Tahani Saad Algarni

Partial oxidation of methane (POM) provides an efficient route to convert methane into hydrogen-rich syngas, with lower energy demands than conventional steam reforming. This work evaluates lanthanum promotion effects on the physicochemical properties and catalytic behaviour of Ni/CeO₂ catalysts. A series of 5Ni + xLa/CeO₂ catalysts with 0–2 wt.% La was synthesised by wetness impregnation and characterized using N₂ adsorption–desorption, Raman spectroscopy, and cyclic H₂-TPR–O₂-TPO–H₂-TPR analysis. The results proved that promoter La has a strong effect on the structure and surface chemistry of the Ni/CeO₂ catalysts, as it modifies the CeO₂ framework, encourages the formation of surface carbonate species, and changes Ni interaction with the support. These structural shifts are closely tied to the enhancement of the catalyst’s performance and stability during POM. Among the catalysts, 5Ni + 1.5La/CeO₂ struck the best balance between textural properties and catalytic performance. At 600 °C and a GHSV of 14,400 mL h⁻¹ g_cat⁻¹, the CH₄ conversion reached about 57–59% and H₂ yield reached 53–55% over 300 min on stream. It also led to more than 70% CH₄ conversion and more than 65% H₂ yield for 22 h at 600 °C and 7200 mL h⁻¹ g_cat⁻¹, showing sustainable hydrogen-rich syngas production during continuous operation. However, increasing the La loading to 2 wt.% strengthened the La–CeO₂ interaction to the point of limiting the accessibility and dispersion of active sites, which lowered catalytic activity. Hence, these findings reveal that 1.5 wt.% La is the optimum loading, which balances support structure, metal–support interaction, surface chemistry, and active-site accessibility, and offers a practical strategy for producing more effective and stable Ni/CeO₂ catalysts for hydrogen-rich syngas production via POM.

The partial oxidation of methane (POM) to syngas is a technologically attractive route for H ₂ production; however, its practical implementation is hindered by catalyst deactivation, carbon deposition and limited long‐term stability. Herein, we elucidate the promotional role of strontium (Sr) in enhancing the structural and catalytic properties of Ni/ZrO ₂ ‐SiO ₂ catalysts. Sr incorporation modulates the electronic structure and redox behavior of the catalyst by strengthening metal‐support interactions and promoting oxygen mobility. Notably, Sr induces the formation of oxygen vacancies, thereby increasing the availability of reactive lattice oxygen species (O ²⁻ /O ₂ ²⁻ ), which facilitates CH ₄ activation and suppresses coke formation. Comprehensive characterization using XPS, TPR and XRD demonstrates that Sr enhances Ni reducibility and stabilizes active sites through surface electronic modification. Among the investigated catalysts, Ni3Sr/SZ (3 wt.% Sr) exhibits optimal performance, achieving 54.0% CH ₄ conversion and 52.0% H ₂ yield with a H ₂ /CO ratio of 2.6 at 600°C under CH ₄ :O ₂ = 2:1 condition, corresponding to an enhancement of > 15% compared to the unpromoted system. Furthermore, the catalyst maintains stable activity over 250 min without noticeable deactivation, attributable to its improved resistance to carbon accumulation. The superior performance is ascribed to the synergistic interplay between enhanced oxygen mobility, increased oxygen vacancy concentration, and strengthened metal‐support interactions. This work provides fundamental mechanistic insights into Sr‐promoted Ni catalysts and offers a scalable strategy for the rational design of robust catalytic systems for hydrogen‐rich syngas production, with potential applications in Fischer‐Tropsch synthesis and fuel cell technologies.

The Journal retracts the article “Synthesis and Characterization of CeO₂/CuO Nanocomposites for Photocatalytic Degradation of Methylene Blue in Visible Light”

The partial oxidation of methane (POM) is an attractive route for syngas production. However, Ni‐based catalysts often suffer from deactivation due to carbon deposition, metal sintering, and unstable metal–support interactions. In this study, the influence of zirconia (ZrO ₂ ) source and selected oxide promoters on the performance of Ni/ZrO ₂ catalysts in POM was investigated. A series of 5 wt.% Ni catalysts were prepared using ZrO ₂ supports from five commercial sources with different crystalline phases and textural properties. The best‐performing support was further modified by co‐impregnation with 10 wt.% Al ₂ O ₃ , TiO ₂ , and Y ₂ O ₃ . The catalysts were characterized using physicochemical techniques and evaluated in a fixed‐bed reactor at 600°C under CH ₄ /O ₂ = 2.0 (GHSV = 14,400 mL·g ⁻¹ ·h ⁻¹ ). Raman spectroscopy and transmission electron microscopy were used to examine carbon deposition on spent catalysts. The results showed that the crystalline phase and textural properties of ZrO ₂ influenced the catalytic performance. Among the unpromoted catalysts, Ni supported on DK‐type monoclinic ZrO ₂ exhibited the highest CH ₄ conversion (52.2%) and H ₂ yield (51.4%), which was associated with improved Ni accessibility and moderate metal–support interactions. The introduction of oxide promoters further enhanced the activity, with Y‐promoted Ni/ZrO ₂ achieving the highest performance (60% CH ₄ conversion and 58.2% H ₂ yield). XPS and H ₂ ‐TPR analyses suggested an increased contribution of interfacial Ni–O–Zr species together with enhanced reducibility for the Y‐promoted catalyst. These results indicate that both the ZrO ₂ source and promoter type influence the balance between Ni dispersion, reducibility, and catalytic performance in POM.

This journal retracts the article titled “Effects of Cr₂O₃ Content on Microstructure and Mechanical Properties of Al₂O₃ Matrix Composites”

Catalytic methane decomposition offers an attractive and sustainable pathway for producing CO_x-free hydrogen and valuable carbon nanotubes. This work investigates the innovative use of liquid metals, particularly gallium and indium, as promoters for iron catalysts based on a titanium dioxide and alumina composite to improve this process even more. In a fixed-bed reactor operating at 800 °C and atmospheric pressure, all catalyst activities for methane decomposition were thoroughly assessed while keeping the gas hourly space velocity at 6 L/g h. Surface area and porosity, H₂-temperature programmed reduction/oxidation, X-ray diffraction, Raman spectroscopy, scanning transmission electron microscopy, and thermogravimetry analysis were utilized to investigate the physicochemical properties of the catalyst. The result showed that iron supported on a titanium-alumina catalyst exhibited higher activity, stability, and reproducibility with a methane conversion of 90% and hydrogen production of 81% after three cycles, with 240 min for each cycle and stability for 480 min. In contrast, the liquid metal-promoted catalysts improved the metal-support interaction and textural properties, such as surface area, pore volume, and particle dispersion of the catalysts. Still, the catalytic efficiency significantly improved. However, the gallium-promoted catalyst displayed excellent reusability. The characterization of the spent catalyst proved that both the iron supported on a titanium-alumina and its gallium-promoted derivative produced graphitic carbon; on the contrary, the indium-promoted catalyst produced amorphous carbon. These results demonstrate how liquid metal promoters can be used to adjust the characteristics of catalysts, providing opportunities for improved reusability and regulated production of carbon byproducts during methane decomposition.

Local Khulays clay was modified to prepare polystyrene clay nanocomposite (PCN) coatings on carbon steel. The PCN coatings were added to microcapsules (MCs) loaded with the corrosion inhibitor PCN(MC). The microcapsules were prepared by the encapsulation of rare-earth metal Ce⁺³ ions and isobutyl silanol into polystyrene via the double emulsion solvent evaporation (DESE) technique. From characterization techniques, Fourier-transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), transmission electron microscopy (TEM), and scanning electron microscopy (SEM) with EDX. SEM and FT-IR confirmed the success of the preparation of the PCN(MC). Nanoindentation tests were performed on the thin-film samples. A significant reduction in both the hardness and the reduced modulus was observed for the PCN film compared to the PS film. Electrochemical impedance spectroscopy (EIS) and electrochemical frequency modulation (EFM) all showed an enhanced protection efficiency (%PE) of 3% PCN(MC) over 3% PCN at high temperatures and at different times. The smart coatings were proven by applying the thermal and the mechanical triggers for the 3% PCN(MC) coating. The mechanism of the release of inhibitors was discussed. The self-healing properties of 3% PCN(MC) were evaluated. The enhanced properties of the developed PCN(MC) coatings make them attractive for potential applications in the oil and other industries.