Tafel Slope Analyses for Homogeneous Catalytic Reactions

Multiprocessing Substrates Enhanced Ta2O5/NiCo2O4 Spinel Nanocomposites for Effective Electro-/Photocatalytic and Toxicological Effects via the Caenorhabditis elegans Model

NiCo2O4 spinel composites decorated with metal oxides (Ta2O5), reduced graphene oxide (rGO), polyaminoanthraquinone (PAAQ), and layered double hydroxide hydrotalcite (HTs) were synthesized by the hydrothermal route. The synthesized composites were characterized using X-ray powder diffraction (XRD), Brunauer-Emmett-Teller (BET), high-resolution transmission electron microscopy (HR-TEM), and X-ray photoelectron spectroscopy (XPS) analyses for structural parameters such as surface area, morphology, chemical composition, etc. The production of oxygen by the water oxidation technique is the most suitable eco-friendly method, where rGO@Ta2O5/NiCo2O4 (RTNCO) showed an efficient oxygen evolution reaction (OER) performance under 1 M KOH electrolyte. Lower Tafel slope and overpotential values of 76 mV dec-1 and 315 mV, respectively, were calculated for RTNCO. The photocatalytic degradation efficiencies calculated were MB = 97.86%, RhB = 94.75%, and AP = 96% under UV light illumination within 120 min. The degraded dye solution was tested on mung bean (Vigna radiata) plants to determine the toxicity of the dye solution after 15 days, and the results showed good seed germination similar to that in water as the control. The synthesized materials exhibited better antibacterial activity against Bacillus cereus, Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli. Interestingly, the toxicological effects of the degraded dyes and drug solutions were effectively studied in the Caenorhabditis elegans model. The overall results revealed that the synthesized composites are promising for electro-/photocatalytic and biological applications.

Tb- and Eu-doped yttrium oxyselenides as novel absorber layers for superstrate thin-film photovoltaics: improved spectral optical absorption and green-red phosphor activation

To generate and deliver alternative sustainable energy in the face of the current energy crisis, new materials that can capture solar energy and transform it into other useful energies are required. Rare-earth (RE) oxychalcogenides are now being used more frequently as up/down-conversion materials in established photovoltaic (PV) devices to boost their PV performance. Here, through an efficient microwave assisted synthesis procedure, novel nanoplate/sheet shaped nanomaterials of yttrium oxyselenide (YOSe) and its analogues doped with Tb and Eu (YOSe:Tb and YOSe:Eu) were successfully synthesized. Analyses of the structure, stability, morphology, light absorption, and electrochemistry were performed. This work showed that the parent YOSe exhibited green (543 nm) and red (615 nm) emission luminescence when doped with Tb and Eu with a luminescence quantum yield (LQY) of 0.56 and 0.53 for YOSe:Tb and YOSe:Eu nanomaterials, respectively. The surface and material conductivity of YOSe improved with the addition of the dopant elements, with the best outcome shown in YOSe:Eu, according to electrokinetic research evidenced by the enhanced current peaks, reduced charge-transfer resistance (Rct) and low impedance magnitude (Zmag) through electrochemical experiments. These improvements were induced by the distinctive properties of the dopant elements. PCEs of 0.25%, 0.67%, and 1.20% were obtained for YOSe, YOSe:Tb, and YOSe:Eu-based PV devices, respectively, using the nanomaterials as novel absorber layers in a superstrate device design. Our results can initiate further exploitation of the doped host structure for effective down-conversion NIR luminescence for applications in PV devices and to boost the PV performance of existing solar cells.

Experimentally revealed and theoretically certified synergistic electronic interaction of V-doped CoS for facilitating the oxygen evolution reaction

Since electrocatalytic oxygen evolution (OER) is a four-electron transfer reaction with very slow kinetics, there is great competition to develop cheap, durable and efficient catalysts for oxygen evolution. A molecular model is designed for density functional theory (DFT) simulation calculations to guide the experiment, and this hypothesis is fully supported by the experimental data. Herein, regulating the composition and morphology of the bimetallic VCo and MoCo sulfide and monometallic sulfide nanoparticles (NPs) at the oil-water interface was achieved via a one-step hydrothermal method for efficient and durable OER electrocatalysts. Compared to CoS and MoCoS, the VCoS NPs show superior OER performance. By adjusting the atomic composition ratio of the VCoS nanoparticles, the VCoS NPs (1 : 2 : 1.5 mole ratio) showed a significant OER overpotential η = 255 mV (10 mA cm-2), and their outstanding stability was demonstrated after 48 h of continuous testing. The CoS and MoCoS NPs were also tested for comparison. Density functional theory (DFT) calculations showed that appropriate V doping (VCoS) can heighten the density of states (DOS) of the Fermi level, which generates more charge density and reduces the intermediate adsorption energy. This study not only provides efficient and powerful integrated catalysts, but also details a DFT calculation model guided by experiments to regulate the oxygen insertion technology, thus leading to the design of ideal materials and enabling more far-reaching applications in electrocatalysis.