Pulsed Laser Ablation of Oxygen deficiency Enriched Superlattice Vanadium Pentoxide (V2O5) Ultrathin Nextrode aiming for Flexible Binder-less Tandem Energy Harvesting Devices.

For the initial instance, oxygen deficiency-enriched vanadium pentoxide (O─V2O5@500) thin film electrodes are tuned by the Pulsed Laser Ablation technique. The O─V2O5@500 thin film electrode shows remarkable electrochemical performances confirming the greater potential window of -0.4 to 0.9 V versus Hg/HgO in an alkaline electrolyte; also, the O─V2O5@ 500 thin film electrode exhibits a noteworthy volumetric capacity of 167.7 mAh cm-3 (areal capacity of 73.3 µAh cm-2). Additionally, Density Functional Theory (DFT) theory calculations are carried out for oxygen-deficient V2O5. From the partial density of states (pDOS) and partial charge density analysis, it is clear that oxygen vacancy improves the electrical conductivity due to the higher degree of electron delocalization of V─O─V near the vacancy and enhances the redox properties due to the formation of in-gap states. Further, it is reported that a O─V2O5@ 500 ||PVA-KOH|| Bi2O3 A-650 thin film supercapbattery (TFSCB) device attains an exceptional discharge volumetric capacitance of 182.85 F cm-3 (equal volumetric capacity of 124.5 mAh cm-3). Furthermore, the TFSCB device exhibits an extraordinary maximum volumetric energy (power) density of 14.28 mWh cm-3 (1.66 W cm-3); TFSCB succeeds in supreme capacity retention of 86% with outstanding coulombic efficiency of 94.4% after 21 000 cycles.

Acetylene-Mediated Borophosphene Dirac Materials as Efficient Anode Materials for Lithium-Ion Batteries.

Generally, graphynes have been generated by the insertion of acetylenic content (-C≡C-) in the graphene network in different ratios. Also, several aesthetically pleasing architectures of two-dimensional (2D) flatlands have been reported with the incorporation of acetylenic linkers between the heteroatomic constituents. Prompted by the experimental realization of boron phosphide, which has provided new insights on the boron-pnictogen family, we have modelled novel forms of acetylene-mediated borophosphene nanosheets by joining the orthorhombic borophosphene stripes with different widths and with different atomic constituents using acetylenic linkers. Structural stabilities and properties of these novel forms have been assessed using first-principles calculations. Investigation of electronic band structure elucidates that all the novel forms show the linear band crossing closer to the Fermi level at Dirac point with distorted Dirac cones. The linearity in the hole and electronic bands impose the high Fermi velocity to the charge carriers close to that of graphene. Finally, we have also unravelled the propitious features of acetylene-mediated borophosphene nanosheets as anodes in Li-ion batteries.

Electrochemical and DFT studies of andrographolide on electrochemically reduced graphene oxide for anti-viral herbaceutical sensor.

Herbal extracts are re-emerging as potential remedies for various vector-borne diseases. Amongst several phytochemicals, active ingredients of Andrographis paniculata extract is regarded as promising for dengue fever, caused by Aedes species. However, fingerprinting the active phytochemicals from herbal extracts are often relies on sophisticated analytical techniques which are not universally accessible. Herein, an electrochemically reduced graphene oxide on glassy carbon electrode (ErGO/GCE) has been devised as user-friendly and cost-effective sensor platform for fingerprinting of andrographolide (AG) in anti-dengue polyherbal formulation, i.e., Nilavembu kudineer powder. Confocal laser Raman and X-ray photoelectron spectral analyses revealed that the ErGO surfaces exert structural defects augmenting the conductivity at the electrode interface. DFT investigations enabled that C-3 and C-18 OH groups in AG is involved in the electrooxidation and adsorption-diffusion at the ErGO interface, respectively. Complementary electrochemical studies revealed that the diffusion-controlled process follows 1e-/1H+ transfer. Under optimal experimental conditions, ErGO sensor platform exhibit an amplified current sensitivity of 13.3 µA µM-1. cm-2 in the studied analyte concentration range of 10-400 µM. From the polyherbal extract and clinical sample analysis, the proposed sensor system offers selective, and sensitive detection of target AG regardless of common interferents.

Azulene Bridged π-Distorted Chromophores: The Influence of Structural Symmetry on Optoelectrochemical and Photovoltaic Parameters.

Conjugated chromophores possessing π-twisted functionality such as tetracyanobutadiene (TCBD) have emerged as promising active layer materials for organic photovoltaics (OPVs). In this study, we disclose the synthesis of two azulenyl chromophores containing one and two TCBD groups. The symmetrical and unsymmetrical structural characteristics of these molecules inflict dissimilar optoelectronic and electrochemical properties. Based on molar absorptivity, aggregation behavior, HOMO-LUMO energies and other quantum chemical parameters, the symmetrical molecule (TATC2) appears to be a better non-fullerene acceptor (NFA) compared to its unsymmetrical counterpart (TATC1). For instance, higher absorptivity and deeper HOMO-LUMO levels for TATC2 (23950 M-1 cm-1 ; -6.01 eV/-3.86 eV) over TATC1 (12200 M1 cm-1 ; -5.46 eV/-3.64 eV) was observed. Validating this structure-property relationship on solar cell prototypes exhibited higher photovoltaic parameters (VOC =0.54 V, FF=0.48, JSC =6.42 mA/cm2 ) for TATC2 than TATC1 (VOC =0.47 V, FF=0.38, JSC =5.77 mA/cm2 ). Though the device parameters are not high, this work uncovers the intrinsic properties of azulene-tethered twisted chromophores as potential π-semiconductor choice for NFA solar cells. In particular, this report explores the utility of azulene-based π-twisted semiconductors as acceptor material for OPVs with cell efficiencies of 1.70 and 1.04 % for TATC2 and TATC1 respectively.

Enhancing Hydrogen Evolution Reaction Activities of 2H-Phase VS2 Layers with Palladium Nanoparticles.

Effective hydrogen (H2) production with surface engineering of less active catalysts by an innovative approach is followed here. In this work, a non-noble 2H phase of VS2 layers, which showed poor activity for hydrogen evolution reaction (HER) in 0.5 M H2SO4, was made highly active by decorating palladium (Pd) nanoparticles (NPs) over VS2 layers. A density functional theory (DFT) study confirmed the successful binding of Pd with VS2, and the bond length in a Pd4 tetrahedron was measured to be 2.60 Å. In VS2-Pd, Pd as a Pd4 tetrahedron is pointed toward the VS2 layer, and the calculated Pd-S bond distance is 2.42 Å with some expansion of three Pd-Pd bonds (2.85 Å). From the density of states, it was confirmed that the band gap was too high for VS2 (0.2 eV; 2H phase) and was reduced to nearly zero in VS2-Pd (0.05 eV). In the electrocatalytic HER part, the obtained ΔGH values from DFT were 0.05, -0.45, and 0.22 eV for VS2/Pd4, Pd4, and VS2, respectively, which imply that VS2-Pd4 had improved HER activity compared to pristine VS2 and Pd4. A concentration-dependent study was carried out with molar ratios of Pd at 0.01, 0.05, and 0.1 M with VS2 layers. From the HER polarization study, VS2-Pd (0.05 M) showed an overpotential of 157 mV at 20 mA cm-2, which is 373 mV less than only VS2 with a Tafel slope of 75 mV dec-1 with overwhelming stability. These highly promising results will be interesting to make less active stable phases by incorporating metal NPs for efficient and stable H2 production.

V3+ Incorporated ß-Co(OH)2: A Robust and Efficient Electrocatalyst for Water Oxidation.

Catalyzing oxygen evolution reaction (OER) with the lowest possible overpotential is a key to ensure energy efficiency in the production of hydrogen from water electrochemically. In this report, we show the results that astonished us. Co hydroxide containing trivalent V was prepared chemically and screened for electrochemical water oxidation in rigorously Fe free 1 M KOH (pH 13.8). Overpotential of 198 mV at 10 mA cm-2 was observed for the synthesized Co-V hydroxide with the optimal Tafel slope of 60 mV dec-1. This is the lowest overpotential at this current density ever reported for OER in alkaline conditions while utilizing Co based electrocatalysts. Density function theory (DFT) calculations showed that the third elementary step (oxyhydroxide formation and delivery of O2) was spontaneous on V site that is bridging two adjacent Co sites which was attributed to the observed enhancement.