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Fossil fuel depletion and environmental impacts caused by greenhouse gas emissions such as CO2 are significant issues securing nature preservation within a sustainable economy. CO2 methanation is a promising process to mitigate CO2 emissions and reuse it to produce CH4, serving as fuel, chemical feedstock, and energy source. A series of LDH‐derived Ni‐Al catalysts promoted by Li, Mg, Ca, and La were prepared via co‐precipitation. Characterization by N2 physisorption, X‐ray diffraction (XRD) and photoelectron spectroscopy (XPS), as well as thermal techniques such as temperature programmed reduction (H2‐TPR), desorption (CO2‐TPD, H2‐TPD), and oxidation (TPO) analyses were performed. Low‐temperature catalytic tests (200–400 °C) revealed that alkali metal modification improves performance even at 200 °C, where the Ni55Ca11Al33 catalyst achieved 74 % CO2 conversion with 100 % CH4 selectivity by enhancing basicity and metal‐support interaction, high Ni dispersion and small crystallite sizes, providing proper sites to adsorb and activate CO2. Moreover, the catalysts presented excellent resistance to deactivation, maintaining high stability during 10 h on stream. These results prove that Ni‐Al mixed oxides, LDH‐derived catalysts performances can be further improved by incorporating alkali metals into less energy‐spending, low‐temperature CO2 methanation processes. [ABSTRACT FROM AUTHOR]

• Bimetallic core-shell Ni-Ru NPs were prepared in BMI.NTf 2 ionic liquid. • hydrophobic ionic liquid affords mainly C 2 + hydrocarbons. • Ru-Ni NPs in hydrophilic ionic liquid gives CO during CO 2 hydrogenation. • Positive catalytic synergistic effect is observed. • Metal segregation was observed experimentally during the catalysis. The direct conversion of carbon dioxide to hydrocarbons is one of the key solutions to both the reduction of the greenhouse effect and the sustainable production of fuels and lubricants. Here, it is demonstrated that simple bimetallic Ru/Ni nanoparticles (NPs) (2–3 nm, Ru-rich shell, and Ni-rich core) in a hydrophobic ionic liquid (IL) promote the direct hydrogenation of CO 2 to light hydrocarbons (HCs) under very mild reaction conditions in a simple batch reactor. The reaction of CO 2 with hydrogen (1:4, 8.5 bar) at 150 °C with the Ru/Ni NPs (3:2) in bis((trifluoromethyl)sulfonyl)amide (BMI.NTf 2) hydrophobic IL affords C 2 + hydrocarbons (79% alkanes and 16% olefins) with 5% CH 4 at 30% conversion. However, the reaction performed in the hydrophilic IL 1- n -butyl-3-methyl-1 H -imidazol-3-ium tetrafluoroborate affords mainly CO. The catalytic hydrogenation of CO 2 towards HCs proceeds by a two-step process with the initial conversion of CO 2 into CO by reverse gas shift reaction (RWGS), followed by Fischer-Tropsch Synthesis (FTS). The bimetallic NPs have higher catalytic efficiencies than their monometallic counter- parts, owing to strong synergy between the metals. The presence of Ni in the bimetallic NPs yields a more active RWGS catalyst, and the Ru increases the FTS towards heavier HCs. [ABSTRACT FROM AUTHOR]

Rh 0.5 Pd 0.5 /CeO 2 bimetallic nanoparticles were subjected to reducing and oxidizing atmospheres at different temperatures and characterized by means of the Ambient Pressure X-Ray Photoelectron Spectroscopy (AP-XPS). The surface atomic population is calculated for all cases. By using a high temperature pre-treatment at 480 °C in H 2 atmosphere, it was possible to control the surface atomic population with Pd atoms frozen at the skin layer even in an oxidizing atmosphere, which is not observed without high temperature pre-treatment (Rh atoms at the skin layer). The change of the Rh/Pd surface segregation behavior after the high temperature pre-treatment is attributed to the geometrical factor of Strong Metal Support Interaction (SMSI) effect, i.e., the occurrence of the ceria capping layer around nanoparticles. [ABSTRACT FROM AUTHOR]

The structural properties of (Ti,Zr,Hf)CoSb thermoelectric Half-Heusler compounds were investigated by synchrotron radiation based techniques. The short-range order, in particular the environment of the Co atoms, was studied by extended X-Ray absorption fine structure spectroscopy and the long range order by powder X-Ray diffraction. Structural models were obtained for the single phase materials TiCoSb 0.85 Sn 0.15 , ZrCoSb 0.85 Sn 0.15 , and HfCoSb 0.85 Sn 0.15 . These models were transferred for the phase-separated material Ti 0.5 Hf 0.5 CoSb 0.85 Sn 0.15 . As a result, proving that each Half-Heusler phase was well ordered, apart from the intermixing of Ti and Hf on its designated crystallographic lattice site. [ABSTRACT FROM AUTHOR]

In Biofloc Technology (BFT), the disposal of solid waste represents a sustainability gap within. The presence of polyphenols in biofloc extracts has been reported, and these molecules have been widely explored for the synthesis of silver nanoparticles (AgNPs) in green nanotechnology. Polyphenols are employed to reduce silver ions and stabilize AgNPs. Compared to conventional methods (chemical synthesis), green synthesis makes the production of AgNPs sustainable and environmentally friendly by offering lower costs and avoiding the generation of hazardous waste that could impact the environment. This study proposes the extraction of polyphenols from bioflocs and their use as reducing and capping agents in the green synthesis of silver nanoparticles as a way to add value to the waste generated in BFT. Response Surface Methodology was used to obtain better extraction conditions by investigating the influence of four reaction variables (temperature, time, ethanol concentration, and solvent/solute ratios). The obtained extract was used to synthesize silver nanoparticles (BFAgNPs), which were used to determine the minimum inhibitory activity (MIC) and bactericidal activity (MBC) against Acinetobacter baumannii and Pseudomonas aeruginosa , as well as their anti-biofilm activity (inhibition and destruction) against A. baumannii. The highest polyphenol content was 1,918 μg gallic acid equivalents/g and the antioxidant activity was 1,278 μM Trolox equivalents/g for DPPH and 12,513 μM Trolox equivalents/g for ABTS. BFAgNPs exhibited an average diameter of 25.3 nm, as observed by transmission electron microscopy. Dynamic light scattering indicated a particle diameter of 123.2 nm, and polydispersity index (PDI) of 0.15. The zeta potential was measured at −22.5 mV. Fourier-transform infrared spectroscopy revealed distinct bands at 3616, 2924, 1682, 1532, 1234, and 1042 cm-1. BFAgNPs demonstrated MIC (38.8 μg/mL and 19.4 μg/mL for A. baumannii and P.aeruginosa), and MBC (77.5 μg/mL and 38.8 μg/mL for A. baumannii and P.aeruginosa) and antibiofilm activity, (47.3% inhibition and 27.8% destruction, respectively). It was concluded that the biofloc residue constitutes a source of polyphenols useful for the synthesis of AgNP with antibacterial capacity, thus representing a potential alternative for the waste valorization of BFT effluent. [Display omitted] • Biofloc residues generated in the BFT system are sources of polyphenols. • Polyphenols extracts were used to syntethize silver nanoparticles (AgNP). • AgNP exhibit inhibitory activity against Acinetobacter baumannii and Pseudomonas aeruginosa. • AgNP presented anti-biofilm activity against A. baumannii. • Biofloc residues show potential for the green synthesis of AgNP. [ABSTRACT FROM AUTHOR]

Oxygen vacancies are one of the most active defects existing at the surface of metal oxides. Engineering of defect chemistry, especially oxygen vacancies, represents the possibility of controlling the catalytic properties of nanoparticles. This work was dedicated to study the reduction properties of CeO 2-x nanoparticles prepared using different synthesis parameters when exposed to a CO reducing atmosphere. Near Ambient Pressure X-ray Photoelectron Spectroscopy (NAP-XPS) and in situ time-resolved X-Ray Absorption Near Edge Spectroscopy (XANES) techniques were used to probe in situ the electronic properties of these nanoparticles exposed to the CO atmosphere. Compared to typical results found for CeO 2-x nanoparticles, an improved reduction tendency is observed for these synthesized nanoparticles. It was possible to tune the oxygen vacancy population and the reduction temperature ( T R ) by means of the combination of synthesis and CO reducing atmosphere. The T R and Ce(III) fraction values reached can be as low as 108 °C and as high as 0.92, respectively. The influence of structural and electronic properties of the nanoparticles on the reduction kinetics of the CeO 2-x reduction is elucidated. The results provide a valuable route for the rational design of CeO 2-x nanoparticles with the desired oxygen vacancy population, and then preparing them in the best conditions for applications. [ABSTRACT FROM AUTHOR]

The magnetron-sputtering approach was used for the deposition of small (ca. 3.7 nm) and uniformly distributed Pd(0)- fcc nanoparticles (Pd-NPs) with partially oxidised surfaces on commercially available carbon black. The pores of the support were uniformly filled by Pd-NPs, and the surface area was drastically reduced by blockage of the pores. The metal concentration increases with the augmentation of the sputtering time without changing the metal NP size. These Pd-nanocatalysts are high efficient for the hydrogenation of nitrobenzene to aniline (TOF up to 141.7 min −1 ), 1,3-cyclohexadiene to cyclohexene (TOF up to 24.0 s −1 ), and cyclohexene to cyclohexane (TOF up to 35.1 s −1 ) under 4 bar of dihydrogen (H 2 ) at mild temperatures (75–90 °C). The magnetron sputtering is one of the simplest, reliable, fast, clean and cheap methods for the preparation of Pd/C catalysts. [ABSTRACT FROM AUTHOR]

The purpose of this study is to investigate, for the first time, the biocompatibility and antibacterial behavior of coatings obtained by plasma electrolytic oxidation (PEO) on the Ti6Al4V ELI alloy manufactured through the direct metal laser sintering (DMLS) additive manufacturing technique, implanted with two different concentrations of Cu ions by ion plating diversified (IPD). The surface morphology, elemental composition, and phase characteristics of the PEO coatings were investigated by SEM/EDS, GDOES, XRD, and XPS. The cytotoxicity in stem cells and the antibacterial effect were evaluated. The XPS analysis confirmed the successful incorporation of Cu at both concentrations, which appeared in the form of two different chemical components: CuO (92%) and Cu 2 O (8%). Stem cells were able to adhere and spread on the surface of the Ti6Al4V ELI alloy, with or without PEO coatings and ionic implantation of Cu particles; the materials and coatings were not cytotoxic. Quantitative cell viability assays for Staphylococcus aureus and Pseudomonas aeruginosa bacteria did not show significant differences. However, the staining of the viability wells, mainly for S. aureus , indicates a change in the behavior of these bacteria in coatings that contained the implantation of Cu oxides. This research demonstrated the potential that the union of the properties of the substrate manufactured in additive manufacturing (great versatility), PEO coatings (wear resistance and cell viability), and IPD ion implanted Cu particles can have in different applications. • Optimization of surface properties by associating additive manufacture, PEO coatings and IPD process. • From IPD process, it was possible to implant copper ions, mainly forming cupric oxide (CuO). • Ionic implantation of Cu was not cytotoxic for stem cells. • Bacteriological behavior was influenced by the presence of Cu oxides. [ABSTRACT FROM AUTHOR]

Since the earliest reports on catalytic benzene hydrogenation, 1,3-cyclohexadiene and cyclohexene have been proposed as key intermediates. However, the former has never been obtained with remarkable selectivity. Herein, we report the first partial hydrogenation of benzene towards 1,3-cyclohexadiene under mild conditions in a catalytic biphasic system consisting of Ru@Pt nanoparticles (NPs) in ionic liquid (IL). The tandem reduction of [Ru(COD)(2-methylallyl)2] (COD=1,5-cyclooctadiene) followed by decomposition of [Pt2(dba)3] (dba=dibenzylideneacetone) in 1- n-butyl-3-methylimidazolium hexafluorophosphate (BMI ⋅PF6) IL under hydrogen affords core-shell Ru@Pt NPs of 2.9±0.2 nm. The hydrogenation of benzene (60 °C, 6 bar of H2) dissolved in n-heptane by these bimetallic NPs in BMI ⋅PF6 affords 1,3-cyclohexadiene with an unprecedented 21 % selectivity at 5 % benzene conversion. Conversely, almost no 1,3-cyclohexadiene was observed when using monometallic Pt0 or Ru0 NPs under the same reaction conditions and benzene conversions. This study reveals that the selectivity is related to synergetic effects of the bimetallic composition of the catalyst material as well as to the performance under biphasic reaction conditions. It is proposed that colloidal metal catalysts in ILs and under multiphase conditions ('dynamic asymmetric mixtures') can operate far from the thermodynamic equilibrium akin to chemically active membranes. [ABSTRACT FROM AUTHOR]

[Display omitted] • The electronic factor dominates the low temperature regime of SMSI effect. • The electronic factor is mediated by O p states of Pd-O-Ti entities. • The electronic interaction occurs through charge transfer from Pd nanoparticles to TiO2. • The electronic interaction is enhanced with an oxidizing treatment. Whereas observed and explored for over 40 years, there are still open questions regarding the nature of the Strong Metal-Support Interaction (SMSI) effect. The lack of a precise determination of the atomic mechanisms of electronic and geometrical factors of the SMSI effect hinders the application of metal-support systems towards several catalytic reactions. The present study sheds light on the electronic factor of the SMSI effect in Pd/TiO 2 nanoparticles by using Near Ambient Pressure Photoelectron Spectroscopy (NAP-XPS), Ultraviolet Photoelectron Spectroscopy (UPS), and Density Functional Theory (DFT) calculations. The electronic and geometrical factor of the SMSI effect were observed during reduction treatment at 300 °C and 500 °C, respectively. The results enable mapping the electronic factor during reduction treatment at 300 °C, where a charge transfer from Pd nanoparticles to TiO 2 support through Pd-O-Ti entities existing at the Pd-TiO 2 interface is observed. Furthermore, the charge transfer is mediated by O p states present at the Pd-TiO 2 interface. [ABSTRACT FROM AUTHOR]

Metal oxide nanotubes (NTs) semiconductors prepared by anodization are promising materials due to their expected unique optical and electric properties. However, most of the work reported to date did not find photoelectrochemical devices with higher efficiency than those assembled with nanoparticles. Moreover, this behavior is due to the difficulty of having non-defective crystalline structures and the disruption of the tubular shape during thermal treatment while trying to reduce oxygen vacancies. This work describes in detail the local atomic configuration, surface area and morphology properties of Ta2O5 NTs prepared by anodization as a function of the temperature and the crystallization time by using X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS). The crystallization process of adhered and freestanding Ta2O5 NTs is discussed. Adhered NTs crystallized at 550 °C due to the oxidation of the Ta metal during annealing in the air atmosphere and not the NT array itself. Freestanding Ta2O5 NTs crystallized after annealing at 800 °C. Rietveld refinements were performed to investigate the effects of the temperature and the annealing time on the grain size and microstrain and obtain information about Ta-O interatomic distances. The local structure of amorphous and crystalline Ta2O5 NTs was investigated with EXAFS. Low coordination numbers were found in the as-anodized samples as well as the samples annealed for 30 min at 800 °C. The coordination number increased when annealing was performed above 800 °C or when the annealing time was longer than 30 min. Moreover, the decrease of defects was followed by an increase in the crystal size and collapse of the tubular shape due to the increase in internal stress generated by the increase in the crystallinity of the tubes and the orthorhombic Ta2O5 crystal size. [ABSTRACT FROM AUTHOR]

This work reports on the electronic and crystalline structure and the mechanical, magnetic, and transport properties of the polycrystalline Heusler compound Co2MnGe. The crystalline structure was examined in detail by extended x-ray absorption fine-structure spectroscopy and anomalous x-ray diffraction. The compound exhibits a well-ordered L21 structure as is typical for Heusler compounds with 2:1:1 stoichiometry. The low-temperature magnetic moment agrees well with the Slater-Pauling rule and indicates a half-metallic ferromagnetic state of the compound, as is predicted by ab initio calculations. Transport measurements and hard x-ray photoelectron spectroscopy were performed to explain the electronic structure of the compound. The obtained valence band spectra exhibit small energy shifts that are the result of the photoexcitation process, whereas electron-electron correlation in the ground state is negligible. The vibration and mechanical properties of the compound were calculated. The observed hardness values are consistent to a covalent-like bonding of Co2MnGe. [ABSTRACT FROM AUTHOR]

• Band gap engineering of CeO 2-x nanoparticles shifts absorption from UV to visible. • CeO 2-x nanoparticles of high surface area and surface O vacancy population used for H 2 production. • Improving the activity of CeO 2-x nanoparticles for the photocatalytic H 2 production. High surface area cerium oxide (CeO 2-x) nanoparticles (S = 170 m2/g) were synthesized by the precipitation method with a narrow band gap (2.73 ± 0.03 eV). In comparison to typical band gap values for cerium oxide, it presents a red shift in the light absorption spectrum from UV to visible region. X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), X-ray Absorption Spectroscopy (XAS), X-ray Photoelectron Spectroscopy (XPS) and Ultraviolet Photoelectron Spectroscopy (UPS) measurements were conducted aiming to elucidate this promising property for photocatalytic applications of the nanoparticles synthesized. It was obtained that the high structural disorder and O vacancy population of the nanoparticles synthesized are responsible for the narrow band gap found. Furthermore, the CeO 2-x nanoparticles were applied to the photocatalytic H 2 production reaction and presented activity 10 times higher than the commercial CeO 2-x standard, besides a much better performance than typical results found for CeO 2-x in the literature. [ABSTRACT FROM AUTHOR]

This work reports on the structure of Fe containing, Co2-based Heusler compounds that are suitable for magnetoelectronic applications. The compounds Co2FeZ (where Z=Al, Si, Ga, and Ge) were investigated using the x-ray diffraction (XRD) and extended x-ray absorption fine structure (EXAFS) techniques. Using XRD, it was shown conclusively that Co2FeAl crystallizes in the B2 structure whereas Co2FeSi crystallizes in the L21 structure. For compounds containing Ga or Ge, the XRD technique cannot be used to easily distinguish between the two structures. For this reason, the EXAFS technique was used to elucidate the structure of these two compounds. Analysis of the EXAFS data indicated that both compounds crystallize in the L21 structure. [ABSTRACT FROM AUTHOR]

• Active, isolated gold ion sites on silica surface. • Gold catalyst efficiently applied in diyne cross coupling reactions. • Designing high-performance recyclable heterogeneous catalyst. A new strategy is presented to obtain an efficient heterogeneous gold catalyst constituted by isolated ionic gold sites, which is known to be effective in alkyne coupling reaction. The procedure is based on a significant difference between offered gold amount and available adsorbent sites on the support, ensuring the formation of very active isolated gold ion sites. In order to achieve this purpose, mesoporous silica xerogel was grafted with an ionic silsesquioxane containing charged ammonium quaternary group. The modified silica showed 0.25 mmol of cationic sites per gram of material and presented thermal stability up to 200 °C. This material was applied as support for immobilization of Au(III) ions as square planar AuCl 4 − complex. The gold amount offered was just 12 % of the exchangeable capacity. The catalyst was efficiently applied in the cross coupling reactions, in which only 0.22 mol% was applied to obtain symmetric and non-symmetric 1,3-diynes. [ABSTRACT FROM AUTHOR]