Search Results (1,709)

In this study, TiO₂ nanotube (TNTs) array electrodes were fabricated by electrochemical anodization and subsequently modified through thermal annealing, hydrogenation heat treatment, and chemical decoration with copper species at various immersion times to enhance their electrochemical performance. The structural, morphological, semiconducting, and electrochemical properties of the modified nanotubes were systematically examined. FE-SEM and EDS analyses confirmed the formation of well-aligned TNTs and the successful deposition of copper species, with the most uniform surface distribution achieved for the sample decorated for 45 min. Raman spectroscopy and XRD results revealed that the anatase phase of TiO₂ remained stable after hydrogenation and copper decoration, while minor peak shifts indicated defect evolution and lattice distortion. Electrochemical evaluations, including linear sweep voltammetry, Tafel polarization, electrochemical impedance spectroscopy, and Mott–Schottky analysis, demonstrated a substantial enhancement in electrocatalytic activity following copper decoration. Compared with annealed and hydrogenated electrodes, the decorated samples exhibited markedly lower overpotentials, reduced cathodic Tafel slopes, and decreased charge-transfer resistance. Mott–Schottky analysis confirmed n-type semiconducting behavior for all electrodes, showing that hydrogenation increased donor density, whereas subsequent copper decoration slightly reduced it due to the partial substitution of oxygen vacancies by copper oxide species. Among all samples, the electrode decorated for 45 min (AA′HD45) exhibited the optimal balance between donor density, charge-transfer properties, and electrochemical performance. These results highlight the effectiveness of combining hydrogenation with optimized copper decoration to improve charge transport and interfacial kinetics in TNT electrodes for electrochemical applications. Full article

Hydrogen peroxide (H₂O₂) is widely regarded as a clean and high-value chemical; however, its conventional industrial production remains both energy-intensive and environmentally unsustainable. In this study, sulfur-deficient ZnIn₂S₄ (denoted SDZIS) was developed as an efficient photocatalyst for H₂O₂ generation through oxygen reduction under visible-light irradiation. SDZIS photocatalysts with controllable sulfur-vacancy concentrations were synthesized via a one-step citric-acid-assisted hydrothermal process combined with NaOH etching. The results of transient photocurrent response and electrochemical impedance spectroscopy show that the separation efficiency of charge carriers has been improved. Compared with pristine ZnIn₂S₄, the optimized SDZIS catalyst achieved a nine-fold enhancement in the H₂O₂ production rate, reaching 2711.81 μmol g⁻¹ h⁻¹. Results of experimental and density functional theory calculations suggest that sulfur vacancies can modulate the catalyst work function and the adsorption energy of O₂. Comparative experiments indicate that an appropriate concentration of sulfur vacancies can lead to a high H₂O₂ yield. Combined with scavenger tests, DMPO-EPR, and rotating ring disk electrode measurements, these results support a sulfur-vacancy-associated enhancement in charge separation and a tendency toward a superoxide-involved 2e⁻ ORR pathway for H₂O₂ production. Full article

Oxygen stoichiometry critically governs the phase stability and physical properties of transition-metal oxides, yet a unified understanding of how oxygen-stoichiometry-driven phase reconstruction underlies the cooperative evolution of multiple physical properties in SrCoO_x remains lacking. Here, high-quality epitaxial brown millerite SrCoO_2.5 and perovskite SrCoO_3−δ thin films were grown by pulsed laser deposition under controlled oxygen conditions. Their structural, magnetic, electrical, optical, and photocatalytic properties were systematically compared. SrCoO_2.5 exhibits antiferromagnetic insulating behavior, infrared-dominant transmittance, and higher photocatalytic activity, whereas SrCoO_3−δ shows ferromagnetism, much lower resistivity, and strong optical opacity. First-principles calculations reveal that oxygen-stoichiometry-driven phase reconstruction strongly modifies the electronic structure, accounting for the distinct magnetic, transport, and optical responses. These results establish a direct correlation between oxygen stoichiometry, structural transformation, and multifunctional properties in SrCoO_x, highlighting oxygen-vacancy ordering as an effective route to tailoring correlated oxide functionalities. Full article

Black TiO₂-impregnated electrodes were prepared via a modified dip-coating method, using six deposition layers to investigate the influence of the TiO₂ precursor phase (anatase, rutile, and P25) on their structural and optical properties, as well as their photoelectrooxidation performance toward acetaminophen degradation. A reductive thermal treatment under a H₂/Ar atmosphere successfully modified the band gap energy and promoted the formation of oxygen vacancies (Vo) and Ti³⁺ species, as evidenced by UV–Vis diffuse reflectance spectroscopy and photoluminescence analysis. Among the precursor phases, anatase exhibited the most significant band gap reduction, whereas rutile and P25 showed greater structural stability after the reduction process. Photoelectrochemical experiments revealed that the supporting electrolyte plays a dominant role in the degradation process, with significantly higher removal efficiencies observed in chloride medium (0.1 M NaCl) compared with sulfate medium (0.1 M Na₂SO₄) due to the formation of active chlorine species. Among the tested materials, rutile- and P25-derived electrodes showed the highest degradation efficiencies, reaching concentrations (C/C₀) of 0.631 and 0.650, respectively. The results highlight the combined influence of precursor phase, defect structure, and electrolyte composition on the photoelectrooxidation behavior of black TiO₂ electrodes and provide insights for the design of electrochemical systems for pharmaceutical contaminants removal. Full article

Low charge-separation efficiency is a major factor limiting the photoelectric conversion performance of TiO₂. In this work, oxygen-vacancy-rich porous TiO₂ gel photocatalyst was successfully fabricated. The as-prepared material exhibits a three-dimensional interconnected hierarchical porous architecture with a specific surface area of 62.9 m² g⁻¹. EPR and XPS analyses confirmed the presence of Ti³⁺ defects and oxygen vacancies, which effectively increase the electron density and facilitate the separation and migration of photogenerated charge carriers. The results demonstrated excellent photocatalytic activity, with over 85% of RhB degraded within 50 min under light irradiation. In addition, its photocatalytic performance was further investigated by photocatalytic hydrogen evolution, and the hydrogen production rate reached 850.6 μmol·g⁻¹ h⁻¹. The enhanced photocatalytic performance can be mainly attributed to the synergistic effect of the hierarchical porous structure and oxygen vacancies. Specifically, the hierarchical porous structure improves mass transfer and provides abundant active sites, while oxygen vacancies modulate the electronic structure and promote charge separation, thereby significantly enhancing the catalytic activity. This work provides an effective strategy for improving the photoelectric conversion performance of TiO₂ and offers theoretical guidance as well as experimental support for the defect engineering and structural design of TiO₂-based photocatalytic materials. Full article

N₂O (Nitrous oxide) is a potent greenhouse gas with a global warming potential nearly 300 times that of CO₂ and poses a critical environmental challenge, particularly in semiconductor and display manufacturing, where it is emitted during plasma processes. However, catalytic N₂O abatement in O₂-rich environments remains inefficient because O₂ competitively occupies active sites and hinders the turnover of surface oxygen species. To clarify how support properties govern this inhibition, Co-based catalysts supported on beta zeolite, CeO₂, and TiO₂, together with unsupported Co₃O₄, were comparatively evaluated for direct N₂O decomposition. Among them, Co/Beta exhibited the highest performance, achieving >95% N₂O conversion at 450 °C in the presence of 5% O₂ with excellent long-term stability. Co/Beta possessed a high specific surface area (649 m² g⁻¹) and a mesoporous framework that favored uniform Co dispersion and reactant accessibility, while its high Co²⁺/(Co²⁺ + Co³⁺) ratio (75.5%) and large fraction of chemisorbed oxygen species (79.9%) promoted oxygen-vacancy formation and facile oxygen exchange. These results indicate that the ability of Co/Beta to maintain high activity in the presence of oxygen stems from support-modulated cobalt surface states and enhanced oxygen turnover behavior. These findings provide a support-design principle for stable N₂O decomposition under oxygen-containing exhaust conditions. Full article

Biotemplated strategies inspired by natural architecture have emerged as an effective strategy to improve the performance of photocatalytic materials. In this work, TiO₂-based photocatalysts were synthesized using olive leaves as a biological template to reproduce their hierarchical microstructure and enhance photocatalytic hydrogen production. The artificial olive leaf (AOL) support was obtained through a biotemplated ion-exchange process followed by hydrolysis and calcination. It was then modified by photodeposition of Au or Pt nanoparticles. The materials were characterized by SEM, XRD, N₂ adsorption–desorption, UV–Vis spectroscopy, and XPS to evaluate their structural and optical properties. SEM confirmed the successful replication of both the external morphology and internal architecture of the olive leaf, while XRD revealed low crystallinity with anatase as the only TiO₂ phase. Optical characterization showed a reduced band gap (~2.97 eV), and extended absorption toward the visible region, with Au nanoparticles exhibiting a plasmonic band at ~550 nm, whereas Pt enhanced light-harvesting efficiency. XPS indicated the presence of oxygen vacancies and Ti³⁺ species that promote metal–support interactions. Photocatalytic glycerol photoreforming showed a strong enhancement in hydrogen production after noble metal incorporation, reaching up to 14-fold under UV irradiation and 23-fold under simulated solar light for the Pt-modified catalyst, highlighting the synergy between biotemplated structuring and noble metal deposition. Full article

Hafnium oxide thin films have been extensively investigated for high-speed and low-power memory applications. Herein, we investigated the influence of oxygen vacancies and external stress on the ferroelectric characteristics of Al-doped HfO₂ (HfAlO). Compared with HfAlO with 14% oxygen vacancies, films with 21% oxygen vacancies could lower the polarization switching barrier and increase the fraction of the ferroelectric phase. Furthermore, significant external stress promotes ferroelectric phase formation, thereby enhancing ferroelectric characteristics. The remanent polarization achieved with W electrodes (2Pr = 38 µC/cm²) is about 18 times that of Au electrodes, owing to the lower thermal expansion coefficient of W electrodes. Density functional theory calculations and finite element analysis provide theoretical insights corroborating the experimental results, helping to pave the way for developing hafnium-based materials for next-generation in-memory computing applications. Full article

In this work, Ce-doped ZnO thin films at various contents of cerium were deposited on glass substrates by thermal vacuum evaporation to study the influence of Ce concentration on their optical, structural, morphological, and photocatalytic behavior. Pure ZnO and Ce-doped ZnO films doped with 2% and 5% Ce were characterized by SEM, XRD, AFM, UV–VIS spectroscopy, and ellipsometry. The XRD analysis confirmed that all the films retained the hexagonal wurtzite structure, while Ce incorporation induced lattice strain and reduced crystallite size, particularly at higher doping levels. SEM and AFM studies showed that films with 2% Ce exhibited smaller grain size and lower roughness, whereas 5% Ce-doped films showed grain growth and increased roughness. Pure ZnO films displayed high transparency (>90%), whereas Ce incorporation caused a red shift in the absorption edge and narrowing of the optical band gap due to defect-related states and lattice distortion. Photocatalytic experiments revealed that Ce doping improved charge carrier separation and increased the number of oxygen vacancies. Among all samples, the 2% Ce-doped ZnO film demonstrated the highest photocatalytic efficiency. These findings highlight the importance of controlled Ce doping in tuning the microstructure, optical properties, and photocatalytic performance of ZnO thin films, making them suitable for environmental remediation and optoelectronic applications. Full article

Ventilation air methane (VAM) has an extremely low concentration, making its abatement exceptionally challenging. Catalytic oxidation offers a promising route for VAM treatment, but industrial application requires integrated catalysts with high activity and efficient mass transfer. In this study, a novel straight-channel NiO/CeO₂ ceramic reactor was fabricated via mesh-assisted phase inversion, with NiO content systematically optimized to screen the optimal ratio. The 60 wt% NiO was the optimal composition, exhibiting excellent VAM oxidation performance. Brunauer–Emmett–Teller (BET) analysis confirmed that this optimal ratio yielded the largest specific surface area. Furthermore, H₂-temperature-programmed reduction (H₂-TPR) and X-ray photoelectron spectroscopy (XPS) confirmed that this optimal ratio facilitated the formation of abundant NiO–CeO₂ active interfaces, effectively inducing surface Ce³⁺ species and oxygen vacancies. These merits significantly enhanced the reactor’s oxygen adsorption capacity and redox properties, thus realizing efficient methane activation in catalytic oxidation. Moreover, the optimal reactor successfully passed 10 thermal cycle tests, further verifying the thermal stability of the catalytic structure. In addition, it exhibited outstanding long-term stability during a 100 h test, with no carbon deposition or active phase sintering observed. This work develops an optimized straight-channel NiO/CeO₂ ceramic reactor and offers a practical and scalable design strategy for VAM oxidation. Full article

Cobalt–copper bimetallic oxides (CoCuO_x) show great potential for constructing high-performance micro-supercapacitors (MSCs) for micro-electronic applications. However, their poor conductivity and complex preparation procedures significantly hinder their broad applications. To address these challenges, oxygen-vacancy-modified CoCuO_x-based binder-free electrodes were fabricated using a one-step computer numerical control wire electrical discharge machining (CNCWEDM) strategy. This approach enabled the fabrication of CoCuO_x-based maze-like MSCs (CoCuMMSCs) with designable electrochemical performance, which could be simply controlled by their geometric shape and machining voltage. Subsequently, theoretical simulations were conducted for studying the effect of MSCs geometric shape on their capacitive behavior. Remarkably, the CoCuMMSCs fabricated by a machining voltage of 100 V achieved the maximum capacitance of 32.8 mF cm⁻² at 0.15 mA cm⁻². Furthermore, the CoCuMMSCs demonstrated outstanding performance at ultrahigh scan rates of up to 50,000 mV s⁻¹, exceeding by more than two orders of magnitude the values previously reported in the literature. The obtained results proved that the development of the CNCWEDM technique facilitated manufacturing CoCuMMSCs devices with excellent performance by the comprehensive utilization of oxygen-vacancy incorporation, synergistic effect of cobalt and copper oxides, binder-free electrode design, proper device construction and controllable machining voltage. The advanced CNCWEDM strategy creates a new pathway for the high-efficiency fabrication of high-performance bimetallic-oxide-based micro-electronic devices, such as MSCs, intelligent micro-sensors and micro-batteries. Full article

A Ce-doped photocatalytic composite with easy solid–liquid separation capability was prepared and a heterojunction was constructed between BiVO₄ and Fe₃O₄ via a co-precipitation method. A variety of characterization techniques were employed, such as X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), ultraviolet–visible spectroscopy (UV-vis), transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDS), as well as other related methods. Its photocatalytic performance for the degradation of Rhodamine B (RhB) was also studied. The results indicate that the photocatalytic efficiency of BiVO₄/Fe₃O₄ is 1.4 times that of the pure BiVO₄ matrix. In particular, the photocatalytic efficiency of Ce_1.5%-BiVO₄/Fe₃O₄ was 2.2 times higher than that of the pure BiVO₄ matrix, and a 100% degradation rate of RhB was achieved within 30 min. The introduction of Fe₃O₄ not only forms a heterojunction with BiVO₄, increasing the active sites and surface oxygen vacancies of the material and effectively suppressing the recombination of photogenerated electron (e^-)-hole (h⁺) pairs, but it also enables the rapid separation of the material from the wastewater solution by the magnetic properties of Fe₃O₄. Additionally, the partial substitution of Ce for Bi in the BiVO₄ lattice reduces the bandgap energy, which enhances the utilization efficiency of visible light and improves the photocatalytic performance of the composite material. The mechanism of RhB degradation by Ce_1.5%-BiVO₄/Fe₃O₄ composite materials is also analyzed in this study. Quenching experiments and EPR tests revealed that h⁺ and ${·\mathrm{O}}_2^{-}$ were the primary reactive species in the degradation process. Full article

A nano-CuO/ZnO desulfurizer was successfully prepared via a homogeneous precipitation method, and the effects of Cu doping on its microstructure, oxygen species, desulfurization performance, and reaction mechanism were systematically investigated. The results show that an appropriate Cu doping amount (TZ2, Cu:Zn = 1:18.40) significantly reduces the particle size (to ~10.9 nm) compared with pure ZnO (14.3 nm), leading to an increased number of surface-active sites. XPS and TG analyses reveal that Cu incorporation increases the proportion of lattice oxygen and decreases the concentration of oxygen vacancies, indicating that the modification effect of Cu dominates over the particle size effect in regulating surface oxygen species. Despite the reduced oxygen vacancy concentration, the desulfurization performance is markedly enhanced, with TZ2 exhibiting the longest breakthrough time under oxygen-free conditions at room temperature. This improvement is attributed to the strong interaction between highly dispersed Cu species and the ZnO matrix, which promotes H₂S adsorption and activation. Mechanistic studies demonstrate that, unlike pure nano-ZnO, where oxygen vacancy-mediated reactions dominate, the CuO/ZnO system follows a chemisorption-driven pathway involving the formation of copper sulfides and highly reactive polysulfide intermediates. Furthermore, the presence of oxygen significantly influences the reaction behavior, with an optimal oxygen concentration (~10%) maximizing desulfurization performance by balancing the generation of reactive oxygen species and sulfur intermediates. This work provides new insights into the design of high-performance ZnO-based desulfurizers and highlights the critical role of Cu-induced mechanism transformation. Full article

Zinc oxide (ZnO) nanomaterials have attracted widespread attention from researchers due to their morphology-dependent properties, eco-friendly characteristics, and potential as a sustainable photocatalyst with a broad range of applications. Therefore, in this study, three different ZnO nanostructures—nanosheets (NSs), nanoflowers (NFs), and nanorods (NBs)—were synthesized via a controlled precipitation method. Among these, NFs exhibited the highest photocatalytic efficiency. The obtained samples exhibited broad optical absorption edges extending into the visible region (corresponding to apparent energies of 1.81–2.09 eV), which is attributed to the sub-bandgap states induced by oxygen vacancies rather than intrinsic bandgap narrowing—far lower than the bandgap of bulk ZnO (3.37 eV). Their photocatalytic performance was evaluated by the degradation of Methyl Blue (MB), Methyl Orange (MO), and Rhodamine B (RhB) under UV or sunlight. Notably, the NFs achieved rapid degradation of MB and RhB within 90 min under UV irradiation without the addition of any H₂O₂, demonstrating their effectiveness and cost-effectiveness for practical applications. Although H₂O₂ inhibited the degradation of MB and RhB, it promoted the decomposition of MO. Furthermore, the ZnO NFs exhibited excellent recyclability in five consecutive degradation cycles. The self-synthesized ZnO nanomaterials in this study, with their broad-spectrum absorption, high stability, and eco-friendly properties, demonstrate their potential as an efficient and low-cost photocatalyst for large-scale wastewater treatment. Full article

In this study, the indium (In) composition in amorphous indium gallium zinc oxide (a-IGZO) thin films was systematically varied from 33% to 84% using a sol–gel process. Subsequently, aluminum/IGZO/aluminum (Al/IGZO/Al) metal–semiconductor–metal (MSM) UV photodetectors were fabricated to investigate the influence of composition on the structural, optical, and photoelectric properties. The results indicate that all films maintain an amorphous structure despite the increasing In content, while the ratio of oxygen vacancies, O_vac/(M-O + O_vac), rises from 36% to 52%. Concurrently, the optical bandgap decreases from 2.92 eV to 2.32 eV. Under a bias of 20 V, the dark current increases from 2.11 × 10⁻⁹ A to 1.90 × 10⁻⁵ A as the In content rises. When illuminated by a 360 nm LED with a power density of 8.6 mW/cm², the device with 60% In exhibits a photocurrent-to-dark-current ratio of approximately 10⁴, a responsivity of 19.45 A/W, and a specific detectivity of 8.19 × 10¹² Jones. The response time and recovery time of this device are 39.8 s and 577.4 s, respectively. These findings reveal a competitive relationship between enhanced optical absorption and defect generation induced by In composition, providing valuable guidance for the performance optimization of a-IGZO UV photodetectors through compositional engineering. Full article