Search Results (1,734)

The selective hydrogenation of p-chloronitrobenzene (p-CNB) to p-chloroaniline (p-CAN) is of great importance for the production of dyes, pesticides, and pharmaceuticals, but it is often plagued by the undesired hydrodechlorination side reaction. In this work, we report a PtNi bimetallic catalyst supported on nano-sized LTL zeolite (PtNi/Nano-HL) for the selective hydrogenation of p-chloronitrobenzene under mild conditions. The catalyst was systematically characterized by X-ray diffraction (XRD), nitrogen sorption (N₂ sorption), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and ammonia temperature-programmed desorption (NH₃-TPD). The results reveal abundant oxygen vacancies (RIR = 0.73) and an optimized distribution of medium–strong acid sites on the catalyst surface, as well as electronic interaction between Pt and Ni, which collectively enhance the catalytic performance. Remarkably, the PtNi/Nano-HL catalyst achieves 100% conversion and over 99% selectivity for p-chloroaniline under ambient conditions (30 °C, 0.1 MPa H₂) using ethanol as a solvent. Even after 24 recycling runs, it retains 100% conversion and >93% selectivity, demonstrating excellent stability. Moreover, the catalyst requires an extremely low Pt loading (only 0.11 wt%) and exhibits good substrate universality for various substituted nitroarenes. This work provides a promising strategy for designing high-performance bimetallic catalysts on nano-zeolite supports for the selective hydrogenation of halonitrobenzenes. Full article

Ba₂Li_2/3Ti_16/3O₁₃ (BLTO) tunnel structure titanate was successfully synthesized using a solvothermal methodology evaluating the effect of different solvents (isopropanol, ethylene glycol, and propylene glycol) on structural, optical, and electronic properties, as well as on photocatalytic hydrogen production using methanol as a sacrificial agent. The structural characterization revealed that the synthesis solvent greatly influences the phase purity, with ethylene glycol being the one that promoted the formation of a purer BLTO phase (96.1%), while the samples prepared with other solvents exhibited slightly higher amounts of BaTiO₃, and BaTi₅O₁₁ impurities. All samples showed similar morphology and bandgap; however, differences in surface-defect chemistry were observed. In particular, the sample prepared using ethylene glycol exhibited a higher concentration of oxygen vacancies, which contributed to a more efficient separation of the photogenerated charges, as evidenced by the photoluminescence measurements. As a result, this sample showed enhanced photoactivity for hydrogen production. Additionally, it was observed that the BLTO material exhibited good stability over repeated irradiation cycles, highlighting its potential as a photocatalyst for hydrogen generation. Full article

This study investigates the modulation of coercivity and magnetodielectric coupling in heat-treated, nickel-substituted lanthanum ferrite. LaFe_0.7Ni_0.3O₃ samples were synthesized by high-energy ball milling and sintered at temperatures between 1073 and 1473 K. Chemical composition, crystalline structural evolution, surface morphology, magnetic, dielectric, and electrical properties, as well as magnetodielectric coupling, were analyzed. The XPS spectra revealed the presence of adsorbed oxygen, associated with the high oxygen affinity of the material. This behavior is interpreted as a charge-compensation mechanism, related both to the formation of oxygen vacancies and to the partial oxidation of Fe³⁺ to Fe⁴⁺. XRD and Rietveld refinement confirmed a single-phase orthorhombic Pnma structure, and structural simulations revealed progressive octahedral distortions with increasing temperature, affecting the octahedral tilting and electronic bandwidth. Magnetic characterization revealed that thermal processing modifies the magnetic behavior, inducing weak ferromagnetism and a significant increase in coercivity, correlating with progressive densification, greater domain stability, and reduced microstrain. Impedance measurements revealed magnetodielectric coupling, the Maxwell–Wagner interfacial polarization mechanism, and reduced dielectric losses. These findings demonstrate that the coercivity and magnetodielectric response in cationic nickel-substituted lanthanum ferrite can be tuned through thermal processing. A semi-empirical magnetocrystalline anisotropy model is proposed to explain the coercivity evolution and associated multiferroic behaviors, thus contributing to the study of functional ferrites as sustainable alternatives to rare-earth magnetic materials with potential in sensors and memory devices. Full article

MgCr₂O₄ nanospinel samples were synthesized using a modified Pechini method, followed by controlled calcination. The resulting materials were evaluated in terms of crystal structure, particle morphology, and optical and electronic properties. Their oxidative activity towards the degradation of organic dyes was investigated via photocatalysis, Fenton-like, and photon-Fenton-like processes. Various analytical techniques were employed to characterize the samples, including X-ray diffraction (XRD) with Rietveld refinements, infrared (IR) spectroscopy, UV–Vis spectroscopy, colorimetry, and transmission and high-resolution transmission electron microscopy (TEM/HRTEM). Structural characterization revealed that MgCr₂O₄ crystallized after calcination at 600 °C, and Rietveld refinements confirmed cubic Fd-3m symmetry. IR spectra confirmed the short-range order through the presence of vibrational modes assigned to CrO₆^2- octahedra. UV–Vis spectroscopy indicated mixed Cr valences (Cr³+/Cr⁶+) for samples calcined at temperatures below 900 °C, with Cr⁶+ eliminated at higher temperatures, confirmed by electron paramagnetic resonance (EPR) spectroscopy. This suggests that an oxidation reaction occurred due to oxygen vacancies in the lattice. Optical bandgap (Eg) increased with temperature. Samples calcined at low temperatures were dark green and became more saturated at temperatures above 900 °C, suggesting photoresponse to visible light, as indicated by the Eg values. The oxidative activity of the nanospinels in degrading the dyes methylene blue (MB) and rhodamine B (RhB) under visible light depended on the nature of the dye, the catalyst concentration, and the use of H₂O₂ in the process to improve the formation of hydroxyl radicals (•OH), as confirmed by photohydroxylation of terephthalic acid (TA). The highest degradation rate was observed in the photo-Fenton-like process, with 96% and 97% degradation of RhB and MB dyes in 60 min, reaching a kinetic rate constant (${\mathit{K}}_{app}$) of 0.055 min⁻¹ and 0.051 min⁻¹, respectively. This study highlights the importance of controlling various parameters to promote the formation of reactive oxygen species (ROS) required for oxidative degradation by nanospinels. Full article

In this study, NiO/ZnO heterojunction materials were prepared by calcining metal–organic frameworks (MOFs). The structural and morphological characteristics of the NiO/ZnO composite were investigated using various characterization methods, including X-ray diffraction, X-ray photoelectron spectroscopy, and scanning electron microscopy. Gas-sensing tests showed that at the operating temperature of 190 °C, the NiO/ZnO heterojunction (with a molar ratio of 1:1) exhibited the highest response value (R_a/R_g = 201.7) and good selectivity toward 100 ppm n-propanol. Compared to pure ZnO and NiO, the response of NiO/ZnO was significantly improved (ZnO: 6, NiO: 14.6), with increases of 33.5-fold and 13.8-fold, respectively. The response and recovery times were 92 and 30 s, respectively. Additionally, to enable rapid identification of n-propanol gas concentrations, this study developed and validated a method by training and predicting response curves using a random forest algorithm, achieving identification of n-propanol gas at different concentrations (2–100 ppm) within 7 s. Finally, the enhanced sensing performance was mainly attributed to the formation of the interfacial p-n heterojunction between NiO and ZnO, together with increased surface active sites, oxygen vacancies, and chemisorbed oxygen species. Full article

B-site ordering of Li-modified Pb_0.95Li_0.05(Yb_1/2Nb_1/2)O₃ (PLYN) ceramics can be changed by duration during sintering. In this paper, the conventional solid-state reaction method was employed to prepare antiferroelectric perovskite Li-substituted PLYN ceramics. Crystal structure evolution dependence of sintering time was investigated using X-ray diffraction (XRD), Raman spectroscopy, and dielectric response. Two dielectric anomalies responses, attributed to the transition from B-site order to disorder and antiferroelectric-paraelectric phase transition depend on B-site ordering. The high-temperature dielectric relaxation associated with charged carries (oxygen-vacancy hopping) was characterized by isothermal electric modulus and universal dielectric response. Impedance spectroscopy was used to uncover the relationship between defect type and the oxygen partial pressure (pO₂) dependence on sintering time in PLYN systems. These findings provide new insights into the interplay among B-site ordered phase structure, dielectric response, and defect types. Full article

Catalytic oxidation has become a crucial technology for removing CO from industrial flue gas. However, the complex composition of flue gas (including NH₃, NO, SO₂, H₂O, etc.) poses significant challenges to the catalytic activity and stability of catalysts. In this work, we propose a new strategy for constructing highly efficient catalysts by loading a Pd component onto TiO₂ nanosheets (NSs) with predominantly exposed {001} facets. It has been revealed that the well-connected channels, abundant oxygen vacancies and Ti³⁺ species on the TiO₂(NS) support facilitate the formation of highly dispersed and electron-rich Pd nanoparticles. The weak adsorption of impurities such as NH₃, SO₂, NO and H₂O on these active sites promotes the adsorption and activation of the target reactants (CO and O₂), thereby enhancing catalytic activity. Furthermore, such reduced adsorption inhibits the aggregation of Pd nanoparticles and synergizes with the intrinsically weak NH₃ adsorption of TiO₂(NS) to suppress ammonium sulfate species deposition, thereby enhancing long-term catalytic stability. This work advances TiO₂ facet engineering in catalysis and offers new design concepts for efficient CO oxidation catalysts in complex atmospheres. Full article

In this study, a hierarchically confined Pt/MnO₂–meso-Al₂O₃ catalyst with 0.5 wt% Pt loading was synthesized via a precipitation method using MnO₂ as a promoter and mesoporous Al₂O₃ (m-Al₂O₃) as a support, and its methane catalytic combustion performance and structure–activity relationship were systematically investigated. The results demonstrate that the 0.5 wt% Pt-loaded Pt-MnO₂/m-Al₂O₃ catalyst achieved 90% methane conversion at 236 °C. The enhanced performance is attributed to three synergistic mechanisms: (1) Pt doping induced lattice contraction in MnO₂ (XRD revealed a 0.03 Å reduction in the (001) interplanar spacing), which facilitated the formation of Mn³⁺–oxygen vacancy pairs (XPS indicated a Mn³⁺- content of 79.87%); (2) the MnPt₃O₆ interfacial structure (HAADF-STEM confirmed lattice spacings of 0.21 nm) accelerated oxygen species cycling, with the 0.5 wt% Pt-loaded catalyst for lattice oxygen desorption capacity (O₂-TPD) increasing by 54% compared to undoped samples; (3) the mesoporous m-Al₂O₃ carrier provided effective confinement, achieving a high specific surface area (27.6 m²/g) and sub-nanometer Pt dispersion (particle size < 2 nm). Under conditions of 1000 ppm CH₄ and a space velocity of 30,000 h⁻¹, the catalyst maintained a methane conversion rate of 98.2 ± 0.5% during continuous operation for 300 h. Post-cycling characterization revealed a stable crystalline structure (XRD full width at half maximum of 0.35° ± 0.02°) and grain size (15.5 ± 0.5 nm), confirming its robustness for industrial applications. This study provides theoretical and experimental foundations for the rational design of highly efficient catalysts for low-concentration methane elimination. For comparison, a Co-doped catalyst (1.0 wt% Co–MnO₂/Al₂O₃) was also prepared, which exhibited significantly lower activity (T₉₀ = 251 °C), underscoring the unique role of Pt in the confined architecture. This study provides theoretical and experimental foundations for the rational design of highly efficient catalysts for low-concentration methane elimination. Full article

The sluggish kinetics of the OER in alkaline media demand efficient non-precious electrocatalysts. This study develops a strategy of B-site Ru doping in Sr-substituted LaCoO₃ perovskite to engineer its electronic structure, thereby activating the LOM. DFT calculations and electrochemical measurements were employed to investigate the electronic structure and catalytic performance. The synthesized La_0.6Sr_0.4Co_0.9Ru_0.1O₃ (LSCR-0.1) catalyst achieves a low overpotential of 256.8 mV at 10 mA cm⁻² and a Tafel slope of 84.88 mV dec⁻¹, along with excellent long-term stability in alkaline electrolyte. The results show that Ru doping shifts the O 2p-band center and lowers the oxygen vacancy formation energy, significantly reducing the energy barrier of the rate-determining step. This work concludes that B-site doping on A-site substituted perovskites offers a general and effective strategy for modulating their electronic structure to enhance OER performance. Full article

Perovskite-type oxides are among the most promising cathodes for intermediate-temperature solid oxide fuel cells (IT-SOFCs) due to their mixed ionic–electronic conductivity and compositional flexibility. Many high-performance cathodes rely on Sr substitution at the A-site, often associated with surface segregation and long-term degradation. In this work, we explore an alternative strategy based on defect engineering and phase interactions in Sr-free composites. Perovskite-fluorite composites based on LaFe_0.8Co_0.2O₃ were synthesized through a one-pot route designed to promote the formation of a perovskite phase and a limited amount of fluorite-type ceria. This approach allows the introduction of small fractions of Ce into the perovskite lattice, favoring the cooperative coexistence with La-doped CeO₂. Structural, microstructural and spectroscopic characterization indicates that Ce influences the crystallization pathway and composite defect chemistry. Variations in lattice parameters and Raman features suggest modifications of perovskite structure consistent with defect formation and lattice distortion. Reduction properties and electrical conductivity measurements indicate that Ce incorporation in the perovskite and oxide interaction affect charge transport and oxygen mobility. The electrochemical results demonstrate that the optimal trade-off between activation energy (Ea) and polarization resistance (Rp) is achieved for the sample, with a nominal cerium content, Ce/(La + Ce) of 0.16. Moreover, the electrochemical properties are found to correlate with the nominal cerium content, which regulates defect chemistry and the resulting composite composition. Overall, results suggest that the one-pot synthesis promotes beneficial interactions between the perovskite and ceria phases, allowing the development of Sr-free ferrite-based materials with enhanced functional properties, minimizing the amount of ceria in the composite. Full article

CeO₂ is a representative oxygen-storage oxide because its fluorite lattice can reversibly release and reincorporate oxygen through the Ce⁴⁺/Ce³⁺ redox couple and the associated formation and annihilation of oxygen vacancies. Although doped CeO₂ has been studied extensively, the literature has often treated oxygen-storage enhancement mainly in terms of dopant identity and composition, whereas the more fundamental issue is how a given doping strategy constructs a specific defect state within the fluorite host. Here, oxygen-storage enhancement is discussed from the standpoint of defect-state engineering. The discussion focuses on three routes, as follows: rare-earth single doping, cation–anion co-doping, and route-dependent dopant incorporation. Rare-earth single doping correlates aliovalent substitution with lattice expansion, vacancy generation, and finite oxygen-storage-capacity (OSC) optima. Cation–anion co-doping further shows that simultaneous perturbation of the cationic and anionic sublattices can amplify the defect response, while also demonstrating that vacancy concentration alone does not fully account for OSC enhancement. Route-dependent doping adds an additional dimension by showing that the same dopant can produce different lattice responses, defect populations, and oxygen-release behaviors when introduced through different pathways. On this basis, the review argues that OSC in doped CeO₂ is more meaningfully rationalized through a coupled descriptor set involving lattice accommodation, Ce³⁺/Ce⁴⁺ redistribution, oxygen-vacancy abundance, and dopant incorporation pathway. Taken together, these observations shift the design logic of oxygen-storage ceria from empirical dopant screening toward deliberate defect-state construction. Full article

This paper reports the controlled synthesis of ZrO₂ nanocrystals via a peroxide-assisted hydrothermal (HT) route at 120 °C, with processing times ranging from 12 to 72 h, and investigates the correlation between structural evolution, defect chemistry, and functional properties. X-ray diffraction (XRD) combined with Rietveld refinement confirmed the formation of a monophasic monoclinic structure with high structural reliability. Microstructural analysis revealed progressive crystallite growth and lattice ordering with increasing reaction time, accompanied by subtle distortions in local coordination environments. Micro-Raman spectroscopy indicated improved medium-range structural organization at longer synthesis durations, while transmission electron microscopy showed quasi-spherical and nanorod-like aggregates formed through oriented attachment, with particle sizes of 6–9 nm. Optical investigations using diffuse reflectance spectroscopy revealed band gap energies of 3.45–3.65 eV, attributed to defect-induced intermediate electronic states associated primarily with oxygen vacancies. A comprehensive photoluminescence (PL) analysis suggests that the observed emission arises from defect-mediated recombination pathways involving localized states within the band gap, modulated by the interplay between structural order and residual defects. The role of hydrogen peroxide is discussed in terms of regulating oxygen vacancy concentration, promoting structural stabilization while preserving functional defect states. The results demonstrate that precise control of HT processing time enables tuning of structural disorder, defect density, optical response, and the enhanced photocatalytic performance of ZrO₂ toward RhB dye degradation, highlighting its potential for optoelectronic applications. Full article

ZnO nanorods were synthesized on AZO substrates by chemical bath deposition, and were subsequently annealed under an air and vacuum ambient. Both annealing processes could improve the crystallinities of ZnO nanorods. The air-annealed ZnO nanorods showed higher crystallinity and partial reduction of oxygen-vacancy-related defects. The air-annealed ZnO nanorods exhibited a much higher photodegradation efficiency of 70% degradation for methyl red. In addition, as-grown ZnO nanorods were coated with undoped and Al-doped ZnO by mist chemical vapor deposition. Both coated thin layers modified the surface of ZnO nanorods, while the AZO-coated ZnO nanorods showed higher crystallinity and light absorption which resulted in the improvement in the photodegradation rate of methyl red. These findings demonstrate that appropriate annealing treatment and AZO surface engineering for ZnO nanorods are effective approaches for improving crystallinity, which leads to improvement of the photocatalytic efficiency of ZnO-based materials. Full article

In advanced oxide materials, additive selection is increasingly constrained by the simultaneous requirements of functional response, phase stability, morphology control, processing tolerance, scalability, and critical raw material security. This study develops a ZnO-centered framework to compare boron-based strategies (direct B doping, B₄C/ZnO composite formation, and h-BN/ZnO interface engineering) with rare-earth strategies (Ce/CeO₂, La/La₂O₃, and Y/Y₂O₃). Structural, morphological, chemical-state, and vibrational evidence from XRD, FE-SEM/EDX, XPS, Raman, and FT-IR studies is interpreted through an evidence hierarchy that separates lattice incorporation, surface/grain-boundary segregation, and deliberate secondary-phase or heterointerface formation. The synthesis shows that boron-containing routes usually provide broader phase retention, lower agglomeration tendency, more gradual defect modulation, and greater processing robustness, whereas rare-earth routes offer stronger oxygen-vacancy regulation, redox activity, luminescence tuning, and heterojunction-assisted function but require tighter process control and more rigorous verification of incorporation mode. Reanalysis of seven primary experimental pathways indicates that B₄C/ZnO and h-BN/ZnO are mechanistically non-equivalent: B₄C supports rigid composite-interface growth, while h-BN promotes sheet-mediated interface multiplication and Maxwell–Wagner–Sillars polarization. Türkiye is treated as an illustrative boron-rich producer case within a transferable producer/importer decision model. Dopant selection is therefore framed as a multi-criteria decision involving performance thresholds, reproducibility, technology-readiness potential, and supply-security exposure, not peak output alone. Full article

Heterogeneous catalytic ozonation has attracted increasing research attention as a strategy for advanced wastewater polishing; yet the recent literature has advanced the attribution of non-radical pathways at a pace that has outstripped rigorous demonstration of their practical process advantage. This article constitutes an evidence-centered critical review—rather than a formal systematic review—organized around a central evaluative question: under what conditions are non-radical mechanistic claims in catalytic ozonation sufficiently persuasive, wastewater-relevant, and defensible to warrant consideration for process translation. Recent studies, drawn primarily from the period 2023–2026, are evaluated through an explicit evidence-grading framework that distinguishes among radical, singlet-oxygen-mediated, surface-bound oxygen-transfer, direct electron-transfer, and high-valent metal-oxo pathways. The review further examines whether reported parent-compound removal is corroborated by complementary lines of evidence encompassing bromate formation, transformation product characterization, effluent toxicity assessment, catalyst leaching quantification, operational durability, and reactor-scale performance. The synthesis reveals that single-atom catalysts currently provide the most robust active-site mechanistic evidence; however, even these systems remain constrained by their reliance on simplified aqueous matrices, incomplete transformation byproduct accounting, and unresolved long-term stability. Accordingly, the article proposes standardized reporting protocols and benchmark performance metrics—including a bromate-normalized treatment benefit index—to delineate mechanistic elegance from process realism. Full article