Facile Solvothermal Synthesis of CuCo₂S₄ Yolk-Shells and Their Visible-Light-Driven Photocatalytic Properties

In this present work, we synthesized a yolk-shell shaped CuCo2S4 by a simple anion exchange method. The morphological and structural properties of the as-synthesized sample were characterized using X-ray diffraction (XRD), UV-vis diffuse reflectance spectra (UV-vis DRS), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The SEM and TEM results confirmed that the uniform yolk-shell structure was formed during the solvothermal process. The band gap was about 1.41 eV, which have been confirmed by UV⁻vis DRS analysis. The photocatalytic property was evaluated by the photocatalytic degradation of methylene blue (MB) dye as a target pollutant under the visible-light irradiation. The experimental results confirmed the potential application of yolk-shell shape CuCo2S4 in visible-light photocatalytic applications

Hexamethonium Bis(Tribromide) (HMBTB) a recyclable and high bromine containing reagent

A recyclable and high bromine containing di-(tribromide) reagent, Hexamethonium Bis(Tribromide) (HMBTB) has been synthesized and utilized for the bromination of various organic substrates. The spent reagent Hexamethonium Bromide (HMB) can be effectively recycled by regenerating and reusing it without significant loss of activity. The crystalline and stable bis(tribromide) is an effective storehouse of very high percentage of active bromine requiring just half an equivalent of it for complete bromination. Both the Br₃⁻ moieties in HMBTB are nearly linear with Br–Br–Br angle of 179.55°

Synthesis of yttrium doped BiOF/RGO composite for visible light: Photocatalytic applications

In this present work, yttrium doped bismuth oxy fluoride/reduced graphene oxide (Y-BiOF/RGO) composite was synthesized using a simple solvothermal method. As synthesized composite was characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), UV–Vis diffuse reflectance spectroscopy (DRS), photoluminescence spectroscopy (PL), field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) techniques. The photocatalytic property was evaluated towards the degradation of methylene blue (MB) dye under the visible-light irradiation. The characterization results highlighted that the efficient incorporation of both yttrium ions and RGO greatly reduced the recombination rate of BiOF and extended the visible-light absorption ability. As synergistic effects, the prepared Y-BiOF/RGO composite exhibited maximum degradation rate of 98% in 360 min, which is 6.5 times higher than pure BiOF. The clear mechanism for the enhanced photo-activity by Y-BiOF/RGO was discussed. Keywords: BiOF, Graphene, Yttrium, Semiconductors, Visible light, Photocatalyst

Morphologically controlled cobalt oxide nanoparticles for efficient oxygen evolution reaction

Electrochemical water oxidation is one of the thrust areas of research today in solving energy and environmental issues. The morphological control in the synthesis of nanomaterials plays a crucial role in designing efficient electrocatalyst. In general, various synthetic parameters can direct the morphology of nanomaterials and often this is the main driving force for the electrocatalyst in tuning the rate of the oxygen evolution reaction (OER) for the electrochemical water-splitting. Here, a facile and cost-effective synthesis of spinel cobalt oxides (CoO) via a one-pot hydrothermal pathway with tunable morphology has been demonstrated. Different kinds of morphologies have been obtained by systematically varying the reaction time i.e. nanospheres, hexagon and nanocubes. Their catalytic activity has been explored towards OER in 1.0 M alkaline KOH solution. The catalyst CoO-24 h nanoparticles synthesized in 24 h reaction time shows the lowest overpotential (η) value of 296 mV at 10 mA cm current density, in comparison to that of other as-prepared catalysts i.e. CoO-pH9 (311 mV), CoO-12 h (337 mV), and CoO-6 h (342 mV) with reference to commercially available IrO (415 mV). Moreover, CoO-24 h sample shows the outstanding electrochemical stability up to 25 h time

Novel porous metal phosphonates as efficient electrocatalysts for the oxygen evolution reaction

Recently, metal-doped organic-inorganic hybrid nanomaterials have attracted substantial attention for their high catalytic activity in the electrochemical oxygen evolution reaction (OER). Here, we report three novel porous metal phosphonates, cobalt phosphonate (CoPIm), nickel phosphonate (NiPIm), and nickel-cobalt phosphonate (NiCoPIm), using iminodi(methylphosphonic acid) as an organophosphorous precursor via a hydrothermal nontemplated synthetic route. All three materials have been explored as electrocatalysts for the OER. Notably, the CoPIm material exhibits excellent electrocatalytic behavior among all of the as-prepared catalysts. The high surface area and the formation of active CoOOH species on the catalyst surface during the OER process are the main driving force for a superior electrochemical OER. The CoPIm catalyst requires a very small overpotential (334 mV) to reach the current density of 10 mA cm in 1.0 M KOH solution with a Tafel slope of 58.6 mV dec as compared to NiPIm, NiCoPIm, and commercial IrO. Additionally, the prepared CoPIm catalyst shows excellent stability up to 25 h, suggesting its potential in electrochemical water splitting

Utilization of Biowaste-derived Catalyst for Biodiesel Production: Process Optimization Using Response Surface Methodology and Particle Swarm Optimization Method

In this experimental and optimization study, banana (Musa acuminata) flower petals ash has been considered as an effective catalyst in the room temperature (28 °C) assisted transesterification to produce biodiesel from waste cooking oil (WCO). The transformation of Musa acuminata flower petals to ash catalyst has been performed by simple conventional open-air burning process. Three important parameters (catalyst concentration, methanol/oil (M/O) molar ratio and time) that play significant role in conversion of WCO to waste cooking methyl ester (WCME) were investigated. In order to maximize the conversion rate these key transesterification parameters were optimized using central composite rotatable design (CCRD) of response surface methodology (RSM). A metaheuristic algorithm popularly known as Particle swarm algorithm (PSO) has been used to observe a clear picture of the global optimum points scattered around the search domain. PSO has also been used to validate the results obtained from CCRD. The chemical composition and morphology of ash catalyst has been investigated using several analytical techniques such as X-Ray Diffraction (XRD), Fourier Transformation Infrared Spectroscopy (FTIR), X-Ray Fluorescence Spectroscopy (XRF), X-ray Photoelectron Spectroscopy (XPS), Thermal Gravimetric Analysis (TGA), Energy Dispersive Spectroscopy (EDS), Brunauer-Emmett-Teller (BET), Scanning Electron Microscope (SEM), Transmission Electron Microscope (TEM) and Hammett Indicator method. It was observed that the catalyst remained active till 4th reaction cycle. The catalyst’s reusability, renewability and robust activity in the reaction makes it efficient, economic, green and industrially applicable

Microporous nickel phosphonate derived heteroatom doped nickel oxide and nickel phosphide: Efficient electrocatalysts for oxygen evolution reaction

Designing low-cost and highly efficient electrocatalysts based on widely abundant elements is highly desirable for future green energy production. Transition metal oxides and phosphides have recently been demonstrated to be promising and cost-effective electrocatalysts due to their distinct surface properties and good conductivity. Herein, we have synthesized a new microporous organic-inorganic hybrid nickel phosphonate (NiPPA) material under hydrothermal reaction condition without the use of structure directing agent. The microporous NiPPA material can be converted to N, P-codoped nickel oxide (NP/NiO) and N, O-codoped nickel phosphide (NO/NiP) following pyrolysis under air and nitrogen atmospheres, respectively. These high surface area materials are subsequently explored as electrocatalysts towards oxygen evolution reaction (OER) in alkaline media. Among the three catalysts, NP/NiO exhibits the highest electrocatalytic activity for OER with an overpotential of 332 mV to reach a current density of 10 mA cm and a low Tafel slope of 65.6 mV dec in 1.0 M KOH solution. Furthermore, the as-prepared NP/NiO catalyst displays an outstanding stability over a period of 15 h, suggesting the high durability of this catalyst for OER