Electro-tuned catalysts: voltage-controlled activity selection of bimetallic exsolution particles

In this work, we show how the activity states of bimetallic Ni0-Fe0 catalysts exsolved from Nd0.6Ca0.4Fe0.97Ni0.03O3-δ (NCFNi) can be influenced electrochemically. The NCFNi parent oxide was employed in the form of thin film mixed conducting model electrodes, which were operated in a humid hydrogen atmosphere. By precisely controlling the oxygen chemical potential in the parent oxide electrode via applying an electrochemical polarisation, we managed to selectively exsolve Ni nanoparticles from the perovskite lattice and study their catalytic activity switching characteristics. To be able to track the surface chemical changes during the switching process, electrochemical polarisation experiments were combined with near ambient pressure X-ray photoelectron spectroscopy (NAP-XPS) measurements. This in situ analytical approach allowed relating the difference we observed in the switching behaviour of Ni particles here and of Fe particles in a recent study, to a different kinetic interplay between electrochemical driving force and atmosphere. We propose that slow oxygen transport through nickel oxide, located at the particle/perovskite interface, is mainly responsible for the observed difference to iron exsolutions, which becomes especially evident for larger nickel particles. In addition, in the case of bimetallic exsolutions and with applied bias voltage as a control parameter, we are able to reversibly switch between three different activity states, namely bimetallic Ni0-Fe0 (medium activity), pure Ni0 (high activity), and the inactive oxides.

Modeling and simulation of multifaceted properties of X2NaIO6 (X = Ca and Sr) double perovskite oxides for advanced technological applications

CONTEXT

In this study, the authors have investigated the structural, optoelectronic, thermoelectric, and thermodynamic properties of Ca2NaIO6 and Sr2NaIO6 double perovskite oxides. Both materials exhibit semiconductor behavior with direct band gaps (Eg) of 0.353 eV and 0.263 eV, respectively. Optical parameters like absorption coefficient α(ω), reflectivity R(ω), dielectric constants, and refractive index have been calculated. The most notable absorption peaks are identified at 5.52 eV (equal to 108.33 × 104 cm-1) in the case of Ca2NaIO6 and at 11.16 eV (equivalent to 118.17 × 104 cm-1) for Sr2NaIO6. These findings suggest a promising outlook for applications in optoelectronics. Moreover, their commendably low thermal conductivity and a high figure of merit, particularly at low temperatures (100 K), indicate their effectiveness as thermoelectric materials. This analysis underscores that these materials hold potential as suitable candidates for n-type doping, making them well-suited for use in thermoelectric devices. Studying thermal properties, including thermal expansion, bulk modulus, acoustic Debye temperature, entropy, and heat capacity, contributes to understanding the materials' thermodynamic stability. The titled materials are dynamically stable. The analysis of these double perovskite materials highlights their potential across various technological applications due to their advantageous structural, electronic, optical, and transport properties, offering new possibilities in material science and technology development.

METHODS

The study utilized the full potential linearized augmented plane wave (FP-LAPW) method in conjunction with density functional theory within the WIEN2k simulation code. This approach is widely recognized as one of the most dependable methods for evaluating the photovoltaic characteristics of semiconducting perovskites. The thermoelectric properties were ascertained using the rigid band approach and the constant scattering time approximation, both implemented in the BoltzTraP computational code.

Fabrication of Efficient Electrocatalysts for Electrochemical Water Oxidation Using Bimetallic Oxides System

The study focused on the fabrication of nickel, cobalt, and their bimetallic oxide via a facile electrodeposition approach over the surface of conducting glass has been reported here. Fabricated electrodes have been employed as binder-free and effective anode materials toward oxygen evolution reactions (OER) in electrochemical water splitting at high pH. Nickel and cobalt oxides showed overpotential values of 520 mV and 536 mV at the current density of 10 mAcm^-2 with charge transfer resistances of 170 and 195 Ω. For bimetallic oxides (NiCoO@FTO), the overpotential depressed up to 460 mV and lower charge transfer value of 80 Ω. Additionally, double-layer capacitance also boosted for the bimetallic oxide with a value of 199 μF as compared to monometallic nickel oxide (106 μF) and cobalt oxide (120 μF). Multimetal oxides of Ni-Co showed the best performance, which was further supported with larger electrochemical surface area. This facile approach toward the electrode fabrication could be a charming alternate to replace the Ru- and Ir-based expensive materials for OER in electrochemical water splitting.

Paracetamol and amoxicillin adsorptive removal from aqueous solution using phosphoric acid activated-carbon

Charcoal-based materials have attracted much attention for the removal of pharmaceutical agents. The charcoal-based carbon materials have green synthetic routes, high surface area, numerous active site with active functional groups available for physico-chemical interactions with adsorbate for surface-adsorptive removal of toxins. In this study, acid treated activated carbon was developed from the peach seeds using thermal pyrolysis approach. Phosphoric acid activated carbon (PAC) was further modified by HNO3 and employed as an adsorbent for the removal of amoxicillin and paracetamol and process variables were optimized for enhanced removal of amoxicillin and paracetamol. The adsorption of pharmaceutical agents was significantly affected by temperature, pH and reaction time. The amoxicillin and paracetamol sorption process onto PCA followed a pseudo second order kinetics and Langmuir isotherm model with a maximum removal capacity of 51.8 mg/g and 51.1 mg/g, respectively. The results revealed that acid activated carbon has promising efficiency for the removal of amoxicillin and paracetamol from aqueous medium and peach seeds derived PCA could be employed for the removal of these pharmaceutical agents from effluents and PAC is also extendable for the removal of other drugs from pharmaceutical wastewater streams.

Kinetic studies and conditions optimizations for the removal of direct red 80 dye from wastewater using cotton calyx and iron oxide composite

This study focusses on the adsorption efficiency of cotton pod (Gossypium arboreum) for biosorption of direct red (DR) 80 dye. The effect of dye concentration, pH, shaking time, adsorbent dose and temperature was considered to evaluate the adsorption efficiency of the cheapest raw material on the removal of dye. Various concentrations (10–50 ppm) were examined and maximum percentage removal of the adsorbent was obtained at pH 1 with adsorbent dose of 0.9 g and shaking time of 60 min. To enhance the adsorption efficiency of the adsorbent, the cotton calyx was treated with FeSO4.7H2O and investigated the removal of the raw adsorbent and the composite. It was examined that the removal efficiency of the composite is more than that of raw adsorbent. The composite was more efficient as dye removal reached up to 97%. FTIR of the composite shows an additional peak at 650 cm−1 for presence of Fe-O group and confirmation of composite formation. SEM micrograph showed that the particles in composite are more packed compared to the raw adsorbent. Mathematical models were applied and kinetic studies also have been done to provide better results regarding to the experimental data. It is concluded that the prepared adsorbent could be used as a tool for the removal of toxic pollutants from textile wastewater.

Adsorption kinetics for the removal of toxic Congo red dye by polyaniline and citrus leaves as effective adsorbents

This study focusses on the synthesis of polyaniline (PANI) and polyaniline base adsorbent utilizing Citrus limon leaves (CL) powder. The polyaniline base adsorbent with C. limon was synthesized using the same process as polyaniline synthesis, but with the addition of leaves powder. PANI and PANI based adsorbent with C. limon leaves powder (PANI/CL) were characterized by Fourier Transform Infra-Red (FTIR), UV-Visible spectroscopy and Scanning Electron Microscopy (SEM). This synthesized material was employed for the removal of congo red (CR) dye from industrial wastewater. Furthermore, the Langmuir, Temkin and Freundlich isotherms were also applied to evaluate experimental results. PANI is an efficient adsorbent for CR removal with 71.9 mg/g, while PANI/CL is an efficient adsorbent with 80 mg/g removal of dye according to a comparison of maximal adsorption capabilities. The data concludes that the prepared adsorbents could possibly be employed for the removal of toxic dyes from industrial effluents at large scale and ultimately could help in improving the environment.

Microwave assisted green synthesis of ZnO nanoparticles using Rumex dentatus leaf extract: photocatalytic and antibacterial potential evaluation

In the present study, biological method was opted to synthesize ZnO NPs from Rumex dentatus plant. 0.1 M solution of zinc nitrate hexahydrate is mixed with the aqueous solution of R. dentatus plant leaves extract. The proportion of each solution was 1:1. Extract of plant leaves act as reducing agent. Firstly, the color changed from dark green to brown was observed and precipitates of light brown color appeared. Characterization of produced ZnO NPs was done using UV–Visible spectroscopy, scanning electron microscopy (SEM), energy dispersive X-rays (EDX) and X-ray diffraction (XRD) spectroscopy. The prepared ZnO NPS shows maximum absorption at 373 nm, in UV–Visible range. The shape of synthesized ZnO NPs is displayed by SEM. XRD analysis explains the average size of NPs is 6.19 nm. EDX tells about the percentage composition of synthesized ZnO NPs. Antibacterial analysis declared the NPs as good antibacterial agents. Photocatalytic activity of ZnO NPs was done using methyl orange dye. It was concluded that ZnO NPs can degrade toxic pollutants especially dyes.

Catalytic degradation of MO and MB dyes under solar and UV light irradiation using ZnO fabricated using Syzygium Cumini leaf extract

Zinc oxide nanoparticles (ZnO NPs) were fabricated using Syzygium cumini leave extract as a reducing and capping agent. The ZnO NPs were characterized using various techniques including scanning electron microscopy, UV-Visible and energy dispersive X-ray (EDX) techniques. The ZnO nanoparticles size was in 0.2–1 µm range and spherical in shape. Photocatalytic efficiency of ZnO NPs for the removal of MB (methylene blue) and MO (methyl orange) was investigated under solar and UV light expire. Photocatalytic efficiency of ZnO NPs was promising, which was found to be high under UV irradiation versus solar light. The ZnO NPs was confirmed as appropriate photocatalytic agent with significant potential for the removal of dye from wastewater.

Cephradine drug release using electrospun chitosan nanofibers incorporated with halloysite nanoclay

The chitosan/polyvinyl alcohol/halloysite nanoclay (CS/PVA/HNC) loaded with cephradine drug electrospun nanofibers (NFs) were fabricated and characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA) techniques. FTIR analysis confirmed the hydrogen bonding between the polymer chain and the developed siloxane linkages. SEM analysis revealed the formation of uniform NFs having beads free and smooth surface with an average diameter in 50–200 nm range. The thermal stability of the NFs was increased by increasing the HNC concentration. The antimicrobial activity was examined against Escherichia  coli and staphylococcus strains and the NFs revealed auspicious antimicrobial potential. The drug release was studied at pH 7.4 (in PBS) at 37 °C. The drug release analysis showed that 90% of the drug was released from NFs in 2 h and 40 min. Hence, the prepared NFs could be used as a potential drug carrier and release in a control manner for biomedical application.

Highly photosensitized Mg4 Si6O15 (OH)2·6H2O@guar gum nanofibers for the removal of methylene blue under solar light irradiation

In the present investigation, photosensitized nanofibers (NFs) based on guar gum (GG)/poly(vinyl alcohol) (PVA)/Mg4Si6O15(OH)2·6H2O (SP) (modified by 1, 4-diamminobutane [DAB]) was fabricated by electrospinning approach and same was used for the degradation of dye under solar light irradiation. For electrospinning of NFs, the acceleration voltage, nozzle flow rate and collector distance levels of 19,000 KV, 0.5 mL/h and 3 cm were optimum conditions along with 7% (w/v) blend of GG/PVA (1.4:5.6 wt/wt) and 0.01 g modified Mg4Si6O15(OH)2·6H2O. The exfoliation, intercalation and clay organophilization in GG/PVA/Mg4Si6O15(OH)2·6H2O (GG/PVA/SP) NFs were examined by FTIR analysis. The photocatalytic activity (PCA) of NF was studied under the solar light irradiation for methylene blue (MB) dye degradation. The photosensitized GG/PVA/SP2 (G3) showed promising PCA under visible light and G3 furnished higher degradation of MB dye (99.1%) within 10 min of irradiation. Results revealed that GG/PVA/SP based NFs are highly active under solar light, which can be applied for the treatment of wastewater.