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In this work, a first-principles systematic study of (Pt3Cu)n, n = 1–9, clusters was performed employing the linear combination of Gaussian-type orbital auxiliary density functional theory approach. The growth of the clusters has been achieved by increasing the previous cluster by one Pt3Cu unit at a time. To explore in detail the potential energy surface of these clusters, initial structures were obtained from Born–Oppenheimer molecular dynamics trajectories generated at different temperatures and spin multiplicities. For each cluster size, several dozens of structures were optimized without any constraints. The most stable structures were characterized by frequency analysis calculations. This study demonstrates that the obtained most stable structures prefer low spin multiplicities. To gain insight into the growing pattern of these systems, average bond lengths were calculated for the lowest stable structures. This work reveals that the Cu atoms prefer to be together and to localize inside the cluster structures. Moreover, these systems tend to form octahedra moieties in the size range of n going from 4 to 9 Pt3Cu units. Magnetic moment per atom and spin density plots were obtained for the neutral, cationic, and anionic ground state structures. Dissociation energies, ionization potential, and electron affinity were calculated, too. The dissociation energy and the electron affinity increase as the number of Pt3Cu units grows, whereas the ionization potential decreases. [ABSTRACT FROM AUTHOR]

In this work, recent research progresses in the formation of Pt3Cu nanoparticles onto the surface of graphene are described, and the obtained results are contrasted with previously published theoretical studies. To form these nanoparticles, tetrabutylammonium hexachloroplatinate, and copper acetylacetonate are used as platinum and copper precursors, respectively. Oleylamine is used as a reductor and a solvent. The obtained catalyst is characterized via X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and energy dispersive spectroscopy X-ray (EDS). To assess the catalytic activity, the graphene-supported Pt3Cu material is tested with cyclic voltammetry, "CO stripping", and oxygen reduction reaction potentiodynamic curves to find the nature and the intrinsic electrochemical activity of the material. It can be observed that the tetrabutylammonium cation plays a critical role in anchoring and supporting nanoparticles over graphene, from which a broad discussion about the true nature of the anchoring mechanism was derived. The growth mechanism of the nanoparticles on the surface of graphene was observed, supporting the conducted theoretical models. With this study, a reliable, versatile, and efficient synthesis of nanocatalysts is presented, demonstrating the potentiality of Pt3Cu/graphene as an effective cathode catalyst. This study demonstrates the importance of reliable ab inito theoretical results as a useful source of information for the synthesis of the Pt3Cu alloy system. [ABSTRACT FROM AUTHOR]

A first-principle study of (Pt 3 Cu) n n = 10–11 nanoclusters was performed using the linear combination of Gaussian-type orbitals within the auxiliary density functional theory (ADFT) framework. Neutral, anionic and cationic clusters species were studied. To carry on a detailed exploration of the potential energy surface of these systems, Born-Oppenheimer molecular dynamics (BOMD) simulations have been performed. Several dozens of structures were taken along the generated BOMD trajectories as initial geometries for geometry optimizations. Successive geometry optimizations of these systems, in different electron spin multiplicities and without any type of restriction, were computed. The obtained optimized structures have been characterized by frequency analysis calculations. Computed minima structures, harmonic frequencies, average bond lengths, magnetic moments, spin density plots, dissociation energy, ionization potential and electron affinity are reported. The formation of octahedra moieties has been observed in the most stable structures. The findings of the growing pattern of these clusters can serve as guide to search a synthetic route that can yield nanoparticles with desired geometries and high stability. [ABSTRACT FROM AUTHOR]

Population growth increases the challenge of meeting basic human needs, such as water, a limited resource. Consumption habits and water pollution have compromised natural resources to unsustainable levels. Sustainable effluent treatment practices, such as decentralized systems focused on energy, nutrients, and water recovery, have attracted the attention of the scientific community. Human urine (HU) is a physiological liquid waste whose main component is water (~95%). HU has a significant amount of nutrients, such as N, P, K, and organic matter, which are usually lacking in fecal coliforms. Therefore, the possibility exists of recovering nutrients and energy from HU using sustainable and non-sustainable technologies. Treating HU in bioelectrochemical systems (BES) is a novel alternative to obtaining byproducts from this effluent more sustainably than in electrochemical systems. Microbial fuel cells (MFCs) are an interesting example, contributing to HU revalorization from unwanted waste into a valuable resource of nutrients, energy, and water. Even when urine-operated MFCs have not generated attractive potential outputs or produced considerable amounts of bioelectricity, this review emphasizes HU advantages as nutrients or water sources. The aim of this review was to analyze the current development of BES for HU treatment based on the water circular economy, discussing challenges and perspectives researchers might encounter. [ABSTRACT FROM AUTHOR]

Climate change, urbanization, and population growth, particularly in urban areas such as Acapulco, Mexico, put pressure on water availability, where although surrounded by water, the inhabitants lack enough good-quality water, especially in the rainy season. In addition, water scarcity, socioeconomic factors, and infrastructure problems limit the satisfaction of water demand in this context, e.g., operational issues in the water treatment plants and problems in the distribution network caused by hurricanes. The objectives of this research were: (i) to determine the rainwater quality in Acapulco, Mexico; (ii) to propose a domestic water efficiency retrofit (WER) design implementing a rainwater harvesting system (RWHS); and (iii) to determine the RWHS efficiency in terms of economic savings, considering rainwater's social acceptance for domestic consumptive uses. The WER design was developed in an SFH in Acapulco, Mexico. The RWHS catchment surface area was 29 m2. The device comprises a first-rain separator (20 L) and a storage tank (1200 L). The rainwater harvesting potential (RWHP) was evaluated during the 2020 and 2021 rainy seasons, whereas the harvested rainwater quality (HRWQ) was analyzed in samples from 2021. Alkalinity, pH, electrical conductivity, total dissolved solids, chlorides, nitrates, sulfates, and heavy metals and potentially toxic metalloids were analyzed. Additionally, 168 surveys were applied to SFH owners to evaluate WER acceptance. Results showed that the RWHP was ca. 44 and 21 L/m2 in 2020 and 2021, respectively. All the rainwater quality parameters met the World Health Organization guidelines for consumptive uses except for drinking water. The perception study showed a 95% willingness to adopt the WER. Due to the RWHP and the HRWQ, the WER of SFHs is a promising solution to address Acapulco hydric stress under the nature-based solutions approach. [ABSTRACT FROM AUTHOR]

To evaluate supports' effects on catalytic activity toward the oxygen reduction reaction (ORR), a simple and controlled chemical synthesis, involving the hot injection of metal precursors, was developed to produce bimetallic PtNi nanoparticles (75 wt.% Pt and 25 wt.% Ni), supported on carbon nanotubes (CNTs) and carbon nanofibers (CNFs). The synthesized electrocatalyst was characterized using X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS), and scanning transmission electron microscopy (STEM). To determine the catalytic activity, an electrochemical evaluation of the synthesized catalysts in an acidic medium was performed using cyclic voltammetry (CV), CO stripping, and rotating disk electrode (RDE) tests. The presence of Pt and Ni in the nanoparticles was confirmed by EDS and XRD. Based on the STEM micrographs, the average particle size was 30 nm. Compared to the commercial Pt/C catalyst, the PtNi/CNT catalyst exhibited higher specific activity and slightly lower mass activity toward ORR in a 0.1 M HClO4 electrolyte solution. [ABSTRACT FROM AUTHOR]

In this work, the growth behavior, structures, energetic and magnetic properties of Co n Pd n and Ni n Pd n (n = 1–10) clusters were investigated employing auxiliary density functional theory (ADFT). Initial geometries for successive optimization were extracted from Born–Oppenheimer molecular dynamics (BOMD) trajectories. It is demonstrated that when the cluster size increases, the Co and Ni atoms became shrouded by Pd atoms, leading to the initial formation of M@Pd (M = Co and Ni) core–shell structures. The spin multiplicities of the Co n Pd n and Ni n Pd n (n = 1–10) clusters increase with cluster size. The CoPd clusters exhibit higher spin multiplicity and are characterized by higher spin magnetic moments than the NiPd counterparts. This study reveals that the spin density distributions are located on the Co and Ni atoms in the respective clusters. As the cluster size increases both systems tend to donate more easily electrons and the binding energies per atom grows monotonically. [ABSTRACT FROM AUTHOR]

Very recently, several successful enzymatic processes performed with mechanical activation have been disclosed; that is, despite the mechanical stress caused by High‐Speed Ball‐Milling, immobilized enzymes can retain activity. In the present study, the effect of thermal and mechanical stress was examined as potential inducers of enzymatic denaturation, when using either free, immobilized, or ground immobilized enzyme. The recorded observations show a remarkable stability of ground immobilized enzyme. Moreover, ground biocatalyst turns out to exhibit an increase of one order of magnitude in the efficiency of the catalytic process, maintaining excellent enantiodiscrimination, without significant activity loss even after four milling cycles. These observations rule out enzyme inactivation as direct consequence of the milling process. Additionally, boosted enzyme efficiency was used to optimize a relatively inefficient chiral amine resolution reaction, achieving a 25 % faster biotransformation (in 45 min) and yielding essentially enantiopure products (ee>99%, E>500). [ABSTRACT FROM AUTHOR]

Polymeric carbon nitride was synthesized from urea and doped with Cu and Fe to act as co-catalysts. The material doped with Fe was a new composite material composed of Fe(III) oxides (acting as a co-catalyst) wrapped by the polymer layers and amorphous carbon. Furthermore, the copper doped material was described in a previous report. The photocatalytic degradation of the azo dye direct blue 1 (DB) was studied using as photocatalysts: pure carbon nitride (CN), carbon nitride doped with Cu (CN-Cu) and carbon nitride doped with Fe (CN-Fe). The catalysts were characterized by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), by X-ray photoelectron spectroscopy (XPS) and Brunauer–Emmett–Teller method (BET), etc. The adsorption phenomenon was studied using the Langmuir and Freundlich models. For the kinetic study, a solution of 500 mg L−1of DB1 was treated with each catalyst, visible light and H2O2. The dye concentration was measured by spectrophotometry at the wavelength of 565 nm, and the removal of the total organic content (TOC) was quantified. BET analysis yielded surface areas of 60.029, 20.116 and 70.662 m2g−1for CN, CN-Cu and CN-Fe, respectively. The kinetics of degradation were pseudo-first order, whose constants were 0.093, 0.039 and 0.110 min−1for CN, CN-Cu and CN-Fe, respectively. The total organic carbon (TOC) removal reached the highest value of 14.46% with CN-Fe. [ABSTRACT FROM AUTHOR]

A first-principle investigation of structures and properties of NiPd (n=1-5) clusters is presented. For this study, the linear combination of Gaussian-type orbitals auxiliary density functional theory (LCGTO-ADFT) method has been employed. In order to determine the lowest energy structures, several isomers in different spin multiplicities were studied, for each cluster size. Initial structures, for which successive geometry optimization was computed without any constrain, were taken along Born-Oppenheimer molecular dynamics (BOMD) trajectories. To discriminate between minima and transition state structures, harmonic frequency analyses were performed at the optimized structures. Ground state structures, bond lengths, harmonic frequencies, dissociation energy, ionization potential, electron affinity and spin density plots are presented. This work demonstrates, that the Pd atoms prefer to allocate on the surface of the cluster structures whose core is formed by the 3d TM atoms type. Moreover, it has been observed that the ground-state structure spin multiplicity increases as the system size grows. The results of this study contribute to gain insight into how structures and energy properties change with cluster size in bimetallic Pd-based alloys. [ABSTRACT FROM AUTHOR]

The emulsion/internal gelation method is highly effective to produce microcapsules ofBacillus thuringiensis(Bt) in a short time; however, it has the limitation to produce microcapsules within a wide range of diameters (1–1000 µm). The aim of this study was to reduce the range of small microcapsule diameters by using a water/corn-oil (W/CO) micro-emulsion as the dispersing medium and the mixture Tween 80–Span 80 as the surfactant. It involved the development of the W/CO micro-emulsion and the determination of the suitable agitation time to disperse the gelling medium (sodium alginate) through the micro-emulsion. A micro-emulsion formulation that allowed reduction of the microcapsule diameter was composed of 82% corn oil, 12% alginate solution and 6% surfactant mixture Tween80–Span80 (31:69). Evaluation of four dispersing times showed that 45 min was suitable to produce 75% of microcapsules of an average diameter of 3.1 ± 1 µm containing the spore–protein complex (SPC) produced byBt. Bioassays carried out at low concentrations of microencapsulated formulations of cry proteins allowed determination of how its insecticidal effect increased if the range of microcapsule diameters was reduced in the range 1–9 µm. Furthermore, the SPC formulation in alginate microcapsules showed high resistance to extreme irradiation (2.9 ± 0.5 × 108erg) of a long wavelength (365 nm), which made the microencapsulated formulation profitable and of high yield since repeated applications of the biopesticide during the same harvest period may not be necessary. [ABSTRACT FROM PUBLISHER]

A complex of copper sulfate was formed by impregnation of the cyanuric acid melamine adduct (CAM) with a solution of copper (II) sulfate. A thermal treatment at 250°C of the dried compound delivered a greenish powder. The UV-Vis spectroscopy showed that an absorption around 700 nm is compatible with a copper (II) sulfate complex coordinated inside the supramolecular structure of CAM. No copper or copper oxide particles were found by means of either transmission or scanning electron microscopy. X-ray photoelectron spectroscopy showed that on the surface there was a considerable amount of Cu(I) (66%) probably coordinated also inside the CAM channels. A brief catalytic test showed the ability of the copper complexes to oxidize sucrose to gluconic acid. [ABSTRACT FROM PUBLISHER]

Polymeric carbon nitride doped with copper through a solid-state reaction was characterized by several techniques, among them are UV-visible spectroscopy, infrared spectroscopy, X-ray photoelectron spectroscopy, etc. The material is a semiconductor with a wide band gap of 2.74 eV. Sites of both Cu(I) and Cu(II) were detected, apparently only coordinated by the polymer. The material comprises crumpled nanosheets, and is substantially an amorphous layered material with a prevalent 2D structure with low inter-planar interactions, as shown by X-ray diffractometry and TeraHertz spectroscopy. Photo-oxidation of benzyl alcohol was used to probe the active sites of the material, comparing them with the non-doped material. The higher activity and selectivity toward salicylic alcohol of the non-doped material can be due to both a more localized electron transfer and a longer lifetime of the hole–electron pair. Cu-CN favored the oxidation of hydroxymethyl group. Therefore, the presence of copper can favor different reaction pathways with respect to the non-doped material. [ABSTRACT FROM PUBLISHER]

The purpose of this research was to evaluate the biodegradation of lindane with simultaneous electricity generation in an electrobiochemical slurry reactor (EBCR). The EBCR was inoculated with a sulfate reducing inoculum acclimated to lindane, further characterized, and batch operated for 30 day at room temperature. No external carbon source and supplementation with a stock solution of sucrose: sodium acetate: lactate was performed in experiments with soil concentrations 66% and 33%, respectively. Electrochemical impedance characterization of the EBCR (concentration of soil was 66%) showed that the equivalent circuit had a high anodic resistance R1=2064Ω, cathodic resistance R3 = 192 Ω, and electrolyte/membrane resistance R2 = 7Ω, totaling a high overall internal resistance Rint of 2263 Ù. During the batch operation, the EBCR showed a 30% lindane removal efficiency along with a maximum volumetric power of 165 mW m-3. The organic matter removal was very high (72% as soluble COD, NOM) whereas the coulombic efficiency was low (5.4%). In the experiment where the concentration of soil was 66% both cell characteristics and performance significantly improved. The internal resistance as determined by polarization curve was 102 Ω when the two-electrode sets were connected in parallel. During the batch operation, the EBCR showed a 78% lindane removal, a maximum power of 634 mW m-3, the organic matter removal was 76%, and coulombic efficiency of 15%. Therefore, it can be concluded that the EBCR exhibited a high lindane removal capability and holds promise for bioremediation of soils with the bonus of electricity generation. [ABSTRACT FROM AUTHOR]

This work aimed to synthesize and characterize nanoscale zero-valent iron (nZVI), supported on diatomaceous earth (DE) at two different molar concentrations, 3 and 4 M (nZVI-DE-1 nZVI-DE-2), to test the decolorization treatment of acid blue dye (AB) and perform a toxicological test using zebrafish. The synthesis of the nanoparticles was obtained using the chemical reduction method. The material was fully characterized by X-ray diffraction, scanning electron microscopy (SEM), energy-dispersive X-ray (EDX), and transmission electron microscopy and specific surface area (BET). The results showed spherical forms in clusters between 20 and 40 nm of zero-valent iron supported on diatomaceous earth. The removal of 1 g/L of AB from water treated with nZVI-DE-1 and nZVI-DE-2 reached the decolorization of 90% and 98% of all dye. By contrast, controls such as nZVI and DE-1 and DE-2 removed 40%, 37%, and 24% of the dye. Toxicological analysis using zebrafish showed that AB causes a severe defect in development, and embryos die after exposure. However, the water samples treated with nZVI-DE-1 and nZVI-DE-2 are not harmful to the zebrafish embryos during the first 24 h. However, all embryos exposed to the new material for more than 48 hpf had cardiac edema, smaller eyes, and curved and smaller bodies with less pigmentation. [ABSTRACT FROM AUTHOR]

The model developed in the first part of this work is used to predict the cell potentials and the irreversible Gibbs free energy of a stack of 15 cells. The model starts from a phenomenological equation of a polarization curve with the extent of reaction as the independent variable. Two extreme kinds of flow of reagents, defined as Chain and Separate Flows respectively, are considered. The cell potentials are obtained by a combination of the potential of the two extreme cases of flow. The stack cell potentials and the efficiencies, estimated by the model, reproduce the general characteristics obtained by the experiments. [ABSTRACT FROM AUTHOR]

A method to estimate the efficiency of a stack of several identical cells is described on the basis of the electrochemical behavior of a single cell. Efficiency of fuel cell stacks is defined by means of a combination of semi-empirical models of polarization curves and dimensionless variables such as reaction extent and utilization. The connection of flows among the cells is basically divided in two extreme cases and one intermediate case. Higher efficiencies are obtained when the same main flow (both anodic and cathodic) passes consecutively through the stack cells (Chain Flow), because it is favored thermodynamically. It is less favored when the main flow is strictly divided among all the cells (Separate Flow). In the intermediate case, the main flow is divided among all the stack cells and all the outlets are collected in one flow. The latter can spontaneously evolve to the more thermodynamically stable behavior of Chain Flow. [ABSTRACT FROM AUTHOR]

The study of the electrochemical catalyst conversion of renewable electricity and carbon oxides into chemical fuels attracts a great deal of attention by different researchers. The main role of this process is in mitigating the worldwide energy crisis through a closed technological carbon cycle, where chemical fuels, such as hydrogen, are stored and reconverted to electricity via electrochemical reaction processes in fuel cells. The scientific community focuses its efforts on the development of high-performance polymeric membranes together with nanomaterials with high catalytic activity and stability in order to reduce the platinum group metal applied as a cathode to build stacks of proton exchange membrane fuel cells (PEMFCs) to work at low and moderate temperatures. The design of new conductive membranes and nanoparticles (NPs) whose morphology directly affects their catalytic properties is of utmost importance. Nanoparticle morphologies, like cubes, octahedrons, icosahedrons, bipyramids, plates, and polyhedrons, among others, are widely studied for catalysis applications. The recent progress around the high catalytic activity has focused on the stabilizing agents and their potential impact on nanomaterial synthesis to induce changes in the morphology of NPs. [ABSTRACT FROM AUTHOR]

Polycyclic aromatic hydrocarbons (PAHs) are hazardous compounds originating from anthropogenic activity. Due to their carcinogenic properties for humans, several technologies have been developed for PAH removal. Sorption with natural and organic materials is currently one of the most studied due to its low cost and its environmentally friendly nature. In this work, a hybrid sorbent involving functionalized humic acids (HAs) and nano-zeolite is proposed to entrap PAHs. The use of functionalized HAs immobilized in a porous support is designed to address the instability of HAs in solution, which has been already reported. HA functionalization was carried out to increase the non-polarity of HAs and aliphatic group formation. The HAs were functionalized by esterification/etherification with alkyl halides, and their chemical changes were verified by FTIR and NMR. The sorption isotherms of the functionalized HAs in micro- and nano-zeolites were used to assess the performance of the nano-zeolites in adsorbing these HAs. The hybrid support allowed the removal of anthracene and pyrene at percentages higher than 90%; fluoranthene, of angular molecular structure, was adsorbed at 85%. PAHs are ubiquitous in the environment, and a stable sorption of them in solid matrices will allow their removal from the environment through effective and environmentally friendly methods. [ABSTRACT FROM AUTHOR]

Commercialization of the polymer electrolyte membrane fuel cell (PEMFC) requires that electrocatalysts for oxygen reduction reaction (ORR) satisfy two main considerations: materials must be highly active and show long-term stability in acid medium. Here, we describe the synthesis, physical characterization, and electrochemical evaluation of carbon-dispersed Pt2NiCo nanocatalysts for ORR in acid medium. We synthesized a trimetallic electrocatalyst via chemical route in organic medium and investigated the physical properties of the Pt2NiCo/C nanocatalyst by X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy-scanning electron microscope (EDXS-SEM), and scanning transmission electron microscopy (STEM), whereas the catalytic activities of the Pt2NiCo/C and Pt/C nanocatalysts were determined through cyclic voltammetry (CV), CO-stripping, and rotating disk electrode (RDE) electrochemical techniques. XRD and EDXS-SEM results confirmed the presence of the three metals in the nanoparticles, and scanning transmission electron microscopy (STEM) allowed observation of the Pt2NiCo nanoparticles at ~10 nm. The measured specific activity for the synthesized nanocatalyst is ~6.4-fold higher than that of Pt/C alone, and its mass activity is ~2.2-fold higher than that of Pt/C, which is attributed to the synergistic interaction of the trimetallic electrocatalyst. Furthermore, the specific and mass activities of the synthesized material are maintained after the accelerated stability test, whereas the catalytic properties of Pt/C decreased. These results suggest that the Pt2NiCo/C trimetallic nanocatalyst is a promising candidate cathode electrode for use in PEMFCs. [ABSTRACT FROM AUTHOR]

A complete study on the evolution of structures and the variation of the energy properties of MPdn−1 (M = Ni and Cu; n = 2‐13) clusters is presented. The study was performed employing auxiliary density functional theory. The obtained results were compared with the results of Pdn clusters studied with the same methodology. For each cluster size, several structures were studied to determine the lowest energy structures. The initial structures for the geometry optimization were taken along ab initio Born‐Oppenheimer molecular dynamics trajectories. Different potentials energy surfaces were studied. All cluster structures were fully optimized without any symmetry restriction. Stable structures, frequencies, spin multiplicities, averaged bond lengths, spin density plots, different energy properties, dipole and magnetic moments as well as charge transfers are reported. This investigation indicates that the palladium clusters doped with a Ni atom are the most stable and potentially the most chemical active ones. [ABSTRACT FROM AUTHOR]