Search Results (306)

TiO₂ shows improved photocatalytic properties when combined with other oxides, such as ZrO₂. Unfortunately, this material does not exhibit a spectral response in the visible range, but this can be improved by adding WO₃. Here, the effect of the amount of WO₃ and the treatment temperature on TiO₂-ZrO₂-WO₃ materials applied in the solar photocatalytic oxidation of sildenafil was evaluated. The materials were synthesized using the sol–gel method and were characterized by N₂, XRD, UV-Vis RDS, SEM, PL, and XPS. Photocatalytic activity was determined by the degradation and mineralization of sildenafil. The most active photocatalysts were selected for stability testing and to determine the oxidizing species that dominate the reaction mechanism. The optimal amount of WO₃ that improves solar photocatalytic activity at both treatment temperatures was found to be 1% with a reaction mechanism based on OH· and h⁺. WO₃ reduces electron–hole pair recombination. At 500 °C, the crystallinity of the anatase phase is improved, while at 800 °C, the transformation to rutile is suppressed at low WO₃ concentrations. XPS observed the reduction in Ti⁴⁺ to Ti³⁺ and W⁶⁺ to W⁵⁺ in TiO₂–ZrO₂–WO₃ materials, which were found to be photoactive under sunlight with potential for use in industrial-scale reaction systems. Full article

A novel recyclable composite, Fe₃O₄/chitin/BiOCl, was synthesized via a solvothermal approach using cetyltrimethylammonium bromide (CTAB), bismuth nitrate pentahydrate (Bi(NO₃)₃·5H₂O), chitin, and Fe₃O₄ as precursors. The composite was systematically characterized via X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Brunauer–Emmett-Teller (BET) analysis, ultraviolet–visible (UV-vis) spectroscopy, and vibrating sample magnetometry (VSM). Characterization results indicated that the incorporation of chitin significantly improved the porosity and specific surface area of the catalyst. Furthermore, the synergistic effects between chitin and Fe₃O₄ effectively reduced the recombination rate of photogenerated electron–hole pairs. The photocatalytic activity of the composite was evaluated by degrading ciprofloxacin (CIP) under visible-light irradiation. When the contents of Fe₃O₄ and chitin were 5% and 2% (by weight), respectively, the catalyst exhibited excellent photocatalytic performance with a degradation rate of 89.54%, and the rate constant was 5.1 times higher than that of pure BiOCl. Additionally, the catalyst exhibited excellent magnetic recoverability and photocatalytic stability. Full article

CuO/TiO₂ is a highly active visible-light-driven photocatalyst. The precise structural regulation of TiO₂ and the quantum dot-scale loading strategy of CuO have long been researching hotspots and challenges. This work presents an ingenious synthetic strategy, leveraging the photoinduced superhydrophilicity and dark-induced reversible hydrophobicity of TiO₂, coupled with carbon quantum dots (CQDs) as “seeds” to induce the in situ synthesis of CuO quantum dots (CuO QDs). Specifically, CuO QDs with an average diameter of 5–10 nm were successfully anchored onto TiO₂ nanowire arrays (TNWAs) with a diameter of 10–15 nm. By adjusting the dosage of “seeds” (CQDs), the loading amount of CuO QDs can be effectively controlled. Corresponding characterizations were performed, including ultraviolet-visible-near-infrared (UV-Vis-NIR spectroscopy) for optical absorption properties, photoluminescence (PL) spectroscopy for photoluminescent behavior, electron paramagnetic resonance (EPR) spectroscopy for free radical generation capability, and bisphenol A (BPA) degradation assays for photocatalytic performance. Loading 4.78 wt% CuO QDs can effectively inhibit the recombination of electron–hole pairs in TNWAs. Simultaneously, it prolongs the lifetime of charge carriers (photoelectrons) and enhances the yields of hydroxyl radicals (•OH) and superoxide radicals (•O₂⁻). The BPA degradation efficiency of the CuO QDs/TNWA composite is 2.4 times higher than that of TNWAs. Furthermore, we found that the loading of CuO QDs significantly modulates the depletion layer width of the P–N heterojunction, and the underlying mechanism has been discussed in detail. Full article

To enhance the purification of exhaust gas, a g-C₃N₄/CeO₂/Bi₂O₃ dual type-II heterojunction photocatalysis was designed and prepared to suppress the recombination of electron–hole pairs and improve light energy utilization. The dual type-II heterojunction structure effectively reduced the bandgap (Eg) from 2.5 eV to 2.04 eV, thereby extending the light absorption of photocatalysis into the visible region. Following the design of the heterojunction, a self-cleaning process was developed and applied to asphalt pavement rut plates to evaluate its efficiency in degrading vehicle exhaust under real-road conditions. The coating was systematically characterized in terms of exhaust degradation efficiency, hardness, adhesion, water resistance, freeze–thaw durability, and skid resistance. Under 60 min of natural light irradiation, the purification efficiencies for HC, CO, CO₂, and NO_x reached 22.60%, 19.27%, 14.83%, and 50.01%, respectively. After three-repetition tests, the efficiencies remained high at 21.75%, 19.04%, 14.66%, and 49.83%, demonstrating excellent photocatalytic stability. All other road-performance indicators met the relevant China national standards. The application of this self-cleaning coating in road infrastructure presents a viable strategy for environmental remediation in transportation systems. Full article

Water pollution from textile effluents poses serious environmental risks, particularly due to persistent anionic dyes such as Reactive Black 5 (RB5). This study demonstrates that simple deposition of Y₂O₃ onto commercially available, biobased TiO₂ (bTiO₂) significantly enhances photocatalytic degradation efficiency under simulated sunlight, suppressing rapid recombination of electron–hole pairs. Addressing a key research gap, the proposed method replaces expensive nanoscale precursors and complex synthesis routes typically used for Y₂O₃/TiO₂ systems with a low-cost, straightforward approach involving weak complexation and co-precipitation. The resulting Y₂O₃-bTiO₂ composite was characterized using FTIR, XRD, SEM, EDX, TEM, XPS, and UV-DRS techniques, confirming efficient incorporation of Y₂O₃ on the TiO₂ surface. Photocatalytic experiments revealed that nanoparticles calcined at 700 °C achieved complete RB5 degradation within 60 min—reducing the reaction time by half compared to undoped bTiO₂. Systematic studies of initial dye concentration, catalyst loading, and irradiation time confirmed that the degradation followed pseudo-first-order kinetics with a rate constant of 0.064 min⁻¹ (R² = 0.98). Calculated quantum yields corroborated the reduced electron–hole recombination induced by Y₂O₃ deposition. These findings highlight the novelty and practicality of the developed Y₂O₃-bTiO₂ photocatalyst as an efficient, affordable, and environmentally sustainable material for the degradation of industrial dyes. Full article

Titanium dioxide (TiO₂) nanoparticles (NPs) have garnered significant attention as photocatalysts for degrading organic pollutants, particularly synthetic dyes such as rhodamine B (RhB), methylene blue, methyl orange, and others. The impact of several synthesis methods, including sol–gel, hydrothermal, and chemical vapor deposition (CVD) techniques, on the electrical and morphological properties of TiO₂ NPs has been studied, emphasizing the distinctive physicochemical properties of TiO₂ NPs, including their extensive surface area, significant oxidative capacity, and remarkable chemical stability, which are important in the recent advancements in their use for RhB degradation. A detailed examination of TiO₂’s photocatalytic mechanism shows that it is based on the generation of reactive oxygen species (ROS) by photoinduced electron–hole pair formation under ultraviolet (UV) light exposure. In wastewater treatment, TiO₂ degrades RhB into less harmful byproducts by the generation of electron–hole pairs that initiate redox reactions under sunlight. This study includes a thorough overview of significant factors influencing photocatalytic efficacy. The parameters include particle size, crystal phase (anatase, rutile, and brookite), surface changes, and the incorporation of metal or non-metal dopants to enhance visible light absorption. Researchers continually seek methods to overcome challenges, including restricted visible-light responsiveness and rapid electron–hole recombination. The investigated approaches include heterojunction generation, composite development, and co-catalyst insertion. This review article aims to address the deficiencies in our understanding of TiO₂-based photocatalysis for the degradation of RhB and to propose enhancements for these systems to enable more efficient and sustainable wastewater treatment in the future. Full article

Titanium dioxide (TiO₂) nanoparticles (NPs) are useful as a potential photocatalyst for the degradation of dyes such as methyl orange, rhodamine B, and methylene blue (MB). Understanding the mechanism of photocatalysis and the factors influencing photocatalysis is important for engineering TiO₂ NPs to achieve an unprecedented photocatalysis rate. For TiO₂ NPs, their unique physicochemical qualities, such as small size, large surface area, optimum semiconductor bandgap, substantial oxidative potential, and outstanding chemical stability are factors which influence the MB degradation rate. The electron–hole pair separation in TiO₂ NPs allows for photocatalysis, which is not possible in their bulk form. The formation of reactive oxygen species (ROS) via photoinduced generation of electron–hole pairs under light irradiation is the starting point of the mechanism of photocatalysis for TiO₂ NPs. By generating ROS, TiO₂ NPs catalyze the degradation of MB. The photocatalytic performance of TiO₂ NPs is also different for different crystal phases, such as anatase, rutile, and brookite. The addition of metal or non-metal dopants into TiO₂ NPs enhances photocatalysis by enhancing light absorption, which enhances the generation of electron–hole pairs and of ROS. This review article will explain the mechanism of photocatalysis, the parameters influencing photocatalytic activity, active sites and recombination rates, disadvantages, and strategies to overcome these challenges that can improve TiO₂ NPs for a future wastewater treatment that is both efficient and sustainable. Full article

Harnessing solar energy directly through photocatalysis is an effective approach to addressing the energy crisis and environmental pollution. This green technology enables both sustainable energy production and the removal of environmental contaminants simultaneously. Heterojunction photocatalysts demonstrate superior performance by enhancing light utilization efficiency and inhibiting the recombination of photogenerated electron-hole pairs. The reconstruction of active sites in heterojunction photocatalysts, encompassing changes in their valence states and coordination environments, has been extensively studied. However, the unique structural self-adaptive phenomenon displayed by heterojunction photocatalysts that incorporate flexible components during the photocatalysis process has not been extensively investigated. Indeed, this intriguing self-adaptive behavior may be closely linked to their photocatalytic properties. Extensive studies indicate that this structural self-adaptation is predominantly driven by flexible materials, with flexible metal-organic frameworks (MOFs) finding particularly broad application. Based on this understanding, we briefly summarize and offer insights into the structural design and fundamental principles of such photocatalytic heterojunction catalysts while also providing an outlook for future research. Full article

Despite extensive work on FeOCl-based photocatalysts, few studies have explored rare-earth (Ce) doping to simultaneously tune bandgap, suppress charge recombination, and enhance visible light-driven persulfate (PS) activation for the degradation of emerging contaminants. This study synthesized FeOCl/Ce composite photocatalysts via a partial pyrolysis method and systematically characterized their physicochemical properties. The results show that Ce doping significantly lowers the bandgap energy of the photocatalyst, enhances its visible light absorption ability, and effectively suppresses the recombination of photogenerated electron–hole pairs, thereby markedly improving photocatalytic performance under visible light. Analyses including XRD, EDS, XPS, and FT-IR confirm that Ce is incorporated into the FeOCl matrix and modulates the radial growth behavior of FeOCl without altering its intrinsic crystal structure. Morphological observations reveal that FeOCl/Ce exhibits a uniform nanosheet layered structure, with larger particles formed by the aggregation of smaller nanosheets. The nitrogen adsorption–desorption isotherm of FeOCl/Ce shows characteristics of Type IV with a relatively small BET surface area. The broadened optical absorption edge of FeOCl/Ce and the results of PL spectra and I-T curves further confirm its enhanced visible light absorption capacity and reduced electron–hole recombination compared to pure FeOCl. At an initial caffeine (CAF) concentration of 10 μM, FeOCl/Ce dose of 0.5 g/L, PS concentration of 1 mM, and initial pH of 5.06, the FeOCl/Ce-catalyzed PS system under visible light irradiation can degrade 91.2% of CAF within 30 min. An acidic environment is more favorable for CAF degradation, while the presence of SO₄²⁻, Cl⁻, and NO₃⁻ inhibits the process performance to varying degrees, possibly due to competitive adsorption on the photocatalyst surface or quenching of reactive species. Cyclic stability tests show that FeOCl/Ce maintains good catalytic performance over multiple runs. Mechanistic analysis indicates that ^•OH and holes are the dominant reactive species for CAF degradation, while PS mainly acts as an electron acceptor to suppress electron–hole recombination. Overall, the FeOCl/Ce photocatalytic system demonstrates high efficiency, good stability, and visible light responsiveness in CAF degradation, with potential applications for removing CAF and other emerging organic pollutants from aquatic environments. Full article

Nitrogen oxides (NO_x) are major atmospheric pollutants, and their escalating emissions, driven by rapid economic development and urbanization, pose a severe threat to both the ecological environment and human health. Conventional denitrification technologies are often hampered by high costs, significant energy consumption, and stringent operational conditions, making them increasingly inadequate in the face of tightening environmental regulations. In this context, photocatalytic technology, particularly systems based on graphitic carbon nitride (g-C₃N₄), has garnered significant research interest for NO_x removal due to its visible-light responsiveness, high stability, and environmental benignity. To advance the performance of g-C₃N₄, numerous modification strategies have been explored, including morphology control, elemental doping, defect engineering, and heterostructure construction. These approaches effectively broaden the light absorption range, enhance the separation efficiency of photogenerated electron-hole pairs, and improve the adsorption and conversion capacities for NO_x. Notably, constructing heterojunctions between g-C₃N₄ and other materials (e.g., metal oxides, noble metals, metal–organic frameworks (MOFs)) has proven highly effective in boosting catalytic activity and stability. Furthermore, the underlying photocatalytic mechanisms, encompassing the generation and migration pathways of charge carriers, the redox reaction pathways of NO_x, and the influence of external factors like light intensity and reaction temperature, have been extensively investigated. From an application perspective, g-C₃N₄-based photocatalysis demonstrates considerable potential in flue gas denitrification, vehicle exhaust purification, and air purification. Despite these advancements, several challenges remain, such as limited solar energy utilization, rapid charge carrier recombination, and insufficient long-term stability, which hinder large-scale implementation. Future research should focus on further optimizing the material structure, developing greener synthesis routes, enhancing catalyst stability and poison resistance, and advancing cost-effective engineering applications to facilitate the practical deployment of g-C₃N₄-based photocatalytic technology in air pollution control. Full article

Insufficient harvesting of visible photons, limited adsorption, and fast recombination of photogenerated electron-hole pairs restrict the application of graphitic carbon nitride (g-C₃N₄). Here, we propose a straightforward solid-phase synthesis method for fabricating 2D/2D graphitic carbon nitride/reduced graphene oxide (SCN/GR) hybrid photocatalysts. The synthesis process involves the thermal condensation of three precursors: dicyandiamide (as the g-C₃N₄ source), NH₄Cl (as a pore-forming agent), and graphene oxide (GO, which is in situ reduced to rGO during thermal treatment). The incorporation of reduced graphene oxide (rGO) into the g-C₃N₄ matrix not only narrows the bandgap of the material but also expedites the separation of photogenerated carriers. The photocatalytic activity of the SCN/GR hybrid was systematically evaluated by degrading ciprofloxacin in aqueous solution under different light conditions. The results demonstrated remarkable degradation efficiency: 72% removal within 1 h under full-spectrum light, 81% under UV light, and 52% under visible light. Notably, the introduction of rGO significantly improved the visible light absorption capacity of g-C₃N₄. Additionally, SCN/GR exhibits exceptional cyclic stability, maintaining its structural integrity and photocatalytic properties unchanged across five successive degradation cycles. This study offers a simple yet effective pathway to synthesize 2D/2D composite photocatalysts, which hold significant promise for practical applications in water treatment processes. Full article

Water contamination and the global energy crisis are two of the most significant challenges in the world. Titanium dioxide (TiO₂) has garnered attention due to its promising photocatalytic performance. However, its wide band gap energy limits its efficiency under visible light irradiation. To address this, TiO₂-based composite photocatalysts have been developed to narrow the band gap energy and suppress the recombination of electron–hole pairs, thereby enhancing photocatalytic performance. The ultrasonic technique, through acoustic cavitation, facilitates a synthetic process involving localized transient high-pressure and high-temperature conditions to produce photocatalysts with superior photocatalytic capabilities. This review focuses on ultrasonication and ultrasonic-assisted fabrication method for modifying TiO₂ into visible light-driven composite heterostructures. It discusses the parameters of ultrasonication that influence the synthesis and modification of these composites, along with the factors affecting photocatalytic performance. Full article

In this study, structural optimization and trap effect analysis of a 4H-SiC–based p–i–n betavoltaic (BV) cell were performed using Silvaco ATLAS TCAD (version 5.30.0.R) simulations combined with an electron-beam (e-beam) irradiation model. First, the optimum device structure was derived by varying the thickness of the intrinsic layer (i-layer), the thickness of the p-layer, and the doping concentration of the i-layer. Under 17 keV e-beam irradiation, the electron–hole pairs generated in the i-layer were effectively separated and transported by the internal electric field, thereby contributing to the short-circuit current density (J_SC), open-circuit voltage (V_OC), and maximum output power density (P_{out_max}). Subsequently, to investigate the effects of traps, donor- and acceptor-like traps were introduced either individually or simultaneously, and their densities were varied to evaluate the changes in device performance. The simulation results revealed that traps degraded the performance through charge capture and recombination, with acceptor-like traps exhibiting the most pronounced impact. In particular, acceptor-like traps in the i-layer significantly reduced V_OC from 2.47 V to 2.07 V and P_{out_max} from 3.08 μW/cm² to 2.28 μW/cm², demonstrating that the i-layer is the most sensitive region to performance degradation. These findings indicate that effective control of trap states within the i-layer is a critical factor for realizing high-efficiency and high-reliability SiC-based betavoltaic cells. Full article

This research successfully synthesized a novel n-n heterojunction Bi₂O₂CO₃/AgVO₃ nanocomposite photocatalyst via the in situ chemical deposition process. Characterization results strongly confirmed the formation of a tight heterojunction at the Bi₂O₂CO₃/AgVO₃ interface. The nanocomposite exhibited characteristic XRD peaks and FT-IR vibrational modes of both Bi₂O₂CO₃ and AgVO₃ simultaneously. Electron microscopy images revealed AgVO₃ nanorods tightly and uniformly loaded onto the surface of Bi₂O₂CO₃ nanosheets. Compared to the single-component Bi₂O₂CO₃, the composite photocatalyst exhibited a red shift in its optical absorption edge to the visible region (515 nm) and a decrease in bandgap energy to 2.382 eV. Photoluminescence (PL) spectra demonstrated the lowest fluorescence intensity for the nanocomposite, indicating that the recombination of photogenerated electron–hole pairs was suppressed. After 90 min of visible-light irradiation, the degradation efficiency of Bi₂O₂CO₃/AgVO₃ toward methylene blue (MB) reached up to 99.55%, with photodegradation rates 2.51 and 2.79 times higher than those of Bi₂O₂CO₃ and AgVO₃, respectively. Furthermore, the nanocomposite exhibited excellent cycling stability and reusability. MB degradation was gradually enhanced with increasing the photocatalyst dosage and decreasing initial MB concentration. Radical trapping experiments and absorption spectroscopy of the MB solution revealed that reactive species h⁺ and ·O₂⁻ could destroy and decompose the chromophore groups of MB molecules effectively. The possible mechanism for enhancing photocatalytic performance was suggested, elucidating the crucial roles of charge carrier transfer and active species generation. Full article

The increasing presence of emerging contaminants (ECs) has attracted considerable attention due to their potential harm to human health and ecosystems. Graphitic carbon nitride (g-C₃N₄), a semiconductor devoid of metals, stands out due to its distinctive optical properties and strong resistance to chemical degradation, which holds significant promise in the photocatalytic degradation of ECs. However, the inherent limitations of g-C₃N₄, such as its reduced specific surface area and the swift recombination of photogenerated electron-hole pairs, have prompted extensive research on modification strategies to enhance its photocatalytic performance. Current research on g-C₃N₄-based materials is often constrained in scope, with most reviews focusing solely on modification strategies or its application in degrading a single category of emerging contaminants (ECs). In this review, a systematic overview of synthesis methods and advanced modification strategies for g-C₃N₄-based materials is discussed, highlighting their recent advances in the photocatalytic degradation of various ECs using g-C₃N₄-based materials, which underscores their potential for environmental remediation. Moreover, this article critically examines the current challenges and outlines future research directions, with particular emphasis on integrating artificial intelligence and machine learning to accelerate the development of g-C₃N₄-based photocatalysts and optimize degradation processes, thereby promoting their efficient application in the photocatalytic degradation of ECs. Full article