Mani Sakthivel

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.

Star-shaped 3,6-bis(5-(4,4′-bis(3-azidopropyl)-[1,1′:3′,1′-terphenyl]-5′-yl)-thien-2-yl)-2,5-bis(2-ethylhexyl)pyrrolo[3,4-c]pyrrole-1,4(2H,5H)-dione (DPPTPTA) is combined with electrospun bimetallic copper–cobalt phosphide decorated on carbon nanofibers (CuCoP/CNF) and used as a modified layer (DPPTPTA@CuCoP/CNF) on the platinum (Pt) coated counter electrode (CE) of dye-sensitized solar cells (DSSCs). DPPTPTA possesses ladder-like energy levels for efficient charge separation while CuCoP/CNF exhibits high electrocatalytic activity and sufficient electrical conductivity. Overall, the DPPTPTA@CuCoP/CNF heterostructure exhibits attractive performance needed for CE of DSSCs. From electrochemical analysis, it is observed that the DPPTPTA@CuCoP/CNF modified layer ensures efficient charge transfer at the CE/electrolyte interface with low charge transfer resistance. Moreover, the CE/electrolyte interface possesses a small electron recombination rate, since the modified layer has good charge separation ability. Under 1 sun (AM 1.5G, 100 mW cm⁻²) conditions, the proposed DSSC achieved a photoelectric conversion efficiency (η) of 9.50%, an open-circuit voltage (V_OC) of 827 mV, a short-circuit current density (J_SC) of 16.25 mA cm⁻², and a fill factor (FF) of 0.71. Under indoor conditions, the η value at 6000 lux (1.89 mW cm⁻²) reached 25.44%. Finally, the porous three-dimensional nanofiber structure of modified layer can ensure the long-term stability (90% retention after 3000 h). Thus, the DPPTPTA@CuCoP/CNF modified layer-based DSSC can be considered as a promising device for possible renewable energy applications.

A novel multifunctional polymer ionic liquid poly(oxyethylene)-imide-2,2,6,6-tetramethyl-1-piperidinyloxy (POEI-TEMPO) was successfully prepared and used as an additive in iodide electrolyte in quasi-solid-state dye-sensitized solar cells (QSS-DSSCs). The POEI segment in the electrolyte has good mechanical strength; meanwhile, the TEMPO organic radical contains nitroxide as the redox couple (RN-O˙/RNO⁺) acting as a superior mediator in DSSCs. TEMPO has a number of favorable properties, such as fast and reversible redox kinetics, large apparent diffusion coefficient (D_app), positive redox potential, and facile electron self-exchange reaction. As a result, DSSCs were composed of a POEI-TEMPO/iodide electrolyte and a Pt-coated FTO layer on glass as a normal counter electrode (PtCE), whereas the other side of the glass was coated with silver mirror coating (SMC) as the bifacial PtCE/SMC cell. DSSC exhibited a maximum photoelectric conversion efficiency (η) of 9.83%, open-circuit voltage (V_OC) of 812.84 mV, and short-circuit current density (J_SC) of 16.60 mA cm⁻² under 1 sun (AM 1.5 G, 100 mW cm⁻²), whereas the value of η reached 25.99% under an indoor condition with 6000 lux (1.89 mW cm⁻²). Moreover, when POEI-TEMPO is used as an additive, the bifacial cell maintains its high performance with a reasonable long-term stability. The finding is expected to have a practical impact on harvesting the ambient light energy and extending the cell lifetime.

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.

This work reports the fabrication of a highly selective and novel electrocatalyst for electrochemical sensing applications. To this aim, CeMoSe₂ dendrites were synthesized via hydrothermal synthesis and characterized by using various analytical techniques such as X-ray diffraction (XRD), Raman spectroscopy, field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray (EDX) spectroscopy, transmission electron microscopy (TEM) and X-ray photoelectric spectroscopy (XPS). Further, the conductivity of the as-prepared CeMoSe₂ dendritic structure was studied by electrochemical impedance spectroscopy (EIS). The higher conductivity of the CeMoSe₂ dendrites made them essential for the electrochemical detection of 4-nitrophenol (4-NP) using cyclic voltammetry (CV) and linear sweep voltammetry (LSV). Electrochemical studies proved that the CeMoSe₂ dendrite modified electrode (GCE) shows a low detection limit of 0.0035 μM and a higher sensitivity of 1.24 μA μM⁻¹ cm⁻². Besides this, the real time application of the proposed sensor was tested in river water, which resulted in recovery values of 103.3 to 108.6%. The obtained recovery values also proved that CeMoSe₂/GCE is more suitable for the detection of 4-NP. Thus this simplistic 4-NP sensor is also advantageous due to its simplicity, reliability, low cost, and high stability, rendering it suitable for practical applications in real sample systems.