Wide-gap oxides are promising materials for optoelectronic applications due to their exceptional optical, electronic, and structural properties. This paper explores the impact of doping and co-doping on the structural, electronic, magnetic, and optical properties of CeO2 and TiO2 using a first-principles approach based on the full potential linearized augmented plane wave (FP-LAPW) method within the framework of density functional theory (DFT). The results show that doping and co-doping lead to a significant change in the lattice parameters, which is of paramount importance as it affects the fundamental properties of the compounds. The optimized structural parameters authenticate the stability of the ferromagnetic phases, and the formation energies justify the stability conditions of the compounds. Furthermore, a half-metallic character with an indirect band gap (spin-up) and semiconductor features is achieved for doping and co-doping models based on CeO2 and TiO2, respectively. There is no significant difference between single doping and co-doping in terms of total magnetic moment values since both single doping and co-doping compounds contribute a total magnetic moment of 2μB each. In addition, after the doping process, many optical parameters, including the absorption coefficient and dielectric constants, become much better, resulting in amplified absorption peaks in the visible and UV areas. These findings suggest that compounds exhibit interesting features for spintronic and optoelectronic technologies.

A promising research approach is currently oriented toward the investigation of multilayer films, consisting of the combination of metal elements and Al-doped ZnO (AZO) films for potential future applications. In this context, we focus on the preparation, characterization and film thickness effects on different properties of Cu/AZO bilayers. Hence, a multi-source RF magnetron sputtering deposition system in confocal configuration, under optimized conditions, was used to successfully deposit Cu/AZO bilayers on glass substrates with increasing Cu thickness, up to 13 nm, and a constant AZO thickness of 65 nm. The structural, morphological, electrical, optical and luminescent properties of all samples were characterized by X-ray diffraction (XRD), atomic force microscopy (AFM), UV–vis spectroscopy, Hall effect and photoluminescence (PL) techniques. The obtained results indicated that all the samples show a würtzite hexagonal structure with a preferential orientation in the axis c (002). The homogeneity of Cu layers is obtained for 10 and 13 nm thicknesses, and the optical properties are strongly affected by the existence of Cu. Moreover, increasing Cu thickness leads to (i) an improvement of structural and electrical (resistivity, mobility and carrier density) properties, (ii) a decrease in transmittance, (iii) a widening of the optical gap, and (iv) a variation of UV–violet emission intensity. These very interesting results are of great importance for understanding the behavior of Cu/AZO bilayers, which form a milestone for future potential applications in coatings and photovoltaics.

•Ni-, Ce-, and co-doped rutile TiO2 were investigated.•Full potential, linearized augmented, plane wave was used.•(Ni, Ce) co-doping induces impurity energy levels above the valence band maximum.•Increase in impurity energy levels reduces the required transition electron energy.•The co-doped TiO2 has the higher photo-response for visible-light than that of Ni or Ce single doped with.

Ni–Ce and Ni–Pt bimetallic catalysts supported over α-Al2O3 are synthesized by using co-impregnation method, and then reduced, each via radiolytic process or thermal H2-treatment. For Ni-Ce/Al2O3, the structural study reveals that Ce is alloyed with Ni as Ce2Ni7 nanoparticles in the radiation-reduced catalysts, while it segregates to the surface in the form of CeO2 in the H2-reduced catalysts. For Ni-Pt/Al2O3 radiolytic catalysts, Ni, Pt, NiPt and Ni3Pt nanoparticles, which size is 3.5nm, are observed. When the radiation-reduced samples are tested in the benzene hydrogenation, they both display high conversion rate. However, the Ni-Pt/Al2O3 is more efficient than Ni-Ce/Al2O3. The performance of the catalysts is correlated with the high dispersion of the metal and the presence of intermetallic Ni–Pt and Ni–Ce phases. It is compared to that of other radiolytic monometallic/oxide catalysts of the literature.

The radiolysis route is applied to synthesize nickel catalysts deposited on titanium dioxide. The TPR profile of radiation-induced Ni/TiO2 catalyst indicates a more complete reduction of the irradiated catalysts compared to the conventionally H2-reduced one. When tested in the benzene hydrogenation, the radiolytic Ni/TiO2 exhibits catalytic properties with higher efficiency than the H2-reduced catalyst. This observation is assigned to the presence of intermetallic Ni–Ti compounds (Ni2.66Ti1.33 and Ni3Ti) evidenced by XRD. In contrast, the calcined and H2-reduced catalyst contains predominantly the oxidized Ni5TiO7 phase, where the nickel is in strong interaction with the support. The TEM observations show highly dispersed nickel.

A series of nickel nanoparticles are deposited on two metal oxides (α- Al2O3 and CeO2). The nickel precursor is first adsorbed on the support and then it is irradiated under rays. The samples are characterized by various techniques at several steps of their elaboration, such as UV-visible, XRD, SEM equipped with EDS, and H2-TPR. The catalysts present high reducibility, and homogeneity of the metal phase. These properties of the radiolytic catalysts, could be explained by an easier reduction of the nickel in strong interaction with the oxides; which results in highly dispersed nanoparticles. Under benzene hydrogenation reaction test, the Ni/CeO2 catalyst exhibits higher efficiency than Ni/Al2O3 one. This behavior is assigned to the promoter role of ceria. Actually, in addition to the Ni∘ phase, the presence of intermetallic Ni-Ce compounds is detected in the Ni/CeO2 sample, after catalytic test.

This work concerns the study of nickel clusters synthesized by radiation-induced reduction of Ni2+ ions previously adsorbed on ceria by ionic exchange in the aim to test their performance in catalytic hydrogenation. The nickel catalyst and CeO2 support were characterized by SEM coupled to X analysis, XRD, H2-adsorption and H-TPD. The catalyst prepared by irradiation presents high reducibility, dispersion and homogeneity of the metal phase. It is shown that the CeO2 support stores hydrogen during the radiolytic reduction of Ni ions and that the adsorbed hydrogen amounts strongly increase in the presence of nickel. The catalyst displays high catalytic performance in the benzene hydrogenation reaction (total conversion in a large and low temperature range). These properties are assigned to the high dispersion of nickel and to the promoter role of the support: actually, after the catalytic test, intermetallic nickel–cerium compounds (CeNi and CeNi2) are detected in the sample in addition to the Ni0 phase.

A series of Ni aggregates supported on α-Al2O3 at different nickel contents are prepared by ionic exchange of Ni2+ followed by γ-irradiation under inert atmosphere. Characterization techniques are used at each step to select the elaboration conditions optimized for their use as catalysts. X-ray diffraction demonstrates the presence, after the Ni2+ adsorption step, of the phases (NiO)2(Al2O3)9 and (NiO)(Al2O3)16 that are favourable to further performances of the catalyst. After radiolysis, the phases of the oxide NiO and the metal Ni are observed. The relative amount of the Ni metal phase increases with the initial Ni2+ content. The nickel clusters (prepared from the complex [Ni(NH3)6]2+), imaged by Scanning Electron Microscope (SEM)/EDS, are highly dispersed. The H2 adsorption and thermodesorption study by chemisorption and H2-TPD indicates that the sites of the catalyst are occupied by hydrogen generated during irradiation. After H2 treatment at 350°C, it shows high hydrogen adsorption/desorption capacity. When tested in the steam-reforming methane reaction (CH4+H2O→CO+3H2), the radiolytic Ni/α-Al2O3 samples exhibit quite promising catalytic properties, namely a high activity and a remarkably high selectivity in CO even at moderate temperature (80% at 550°C with a conversion of 60%).