ZnO Catalyst Research Articles

Synthesis of TiO2-ZnO n-n Heterojunction with Excellent Visible Light-Driven Photodegradation of Tetracycline

Zinc oxide-based photocatalysts with non-toxicity and low cost are promising candidates for the degradation of tetracycline. Despite the great success achieved in constructing n-n-type ZnO-based heterojunctions for the degradation of tetracycline under full-spectrum conditions, it is still challenging to realize rapid and efficient degradation of tetracycline under visible light using n-n-type ZnO-based heterojunctions, as they are constrained by the quick recombination of electron–hole pairs in ZnO. Here, we report highly efficient and stable n-n-type ZnO-TiO2 heterojunctions under visible light conditions, with a degradation efficiency reaching 97% at 1 h under visible light, which is 1.2 times higher than that of pure zinc oxide, enabled by constructing an n-n-type heterojunction between ZnO and TiO2 to form a built-in electric field. The photocatalytic degradation mechanism of n-n TiO2-ZnO to tetracycline is also proposed in detail. The demonstration of efficient and stable heterojunction-type ZnO photocatalysts under visible light is an important step toward commercialization and opens up new opportunities beyond conventional ZnO technologies, such as composite ZnO catalysts.

BiOBr/SnO2/ZnO Catalyst With Interfacial Effect Enhanced Photocatalytic Degradation of Organic Dye

ABSTRACTBiOBr nanosheets were loaded onto SnO2 quantum dots, ZnO nanosheets, and SnO2/ZnO‐2 (SZ‐2) to form different heterojunction photocatalysts by sonochemistry, respectively. The photocatalytic activity of the prepared photocatalysts was evaluated by degrading the target dye Rhodamine B (RhB). The results showed that the degradation efficiency of BiOBr/SnO2/ZnO (BSZ) for RhB reached 97.5% at 80 min. The significant increase in catalytic activity of BSZ was attributed to the synergistic and interfacial effects among the three materials. Combined with the radical trapping experiments, it can be concluded that the catalytic mechanism of BSZ as a dual Z‐type heterojunction.

Enhanced photocatalytic organic pollutant degradation, H2 production and N2 fixation via a versatile zinc oxide-based nanocomposite: Synthesis, characterization and mechanism Insight

Developing highly efficient photocatalysts for visible light utilization is crucial for water purification, N2 fixation, and H2 generation. This work presents a novel α-Fe2O3/CeO2-ZnO heterostructure photocatalyst synthesized through a facile impregnation technique. The synthesized catalysts were characterized via XPS, TEM, SEM, XRD, BET, PL, EIS, Mott-schottky, etc. analyses. The optimized 25 wt% of α-Fe2O3/CeO2 on ZnO (25-FeCeZ) catalyst achieved 100 % ofloxacin (OFX) photodegradation under light irradiation within 90 min. The charge transfer pathway was investigated via optical analyses within the 25-FeCeZ. Experimental investigations elucidated the potential intermediates, four proposed OFX photodegradation pathways and photocatalytic mechanism. Scavenger experiments and ESR spectroscopy identified •O2–, •OH, and h+ as the primary reactive species. Furthermore, the degraded OFX solution exhibited lower overall toxicity compared to the initial solution, based on QSAR predictions and E. coli viability assays. The 25-FeCeZ catalyst displayed a significantly enhanced hydrogen production rate (2.57mmol g−1h−1) compared to pristine ZnO (0.09 mmol/g·h). Notably, the catalyst achieved an NH3 evolution rate of 335.80μmol g−1h−1 without additional sacrificial agents, which is 4.5 times greater than pure ZnO. Additionally, the optimised photocatalyst depicted a superb stability across all three photocatalytic processes. This study illustrates a promising approach for designing potent ZnO-based photocatalysts for diverse applications, including N2 fixation, H2 generation, and organic pollutant degradation under visible light irradiation.

Green synthesis of ZnO and Ni-doped ZnO from okra stalks for the photocatalytic degradation of Procion Red MX-5B

This study investigates the photocatalytic degradation of Procion Red MX-5B (PRM) using ZnO and Ni-doped ZnO catalysts derived from okra stalks through a green synthesis method. Various parameters, including hydrogen peroxide concentration (HPC), catalyst amount, nickel (Ni) doping amount, initial PRM concentration, and pH, are systematically studied to assess their impact on PRM degradation efficiency. The results reveal that both ZnO and Ni-doped ZnO catalysts exhibit promising photocatalytic activity, with the highest PRM degradation efficiency achieved at the following reaction conditions: 6 mM of HPC, 40 mg of Ni(7%):ZnO catalyst, 10 ppm initial PRM concentration, and pH = 6. Under these conditions, the Ni-doped ZnO catalyst demonstrated a degradation efficiency of 98.08% compared to 82.99% for the ZnO catalyst. The study highlights the potential of these catalysts for efficient organic pollutant removal and provides valuable insights into the factors influencing their photocatalytic performance.

Synthesis of Self-Assembled Mesoporous ZnO Microspheres Designed for Microwave-Assisted Photocatalytic Degradation of Tetracycline.

Microwave-assisted photocatalysis offers a novel approach for degrading antibiotics, while the mechanism of enhancement of microwave-induced photocatalysis remains poorly understood. In this study, tetracycline (TC) was degraded using the method of microwave-assisted photocatalysis with a ZnO catalyst, which was synthesized by the combination of hydrothermal and calcination methods. The self-assembled mesoporous ZnO catalyst exhibited superior catalytic activity in degrading TC. It is found that the degradation efficiency of TC by the ZnO catalysts with microwave-assisted photocatalysis is 4.27 times higher than that of photocatalysis alone. Of particular significance, we found that the optical absorption range of ZnO increased and the band gap decreased when microwave was introduced into the photocatalytic system. Semi-in situ photochemical tests demonstrated that more photogenerated electron-hole pairs were detected under microwave, thus further improving the photocatalytic activity of ZnO. The separation efficiency and charge transfer efficiency of photogenerated electron-hole pairs also improved due to the increase of oxygen vacancies in the synergistic effect. Meanwhile, h+ and ·OH were the main active species in the degradation system. The mechanism of microwave-induced photocatalysis is illustrated, and an efficient way for degrading antibiotic is provided in this work.

Synthesis of isolated ZnO nanorods on introducing g-C3N4 for improved photoelectrocatalytic methanol production by CO2 reduction

The photoelectrocatalytic (PEC) CO2 reduction into fuels has been developed as a prospective approach to resolve the environmental and energy concerns. Herein, a composite catalyst comprising ZnO nanorods dispersed on the g-C3N4 surface (g-C3N4/ZnO) was successfully obtained by simple ZnO seed layer formation and then hydrothermal processes. The synthesized and characterized g-C3N4/ZnO catalytic composite showed 2.8 times enhanced photocurrent density at −1 V applied potential than the bare g-C3N4. The g-C3N4/ZnO catalyst exhibited 2.86 times enhanced the PEC CO2 reduction to methanol than the prepared bare ZnO catalyst. The catalyst’s enhanced the PEC CO2 reduction performance was ascribed to the high surface area, and higher generation and lower recombination of e−/h+ pairs. For the first time, this study showed the enhanced methanol production by the PEC reduction of CO2 over the prepared g-C3N4/ZnO catalytic composite.

Enhanced photocatalytic oxidation of gaseous acetaldehyde using Fe-grafted ZnO nanocomposites in a continuous flow reactor

The purification of indoor air is a crucial application of photocatalysis, emphasizing the urgent need for more efficient photocatalytic systems. While photocatalytic oxidation of volatile organic compounds (VOCs) has been extensively studied in the liquid phase, effective removal of VOCs in the gaseous state in indoor air remains a significant challenge. This study focuses on the continuous gas-phase oxidation of gaseous acetaldehyde using ZnO and different weight percentage of Fe-grafted ZnO catalysts under light irradiation. The surface analysis using XPS and HR-TEM confirmed the presence of Fe(III) species, and UV–Vis-DRS analysis demonstrated a shift in the absorption edge towards the visible region. Real-time gas FTIR monitoring of acetaldehyde oxidation revealed that the 0.7% Fe(III)-grafted ZnO composite catalyst achieved a higher removal efficiency (74%) compared to bare ZnO and other Fe(III)-grafted ZnO ratios. The enhanced photocatalytic efficiency of acetaldehyde by Fe(III)-grafted ZnO supports indicated direct interfacial charge transfer (IFCT) from ZnO to Fe(III) species. Additionally, the Fe(III) cluster effectively improved the separation of electrons and holes, preventing their recombination and accelerating O₂ activation to generate O₂•⁻ radicals, which lead to high photocatalytic performance. The 0.7% Fe(III)-grafted ZnO also maintained its performance over a prolonged period of 360 min, showing excellent structural stability and durability across multiple cycles. This study highlights the possible synergistic effect of the ZnO and Fe systems, offering a new perspective on the photocatalytic decomposition of gaseous acetaldehyde in indoor environments.

An efficient Au/ZnO catalyst for the photocatalytic conversion of methane to formaldehyde

The photocatalytic oxidation of methane to value-added chemical products under mild conditions is crucial for resource utilization and environmental protection. However, inefficient generation of reactive oxygen species partially limits methane activation. To tackle this issue, we have developed highly dispersed Au-modified ZnO nanosheets through photo-deposition method for the photocatalytic oxidation of methane to formaldehyde. The optimized Au0.1/ZnO catalyst (0.1 wt% Au on ZnO) achieves a HCHO yield of 19.14 μmol h−1 with a selectivity of 87.94 %. Electron paramagnetic resonance, Raman, X-ray photoelectron spectroscopy and density functional theory show that Au enhances the concentration of oxygen vacancies (OVs) in ZnO. This enhancement is attributed to a strong interaction between Au and ZnO, which facilitates the transfer of electrons from the ZnO surface to Au. Under irradiation, Au and OVs function as hole and electron acceptors, respectively. This interaction promotes carrier separation, reduces charge recombination, enhances oxygen adsorption, and effectively generates reactive oxygen species, such as ·OH. Subsequently, CH4 is oxidized to ·CH3 by holes from Au. Concurrently, O2 is reduced by electron from OVs, following the pathways O2 → OOH→H2O2 → ·OH. The rapid oxidation of CH3OH by ·CH3 and ·OH results in the formation of HCHO.

Fabrication of double modified electrocatalyst by dual flame synthesis for enhancing electrochemical reduction of carbon dioxide

A rapid dual flame synthesis is developed for one-step preparation and modification of double modified ZnO catalysts with carbon doping and oxygen vacancies. The growth mechanism and nanostructure evolution are also investigated. The double modified ZnO with carbon doping and oxygen vacancies exhibies excellent performance in CO2 reduction to syngas, with a high current density of 14.02 mA/cm2 at −1.1 V vs. RHE and a maximum Faradaic efficiency of 71% for CO production. The maximum adjustable range of the CO/H2 ratio from 0.5 to 2.7. In a flow cell, the double modified ZnO exhibits a large current density of 126.8 mA/cm2 at −1.2 V vs. RHE. The maximum Faradaic efficiency for CO2 reduction to CO is 74.8% at 50 mA/cm2. Double modified ZnO maintains stable potential and Faradaic efficiency for over 5 h of electrolysis. Operando X-ray absorption spectroscopy and density functional theory calculations reveal that the active site is the Zn–Zn configuration, and that carbon dopant and oxygen vacancy promote CO2 activation and CO desorption, and reduce reaction overpotential of CO2RR.

Optimization of the dosage of ZnO photocatalyst for the degradation of sunlight driven multi dose organic dye brilliant green

In this study, we prepared ZnO nanocrystals using a chemical precipitation approach with different precursor concentrations for optimization. The structural, optical, and morphological properties of the synthesized nanocrystals were analyzed. Sunlight-driven photocatalysis was investigated for its ability to degrade a low concentration (70 ppm) of brilliant green (BG) dye using the optimized ZnO at different dosages (0.05, 0.1, and 0.15 g). Among the different dosages of ZnO, it was noted that at a low catalyst concentration of 0.05 g, the degradation efficiency was only 58.47 % even after 120 min of light exposure. When the concentration increased to 0.1 g, the rate of degradation reached 95.33 % within 90 min. At a higher dosage of 0.15 g, only 86.26 % degradation was recorded within 90 min, indicating that the optimal catalyst dosage was 0.1 g. To investigate how the dye dosage affected the degradation efficiency of the catalyst, experiments were performed using higher dye concentrations of 100 and 120 ppm with 0.1 g of catalyst. As the dye concentration was increased, the degradation rate decreased. Tests were conducted using different scavengers, including EDTA (a hole scavenger), benzoquinone (a superoxide radical scavenger), and isopropyl alcohol (a hydroxyl radical scavenger), to determine which free radical was mainly breaking down BG. In the presence of EDTA, the degradation ability of the catalyst decreased to 35 %. When the superoxide radical scavenger benzoquinone was used, the degradation efficiency decreased to approximately 22 %. On the other hand, the hydroxyl radical scavenger IPA reduced the degradation efficiency to 13 %. Based on the above discussion, the synergistic effect of holes and superoxide radicals is mainly responsible for the degradation of brilliant green. To test the practical use of the ZnO catalyst, we conducted an experiment to assess its reusability. Even after the third cycle, the ZnO exhibits 94 % degradation, confirming its reusability.

Facile synthesis, morphological, optical, catalytic and photocatalytic properties of Ag nanoparticles decorated Ce doped ZnO hybrid plasmonic nanorods

Designing plasmonic metal–semiconductor hybrid nanostructures for photodecomposition of industrial textile effluent has been considered as a great way to boost the catalytic and photocatalytic capability by promoting effective separation of photoexcited charge carriers. Herein, fabrication of Ag nanoparticles decorated Ce doped ZnO nanostructures were demonstrated via facile wet chemical method. The morphology and structure of the fabricated photocatalysts were analysed using FESEM, XRD and Raman spectroscopy whereas PL, TRPL and UV–vis absorption spectroscopy were employed to examine their optical behaviour. Catalytic response of the synthesized catalysts was studied for 4-NP to 4-AP reduction and the results are more favourable for Ag loaded Ce doped ZnO catalysts and achieved 96.4 % reduction of 4-NP in only 4 min. Photocatalytic measurements showed that higher Ag NP loading onto Ce doped ZnO nanostructures led to superior photodegradation ability over other photocatalysts for the degradation of synthetic dyes and levofloxacin antibiotic. The sunlight driven photodecolorization of harmful synthetic dyes and levofloxacin were studied and efficacy of 97.5, 97.1, 85.1, and 70.9 % were achieved for MG, MB, RhB and MO dyes, respectively in 12 min and 97.2 % efficiency for degradation of levofloxacin was achieved in 20 min of sunlight exposure. Furthermore, the key reactive species was identified and tentative photodegradation process was explained. This work provides an excellent plasmonic-semiconductor catalyst and photocatalyst with good photostability and practical applicability indicating its enormous potential for application in environmental remediation.

Sustainable Green Synthesis and Molecular Docking Study of a Bis-Fused System Incorporating Pyrido[2,3-d]pyrimidine using Nanocatalyst under Microwave Condition

Aims: This study aimed to employ sustainable green methods in the synthesis of bisfused cycles incorporating pyrido[2,3-d]pyrimidine moiety using a green catalyst nano ZnO catalyst by one-pot, multicomponent reaction among 2,2'-(propane-1,3-diylbis(sulfanediyl)) bis(6-aminopyrimidin-4(3H)-one) 3, 1H-indene-1,3(2H)-dione 4, and aromatic aldehydes 5. Method: The reactions proceeded with both conventional and microwave (MW) irradiation methods. Result:: The microwave-assisted method carried out the reaction in 10 min and had high yields (89-95%). Conclusion: A molecular docking simulation study was conducted using human serum albumin (PDB: ID (2XVQ)). The study revealed that compounds strongly fit into the active sites of the target protein.

Photodegradation of Methylene Blue Using ZnO/Perlite under Ultraviolet Light

The disposal of waste in the continuously growing industries leads to pollution caused by pollutants. One of them is liquid waste originating from the textile industry, which contains toxic coloring agents such as methylene blue that are difficult to decompose in the environment. Therefore, an effort is needed to tackle this issue using photocatalysis. A frequently used photocatalyst material is a semiconductor metal oxide like ZnO. However, ZnO semiconductors still have limitations in their applications. To overcome these limitations, ZnO catalysts will be modified with a supporting material like perlite, which is a lightweight and porous material. This study aims to examine the effectiveness of ZnO/Perlite in degrading methylene blue. The ZnO/Perlite composite with a 20% composition shows the highest photocatalytic activity compared to the ZnO/Perlite composites with 10% and 30% compositions. The optimum condition for ZnO/Perlite 20% in degrading methylene blue is achieved with a mass of 0.3 grams, at pH 11, with 2 hours of stirring under ultraviolet light irradiation, resulting in a photocatalytic activity of 47.59% and a combined adsorption and photocatalytic activity of 78.1%.

Photocatalytic Degradation of Toxic Rhodamine B Dye by Green‐Synthesised Activated Carbon‐Supported Cobalt Doped ZnO With Further Assessment of ZnO Nanoparticles in Antimicrobial Applications

AbstractThis work investigates the synthesis of ZnO nanoparticles, cobalt (Co)‐doped ZnO, and Activated Carbon (AC) ‐Co doped ZnO via green precipitation technique. AC developed from lotus stems and precipitated by lotus leaf extract. Comprehensive structural, optical, and morphological investigations by FT‐IR, XRD, FE‐SEM, EDX, HR‐TEM, UV‐DRS, PL, and XPS studies are used to characterize the photocatalysts. The ZnO nanoparticles are shown to have a hexagonal phase by XRD examination. The results of the FT‐IR analysis proved that specific chemical bonds exist in the ZnO, Co−ZnO, and AC−Co‐doped ZnO nanocomposites. FE‐SEM images revealed spherical morphology with aggregated, randomly distributed particles with an average size range of ZnO, Co−ZnO and AC−Co−ZnO are 59.55, 42.55, 41.16 nm. The band gap energies of ZnO, Co ‐ZnO, and AC−Co‐ ZnO, are found to be 3.10, 2.57, and 1.94 eV, respectively. Rhodamine B is used as a model contaminant to assess the samples under UV‐light driven photocatalytic effectiveness. The photocatalytic degradation efficiency (%) of the pristine ZnO, Co‐doped ZnO, and AC−Co‐doped ZnO catalysts are increased to 61.76, 74.86, and 91.46 % after 140 minutes of under UV‐light irradiation. Degradation rate constant (k) of the AC−Co−ZnO photocatalyst is found to be greater than that of pristine ZnO and Co−ZnO. Due to the synergistic effect of the AC and Co metal dopants and the spherical morphology of the AC−Co−ZnO sample, which boosted UV‐visible light absorption with reduced charge carrier recombination, resulting in outstanding photocatalytic activity. The study also investigated the bioactive effect of the samples on six bacterial species, revealing that the AC−Co‐doped ZnO nanocomposite has the most enhanced inhibitory effects against gram‐positive and gram‐negative bacteria. Consequently, medical wound dressing materials which helps to promote early healing by preventing microbial contamination.

Efficient methane oxidation to formaldehyde via photon–phonon cascade catalysis

The oxidation of methane to value-added chemicals provides an opportunity to use this abundant feedstock for sustainable petrochemistry. Unfortunately, such technologies remain insufficiently competitive due to a poor selectivity and a low yield rate for target products. Here we show a photon–phonon-driven cascade reaction that allows for methane conversion to formaldehyde with an unprecedented productivity of 401.5 μmol h−1 (or 40,150 μmol g−1 h−1) and a high selectivity of 90.4% at 150 °C. Specifically, with a ZnO catalyst decorated with single Ru atoms, methane first reacts with water to selectively produce methyl hydroperoxide via photocatalysis, followed by a thermodecomposition step yielding formaldehyde. Single Ru atoms, serving as electron acceptors, improve charge separation and promote oxygen reduction in photocatalysis. This reaction route with minimized energy consumption and high efficiency suggests a promising pathway for the sustainable transformation of light alkanes.

Stable production of hydrogen peroxide over zinc oxide @ zeolitic imidazolate Framework-8 composite catalysts

A promising method of producing hydrogen peroxide (H2O2) is the electrochemical two-electron water oxidation reaction (2e− WOR). In this process, it is important to design electrocatalysts that are both earth abundant and environmentally friendly, as well as offering high stability and production rates. The research of WOR catalysts, such as the extensively used transition metal oxides, is mainly focused on the modification of transition metal elements. Few studies pay attention to the protective heterostructure of metal oxides. Here, we demonstrate for the first time an organometallic skeleton protection strategy to develop highly stable WOR catalysts for H2O2 generation. Unlike the pure ZnO and zeolite imidazole framework-8 (ZIF-8) catalysts, ZnO@ZIF-8 enabled the production of hydrogen peroxide at high voltages. The experimental results demonstrate that the ZnO@ZIF-8 catalyst stably generates H2O2 even under a high voltage of 3.0 V vs. RHE, with a yield reaching 2845.819 μmolmin−1 g−1. ZnO@ZIF-8 shows a relatively low overpotential, with a current density of 10 mA cm−2 and an overpotential of 110 mV. The ZnO@ZIF-8 catalyst’s maximal FE value was 4.72 %. Moreover, the ZnO@ZIF-8 catalyst exhibits remarkable durability even after an extended 60-hour stability test. Operando Raman and theoretic calculation analyses reveal that the metal–organic skeleton being encapsulated on the metal oxide surface synergizes with each other, not only expanding the electrochemical surface area, but also adjusting the catalyst metal sites’ adsorption capacity. A novel approach to the modification of 2e− WOR metal oxide catalyst is presented in this work.

Mesoporous aluminosilicate materials supported zinc oxide photocatalytic degradation of pharmaceutical pollutants

The current study focuses on the creation of catalysts that have several uses. Supports for attaching ZnO catalysts are made of mesoporous alumino-silicate materials with varying SiO2/Al2O3 ratios (type Siral), and the amount of Al in them ranges from 20 % to 70 %. The alumino-silicate support materials are great for loading active components because they have a lot of surface area, a well-defined regular structure, and few mesopores that are spread out. We carry out the synthesis of the mesoporous alumino-silicate-supported zinc oxide photocatalyst (Siral/ZnO) using a mechano-chemical grinding approach. Different characterization methods, such as UV–visible spectroscopy, X-ray powder diffraction (XRD), SEM, and Brunauer-Emmett-Teller (BET), evaluate the properties of the heterogeneous catalysts and the effectiveness of ZnO addition. We use these supports to enhance their catalytic efficiency by examining responses related to the decomposition of pharmaceutical contaminants and pigments like Ibuprofen (IBP). The finding results revealed that mesoporous structure of Siral/ZnO NCs with an average crystallite size of 1–50 nm with the Type IV N2 adsorption and desorption isotherms show a noticeable photocatalytic activity under UV–visible light irradiation. The efficiency of the photo-degradation increases with increasing the weight percentage from 5 wt% to 60 wt% of ZnO NPs, and it reaches 85.18 % for Siral70/60 % ZnO after 4 h. Siral/ZnO NCs photocatalysts exhibit exceptional photostability and reusability when it comes to the degradation of organic molecules.

Efficient hydrogen production via hydrolysis of NaBH4 by the Co/Co3O4–Cu2O–ZnO catalyst prepared using mixed metal oxides as support material

Efficient hydrogen production via hydrolysis of NaBH4 by the Co/Co3O4–Cu2O–ZnO catalyst prepared using mixed metal oxides as support material

Chemical recycling of mixed textile waste.

Globally, less than 0.5% of postconsumer textile waste is recycled, with the majority incinerated or ending up in landfills. Most postconsumer textiles are mixed fibers, complicating mechanical recycling due to material blends and contaminants. Here, we demonstrate the chemical conversion of postconsumer mixed textile waste using microwave-assisted glycolysis over a ZnO catalyst followed by solvent dissolution. This approach electrifies the process heat while allowing rapid depolymerization of polyester and spandex to their monomers in 15 minutes. A simple solvent dissolution enables the separation of cotton and nylon. We assess the quality of all components through extensive material characterization, discuss their potential for sustainable recycling, and provide a techno-economic analysis of the economic feasibility of the process.

Fe-doped ZnO nanoparticles prepared by high energy ball milling with enhanced sonophotocatalytic performance

Zinc oxidenanostructures were synthesized using a thermal decomposition method and subsequently doped with Fe (III)in this study. Techniques such as X-ray diffraction, Field emission scanning electron microscopy, and Fourier transform infrared spectroscopy were used to investigate the structural and chemical composition of nanomaterials. Fe-doped ZnO was synthesized using a simple, low-cost planetary high-energy ball milling process. The sonophotocatalytic activity of Fe-doped ZnO under visible light and ultrasonic waves was then studied. Another aspect of this study is the utilization of visible light, which is far more accessible and cost-effective than UV light. Malachite green (MG) and phenol were applied as water-soluble contaminants. MG degraded about 87.65% after 1 h in the presence of a Fe-doped ZnO catalyst under visible light and ultrasonic waves simultaneously. Phenolwas degraded by approximately 64.50% under the same conditions.