Co-sensitization effect of N719 dye with Cu doped CdS colloidal nanoparticles for dye sensitized solar cells

This is the final version. Available on open access from Elsevier via the DOI in this recordData availability: Data will be made available on request.Dye-sensitized solar cell’s (DSSC) performances are enhanced by engineering the materials at the interface of various device components owing to easy and inexpensive fabrication steps. Ru (II) polypyridyl-based synthetic dyes are the most widely used photosensitizers for DSSCs due to their superior molar extinction coefficient and facile interaction with metal oxide electrodes. However, these dyes are mostly expensive, and as a result, natural dyes and metal-free organic dyes have become an alternative way for sensitization to reduce the significant drawbacks of synthetic dyes. In this study, minimizing the usage of the N719 dye can be performed through an alternative method for better light-harvesting through supreme optical interfacial interaction with colloidal Cu-doped CdS as a co-sensitizer in a facile approach. This co-sensitization signifies the colloidal CdS (donor), which can corroborate the energy transfer mechanism with the N719 dye (acceptor). The introduction of Cu causes extreme tuning of broad absorption to near-infrared for CdS, enhancing the solar light harvesting entrapment followed by extensive optical interaction with N719 dye. This accelerates the activity of the sensitizers for light absorption enhancement and expects a better performance of DSSC compared to traditional sensitization. A massive improvement in photocurrent density (∼42 %) was observed without sacrificing other photovoltaic parameters, as observed for TiO2-based photoanodes. The sensitizer’s interfacial optical energy transfer process, unless excited electron recombination, may indirectly be used as an excitation source of the acceptor and minimizes the recombination energy loss.Engineering and Physical Sciences Research Council (EPSRC)British Counci

Role of vanadium ions substitution on spinel MnCo2O4 towards enhanced electrocatalytic activity for hydrogen generation

This is the final version. Available on open access from Nature Research via the DOI in this recordData availability: The datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request.Improving efficient electrocatalysts (ECs) for hydrogen generation through water splitting is of significant interest in tackling the upcoming energy crisis. Sustainable hydrogen generation is the primary prerequisite to realizing the future hydrogen economy. This work examines the electrocatalytic activity of hydrothermally prepared vanadium doped MnCo spinel oxide microspheres (MC), MnVxCo2−xO4 (Vx-MnCo MC, where x ≤ 0.4) in the HER (hydrogen evolution reaction) process. Magnetization measurements demonstrated a paramagnetic (at high temperatures) to a ferrimagnetic (at low temperatures) transition below the Curie temperature (Tc) in all the samples. The magnetization is found to intensify with the rising vanadium content of MCs. The optimized catalyst Vx-MnCo MCs (x = 0.3) outperformed other prepared ECs with a Tafel slope of 84 mV/dec, a low onset potential of 78.9 mV, and a low overpotential of 85.9 mV at a current density of 10 mA/cm2, respectively. The significantly improved HER performance of hydrothermally synthesized Vx-MnCo MCs (x = 0.3) is principally attributable to many exposed active sites, accelerated electron transport at the EC/electrolyte interface, and remarkable electron spectroscopy for chemical analysis (ECSA) value was found ~ 11.4 cm2. Moreover, the Vx-MnCo MCs (x = 0.3) electrode exhibited outstanding electrocatalytic stability after exposure to 1000 cyclic voltametric cycles and 36 h of chronoamperometric testing. Our results suggest a feasible route for developing earth-abundant transition metal oxide-based EC as a superior electrode for future water electrolysis applications.British CouncilKACARE Fellowshi

Forming limit diagram and void coalescence analysis of AA5052 coated with molybdenum-based ceramic nanocomposites

Aluminium 5052 alloy sheets of size 75 � 25 mm and 3 mm thickness with double edge semicircular notches of diameter from 2–8 mm have been coated with MoSi2–SiC nanocomposite coatings by sputtering process. The structural morphology of the ceramic coatings was explored by Fourier Transform Infrared (FT-IR) spectroscopy, X-ray Diffraction (XRD) analysis, Scanning Electron Microscopy (SEM), and Atomic Force Microscopy (AFM). The coated and uncoated sheet samples were subjected to tension–compression state of strain up to fracture by varying the notch sizes using INSTRON Universal Testing Machine (UTM). Fracture behaviour studies of the sheets were performed and forming limit diagram (FLD) was drawn. The void coalescence analysis was also carried out by using SEM images and the effect of coating behaviour of combined forming and fracture were analyzed. In the coated sheet, the L/W ratio was very close to 1.0. Thus, no oblate/prolate voids were observed and the heat generated during deformation was retained for longer time and thereby adiabatic shear band formation has occurred with increased formability

Effective Hydrogen Production from Alkaline and Natural Seawater using WO3-x@CdS1-x Nanocomposites-based Electrocatalyst

This is the author accepted manuscript.Offshore hydrogen production through water electrolysis presents significant technical and economic challenges. Achieving efficient hydrogen evolution reaction (HER) in alkaline and natural seawater environments remains daunting due to the sluggish kinetics of water dissociation. We synthesized electrocatalytic WO3-x@CdS1-x nanocomposites (WCSNCs) using ultrasonic-assisted laser irradiation to address this issue. The synthesized WCSNCs with varying CdS content were thoroughly characterized to investigate their structural, morphological, and electrochemical properties. Among the samples tested, the WCSNCs with 20 wt.% CdS1-x in WO3-x (Wx@Sx-20%) exhibited superior electrocatalytic performance for hydrogen evolution in a 1 M KOH solution. Specifically, the Wx@Sx-20% catalyst demonstrated an overpotential of 0.191 V at a current density of -10 mA/cm2 and a Tafel slope of 61.9 mV/dec. The Wx@Sx-20% catalysts exhibited excellent stability and durability even after 24 hours and 1000 CV cycles. Notably, when subjected to natural seawater electrolysis, the Wx@Sx-20% catalysts outperformed in electrocatalytic HER activity and stability. The remarkable performance enhancement of the prepared electrocatalyst can be attributed to the combined effect of sulphur vacancies in CdS1-x and oxygen vacancies in WO3-x. These vacancies promote the electrochemically active surface area, enhance the rate of charge separation and transfer, increase the number of electrocatalytic active sites, and accelerate the HER process in alkaline and natural seawater environments.UK-Saudi Challenge Fund program 2022British CouncilKing Fahd University of Petroleum and Minerals, Dhahran, Saudi ArabiaK.A. CAR

Se-doped magnetic Co-Ni spinel ferrite nanoparticles as electrochemical catalysts for hydrogen evolution

This is the author accepted manuscriptData availability: The datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request.The magnetic Co0.5Ni0.5Fe2O4 spinel ferrites (NSFs) with various (x%) Se (x = 0.00 - 0.20) were synthesized via the sol-gel combustion route in conjunction with an advanced green laser ablation method. The structure and morphology of NSFs were explored through various physicochemical techniques. Interestingly, Se doping has a crucial impact on NSFs’ magnetic properties. While, at room temperature, the pristine sample exhibits a superparamagnetic-like behavior. While the pristine sample and all doped CoNi NSFs + x% Se (x = 0.05 - 0.20) samples exhibited a high value of coercivity and remanence at 10 K, indicating their hard magnetic properties. Our findings indicate that Se can be harnessed to tune the magnetic properties of CoNiFe2O4 structures. In addition, improving effective electrocatalysts for hydrogen evolution reaction (HER) efficiency through water-splitting is also vital to overcome the impending energy crisis due to the rapid depletion of fossil fuels and their injurious impact on the environment. Hence, the optimized ideal catalysts CoNi NSFs + x% Se (x=0.15) were developed, which outperformed as electrocatalysts for HER with a Tafel slope of 91 mV/dec and a very low overpotential of 173.5 mV at a current density of 10 mA/cm2 , which could be attributed to a large number of electrochemically active surface area (5.2 cm2 ), accelerated electron mobility at the electrocatalysts/electrolyte interface, and long-term stability.British Council (Government)King Fahd University of Petroleum and MineralsKing Fahd University of Petroleum and Mineral

Two independent and primitive envelopes of the bilobate nucleus of comet 67P

International audienceThe factors shaping cometary nuclei are still largely unknown, but could be the result of concurrent effects of evolutionary and primordial processes. The peculiar bilobed shape of comet 67P/Churyumov-Gerasimenko may be the result of the fusion of two objects that were once separate or the result of a localized excavation by outgassing at the interface between the two lobes. Here we report that the comet's major lobe is enveloped by a nearly continuous set of strata, up to 650 metres thick, which are independent of an analogous stratified envelope on the minor lobe. Gravity vectors computed for the two lobes separately are closer to perpendicular to the strata than those calculated for the entire nucleus and adjacent to the neck separating the two lobes. Therefore comet 67P/Churyumov-Gerasimenko is an accreted body of two distinct objects with `onion-like' stratification, which formed before they merged. We conclude that gentle, low-velocity collisions occurred between two fully formed kilometre-sized cometesimals in the early stages of the Solar System. The notable structural similarities between the two lobes of comet 67P/Churyumov-Gerasimenko indicate that the early-forming cometesimals experienced similar primordial stratified accretion, even though they formed independently

Large heterogeneities in comet 67P as revealed by active pits from sinkhole collapse

Pits have been observed on many cometary nuclei mapped by spacecraft1,2,3,4. It has been argued that cometary pits are a signature of endogenic activity, rather than impact craters such as those on planetary and asteroid surfaces. Impact experiments5,6 and models7,8 cannot reproduce the shapes of most of the observed cometary pits, and the predicted collision rates imply that few of the pits are related to impacts8,9. Alternative mechanisms like explosive activity10 have been suggested, but the driving process remains unknown. Here we report that pits on comet 67P/Churyumov–Gerasimenko are active, and probably created by a sinkhole process, possibly accompanied by outbursts. We argue that after formation, pits expand slowly in diameter, owing to sublimation-driven retreat of the walls. Therefore, pits characterize how eroded the surface is: a fresh cometary surface will have a ragged structure with many pits, while an evolved surface will look smoother. The size and spatial distribution of pits imply that large heterogeneities exist in the physical, structural or compositional properties of the first few hundred metres below the current nucleus surface