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    Ferroelectric-assisted enhancement of the photocatalytic activity of g-C 3 N 4 / TiO 2 nanotubes heterojunctions through the addition of strontium
    (Elsevier Science Sa, 2024) Alsubaie, Modi Nasser; Alabbad, Sanaa Saad; Alrashidi, Wadha; Alomair, Nuhad Abdullah; Kochkar, Hafedh; Berhault, Gilles; Jomni, Fathi
    The effect of adding strontium to nanocomposites formed of g-C 3 N 4 /TiO 2 nanotubes (TiNT) (g-C 3 N 4 : 4.0 wt%) on the photocatalytic activity was herein investigated using formic acid as a model target pollutant. g-C 3 N 4 material was prepared by a solvothermal method using a mixture of urea and cyanuric chloride as precursors and acetonitrile as a solvent at 220 degrees C for 15 h, while TiNT material was obtained by the alkaline hydrothermal method of P25 at 130 degrees C for 20 h. A series of xSr-gC 3 N 4 /TiNT nanocomposites were then synthesized through progressive incorporation of strontium (from 0.2 to 1.0 wt%) at the surface of the composites. Samples were then characterized mainly using N 2 adsorption - desorption measurements, X-ray diffraction, UV - vis diffuse reflectance, Raman and photoluminescence (PL) spectroscopies, and scanning and transmission electron microscopy (with energy -dispersive X-ray spectroscopy and Z -mapping). The Sr -containing g-C 3 N 4 /TiNT composites were then also fully characterized by electrochemical impedance spectroscopy (EIS) for their dielectric properties, while a deep kinetics analysis was also performed. Such an approach allowed us to establish a correlation between photocatalytic performance and the material ' s propensity to be polarized. Results emphasize the beneficial role of ferroelectricity induced by adding strontium. Indeed, enhancement of the photocatalytic activity by 2.3 times compared to a Sr -free counterpart was related to the material ' s ability to be polarized for Sr loadings <= 0.6 wt%. At higher Sr loadings, supplementary factors (decrease of the anatase crystallinity, formation of TiO 2 (B), disruption of the g-C 3 N 4 /TiO 2 interaction, or lower mobility of photogenerated charges) negatively impact the activity, counterbalancing partly the beneficial ferroelectric effect. In this way, this study emphasizes the role played by ferroelectric effects in enhancing the photocatalytic ability of a given semiconductor.
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    Highly efficient magnetically separable SrFe12O19 for photo-assisted oxidation of benzylic alcohol derivatives under visible light
    (Elsevier Science Sa, 2024) Aldhawi, Zainah A.; Alousi, Latifah; Ercan, Ismail; Ozcelik, Bekir; Kochkar, Hafedh; Benali, Amor
    The selective oxidation of the C alpha- OH group of benzylic alcohols is a crucial process for the conversion of lignin into useful products. In this study, we describe the synthesis and characterization of magnetic strontium hexaferrite, SrFe12O19. The SrFe12O19 nano-powder was produced through coprecipitation at a pH level of 10. The catalyst has been studied using various methods such as X-ray diffraction (XRD), scanning electron microscopy (SEM) combined with energy-dispersive X-ray analysis (EDX), UV-vis diffuse reflectance spectroscopy (DRS), and magnetic field dependence measurements. The study aimed to evaluate the photocatalytic performance of SrFe12O19 in selective oxidation of benzylic alcohols and degradation of methylene blue under visible light. Additionally, the magnetic properties of the catalyst were also investigated. Magnetic properties were also investigated. M-SrFe12O19 with a band near 2 eV, showed excellent photocatalytic degradation performance at ca. 90% of MB under visible light. The photocatalytic degradation activity was evaluated for three cycles, and the results demonstrate that it maintains its photodegradation potency, with significant photo-degradation conversion of 89%, 87%, and 84%. The experiment clearly demonstrated that the reaction kinetics followed a pseudofirst order. The oxidation of benzyl alcohol (BzOH) was successfully carried out over SrFe12O19 in the presence of hydrogen peroxide, a highly effective green oxidant, under visible light. Notably, the experiment results showed a maximum conversion of BzOH, reaching approximately 70%, with absolute selectivity towards benzaldehyde (BzCHO). Furthermore, the yield of aldehyde increases according to the Hammett constant, with the highest yield being obtained for 2-hydroxybenzaldehyde (sigma = -0.37). The synthesized M-SrFe12O19 material shows potential as an eco-friendly method for lignin valorization.
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    The Role of the Ferroelectric Polarization in the Enhancement of the Photocatalytic Response of Copper-Doped Graphene Oxide-TiO2 Nanotubes through the Addition of Strontium
    (Amer Chemical Soc, 2023) Alomair, Nuhad Abdullah; Al-Aqeel, Nouf Saleh; Alabbad, Sanaa Saad; Kochkar, Hafedh; Berhault, Gilles; Younas, Muhammad; Jomni, Fathi
    To evaluate the potential role of in situ formed Sr-Ti-O species as a ferroelectric component able to enhance the photocatalytic properties of an adjacent TiO2 semiconductor, Cu-doped/graphene oxide (GO)/TiO2 nanotubes (TiNTs) composites (with 0.5 wt % Cu and 1.0 wt % GO) have been synthesized while progressive amounts of strontium (up to 1.0 wt %) were incorporated at the surface of the composite through incipient wetness impregnation followed by post-thermal treatment at 400 degrees C. The different resulting photocatalytic systems were then first deeply characterized by means of N2 adsorption-desorption measurements, X-ray diffraction (XRD), UV-vis diffuse reflectance (UV-vis DR), Raman and photoluminescence (PL) spectroscopies, and scanning electron microscopy (SEM) (with energy-dispersive X-ray (EDX) spectroscopy and Z-mapping). In a second step, optimization of the kinetic response of the Sr-containing composites was performed for the formic acid photodegradation under UV irradiation. The Sr-containing Cu/GO/TiNT composites were then fully characterized by electrochemical impedance spectroscopy (EIS) for their dielectric properties showing clearly the implication of polarization induced by the Sr addition onto the stabilization of photogenerated charges. Finally, a perfect correlation between the photocatalytic kinetic evaluation and dielectric properties undoubtedly emphasizes the role of ferroelectric polarization as a very valuable approach to enhance the photocatalytic properties in an adjacent semiconductor.