-conjugated unit should enhance panchromatic light-harvesting and prove to be an excellent core for organic dye. For comparison, the 3,3'-dialkyl-2,2'-bithiophene (BT)-based dye was also prepared. Under 1 sun (100 mW cm-2) illumination, an optimized SBT-6 dye-sensitized cell indicates a short-circuit current density (JSC) of 17.21 mA cm-2, an open-circuit voltage (VOC) of 0.78 V, and a fill factor (FF) of 0.71, corresponding to a power conversion efficiency (η) of 9.47%, which is nearly two times higher than that of alkylated bithiophene (BT)-based chromophores. Finally, the proposed sensitizer SBT-6 exhibited an excellent η of 23.57% under the T5 fluorescent illumination of 6000 lux. To the best of our knowledge, this is the highest power conversion efficiencies (PCE) value reported to date among the studied thiophene or bithiophene-based chromophores.

Enhanced Near-Infrared Photoresponse of Inverted Perovskite Solar Cells Through Rational Design of Bulk-Heterojunction Electron-Transporting Layers.

How to extend the photoresponse of perovskite solar cells (PVSCs) to the region of near-infrared (NIR)/infrared light has become an appealing research subject in this field since it can better harness the solar irradiation. Herein, the typical fullerene electron-transporting layer (ETL) of an inverted PVSC is systematically engineered to enhance device's NIR photoresponse. A low bandgap nonfullerene acceptor (NFA) is incorporated into the fullerene ETL aiming to intercept the NIR light passing through the device. However, despite forming type II charge transfer with fullerene, the blended NFA cannot enhance the device's NIR photoresponse, as limited by the poor dissociation of photoexciton induced by NIR light. Fortunately, it can be addressed by adding a p-type polymer. The ternary bulk-heterojunction (BHJ) ETL is demonstrated to effectively enhance the device's NIR photoresponse due to the better cascade-energy-level alignment and increased hole mobility. By further optimizing the morphology of such a BHJ ETL, the derived PVSC is finally demonstrated to possess a 40% external quantum efficiency at 800 nm with photoresponse extended to the NIR region (to 950 nm), contributing ≈9% of the overall photocurrent. This study unveils an effective and simple approach for enhancing the NIR photoresponse of inverted PVSCs.

Electrochemical sensing of anti-inflammatory agent in paramedical sample based on FeMoSe2 modified SPCE: Comparison of various preparation methods and morphological effects.

We demonstrate the different types of synthesis processes (hydrothermal, microwave and simple chemical synthesis) to prepare the Fe doped molybdenum diselenides (H-FeMoSe2, M-FeMoSe2, and C-FeMoSe2) and investigate their relevant electrocatalytic activities. The Fe doped MoSe2 exhibited an enhanced charge transfer conductivity and electrocatalytic activity. Especially, the H-FeMoSe2 with vertically aligned structures facilitate the abundant exposed active edge sites. Thus, H-FeMoSe2 modified screen-printed carbon electrode (H-FeMoSe2/SPCE) exhibited the lower Rct and better active surface area than that of M-FeMoSe2/SPCE and C-FeMoSe2/SPCE. As well as, the electrochemical sensing of mesalamine (MES) at H-FeMoSe2/SPCE is comparatively 0.46 and 1.28 fold higher than that obtained at M-FeMoSe2/SPCE and C-FeMoSe2/SPCE respectively. Thus, H-FeMoSe2/SPCE was concluded as an excellent electrocatalyst for sensing of MES and performed DPV technique. As the results, very low detection limit (0.8 nM) of MES was achieved at H-FeMoSe2/SPCE. Hence, the selected H-FeMoSe2/SPCE was successfully subjected to the real-time detection of MES by using a paramedical tablet and reported the excellent recovery range.

Synthesis of Surfactant-Free and Morphology-Controllable Vanadium Diselenide for Efficient Counter Electrodes in Dye-Sensitized Solar Cells.

In this study, a transition-metal selenide, vanadium diselenide (VSe2), with various morphologies was synthesized by employing a surfactant-free hydrothermal method under varied temperature conditions (190-220 °C). Although the physical properties of VSe2 have been studied before, only limited morphological change or application were explored. This study, for the first time, applied VSe2 as the electrocatalytic counter electrode (CE) in dye-sensitized solar cells (DSSCs) and showed an attractive cell efficiency. The mechanism of forming the tunable VSe2 morphologies is proposed. The evaluation of solar cell efficiency shows the correlation between morphology and electrocatalytic properties. It was further shown that VSe2-200 with the cauliflower-like morphology shows the highest cell performance of DSSC with an efficiency of 9.23 ± 0.07% under 1 sun irradiance, superior to that of the Pt-based DSSC (8.48 ± 0.08%). An electrochemical technique equipped with a rotating disk electrode system was introduced to confirm the high electrocatalytic performance with this particular morphology. The optimized VSe2 demonstrated good long-term stability with 78% retention after 500 cycles of the consecutive cyclic voltammetry, compared to 60% for the Pt CE. The control in morphology in vanadium diselenide synthesis and its usage in Pt-free CE DSSC have advanced the progress in electrochemistry.

A Pt-free pristine monolithic carbon aerogel counter electrode for dye-sensitized solar cells: up to 20% under dim light illumination.

In this work, pristine carbon aerogels (CAs) were used as Pt-free counter electrodes (CEs) in dye-sensitized solar cells (DSSCs) by varying the molar ratio of their precursors. Pristine mesoporous CAs with controlled resorcinol (R)/formaldehyde (F) and resorcinol (R)/sodium carbonate (C) molar ratios were successfully prepared. The as-prepared CAs were synthesized via a polymeric sol-gel reaction and were labeled as CA-O, CA-Q, CA-F, CA-C, and CA-G. The DSSCs using the as-prepared CA-C CE gave the best power conversion efficiency (PCE, η), 9.08 ± 0.01%, among all the CA CEs. The CA-C CE is further applied to an indoor T5 light source system with an impressive η value of 20.1 ± 0.60% at 2.18 mW cm-2 (T5 lamp with 7000 lux). Moreover, the hardness of CA-C CE is 3.01 GPa (Brinell hardness test), which is comparable to that of the FTO/glass substrate. As a result, the CA-C CE shows great potential to replace traditional CEs based on the Pt/FTO/glass in DSSCs.