The beneficial effects on ZnO and TiO₂ photocatalytic activity resulting from a suitable combination of doping and heterojunctions were proposed and investigated by a synergistic experimental and theoretical study. In detail, the ZnO/N-doped TiO₂ heterojunction was synthesized and tested in the photocatalytic degradation of atrazine under UV and visible light. Wide-angle X-ray diffraction (WAXD) analysis reveals the presence of both ZnO and TiO₂ crystalline phases in the heterojunction. UV–vis DRS analysis shows that the simultaneous presence of ZnO and N-doped TiO₂ in the heterojunction results in a slight increase in the band gap value in the UV region , while the shoulder in the visible region typically of bare N-doped TiO₂ is preserved. On the basis of these experimental observations, density functional theory (DFT) calculations were carried out to model both the N-doped TiO₂ structure and to rationalize the experimental decrease in the band gap energy. The DFT modeling of band alignment of the ZnO/N-doped TiO₂ heterojunction allowed us to define the “minimal band gap” (MBG), corresponding to the interface gap, which resulted in smaller band gap energy than the two separate semiconductor band gaps. Furthermore, the DFT modeling of the electronic structure of N-doped TiO₂ predicted the existence of additional energy levels between the TiO₂ valence and conduction bands, which allowed us to justify the activity of the heterojunction under visible light irradiation. Photocatalytic tests showed that the ZnO/N-doped TiO₂ heterojunction performance was better than that of both N-doped TiO₂ and ZnO alone, allowing us to achieve almost complete atrazine degradation under UV light irradiation, whereas 24% of atrazine degradation was achieved after 180 min of visible light irradiation. Finally, the photocatalytic results achieved by using scavenger molecules for reactive oxygen species showed that ·OH and ·O₂^– are both reactive species in atrazine photocatalytic degradation under UV irradiation, while ·OH is responsible for the photocatalytic processes under visible irradiation. DFT modeling, validated by these results, finally allowed us to define a model of the band alignment and photogenerated charge-transfer mechanism for the ZnO/N-doped TiO₂ heterojunction.

Density Functional Theory (DFT) calculations have been performed to investigate the structural and electronic properties of the ZnO(wurtzite)–ATiO₂(anatase) heterojunction in the absence and presence of substitutional, interstitial nitrogen (N) doping and oxygen vacancies (O_V). We report a detailed study of the interactions between the two nonpolar ZnO and TiO₂ surfaces and on the role of N-doping and oxygen vacancies, which are decisive for improving the photocatalytic activity of the heterojunction. Our calculations show that substitutional N-doping is favored in the ATiO₂ portion, whereas the interstitial one is favored in the ZnO region of the interface. Both substitutional and interstitial N-doped sites (i) induce gap states that act as deep electronic traps improving the charge separation and delaying electron–hole recombination, (ii) facilitate the O_V formation causing a decrease in the formation energy (E_FORM), and (iii) do not affect the band alignment when compared to the undoped analogue system. The presented results shed light on the N-doping effect on the electronic structure of the ZnO(100)–TiO₂(101) heterojunction and how N-doping improves its photocatalytic properties.

The spontaneous formation and long‐term surface stabilization of superoxide radicals are observed on specific TiO₂ hybrid materials in which titanium is coordinated to an organic ligand. Here the rationale for this uncommon phenomenon is investigated by a synergistic theoretical and experimental approach involving density functional theory (DFT) calculations and spectroscopic techniques. Stoichiometric and reduced anatase (101) surfaces modified with acetylacetone, dibenzoylmethane, and catechol are comparatively examined. These results reveal that the interaction between organic ligands and adsorbed O₂ molecules improves when O vacancies are present on the external layer of the surface, promoting O₂ reduction. The electronic features of the ligand play a pivotal role for both an effective electronic interaction with the surface and the stabilization of the generated reactive oxygen species. These results agree with experimental data showing that sol–gel‐derived Ti‐diketonate hybrid oxides spontaneously produce very persistent superoxide radicals under ambient conditions, thus holding a high intrinsic oxidative activity.

Al–air battery has been regarded as a promising new energy source. However, the self-corrosion of aluminum anode leads to a loss of battery capacity and a decrease in battery longevity, limiting its commercial applications. Herein, indole-2-carboxylic acid (ICA) has been added to 4 M NaOH as a corrosion inhibitor. Its impact on the self-corrosion of aluminum alloy and the enhancement of the functionality of Al–air batteries at various concentrations have been investigated. X-ray photoelectron spectroscopy (XPS), attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy, atomic force microscopy (AFM), and scanning electron microscopy (SEM) techniques have been used to examine the compositional and morphological alterations of aluminum alloy surfaces. Electrochemical and hydrogen evolution tests showed that indole-2-carboxylic acid is an efficient corrosion inhibitor in alkaline solutions, and its impact grows with concentration. Our findings demonstrated that when the inhibitor concentration is 0.07 M, the inhibition efficiency is 54.0%, the anode utilization rises from 40.2% to 79.9%, the capacity density increases from 1197.6 to 2380.9 mAh g⁻¹, and the energy density increases from 1469.9 to 2951.8 Wh kg⁻¹. In addition, theoretical calculations have been performed to support the experimental results.

Schematic representation of adsorption and release of cisplatin from CuO NPS.