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Article

Facial One-Pot Synthesis, Characterization, and Photocatalytic Performance of Porous Ceria

by
Amal A. Atran
1,2,
Fatma A. Ibrahim
1,3,
Nasser S. Awwad
4,
Mohd Shkir
5 and
Mohamed S. Hamdy
1,*
1
Catalysis Research Group (CRG), Department of Chemistry, College of Science, King Khalid University, P.O. Box 9004, Abha 61413, Saudi Arabia
2
Department of Chemistry, College of Science, Najran University, P.O. Box 1988, Najran 11001, Saudi Arabia
3
Department of Chemistry, Faculty of Women for Art, Science and Education, Ain Shams University, Cairo 11757, Egypt
4
Department of Chemistry, College of Science, King Khalid University, P.O. Box 9004, Abha 61413, Saudi Arabia
5
Department of Physics, College of Science, King Khalid University, P.O. Box 9004, Abha 61413, Saudi Arabia
*
Author to whom correspondence should be addressed.
Catalysts 2023, 13(2), 240; https://doi.org/10.3390/catal13020240
Submission received: 9 December 2022 / Revised: 1 January 2023 / Accepted: 18 January 2023 / Published: 20 January 2023
(This article belongs to the Special Issue Zeolites as Catalysts: Applications in Chemical Engineering, Energy Sources and Environmental Protection)
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Abstract

:
A facial one-step synthesis procedure was applied to prepare porous sponge-like ceria (CeO2). The synthesis was performed by mixing cerium nitrate with citric acid, followed by thermal treatment. The produced solid material was characterized by several techniques, such as XRD, SEM, N2 sorption measurement, DR-UV-vis, and Raman spectroscopy. The characterization data showed that the nanoparticles of the porous ceria were formed with a three-dimensional pore system. Moreover, the measured surface area of the porous sample was eight times higher than the commercially available ceria. The photocatalytic performance of the porous ceria was investigated in two different applications under visible light illumination. The first was the decolorization of a methyl green aqueous solution, while the second was the photocatalytic elimination of a gaseous mixture consisting of five short-chain hydrocarbons (C1–C3). The obtained results showed that the photocatalytic activity of porous ceria was higher than that of the commercial sample. Finally, the recycling of porous ceria showed low deactivation (less than 9%) after four consecutive runs.

1. Introduction

The main concern of increasing industrial activity around the world is the issue of environmental pollution, and in particular, the pollution of water sources and air contamination [1]. The influence of water pollution is not limited to human life only but extends to other living organisms and, indeed, ecological life [2]. Moreover, air contamination can deteriorate human health and plant health as well. In 1972, researchers developed a cost-effective technique that provides the possibility to remove most of the pollutants either from water or air, which is a photocatalytic technique [3]. Photocatalysis has drawn a lot of interest recently, especially if a sustainable light source is utilized to activate the photocatalyst [4]. Unlike conventional heterogeneous catalysis, in which intensive heating processes may be required, photocatalysis occurs at room temperature and in a simple way using just light as the energy source [5]. The ideal photocatalyst should be photoactive, cost-effective, stable, nontoxic, and able to use visible and/or near UV light [6].
During the past two decades, the demand for active materials that can be used as photocatalysts in the visible light range has increased. Metal oxides (semiconductors), such as TiO2 and ZnO, were among the materials that attracted the most attention and were used as photocatalysts to remove organic pollutants with high efficiency [7]. However, most semiconductors can only utilize light from the UV region, which limits the use of these materials in real industrial applications [8]. Amongst semiconductors, cerium oxide (ceria) is a promising photocatalyst with moderate activity under visible light illumination, which is a big advantage when compared to other metal oxides [9]. Ceria has attracted a lot of interest, and several publications were reported to present its utilization in different photocatalytic applications. The number of publications that deal with ceria has increased dramatically from 466 papers in 2001 to 2367 papers in 2021. Ceria is a cubic fluorite-type oxide that belongs to the rare earth oxides. It exists in both trivalent and tetravalent oxidation states; however, the electronic structure Ce4+([Xe]4f0) is more stable than Ce3+ ([Xe]4f1) [10,11,12]. Moreover, ceria is considered an n-type semiconductor material with a broad bandgap of roughly 3.1–3.44 eV [13]. According to the literature, the overall reaction rate of ceria under sunlight illumination is small due to its reducing potential and also due to the fast recombination of the photogenerated electron-hole pairs [14]. In order to improve the photocatalytic efficiency of ceria, several tactics can be applied, such as doping with other elements, composite formation with other semiconductors, nanoparticle preparation, and the formation of oxygen-defected sites. Increasing the photocatalytic efficiency of ceria will positively reflect on its utilization in industrial processes, such as in water treatment, air purification, and solar cells.
Several attempts were reported to improve the physical and photochemical properties of ceria. Fagen et al. prepared ceria nanoparticles via a precipitation method and produced ceria with a surface area of 24 m2/g [15]. In another study, Ramasamy et al. applied a sol–gel procedure to prepare ceria nanoparticles with an energy gap of ≈3.79 eV [16]. Moreover, Govindhasamy et al. applied a one-step chemical precipitation method to the facial synthesis of ceria nanoparticles with a bandgap energy of 3.2 eV [17]. Mostafa et al. applied the hydrothermal method to prepare ceria nanoparticles with a surface area of 57.5 m2/g [18]. In addition, Yoki et al. synthesized ceria nanoparticles with a bandgap value of 3.48 eV via the sol–gel method [19]. In these studies, the photocatalytic efficiency of ceria under visible light illumination was not as high as expected, which indicates that more improvements are required for ceria nanoparticles to enhance their photocatalytic activity.
In the current study, porous ceria nanoparticles were prepared in a simple one-step thermal technique to improve photocatalytic performance. The produced materials were characterized by several techniques, such as X-ray diffraction (XRD), N2 sorption measurements, ultraviolet–visible spectroscopy (UV–vis), scanning electron microscopy (SEM), and Raman spectrometer. The photocatalytic activity of the prepared porous ceria was evaluated in two different applications under visible light illumination. The first is the decolorization reaction of methyl green (MG) dye in an aqueous solution, while the second is the photocatalytic elimination of a gaseous mixture consisting of five short-chain hydrocarbons (C1–C3). Commercial ceria nanoparticles were involved in the study as a control sample. The kinetics and rate constant of each reaction were calculated, and the obtained results are reported and discussed herewith.

2. Results

2.1. The Characterization Data

The phase composition of the two samples: the porous and the commercial ceria, was studied through XRD analysis, and the obtained patterns are presented in Figure 1. All the diffraction patterns are well indexed to the face-centered cubic-fluorite structure of ceria [20,21], with characteristic indexing planes of (111), (200), (220), (311), (222), and (400). Moreover, the absence of any additional phases in the prepared samples indicates that cerium nitrate was completely transformed into ceria by the applied thermal treatment. It is noteworthy that the commercial ceria sample showed sharp peaks, indicating high crystalline bulky particles. A slight decrease in the intensity of the porous ceria peaks causes the full width to be increased by half the maximum, and thus the particle size is reduced. Further analysis of the lattice and structural parameters was performed. The lattice parameters and unit cell volume were calculated to be a = b = c = 5.41744 Å and V = 158.99458 Å3 (for porous ceria) and 5.40656 Å and V = 158.03847 Å3 (for commercial ceria) using the relations [22,23]: 1/d2 = (h2 + k2 + l2)/a2, here (a111 = √ 3×d), and volume V = a3, which are well matched with the standard card JCPDS#01-0800 of cubic crystal system of ceria. The microstructural parameters, such as crystallite size, dislocation density, and strain values, were determined using the following equations: Lhkl = 0.9λ/(β cosθ), δhkl = 1/L2, and ε = β cosθ/4 and were found to be 4.8 nm, 4.38 × 10−2 nm−1, and 2.93 × 10−2, respectively, for porous ceria and 19.4 nm, 2.93 × 10−3 nm−1, and 7.25 × 10−3, respectively, for the commercial ceria sample. These values show a great variation in crystallite size and hence in other values.
Figure 2 represents the nitrogen sorption isotherm of the commercial ceria compared with that of the porous ceria. BET surface area was remarkably enhanced from 5.96 m2/g in the commercial ceria to 47.18 m2/g in the porous ceria, respectively. The N2 isotherms of the investigated ceria samples are presented in Figure 2. A typical IV adsorption–desorption curve indicates the mesoporous properties of these prepared porous samples, while a typical II for the commercial ceria indicates nonporous properties. Moreover, the textural properties are summarized in Table 1. The pore size and pore volume of the prepared porous sample were 2.8 nm and 0.138 cm3/g. The pore characteristics clearly illustrate the formation of mesopores in the ceria due to the use of citric acid during its synthesis.
The prepared porous ceria was investigated by using Raman spectroscopy (Figure 3). Theoretically, the fluorite-type cubic crystal structure of ceria exhibits only one Raman active fundamental mode at 464 cm−1, which is the triply degenerate F2g mode that corresponds to a symmetric Ce-O stretching vibration in the Oh point group [24]. It can be regarded as a symmetric breathing mode of the six oxygen atoms around the central cerium ion [25]. In Figure 3, the porous ceria sample exhibited a broad peak compared to the commercial sample due to the stretching vibrations of the ceria nanoparticles. Therefore, Raman analysis added further evidence for the formation of ceria nanoparticles without contamination and/or phase change.
The morphological structure of the prepared porous ceria was explored by using SEM, and the obtained micrographs are presented in Figure 4. The SEM micrographs show a great morphological difference between the porous and commercial samples. The commercial ceria consists of agglomerated sheets or layers, while the prepared sample clearly shows a rough, porous nature with a sponge-like structure.
Diffuse reflectance UV-vis spectra are plotted and expressed in the Kubelka-Munk function as a function of the measured wavelength for the porous and commercial ceria samples (Figure 5). Generally speaking, the two samples have strong absorption bands in the UV region; this could be due to charge transfer during the O2p-to-Ce4f transition with Ce4+ and O2− states, which is higher than the 4f1–5d1 transition in ceria with mixed valences [26]. Moreover, the bandgap of the investigated samples was calculated from the equation E = h × c/λ, where h is Plank’s constant (6.626 × 10−34 J s−1), c is the speed of light (3.0 × 108 m s−1), and λ is the cutoff wavelength (nanometers) [27]. However, the bandgap energy (Eg) for the porous ceria shows a slightly smaller bandgap energy (3.08 eV) than the commercial ceria (3.14 eV) despite their nanostructure and the small size of the crystallites, as characterized by XRD studies.

2.2. Photocatalytic Activity

In the photocatalytic study, the activity of the prepared porous ceria (porous CeO2) was compared with two samples: the commercial ceria (com CeO2) and the thermally treated commercial ceria (TT CeO2). The first application, which was applied to investigate the photocatalytic activity of the porous ceria, was the decolorization reaction of methyl green dye under visible light illumination. Several blank experiments were performed at the beginning of the study, such as the photolysis of MG dye, the catalytic decolorization of the dye, and the adsorption of the dye over cerium oxide. The obtained results show that the dye is very stable, and no photolysis could be observed under the light. Moreover, the ceria could not activate the decolorization reaction without light. Finally, the adsorption affinity of ceria towards the investigated dye was insignificant.
The photocatalytic decolorization profiles of the applied dye over the investigated samples are plotted in Figure 6A. The obtained results show the difference in activity between the samples. The porous ceria exhibited the highest activity, with 40% dye decolorization achieved after 120 min, whereas the commercial ceria and the thermally treated sample exhibited a decolorization activity of almost 20% over the same time, i.e., 120 min. Moreover, the decolorization profiles fit perfectly with a first-order reaction rate model, as seen in Figure 6B, with R-squared values of 0.99 as an indication of the highly fitting property. Furthermore, the first-order rate constant (k) of the samples in the decolorization reaction of methyl green is shown in Figure 6C. The calculated rate constants of commercial (ZnO, CeO2, and TiO2) and porous ceria are 9 × 10−4, 1 × 10−3, 2.3 × 10−3, and 3.35 × 10−3 min−1, respectively. In other words, the obtained rate constant of the porous ceria was higher than the other three photocatalysts. The obtained high activity is strong evidence for the positive effect of morphological and textural properties on photocatalytic activity. The reusability study was carried out by using porous ceria for four consecutive runs without sample treatment; the obtained results are plotted in Figure 6D. The calculated (k) of the four reactions shows that the recycling of porous ceria showed small deactivation (less than 9%) after four consecutive runs.
In the second photocatalytic application, the elimination of a gas mixture over the porous and commercial ceria is shown in Figure 7. The gas mixture contained five different gases: methane, ethane, ethene, propane, and propene. Methane was very stable and did not show any elimination over the investigated photocatalysts. Ethane exhibited some resistance over the commercial ceria [28], but over the porous ceria, almost 36% of the 25 ppm ethane was eliminated. For ethene, the first unsaturated hydrocarbon in the gas mixture that was eliminated over the two samples, it took almost 60 min over commercial ceria and 45 min over porous ceria. Almost the same result was obtained for propane, the largest saturated hydrocarbon in the gas mixture. The last hydrocarbon in the mixture was propene, which is the second-most unsaturated hydrocarbon; over porous ceria, total elimination was observed after 30 min, while over commercial ceria, total elimination was obtained after 45 min.
The elimination profiles of the hydrocarbon mixture were fit to the first-order kinetic model, and the first-order rate constant k (min−1) was calculated and plotted (Figure 8). Generally speaking, the obtained results show that the order of hydrocarbon activity can be arranged as follows: propene > propane ≥ ethene >> ethane. However, the calculated rate constants for the elimination of ethene, propane, and propene over porous ceria were 48%, 32%, and 67% higher than those over commercial ceria. These results, again, reflect the high activity of porous (over commercial ceria).

3. Discussion

3.1. The Formation Mechanism of Porous Ceria

The synthesis of porous ceria was performed by using the citric–nitrate combustion process. The synthesis mechanism can be described in four main steps. Step (1) is the complex formation between citric acid and cerium cations. The citric acid (C6H8O7) acts as a readily available, cost-effective, and effective chelating agent. Due to its high complexing ability, citric acid, when in an aqueous solution with cerium nitrate Ce(NO3)3, forms cerium-citric acid complex (Figure 9), as reported by K. Amalajyothi et al. [29].
The gel formation is the second step of the synthesis mechanism. Under vigorous stirring, the citric–cerium complexes can be hydrolyzed to produce the colloidal sol or sometimes gel of cerium hydroxide nanoparticles, with extensive adsorption of citric acid on the surface of the formed nanoparticles. It was reported that the adsorption process of citric acid molecules on cerium hydroxide limits the growth of such crystals and produces nanoparticles [30].
In step (3), the obtained gel solution is subjected to thermal treatment. In this step, a great amount of gas (mainly H2O, CO2 and N2) is released [31]; these gases are responsible for the formation of the voluminous foamy structure [32,33]. Finally, step four is the combustion process. At this stage, very small ceria particles (under 5 nm) are formed without agglomeration [30]. The calcined powders showed characteristic porous features due to the release of large amounts of gas during combustion. The combustion reaction can be expressed as follows:
Ce(NO3)3 · 6H2O + 5/6 C6H8O7 = CeO2 + 5 CO2 + 28/3 H2O + 3/2 N2
As observed, there is no impurity content in the as-synthesized product, which can be attributed to the fact that the heat released during the combustion reaction is lower for the lean fuel composition, thereby yielding powders without any carbonaceous residue. Moreover, a good amount of oxygen will be available for combustion when fuel-deficient composition is used [32]. The combustion reactions with citric acid are less violent and more controllable compared to urea or glycine due to its weak exothermic nature [34]. Citric acid fuel can play dual functions: first, as a fuel, and second, as a chelating agent. So, the morphology of the sample synthesized by citric acid was porous with a sponge-like morphology [35].

3.2. The Higher Photocatalytic Activity of Porous Ceria

The photocatalytic performance of a certain material can be effect by many factors, such as light absorption, chemical composition, the presence of contamination, textural properties, OH surface density, reaction conditions, etc. In this section, the reason for the high photocatalytic performance of porous ceria, when compared to that of commercial ceria, is discussed. Chemical structure and the presence of contaminations factors can be neglected because the two materials have the same chemical composition. Moreover, the presence of contaminations was not observed. As obtained from the bandgap calculation, it was found that the bandgap of the commercial ceria is 3.14 eV, which is very close to earlier reports [36]. However, the bandgap of porous ceria was reduced to 3.01 eV as a result of particle size, which was reduced to a few nanometers. The relationship between bandgap and particle size was discussed earlier by Segets et al. [37,38]. As a result, this small red shift simply means that porous ceria can harvest more photons from the visible light region, and more electron/hole pairs can be formed. On the other hand, different opinions were reported about the role of surface area in photocatalytic activity. Laosiripojana reported a positive opinion about the effect of surface area on ceria [39]. In the current study, it was found that porous ceria is 3.1 times greater than commercial ceria. The obtained high surface area could play a positive role in the photocatalytic activity of porous ceria due to the high number of catalytic centers which are subject to light. Obviously, this can be compared with the high surface area of porous titania (UV-100) over Titania P-25 [40]. Finally, the morphology of the porous ceria may play a role in activity enhancement [41]. The presence of a three-dimensional pore system offers high diffusion of the dye molecules and hydrocarbon gases to and from the catalytic-active centers. A similar hypothesis was proposed earlier by Shen et al. [42,43]. Based on the obtained results, porous ceria seems a promising photocatalyst, either in liquid or gas phase applications.

4. Materials and Methods

4.1. Synthesis

The ceria sample was prepared by using a one-step thermal technique. In a typical synthesis, 5 g of cerium nitrate hexahydrate (97% Sigma) was dissolved in 5 g of demi water, then 1 g of citric acid (98% Aldrich) was added to the solution, and it was stirred until complete dissolution. The solution was moved into a porcelain crucible and dried at 90 °C for 24 h. Finally, the formed solid was calcined in a muffle furnace at 550 °C for 180 min by using a heating ramp of 18 °C/min. The obtained porous ceria was labeled (porous CeO2). On the other hand, for comparison purposes, another sample was prepared by thermal treatment for the commercial ceria (TT CeO2) at 550 °C for 180 min.

4.2. Characterization

A Shimadzu LabX-6000 diffractometer with CuKα radiation (λ = 1.54056 Å) was operated at 40/30 kV/mA at 2°/m between 20–70° angles for structural studies. A JEOL JSM 6310-SEM coupled with an EDX system operating at 20 kV was used to capture e-mapping, elemental composition, and morphology. BET surface area was calculated from nitrogen adsorption/desorption isotherms, which was recorded on a QuantaChromeNOVA2000e instrument. A Shimadzu UV-3600 diffused reflectance spectrophotometer (DRS) setup was used, employed to investigate the optical properties of the prepared samples. The diffuse reflectance spectra were converted into a Kubelka-Munk function F(R) by using the equation F(R) = (1−R)2/2R. Raman spectra were recorded using a THERMO SCIENTIFIC DXRFT-Raman spectrometer with a laser source emitting at 532 nm and had a power of 2 mW.

4.3. Catalytic Activity

The photocatalytic activity of the prepared samples was investigated through the photocatalytic decolorization of methyl green (MG) dye under light illumination. In a typical experiment, 0.1 g of catalyst is dispersed into 50 mL of 0.02 g/L of the dye solution, and the overall mixture is stirred for 1 h to attain a uniform dispersion of catalytic material. Later, the suspension was kept in a photocatalytic chamber containing six Phillips light bulbs (18 W power), and the moment the light turns ON is considered the initial time of the reaction. Then, the samples were taken periodically at equal time intervals, and the absorption spectra were recorded to measure the catalytic activity parameters. After completing the experiments, the catalyst material was removed (by filtering) and was tested for reusability for up to 4 sequential runs. Moreover, the photocatalytic elimination of the hydrocarbon mixture was performed in a stainless-steel reactor with a maximum capacity of 35 mL. A total of 0.1 g of the applied catalyst was spread at the bottom of the reactor, and the reactor was closed tightly. Air was vacuumed from the reactor through the ultra-vacuum pump and then a hydrocarbon mixture was introduced into the reactor. The mixture contained 1% vol. of the five different gases: methane, ethane, ethene, propane, and propene balanced with argon as an inner gas. The applied light source (wavelength range from 300–650 nm) was introduced into the reactor through the glass window. Samples were withdrawn every 15 min through the automated valve and sent to on-line gas chromatography equipped with FID and TCD detectors.

5. Conclusions

Porous ceria nanoparticles were prepared by applying a one-step thermal technique. The prepared material exhibited a surface area eight times greater than commercial ceria. The photocatalytic activity of the porous ceria was higher than other commercial semiconductors under the illumination of visible light. The obtained higher photocatalytic activity of porous ceria can be related to its morphological, textural, and optical properties.

Author Contributions

Conceptualization, M.S.H. and N.S.A.; methodology, A.A.A.; formal analysis, F.A.I. and M.S.; investigation, A.A.A.; resources, N.S.A. and M.S.H.; writing—original draft preparation, A.A.A.; writing—review and editing, M.S.H.; supervision, M.S.H.; project administration, M.S.H.; funding acquisition, M.S.H. All authors have read and agreed to the published version of the manuscript.

Funding

The current research was funded by the Ministry of Education in KSA through project number KKU-IFP2-P-6.

Data Availability Statement

Data are available through direct contact with the corresponding author, Mohamed S. Hamdy: [email protected].

Acknowledgments

The authors extend their appreciation to the Ministry of Education in KSA for funding this research through project number KKU-IFP2-P-6.

Conflicts of Interest

The authors declare no conflict of interest.

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Catalysts 13 00240 g001 550
Figure 1. The XRD patterns of the porous ceria compared to that of commercial ceria.
Figure 1. The XRD patterns of the porous ceria compared to that of commercial ceria.
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Figure 2. (Left) The N2 sorption isotherms of the prepared porous ceria compared with a commercial ceria sample. (Right) the corresponding pore size distribution.
Figure 2. (Left) The N2 sorption isotherms of the prepared porous ceria compared with a commercial ceria sample. (Right) the corresponding pore size distribution.
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Figure 3. Raman spectrum for porous ceria compared to that of commercial ceria.
Figure 3. Raman spectrum for porous ceria compared to that of commercial ceria.
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Figure 4. The SEM micrographs of the porous ceria sample (A,C) and the commercial ceria sample (B,D).
Figure 4. The SEM micrographs of the porous ceria sample (A,C) and the commercial ceria sample (B,D).
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Figure 5. The adsorption behavior of the compared ceria samples expressed as Kubelka-Munk as a function of the measured wavelength (nm). Bandgap calculation was 3.12 and 3.01 eV for the commercial and porous ceria, respectively.
Figure 5. The adsorption behavior of the compared ceria samples expressed as Kubelka-Munk as a function of the measured wavelength (nm). Bandgap calculation was 3.12 and 3.01 eV for the commercial and porous ceria, respectively.
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Figure 6. The obtained photocatalytic data for the decolorization reaction of methyl green dye under the illumination of visible light: (A) the decolorization profiles, (B) the first-order kinetic profiles, (C) the first-order rate constants for samples, and (D) the reusability of porous ceria sample in consecutive four runs.
Figure 6. The obtained photocatalytic data for the decolorization reaction of methyl green dye under the illumination of visible light: (A) the decolorization profiles, (B) the first-order kinetic profiles, (C) the first-order rate constants for samples, and (D) the reusability of porous ceria sample in consecutive four runs.
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Figure 7. The elimination profile of (A) ethane, (B) ethene, (C) propane, and (D) propene over porous, commercial, and thermally treated ceria.
Figure 7. The elimination profile of (A) ethane, (B) ethene, (C) propane, and (D) propene over porous, commercial, and thermally treated ceria.
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Figure 8. The first-order rate constant of the hydrocarbon elimination over porous, commercial, and thermally treated ceria.
Figure 8. The first-order rate constant of the hydrocarbon elimination over porous, commercial, and thermally treated ceria.
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Figure 9. The formed complex between citric acid and cerium cation.
Figure 9. The formed complex between citric acid and cerium cation.
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Table
Table 1. The textural properties of the porous ceria compared with that of commercial ceria, as obtained from N2 sorption measurements.
Table 1. The textural properties of the porous ceria compared with that of commercial ceria, as obtained from N2 sorption measurements.
SampleSurface Area (m2/g)Pore Volume (cm3/g)Pore Size (nm)
Com CeO25.960.51-
Porous CeO247.180.1382.8
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Atran, A.A.; Ibrahim, F.A.; Awwad, N.S.; Shkir, M.; Hamdy, M.S. Facial One-Pot Synthesis, Characterization, and Photocatalytic Performance of Porous Ceria. Catalysts 2023, 13, 240. https://doi.org/10.3390/catal13020240

AMA Style

Atran AA, Ibrahim FA, Awwad NS, Shkir M, Hamdy MS. Facial One-Pot Synthesis, Characterization, and Photocatalytic Performance of Porous Ceria. Catalysts. 2023; 13(2):240. https://doi.org/10.3390/catal13020240

Chicago/Turabian Style

Atran, Amal A., Fatma A. Ibrahim, Nasser S. Awwad, Mohd Shkir, and Mohamed S. Hamdy. 2023. "Facial One-Pot Synthesis, Characterization, and Photocatalytic Performance of Porous Ceria" Catalysts 13, no. 2: 240. https://doi.org/10.3390/catal13020240

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