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Cu serves as a promising electrocatalyst for converting CO2 into valuable C2 products in CO2 reduction reactions (CO2RR). However, instability in CO* formation is crucial for CO2 adsorption‐ desorption still remains a challenge under reduction conditions. This study explores the impact of lanthanide oxide, particularly CeO2, on Cu‐based catalytic performances. By leveraging Ce's distinctive electronic structure, CO* species are stabilized during the reaction in CeO2─Cu2O, resulting in exceptional catalytic performance for CO2 electroreduction to C2 products. Hybridizing CeO2‐Cu2O with graphene aerogel enhances electrochemical active surface area and CO2RR efficiency. The resulting CeO2─Cu2O(10%)/GA electrocatalyst exhibits a remarkable faradaic efficiency for C2 products, exceeding 62%, alongside exceptional stability over 80 h with wide potential window (−0.8 to −1.2 V) using a H‐cell. Systematic investigations elucidate the intricate interplay between surface properties and catalytic activity. Furthermore, a solar cell‐ powered CO2 reduction system demonstrates consistent performance (−27.8 mA cm−2 at 3.46 V) under solar radiation of ≈100 mW cm−2, showcasing outstanding stability with nearly 100% retention over 4 h of continuous illumination. In short, by harnessing catalytic and electronic effects, this innovation advances the development of electrocatalysts with heightened CO2‐to‐C2 selectivity, bridging fundamental research with technological innovation to tackle critical global challenges. [ABSTRACT FROM AUTHOR]

In this study, V2O5, 5ZnO/10V2O5, and ZnO, 10ZnO/10V2O5 nanocomposites were synthesized by the sol–gel method. The sol–gel technique is an important process for the fabrication of advanced oxide materials with desirable catalytic, optical, and structural properties. The varieties and flexibilities of sol–gel techniques help in preparing materials with extremely specific properties. For the presented samples, three types of phases were assessed. The average crystalline size of V2O5, 5ZnO/10V2O5 and ZnO, 10ZnO/10V2O5 nanocomposites were found to be 25, 26, 14.5, and 15.5 nm, respectively. SEM images showed three different shapes of semi-tube, semi-spherical, and semi-flower. The pure samples of V2O5 and ZnO showed semi-tube shapes. 5ZnO/10V2O5 shows a spherical shape with average dimeter of 0.6 µm. Strong dependence of the direct optical band gap was observed on different compositions that varied within the range of (2.33–2.73 eV). Conversely, the indirect values varied within the range of 2.119–2.35 eV. On the other hand, 10ZnO/10V2O5 has semi flower shape with different layers. Optical parameters, such as optical band gap, extension coefficient, tails of localized states, and refractive index, were gauged for these nanocomposites. In addition, the mean refractive index of ZnO is lower than that of V2O5, with differences observed between 5ZnO/10V2O5 and 10ZnO/10V2O5 nanocomposites.

Environmental remediation evinces sensitive detection and elimination of contaminants from the environment. Recent investigations delineate nanomaterials as potentially useful agents in environment remediation. In this investigation, we have developed multifunctional CdO‐ZnO nanocomposite (NCs) for efficient degradation of organic dyes and sensitive detection of nitrite ions which also exhibits excellent luminescence and antioxidant properties. The CdO‐ZnO NCs were developed through a facile method which improved the yield quantity by decreasing the energy consumption there by reducing the cost. Thus synthesized CdO‐ZnO NCs were characterized through X‐ray diffraction, FT‐IR, SEM, TEM, EDX studies. These studies confirmed the successful formation of CdO‐ZnO composite and the average particle size of the NCs was found to be ~50 nm. Selective reduction of harmful industrial organic dyes from the water bodies is one of the important aspects of water pollution. As prepared CdO‐ZnO NCs degraded the MB dye completely in 30 min under visible light irradiation. The effect of various parameters such as catalytic load, dye concentration and pH on the degradation of dye was assessed and the NCs exhibited maximum degradation efficiency at 25 mg of catalytic load and alkaline pH of 11. The photoluminescence studies reveal that the NCs have inherent excellent luminescence property by exhibiting the emission band at 277 and 282 nm. From electrochemical studies, the CdO‐ZnO NCs proclaimed magnificent nitrite sensing property with the LOD value of 9.8 μM. Additionally, antioxidant studies disclosed that NCs remarkably scavenged the DPPH free radicals with IC50 value of 249 μg/mL. Thus, this study establishes simple method for the development of efficient mixed oxide material CdO‐ZnO for multifunctional properties that could find industrial applications. [ABSTRACT FROM AUTHOR]

Four-component oxide catalysts MnOx–CuO–ZrO2–CeO2 are synthesized by co-precipitation with varying the calcination temperature from 400 °C to 800 °C. Formation and decomposition processes in mixed oxides are studied by X-ray diffraction, transmission electron microscopy, and X-ray photoelectron spectroscopy. The redox properties of the obtained samples are tested by temperature-programmed hydrogen reduction, and the catalytic characteristics are examined in the CO oxidation reaction. At 400-600 °C homogeneous solid solution MnxCuyZrzCeqO2 with the fluorite structure is formed. Temperature elevation to 700-800 °C facilitates the gradual decomposition of initial oxide, with manganese and copper cations leaving its composition in the form of highly dispersed CuO and CuxMn3–xO4 particles. The occurrence of different active states in the catalyst and their transitions into each other under the temperature effect is shown to maintain the high activity in the CO oxidation reaction up to 800 °C. [ABSTRACT FROM AUTHOR]

Acid–base M2+MgAlO and M2+AlO mixed oxides (where M2+ = Mg, Cu, Co, Zn, and Ni) were obtained by thermal decomposition of the corresponding layered double hydroxide (LDH) precursors and used as catalysts for cyclohexanol and benzaldehyde condensation under solvent-free conditions. The catalysts were characterized by X-ray diffraction (XRD), X-ray fluorescence (XRF), scanning electron microscopy (SEM), and temperature-programmed desorption of CO2 (TPD-CO2). Gas chromatography–mass spectroscopy (GC/MS) was used for the identification and quantification of the product mixtures. In the reaction of cyclohexanol and benzaldehyde on M2+MgAlO and MgAlO catalysts, a 2,6-dibenzylidene-cyclohexanone was obtained as the main product as a result of consecutive one-pot dehydrogenation of cyclohexanol to cyclohexanone and subsequent Claisen–Schmidt condensation. In the reaction mixture obtained in the presence of NiAlO, CoAlO, and ZnAlO catalysts, a cyclohexyl ester of 6-hydroxyhexanoic acid was detected together with the main product. This is most likely a by-product obtained after the oxidation, ring opening, and subsequent esterification of the cyclohexanol. [ABSTRACT FROM AUTHOR]

Catalytic studies hydrogen production via steam reforming of ethanol (SRE) are essential for process optimization. Likewise, selecting the ideal support for the active phase can be critical to achieve high conversion rates during the catalytic steam reforming process. In this work, copper-based catalysts were synthesized using two different supports, NaY zeolite and Nb2O5/Al2O3 mixed oxides. The materials were prepared using wet impregnation and characterized for their physicochemical properties using different analytical techniques. Differences in the catalyst morphologies were readily attributed to the characteristics of the support. The Cu/NaY catalyst exhibited a higher specific surface area (210.40 m2 g−1) compared to the Cu/Nb2O5/Al2O3 catalyst (26.00 m2 g−1), resulting in a homogeneous metal dispersion over the support surface. The obtained results showed that, at 300 °C, both the Cu/Nb2O5/Al2O3 and Cu/NaY catalysts produced approximately 50% hydrogen and 40% acetaldehyde, but with significant differences in conversion (6% and 56%, respectively). At 450 °C, a greater product distribution and a 10% higher conversion were observed when the catalyst was supported on NaY compared to Nb2O5/Al2O3. Hence, the performance of copper-based catalysts was influenced significantly by the textural properties of the support. [ABSTRACT FROM AUTHOR]

Photocatalytic hydrogen evolution from water is investigated in Ba–Sr–Ta–O layered compounds possessing two different crystal structures: Sr 2 Ta 2 O 7 (S.G. Cmcm, a (110) type layered pervoskite), and BaSrTa 2 O 7 (S.G. Immm, a (100) type layered perovskite). High purity samples of BaSrTa 2 O 7 and Sr 2 Ta 2 O 7 are successfully prepared by solid state reaction. Hydrogen production under UV irradiation is 26% larger in BaSrTa 2 O 7 (15.2 mmol g−1) than in Sr 2 Ta 2 O 7 (11.4 mmol g−1). The band gaps determined by diffuse reflectance spectroscopy (DRS) are 4 eV and 4.6 eV for BaSrTa 2 O 7 and Sr 2 Ta 2 O 7 , respectively. Density Functional Theory (DFT) calculations provide insights into the crystal and electronic structures of Sr 2 Ta 2 O 7 , BaSrTa 2 O 7 , and their derived series Sr 2-x Ba x Ta 2 O 7 (0 ≤ x ≤ 1). It is found that independently of the Sr/Ba content, the BaSrTa 2 O 7 -derived series show a ∼0.6 eV lower band gap and a wider conduction band than the Sr 2 Ta 2 O 7 -derived series. DFT results indicate that the enhanced hydrogen production of BaSrTa 2 O 7 is related to particular features of its crystal structure which favor Ta–Ta interactions. [Display omitted] • Two Ta-layered perovskites with different structure are unveiled as UV-photocatalysts • Accumulated H 2 evolution is 26 % higher in BaSrTa 2 O 7 than in Sr 2 Ta 2 O 7 • Experiments and calculations agree on a narrower band gap for BaSrTa 2 O 7 • Ba/Sr composition has a minor impact on the crystal and electronic structures • The BaSrTa 2 O 7 crystal structure propitiates the enhancement of H 2 production [ABSTRACT FROM AUTHOR]

In this study, the catalytic activity of calcined M3Al (M: Sr, Cd, Ni, Co, and Ca) and the effect of replacing divalent cations with Ca2+ in calcined MxCa3 − xAl hydrotalcite on the catalytic conversion of benzaldehyde and acetophenone to chalcone via Claisen–Schmidt condensation has been investigated. A series of M3Al and MxCa3 − xAl were synthesized by the co-precipitation method and characterized by SEM, BET, FT-IR, EDS, XRD, CO2-TPD techniques, and the Hammett indicator method. The results showed that the synthesized samples have normal surface area, high crystallinity, and three types of moderate, strong, and stronger basic sites. The catalytic activity is effectively dependent on the number of stronger alkaline sites. The effects of different parameters such as calcination temperature, solvents, catalyst amount, catalyst reusability, and the effects of electron-donating and electron-withdrawing groups were investigated. In optimum conditions over 0.04 wt% Sr0.5Ca2.5Al catalyst, at atmospheric pressure, 60 °C, in ethanol, yield (%) of chalcone was achieved at 87%. [ABSTRACT FROM AUTHOR]

Mn3O4/ZnO-Al2O3-CeO2 catalyst was synthesized through a solid-state process from a 3% Mn-doped Zn-(Al/Ce) layered double hydroxide structure. Detailed structural and optical characterization using XRD, FTIR, UV–visible DRS, and TEM was conducted. By investigating clofibric acid (CA) degradation in aqueous solution, Mn3O4/ZnO-Al2O3-CeO2 photocatalytic activity was evaluated. The results show that the heterostructure mixed oxide catalyst has excellent CA photodegradation performance. Further, the characterization reveals that such photocatalytic efficiency can be attributed to two facts that are summarized in the optical properties and the synergic effect between Mn and Ce elements. The sample demonstrated a narrow band gap of 2.34 eV based on DRS. According to the experimental results of the photodegradation, after 120 min of irradiation, the photocatalyst exhibited the highest photocatalytic activity, with a degradation efficiency of 93.6%. Optimization outcomes indicated that maximum degradation efficiency was attained under the following optimum conditions: catalyst dose of 0.3 g/L, initial dye concentration of 20 mg/L, pH 3.86, and 120 min of reaction time. The quenching test demonstrates that photogenerated electrons and superoxide radicals are the most powerful reactive species. The catalyst could be useful in decreasing the photogenerated charges recombination, which offers more redox cycles simultaneously during the catalytic process. The strong Ce-Mn interaction and the formation of their different oxidation states offer a high degradation efficiency by facilitating electron–hole transfer. The introduction of Mn3O4 in the catalyst can effectively improve the visible absorption properties, which are beneficial in the photocatalytic process by reaching a high catalytic efficiency at a low cost. [ABSTRACT FROM AUTHOR]

Powdered Ni-based catalysts exhibit good performance in the dry reforming of methane (DRM); however, they suffer from limited industrial applicability. Structured monolithic catalysts can overcome these limitations. In this sense, we present the synthesis of Ni–Ce mixed oxide-type catalysts immobilized in cordierite monoliths using a simple coprecipitation method and slurry coating without additives using hydrotalcite precursors for catalyst preparation. Our research explores the role of Ce (0–7 % w/w) as a promoter and the impact of immobilizing mixed oxides (MO) within cordierite monoliths on the physicochemical properties and catalytic performance of non-previously H 2 -reduced materials in DRM at 700 °C. Our findings reveal the favorable impact of Ce on the physicochemical properties of the catalyst in both the powder and monoliths, including smaller crystallite sizes, enhanced CO 2 adsorption, and reducibility with higher Ce loading. The immobilized mixed oxide (MO) maintained its crystalline structure and formed stable, uniform layers with thicknesses below 10 μm in the monoliths. The powders exhibited stable conversions of 70–80% for CH 4 and 66–75% for CO 2 , whereas the monoliths showed conversions of 85–90% for CH 4 and 80–90% for CO 2 at 700 °C and 94,680 mL·g cat −1·h−1. A higher catalyst loading in the monoliths did not result in detrimental catalytic conversion. On average, the monoliths had a higher H 2 /CO ratio (1.25–1.5) compared to the powders (1–1.25), which may explain the increased coke formation rate in the monoliths from methane cracking. Ce improved the stability and reduced coke formation, particularly when the space velocity was lower. This research highlights the significant advantages of immobilizing mixed oxides (MO) in monolithic structures, making them highly promising for potential industrial scale-up. Their stability, recoverability, elimination of high-cost H 2 reduction, and reusability in subsequent catalytic tests contributed to their favorable characteristics. [Display omitted] • Coprecipitation simplifies slurry coatings for monolith immobilization. • Monoliths were prepared without additives. • The monoliths exhibited high stability and consistent performance upon reuse. • Ce improved stability and reduced coke formation at lower space velocities. • Immobilized catalysts produced more carbon, but no pressure drops were observed. [ABSTRACT FROM AUTHOR]

The rapid emergence of intelligent textile-based sensors has sparked considerable interest within the scientific community. A pivotal factor in advancing these sensors is the development of semiconductors with tailored band energy levels to enhance their optical properties. This enhancement primarily arises from efficient carrier separation and interfacial charge transfer processes. In pursuit of these objectives, our study presents a novel approach to fabricate flexible thin films composed of mixed oxides, specifically zinc oxide and cadmium tungstate (ZnO/CWO), within a chitosan (CS) matrix, utilizing a cost-effective method. We conducted a comprehensive characterization of the fabricated samples, encompassing structural, morphological, and optical analyses. Techniques such as X-ray diffraction (XRD), Raman spectroscopy, field-emission scanning electron microscopy (FESEM), iono/photoluminescence, and scintillation strategies were employed. The findings from XRD and Raman spectroscopy unequivocally confirm the presence of hexagonal ZnO and monoclinic CdWO4 structures within the thin film. Notably, the ZnO/CWO composite thin films exhibit robust emissions in the blue-green and orange spectral regions compared to pure CS at room temperature. This phenomenon occurs following excitation by a 290 nm wavelength light source and a proton beam serving as an ionizing radiation source. Furthermore, FESEM/TEM analysis reveals that the synthesized ZnO/CWO composite nanoparticles predominantly exhibit a diverse range of shapes, including cubic, rod-like, and spherical, with an average diameter size of approximately 20–80 nm, demonstrating excellent dispersion within the chitosan matrix. The results obtained in this study suggest that the prepared flexible composite film holds significant promise for future applications in adaptable optical devices. [ABSTRACT FROM AUTHOR]

AbstractOptimizing materials and associated structures for detecting various environmental gas pollutant concentrations has been a major challenge in environmental sensing technology. Semiconducting metal oxides (SMOs) fabricated at the nanoscale are a class of sensor technology in which metallic species are functionalized with various dopants to modify their chemiresistivity and crystalline scaffolding properties. Studies focused on recent advances of gas sensors utilizing metal oxide nanostructures with a special emphasis on the structure-surface property relationships of some typical n-type and p-type SMOs for efficient gas detection are presented. Strategies to enhance the gas sensor performances are also discussed. These oxide material sensors have several advantages such as ease of handling, portability, and doped-based SMO sensing detection ability of environmental gas pollutants at low temperatures. SMO sensors have displayed excellent sensitivity, selectivity, and robustness. In addition, the hybrid SMO sensors showed exceptional selectivity to some CWAs when irradiated with visible light while also displaying high reversibility and humidity independence. Results showed that TiO2 surfaces can sense 50 ppm SO2 in the presence of UV light and under operating temperatures of 298–473 K. Hybrid SMO displayed excellent gas sensing response. For example, a CuO–ZnO nanoparticle network of a 4:1 vol.% CuO/ZnO ratio exhibited responses three times greater than pure CuO sensors and six times greater than pure ZnO sensors toward H2S. This review provides a critical discussion of modified gas pollutant sensing capabilities of metal oxide nanoparticles under ambient conditions, focusing on reported results during the past two decades on gas pollutants sensing. [ABSTRACT FROM AUTHOR]

The hydrogen production by ethanol steam reforming over Ni–Co–Al mixed oxides derived from layered double hydroxides is evaluated in this work. The catalysts were prepared via coprecipitation and characterized through N2 adsorption and desorption measurements, X-ray diffraction (XRD), temperature programmed reduction (TPR), CO2 desorption and oxidation, and scanning electron microscopy. The catalyst activity was evaluated in a fixed bed reactor between 400 and 600 °C, using ethanol and water in a 1:3 ratio, with online analysis of products by gas chromatography. Increasing the amount of Co increased surface area. XRD analysis revealed a mixture of Ni–Al and Co-Al oxides after calcination. The TPR profiles revealed that an increase in Co content leads to a more stable mixed oxide phase. The activity results showed that H2 selectivity increases with reaction temperature and Co content in the catalyst. The high selectivity for H2 is attributed to methane decomposition being favored. Hence the larger production of carbon is promoted by the excess of Co in the catalyst with the highest amount of Co. The decomposition of ethanol producing CO, CH4, and H2 is favored at higher temperatures. The selectivity for H2 remained above 90% in long term tests at 600 °C. XRD analysis after reactions showed that the presence of Co decreases the sintering of catalysts. The compromise between resistance to sintering and carbon deposition points to a medium amount of Co in the catalyst. All catalysts showed metallic phases after the reaction, demonstrating that the reduction step is not necessary for this reaction. [ABSTRACT FROM AUTHOR]

Catalysts based on CoCuMgAl mixed oxides were synthesized and studied in the hydrogenations of furfural and 5-hydroxymethylfurfural under different conditions. The changes in the structural properties of the catalysts at different stages of their preparation were studied using a set of physical methods (XRD, SEM, and TEM). It was shown that the fine regulation of the chemical compositions of the mixed oxides (i.e., changes in the Co/Cu ratio) made it possible to vary the structure, morphology, and catalytic properties of the samples. The phase composition of catalysts with Co/Cu = 1 did not change during the catalytic reaction, although the initial catalysts had a less-homogeneous morphology. 5-hydroxymethylfurfural conversion was higher for the samples with Co/Cu = 1. Furfural conversion increased when raising the Co/Cu ratio. The selectivity toward furfuryl alcohol for the catalyst with Co/Cu = 2 under mild conditions of furfural hydrogenation was more than 99%. The results obtained are important for the development of the scientific foundations of the preparation of hydrogenation catalysts with a fine-tunable composition in order to obtain the desired hydrogenation products. [ABSTRACT FROM AUTHOR]

The mesoporous catalytic composite material was prepared from both stover ash (as a source of mixed oxides) and treated rice straw with very low residue on ignition (as a pore-capping agent). X-ray diffraction and BET surface analyses of the as-prepared mesoporous mixed oxides (MMO) exhibited a partially crystalline structure with an average pore diameter of 16.4 nm. To modify the optical properties, Ni nanoparticles were loaded onto the MMO surface via the reduction with hydrazine. Both MMO and the modified material, namely Ni-MMO, were investigated by HR-TEM, IR, X-ray diffraction, BET surface analyses, XPS, PL spectra, and UV-Visible reflectance measurements. In a good agreement, all tests confirmed that Ni nanoparticles interacted with oxides on the surface with restructuring and a new potential crystal system. XPS revealed that Ni generates surface oxygen vacancies (SOV) which induced sub-band levels to stabilise e-/h* pairs. Ni-MMO with low PL intensity showed a high photocatalytic activity in degradation of Rhodamine B dye with a maximum of 99.1% after 180 min under visible irradiation and catalyst dose of 1 g L−1. The reusability test for Ni-MMO exhibits the catalyst stability in four consecutive cycles. [ABSTRACT FROM AUTHOR]

A study of mixed systems based on zirconium oxide is carried out using X-ray absorption fine structure (XAFS: XANES, EXAFS) spectrocscopy. New reliable information concerning zirconium and yttrium on the state of Zr—Y and Zr–Y–Mg samples, parameters of the local atomic structure, interatomic distances, and coordination numbers is obtained; the possible variants of structural models are considered. An analysis of the XAFS data based on the pyrochlore and fluorite models and taking into account the abnormally low coordination numbers for zirconium and the shortening of the Zr–O bond lengths (in comparison with bulk reference points) unambiguously indicates the formation of a number of oxygen vacancies. The disordering of both sublattices (due to structural distortions of the zirconium lattice) increases in the series of samples Zr—Y and Zr–Y–Mg. With respect to yttrium, in the studied samples, the formation of both a distorted ZrYzOx fluorite nanophase (partially amorphized) with significant defects in the anion and cation sublattices, and a large amount of a distorted yttrium-oxide phase (nanophase, nanoclusters) is possible. It should also be noted that the state and local environment of yttrium is more stable than that of zirconium. The data obtained using X-ray absorption near edge spectroscopy (XANES) and extended X-ray absorption fine structure (EXAFS) spectroscopy are in good agreement with each other. [ABSTRACT FROM AUTHOR]

This work reports on the ultrasonic synthesis of layered double hydroxides (LDH), also known as hydrotalcite-type materials. We have studied the influence of ultrasonic irradiation parameters (power, time, temperature) on the physicochemical properties of Ni2Mg4Al1.8La0.2 hydrotalcite-type precursors and related mixed oxides (MO). The low-frequency acoustic cavitation (22 kHz) was applied during the precipitation and aging steps of co-precipitation synthesis and the results were compared to the classical preparation route. The materials were characterized by ATR-FTIR, XRD, N2 adsorption–desorption, SEM-EDX, S/TEM-HAADF, and XPS. Using the combination of acoustic cavitation-assisted precipitation and aging steps, XRD experiments show a higher purity hydrotalcite phase and a better incorporation of lanthanum ions into the LDH structure. As expected, morphological characterization shows a reduction in average crystallite size and an increase in surface area and pore volume, combined with a drastic reduction in synthesis time (45 min at room temperature versus 19 h at 60 °C in conventional synthesis). The insertion of a larger quantity of La is observed by S/TEM-EDSX mapping which also shows a better distribution of lanthanum atoms within the LDH and mixed oxide structures.

Single phase CuCoMgAl-layered hydroxides were obtained by making fine adjustment to their composition through changing the (Co + Cu)/Mg = 0.5; 1; 2; 3 and Co/Cu = 0.5; 1; 2 ratios. The rise of Co/Cu in systems contributed to the increase in their thermal stability. CuCoMgAl-catalysts showed high selectivity of carbonyl group hydrogenation in furfural and 5-hydroxymethylfurfural. In furfural hydrogenation, the selectivity to furfuryl alcohol was more than 99%, and in 5-hydroxymethylfurfural hydrogenation, the selectivity to 2,5-hydroxymethyl furfural was 95%. The surface of the samples with different Co/Cu after calcination and reduction was the same and had a «core-shell» structure (TEM). «Core» consisted of Cu and Co metallic particles. «Shell» consisted of CuCoMgAlOx mixed no-stoichiometric spinel oxides. There was no sintering or change in size of the metallic particles after the reaction. For the sample with Co/Cu = 1, their phase composition after reaction remained unchangeable. The increase of Co/Cu led to the formation of an X-ray amorphous phase after the reaction. This suggests the decrease in structural stability of this sample. The obtained results prove the prospects of using bimetallic CoCu-systems for hydrogenation of furan aldehydes, and opens up new directions for further research and improvement.

Acid–base M2+MgAlO and M2+AlO mixed oxides (where M2+ = Mg, Cu, Co, Zn, and Ni) were obtained by thermal decomposition of the corresponding layered double hydroxide (LDH) precursors and used as catalysts for cyclohexanol and benzaldehyde condensation under solvent-free conditions. The catalysts were characterized by X-ray diffraction (XRD), X-ray fluorescence (XRF), scanning electron microscopy (SEM), and temperature-programmed desorption of CO2 (TPD-CO2). Gas chromatography–mass spectroscopy (GC/MS) was used for the identification and quantification of the product mixtures. In the reaction of cyclohexanol and benzaldehyde on M2+MgAlO and MgAlO catalysts, a 2,6-dibenzylidene-cyclohexanone was obtained as the main product as a result of consecutive one-pot dehydrogenation of cyclohexanol to cyclohexanone and subsequent Claisen–Schmidt condensation. In the reaction mixture obtained in the presence of NiAlO, CoAlO, and ZnAlO catalysts, a cyclohexyl ester of 6-hydroxyhexanoic acid was detected together with the main product. This is most likely a by-product obtained after the oxidation, ring opening, and subsequent esterification of the cyclohexanol.

Examining proficient electro‐catalyst from earth abundant and sustainable material is highly required for clean energy generation and a step toward fuel cell. In this study, ZnO/ZrO2 mixed metal oxide has been synthesized using organic chemicals in a straightforward and environmentally friendly manner. The greener routes are not only employed for the synthesis of nano structured material but they also improve the charge transfer properties of material in term of high surface area. The as prepared nano‐oxides were probed for phase structure, morphology, surface chemistry and optical properties by spectroscopic techniques. The embedded phyto‐functionalized compounds in the prepared nano‐material were probed by FTIR and GC–MS demonstrating the phyto‐functionalization of ZnO/ZrO2 nanomaterial. Thereafter, effects of functionalization were observed on the electrochemical behavior of synthesized material. The electrochemical investigation revealed remarkable catalytic activity of fabricated ZnO/ZrO2 with small overpotential and Tafel slope for current density of 10 mA cm−2. Therefore, current work demonstrated the promising electrocatalytic potential of fabricated mixed metal oxide and paved a cost effective and efficient organic template to synthesize binary or ternary mixed oxide with enhanced electrocatalytic properties. [ABSTRACT FROM AUTHOR]

[Display omitted] • Brønsted sites generated by SiO 2 on Lewis acidic ZrO 2 , TiO 2 , Nb 2 O 5 , or Al 2 O 3. • Acid strength quantified by TMPO chemisorption 31P NMR. • Brønsted acid strength increased with MOx Lewis acidity, as Al 2 O 3 > Nb 2 O 5 > TiO 2 > ZrO 2. • Hydroalkoxylation rates maximized at near-monolayer silica loading. • Hydroalkoxylation rates scaled with Brønsted acidity. Mixed oxides are ubiquitious solid acid catalysts for a number of transformations. Here, the chemistry of mixed oxide interfaces was experimentally probed by constructing model SiO 2 on MO x interfaces using a liquid-phase, stoichiometrically-controlled deposition of tetraethyl orthosilicate (TEOS). Catalytically active Brønsted sites were generated in four series of overcoated SiO 2 on metal oxide materials prepared by depositing TEOS onto Al 2 O 3 , anatase TiO 2 , Nb 2 O 5 , and ZrO 2. Pyridine DRIFTS studies indicate that the acidity of deposited silanol groups was enhanced by interaction with the metal oxide surface, suggesting that pseudo-bridging silanol type structures were formed. Trimethylphosphine oxide (TMPO) 31P NMR experiments showed that Brønsted acid strength varied in the overcoated materials, with increasing strength in the following order: SiO 2 /ZrO 2 < SiO 2 /TiO 2 < SiO 2 /Nb 2 O 5 < SiO 2 /Al 2 O 3. This order correlated with the Lewis acidity and chemical hardness of the underlying metal oxides. The catalytic performance of the materials was evaluated in the liquid-phase hydroalkoxylation of dihydropyran with n-octanol, revealing that activity was highly dependent on SiO 2 loading, which impacted the density of acid sites, and scaled exponentially with Brønsted acid strength, determined by the core metal oxide identity. Brønsted acid strength appears to be the key driver of the materials' activity, with the highest areal rate of 2.2 mmol / m2 – h being measured over SiO 2 /Al 2 O 3. This study shows that SiO 2 -overcoated materials are a systematically tunable class of catalysts that can be applied to acid catalyzed reactions. [ABSTRACT FROM AUTHOR]

A novel bimetallic mixed oxide catalyst Mn2CoO4 was prepared by co-precipitation method・ The catalyst was characterized and analyzed by X-ray diffraction analysis, electron microscope-energy spectrum analysis and other means・ It is used to activate persulfate (PMS) to degrade Rhodamine B (RhB). The results show that when the dosage of Mn2CoO4 is 0. 25 g/L and the dosage of PMS is 0. 5 mmol/L, the removal efficiency was highest of RhB after 15 min of reaction. The removal rate is 99. 13%, the first-order reaction rate constant is as high as 0. 343 9 min 1, and the reusability is excellent. The quenching test results showed that the sulfate radical (SO4 •) played a major role in the degradation process, and the hydroxyl radical (• OH) only played a weak role, and the superoxide radical (• O2) did not participate in the reaction. [ABSTRACT FROM AUTHOR]

Single phase CuCoMgAl-layered hydroxides were obtained by making fine adjustment to their composition through changing the (Co + Cu)/Mg = 0.5; 1; 2; 3 and Co/Cu = 0.5; 1; 2 ratios. The rise of Co/Cu in systems contributed to the increase in their thermal stability. CuCoMgAl-catalysts showed high selectivity of carbonyl group hydrogenation in furfural and 5-hydroxymethylfurfural. In furfural hydrogenation, the selectivity to furfuryl alcohol was more than 99%, and in 5-hydroxymethylfurfural hydrogenation, the selectivity to 2,5-hydroxymethyl furfural was 95%. The surface of the samples with different Co/Cu after calcination and reduction was the same and had a «core-shell» structure (TEM). «Core» consisted of Cu and Co metallic particles. «Shell» consisted of CuCoMgAlOx mixed no-stoichiometric spinel oxides. There was no sintering or change in size of the metallic particles after the reaction. For the sample with Co/Cu = 1, their phase composition after reaction remained unchangeable. The increase of Co/Cu led to the formation of an X-ray amorphous phase after the reaction. This suggests the decrease in structural stability of this sample. The obtained results prove the prospects of using bimetallic CoCu-systems for hydrogenation of furan aldehydes, and opens up new directions for further research and improvement. [ABSTRACT FROM AUTHOR]

The increase of consciousness towards global warming and the need to reduce greenhouse gas emissions lead to the necessity of finding alternative applications based on easy-to-use materials in order to control and reduce global CO2 emissions. Layered Double Hydroxides (LDHs) and LDH-derived materials are potentially good adsorbents for CO2, thanks to their low cost, easy synthesis, high sorption capacity, and surface basicity. They have been intensively studied in CO2 capture at high temperature, presenting variable sorption capacities for MgAl LDHs with the same composition, but prepared under different synthesis conditions. The ambient temperature coprecipitation synthesis method is an attractive one-step procedure to synthesize LDHs under mild conditions, with low energy consumption and short synthesis time. The present study is based on the synthesis and characterization of hydrotalcites by a mild-conditions coprecipitation process and the production of derived mixed oxides to be used as CO2 adsorbents. A critical comparison to similar materials is reported. Moreover, the effect of the surface basicity of the derived mixed oxides (measured by adsorption calorimetry) and the CO2 sorption capacity are discussed, showing a linear correlation between the amount of weak and very strong basic sites and the CO2 adsorption behavior. [ABSTRACT FROM AUTHOR]

The CoAl hydroxides with Co/Al ratios of 2 and 4 were synthesized using traditional coprecipitation and a mechanochemical method. The structural properties of the samples at all stages of catalyst preparation, the transformations occurred on the reduction of cobalt from corresponding oxides, the textural characteristics of calcined and reduced systems, and the size, morphology, and composition of particles formed after high-temperature treatments were studied in detail. It was established that the synthesis procedure of CoAl hydroxides has a significant effect on the phase composition and properties of the resulting systems. The layered double hydroxide phase was formed only when the coprecipitation method was used. The mechanochemical approach made it possible to obtain materials with a higher specific surface area. According to TEM data, the samples synthesized by coprecipitation (after oxidative and reductive treatments) had a core–shell structure, where the core included metallic Co atoms and the shell mainly consisted of CoAl spinel. The samples prepared by the mechanochemical method had highly dispersed Co nanoparticles on their surface. The catalysts based on CoAl systems prepared by the mechanochemical method were more active in the hydrogenation of furfural: its conversion reached 97% on a sample with the ratio Co/Al = 4. In this case, the selectivity for furfuryl alcohol formation on the studied catalysts was almost 100% regardless of the synthesis procedure and Co/Al ratio. [ABSTRACT FROM AUTHOR]

A rational synthetic approach is introduced to enable hydrogen insertion into oxides by forming a solid solution of a reducible oxide with a less reducible oxide as exemplified with RuO2 and TiO2 (Ru_x, a mixture of x% RuO2 with (100−x)% TiO2). Hydrogen exposure at 250 °C to Ru_x (Ru_x_250R) results in substantial hydrogen incorporation accompanied by lattice strain that in turn induces pronounced activity variations. Here, we demonstrate that hydrogen incorporation in mixed oxides promotes the oxidation catalysis of propane combustion with Ru_60_250R being the catalytically most active catalyst. [ABSTRACT FROM AUTHOR]

The reaction to obtain furan alcohols is one of the most important in the upgrading of furan derivates. An attractive route is the transfer hydrogenation of furfural using acidic‐basic catalysts. In this work, mixed oxides derived from ternary hydrotalcites were employed to obtain furfuryl alcohol from furfural assisted by microwave irradiation. These materials were characterized via X‐ray diffraction (XRD), N2 adsorption‐desorption isotherms, Fourier‐transform infrared (FTIR) and the CO2 temperature‐programmed desorption (CO2‐TPD) analyses. The lamellar structure of hydrotalcite‐type materials collapses during the calcination process, resulting in the loss of carbonate anions and hydroxyl groups, present in the interlayer space. This leads to the formation of mixed oxides that exhibit larger surface areas. Furthermore, these changes alter the basic nature of these materials, giving rise to the formation of strong basic sites. The reaction was studied using containing Co2+ and Ni2+ in their structure and was then optimized using distinct primary and secondary alcohols as hydrogen donor sources, as well as distinct temperatures and initial concentrations of furfural. The yields to furfuryl alcohol are strongly dependent on the type of Me2+ in layered oxides mainly due to higher basicity and to the donor employed in the reaction. The mixed oxide containing Co2+ showed complete conversion of furfural and higher yields to furfuryl alcohol (>95 %) at short times of reaction (<1 h). [ABSTRACT FROM AUTHOR]

CeO2-TiO2 is an important mixed oxide due to its catalytic properties, particularly in heterogeneous photocatalysis. This study presents a straightforward method to obtain 1D TiO2 nanostructures decorated with CeO2 nanoparticles at the surface. As the precursor, we used H2Ti3O7 nanoribbons prepared from sodium titanate nanoribbons by ion exchange. Two cerium sources with an oxidation state of +3 and +4 were used to obtain mixed oxides. HAADF–STEM mapping of the Ce4+-modified nanoribbons revealed a thin continuous layer at the surface of the H2Ti3O7 nanoribbons, while Ce3+ cerium ions intercalated partially between the titanate layers. The phase composition and morphology changes were monitored during calcination between 620 °C and 960 °C. Thermal treatment led to the formation of CeO2 nanoparticles on the surface of the TiO2 nanoribbons, whose size increased with the calcination temperature. The use of Ce4+ raised the temperature required for converting H2Ti3O7 to TiO2-B by approximately 200 °C, and the temperature for the formation of anatase. For the Ce3+ batch, the presence of cerium inhibited the conversion to rutile. Analysis of cerium oxidation states revealed the existence of both +4 and +3 in all calcined samples, regardless of the initial cerium oxidation state. [ABSTRACT FROM AUTHOR]

Chemical looping applications offer a variety of options to decarbonise different industrial sectors, such as iron and steel and hydrogen production. Chemical looping with water splitting (CLWS) is a chemical looping technology, which produces H2 while simultaneously capturing CO2. The selection of oxygen carriers (OCs) available to be used in CLWS is finite, due to the thermodynamic limitations of the oxidation with steam for different materials at the relevant process temperatures. Iron‐based materials are one of the most widely studied options for chemical looping combustion (CLC), touted for their relative abundance and low cost; likewise, for CLWS, iron is the most promising option. However, when the reduction of iron oxide (Fe2O3) is extended to wüstite (FeO) and iron (Fe), agglomeration and sintering problems are the main challenge for fluidisation. This work presents iron and tungsten mixed oxides as the OCs for a family of chemical looping applications. The OCs were produced via co‐precipitation; performance assessment was conducted in a thermogravimetric analyser and a lab‐scale fluidised bed reactor over continuous redox cycles. The use of tungsten combined with iron results in a solid solution of tungsten within the Fe2O3 matrix that produced a more mechanically stable material during operation, which performed well during multiple redox cycles with no apparent decrease in the oxygen transport capacity and showed no apparent agglomeration. Furthermore, materials containing tungsten showed a resistance to carbon deposition, whereas the reference Fe2O3 showed peaks of CO and CO2 during the oxidation period, thus indicating carbon deposition. © 2023 Society of Chemical Industry and John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

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The structural and compositional flexibility of perovskite oxides and their complex yet tunable redox properties offer unique optimization opportunities for thermochemical energy storage (TCES). To improve the relatively inefficient and empirical‐based approaches, a high‐throughput combinatorial approach for accelerated development and optimization of perovskite oxides for TCES is reported here. Specifically, thermodynamic‐based screening criteria are applied to the high‐throughput density functional theory (DFT) simulation results of over 2000 A/B‐site doped SrFeO3−δ. 61 promising TCES candidates are selected based on the DFT prediction. Of these, 45 materials with pure perovskite phases are thoroughly evaluated. The experimental results support the effectiveness of the high‐throughput approach in determining both the oxygen capacity and the oxidation enthalpy of the perovskite oxides. Many of the screened materials exhibit promising performance under practical operating conditions: Sr0.875Ba0.125FeO3−δ exhibits a chemical energy storage density of 85 kJ kgABO3−1 under an isobaric condition (with air) between 400 and 800 °C whereas Sr0.125Ca0.875Fe0.25Mn0.75O3−δ demonstrates an energy density of 157 kJ kgABO3−1 between 400 °C/0.2 atm O2 and 1100 °C/0.01 atm O2. An improved set of optimization criteria is also developed, based on a combination of DFT and experimental results, to improve the effectiveness for accelerated development of redox‐active perovskite oxides. [ABSTRACT FROM AUTHOR]

Ethanol has been used as a renewable hydrogen‐donor in the conversion of a lignin model molecule in subcritical conditions. Noble metal‐free porous mixed oxides, obtained by activation of Cu−Ni−Al and Cu−Ni−Fe layered double hydroxide (LDH) precursors, have been used as heterogeneous catalysts for Meerwein‐Ponndorf‐Verley (MPV) hydrogen transfer and further hydrogenation by ethanol dehydrogenation products. Both the Cu/(Cu+Ni) ratio and the nature of the trivalent cation (Al or Fe) affect the activity of the catalysts, as well as the selectivity towards the different steps of the hydrogenation reactions and the cleavage of lignin‐like phenylether bonds. Accounting for the peculiar behaviour of Cu2+ and M(III) cations in the synthesis of LDHs, the coprecipitation of the precursors has been monitored by titration experiments. Structural and textural properties of the catalysts are closely related to the composition of the LDH precursors. [ABSTRACT FROM AUTHOR]

The application of open cell foams as catalytic supports has been developed in recent years due to their interesting features: large specific surface area (>300 m2 m−3), high void fractions (>0.9) and enhanced internal mass transport. Catalytic foams are highly appealing for the development of structured reactors, especially for multiphase systems. In this paper, catalytic packing material with potential application in structured reactors was developed. Aluminum foams with different macropore sizes were chosen as support for a TiO2−WOx catalyst. The main features, geometric and structural, of the foams were established. At optimized conditions a maximum catalyst loading of 234 kgcatalyst m−3support was obtained, while maintaining significant void fraction (>0.8). The structured catalyst was successfully implemented in batch reactor for a model reaction, esterification of glycolic acid with ethanol. It was shown that the catalyst does not lose performance during the coating steps and remains active for at least 3 catalytic runs, i. e. 18 h. [ABSTRACT FROM AUTHOR]

Herein, a new method for synthesizing advanced nanocomposite materials based on tungsten, molybdenum, and titanium oxides by pulsed underwater plasma is reported. This is an environmentally friendly, energy‐saving, and simple method for obtaining bimetallic oxide nanoparticles with inhomogeneous defect structures. The chemical composition and morphology of the obtained particles are explored by electron microscopy and X‐ray diffraction spectroscopy. Four types of mixed‐oxide particles of tungsten–molybdenum and tungsten–titanium are synthesized and used to make the photoanodes for dye‐sensitized solar cells (DSSCs). The best DSSC shows a fill factor of 51% and a short‐circuit current density of 4.8 mA cm−2, resulting in a conversion efficiency of 4.11% and an improvement over the cells prepared from pure titanium or tungsten oxides. [ABSTRACT FROM AUTHOR]

Mesostructured mixed metal oxides are one of the best candidates for various oxidations. Here, mesostructured Cux/Cey mixed oxides with various Cu/Ce ratios were prepared using mesoporous silica as a hard template to improve their selectivity and efficiency as the oxidative catalysts. Investigation of the different ratios of Cu/Ce showed that all catalysts are significantly more active than their salts in the oxidation of alcohols and sulfides with some green oxidants. The results demonstrated that the balance of the number of active catalytic centers (concentration of Cu) and the structural characteristics (surface area and oxygen vacancy) determine the activity of the catalysts. It also seems to be a powerful interplay among copper and cerium ions that helps the reduction of both Cu (II) and Ce (IV). [ABSTRACT FROM AUTHOR]

Ni(Mg)Al-layered hydroxides with molar ratios of (Ni + Mg)/Al = 2, 3, 4 and Ni/(Ni + Mg) = 0.1, 0.3, 0.5, 0.7 were synthesized by mechanochemical activation. It has been proven that the phase composition of the samples was presented by a single hydrotalcite phase up to Ni/(Ni + Mg) = 0.5. For the first time, catalysts based on Ni(Mg)Al-layered hydroxides prepared by a mechanochemical route have been studied in the reaction of furfural hydrogenation. The correlation between furfural conversion, the selectivity of the products, and the composition of the catalysts was established. The effect of phase composition, surface morphology, and microstructure on the activity of the catalysts was shown by XRD, SEM, and TEM. It was found that catalysts with Ni/(Ni + Mg) = 0.5 have the highest furfural conversion. Herewith, the product selectivity can be regulated by the (Ni + Mg)/Al ratio. [ABSTRACT FROM AUTHOR]

Catalysts based on CoCuMgAl mixed oxides were synthesized and studied in the hydrogenations of furfural and 5-hydroxymethylfurfural under different conditions. The changes in the structural properties of the catalysts at different stages of their preparation were studied using a set of physical methods (XRD, SEM, and TEM). It was shown that the fine regulation of the chemical compositions of the mixed oxides (i.e., changes in the Co/Cu ratio) made it possible to vary the structure, morphology, and catalytic properties of the samples. The phase composition of catalysts with Co/Cu = 1 did not change during the catalytic reaction, although the initial catalysts had a less-homogeneous morphology. 5-hydroxymethylfurfural conversion was higher for the samples with Co/Cu = 1. Furfural conversion increased when raising the Co/Cu ratio. The selectivity toward furfuryl alcohol for the catalyst with Co/Cu = 2 under mild conditions of furfural hydrogenation was more than 99%. The results obtained are important for the development of the scientific foundations of the preparation of hydrogenation catalysts with a fine-tunable composition in order to obtain the desired hydrogenation products.

In this study, we prepared Al _2 O _3 -TiO _2 (AT) mixed oxides to synthesize NiW catalysts for sulfur removal reactions. The AT support samples were prepared with various surfactants. Additionally, gallium atoms (2.4 wt%) were introduced as an additive to coat the outer surface layers of AT support that lacked Al ^3+ or Ti ^2+ cations. Characterization results showed substantial differences in textural properties, chemical composition, and surface acidity. The x-ray Photoelectron Spectroscopy (XPS) and High-Resolution Transmission Electron Microscopy (HR-TEM) results demonstrated that the NiW/AT-L-Ga sample has a better combination of dispersion, sulfidation, and promotion among materials. The sulfided NiW/AT-L-Ga catalyst had the highest catalytic activity. After incorporating Ga, XPS observed that the activity could be associated with an increase in the NiWS active phase; however, including a surfactant in the synthesis of the support allowed an increase in the amount of NiWS phase. The active phase was modeled considering the HR-TEM results for the slab length, revealing the atoms at the border susceptible to promotion.

Proton exchange membrane (PEM) water electrolysis represents a promising technology for green hydrogen production, but its widespread deployment is greatly hindered by the indispensable usage of platinum group metal catalysts, especially iridium (Ir) based materials for the energy-demanding oxygen evolution reaction (OER). Herein, we report a new sequential precipitation approach to the synthesis of mixed Ir-nickel (Ni) oxy-hydroxide supported on antimony-doped tin oxide (ATO) nanoparticles (IrNi _y O _x /ATO, 20 wt.% (Ir + Ni), y = 0, 1, 2, and 3), aiming to reduce the utilisation of scarce and precious Ir while maintaining its good acidic OER performance. When tested in strongly acidic electrolyte (0.1 M HClO _4 ), the optimised IrNi _1 O _x /ATO shows a mass activity of 1.0 mA µ g _Ir ^−1 and a large turnover frequency of 123 s ^−1 at an overpotential of 350 mV, as well as a comparatively small Tafel slope of 50 mV dec ^−1 , better than the IrO _x /ATO control, particularly with a markedly reduced Ir loading of only 19.7 µ g _Ir cm ^−2 . Importantly, IrNi _1 O _x /ATO also exhibits substantially better catalytic stability than other reference catalysts, able to continuously catalyse acidic OER at 10 mA cm ^−2 for 15 h without obvious degradation. Our in-situ synchrotron-based x-ray absorption spectroscopy confirmed that the Ir ^3+ /Ir ^4+ species are the active sites for the acidic OER. Furthermore, the performance of IrNi _1 O _x /ATO was also preliminarily evaluated in a membrane electrode assembly, which shows better activity and stability than other reference catalysts. The IrNi _1 O _x /ATO reported in this work is a promising alternative to commercial IrO _2 based catalysts for PEM electrolysis.

Samples of La1-3xLixM2xCoO3-δ (M = Ca, Sr, Ba; 0≤x≤0,1) were synthesized by co-precipitation method. It is shown that the region of their homogeneity lies in the range of substitutions 0≤ x ≤0.05. The volume of the unit cell increases with the size of the alkaline earth metal that replaces lanthanum. Surface morphology of the obtained mixed oxides was studied by SEM. In all samples (except strontium - containing) paramagnetic Co2+ ions from the impurity Co3O4, which are in different local environments and have different degrees of exchange interaction with each other, are contained in the form of chain fragments -Co2+-O2--Co2+-O2--Co2+-O2— and contain defective centers Со2+, which are formed during the desorption of lattice oxygen from the surface, or in the process of diffusion of oxygen from the volume of material to the surface. In strontium-containing samples La0,85Lix0,05Sr0,01CoO3-δ there are mainly ferromagnetic clusters Co3+-Co4+.

We report the preparation by three methods (coprecipitation, self-combustion, and microwave-assisted self-combustion) of Pr-promoted Ni-catalysts for H2/CO>1 syngas production by dry reforming of methane (DRM). The catalysts were characterized by a package of techniques to describe their physicochemical properties including several techniques using CO2 as a probe molecule. The catalysts were tested at 600 °C (10 h) and 120 L∙g−1 h−1, without previous H2-reduction. The coprecipitation method allowed obtaining a catalyst with a higher surface area and CO2 capture capacity (3.1 mg∙gcat−1), a higher number of basic sites, lower average Ni0 particle size (5.5 nm), higher catalytic conversions (48–65% of CH4 and 39–42% of CO2) and H2 (H2/CO = 1.15–1.75) yield but higher C formation. In addition, the catalyst obtained by microwave-assisted self-combustion presented better performance (45–51% of CH4 and 35–38% of CO2) than traditional self-combustion (40–45% of CH4 and 33–35% of CO2). The results showed that not only Ni0 particle size but also the presence of basic sites with high thermal stability and grain morphology affect the catalytic activity and coke formation.

Anodic oxides were grown to 50 V on Ta-Nb sputtering deposited alloys, with high Nb content, in acetate ions containing an aqueous solution to study the effect of the anodizing bath composition on anodic layers' dielectric properties. Photoelectrochemical measurements proved the presence of a photocurrent in the band gap of photon energy lower than oxides, due to optical transitions involving localized electronic states as a consequence of acetate ions incorporation. Flat band potential value estimates assessed the insulating nature of the anodic oxides grown in the acetate buffer solution. Differential capacitance measurements showed that the highest capacitance value was measured for the sample grown on Ta-66%Nb. This capacitance value was higher with respect to those estimated for pure Ta and pure Nb anodic layers and with respect to the same alloy anodized in NaOH solution, i.e., acetate-free anodizing bath. [ABSTRACT FROM AUTHOR]

Mixed Ni-Al oxide catalytic precursors with different elemental ratios (20, 50, and 80 wt.% Ni0) were synthesized using green supercritical antisolvent co-precipitation (SAS). The obtained oxide precursors and metal catalysts were characterized in detail by X-ray diffraction (XRD) analysis, atomic pair distribution function (PDF) analysis, CO adsorption, and high-resolution transmission electron microscopy (HRTEM). It was found that the composition and structure of the Ni-Al precursors are related to the Ni content. The mixed Ni1−xAlxO oxide with NiO-based crystal structure was formed in the Ni-enriched sample, whereas the highly dispersed NiAl2O4 spinel was observed in the Al-enriched sample. The obtained metal catalysts were tested in the process of anisole H2-free hydrogenation. 2-PrOH was used as a hydrogen donor. The catalyst with 50 wt.% Ni0 demonstrated the highest activity in the hydrogenation process. [ABSTRACT FROM AUTHOR]