Solar Energy as Renewable Energy for the Degradation of Pollutants using High Active Ag@TiO2/α-Fe2O3 Ternary Nanocomposite Photocatalyst

doi:10.21203/rs.3.rs-1099297/v1

Download PDF

Research Article

Solar Energy as Renewable Energy for the Degradation of Pollutants using High Active Ag@TiO₂/α-Fe₂O₃ Ternary Nanocomposite Photocatalyst

https://doi.org/10.21203/rs.3.rs-1099297/v1

This work is licensed under a CC BY 4.0 License

Version 1

posted

You are reading this latest preprint version

In this work, ternary Ag@TiO₂/α-Fe₂O₃ nanocomposite were synthesized via solvothermal chemical reduction method using N,N-dimethylformamide (DMF) as solvent and reducing agent. The chemical procedure involves the use of only metals precursors without the need to use any other surfactants or capping agents. Physicochemical properties of the designed photocatalyst are found by means of various modern techniques. XRD data confirmed the high crystallinity of the obtained ternary nanocomposite. On the other hand, using TEM and HRTEM instruments, the shape and morphology of the Ag@TiO₂/α-Fe₂O₃ nanocomposite were found to be spherical with an average particle size of 150 nm. The UV-Vis measurement shows that Ag@TiO₂/α-Fe₂O₃ as photocatalyst exhibited good photo response in the visible region. The effect of preparation method and the performance of the designed photocatalyst were evaluated by photodegradation measurements of MB under visible light irradiation. We observed that the combination of metallic silver nanoparticles (AgNPs) and hematite iron oxide (α-Fe₂O₃) with titanium dioxide (TiO₂) enhance the photocatalytic activity of the ternary Ag@TiO₂/α-Fe₂O₃ photocatalyst compared to bare TiO₂ suggesting its potential for many purification applications.

Materials Chemistry

Polymer Science

solvothermal

hydrothermal

silver

titanium dioxide

iron oxide

photocatalyst.

Environmental pollution resulting from numerous artificial and industrial events is essentially constituted of inorganic, organic and harmful pollutants such as antibiotic, pesticides and dyes [1]. Generally, the most adopted methods to decompose pollutions such as chemical, heating, or biological process are found to be very expensive and ineffective mostly for the degradation of antibiotic. In recent years, nanomaterials are found to be very useful for different applications [2–4]. On the other side, photocatalytic reactions have been widely suggested as green solution to decompose many categories of pollutants under mild conditions and under solar light source [5–11]. However, the photodegradation mechanism involves the presence of only a photocatalyst and a light as exciting source. This process can mineralize pollutants to harmless products such as carbon dioxide and water and therefore produces useful products. Among the semiconductor photocatalyst, titanium dioxide (TiO₂) can be considered as the most promising photocatalyst in recent years due to its high stability and easy to prepare in different shape and size [12–20]. On the other hand, unfortunately, TiO₂ nanoparticles suffer from its large energy gap (3.2 eV), which limits its usage under visible light source [14]. The second inconvenient which inhibits the photocatalytic efficiency of TiO₂ is related to the high charge carrier recombination rate during the photodegradation reaction [15]. To resolve this problem, the synthesis of hybrid nanocomposite was found to be very efficient for decreasing the energy gap and the separation of charge carrier recombination. Using a simple two-step hydrothermal and photo-reduction method, Zhang et al. prepared ternary BiVO₄/NiS/Au nanocomposites with efficient charge separations for enhanced visible light photocatalytic performance [11]. They found that the photodegradation activity was enhanced 4.25 times compared to pure BiVO₄. Using the sol-gel method, Khasawnhem et al. [1] designed hybrid Fe₂O₃-TiO₂ heterogenous photocatalyst for the removal of acetaminophen (ACT) pharmaceutical compound. The obtained results revealed that photodegradation rate of ACT was observed at pH=11 and the photocatalytic activity was further optimized compared to bare TiO₂. Sahu et al. developed for the first time a combined sol–gel-assisted hydrothermal method to prepare Copper/TiO₂/graphene oxide ternary nanocomposites (CuTGR) [2]. This photocatalyst exhibited high photocatalytic activity. Indeed, preliminary results show that an optimal loading of Cu and graphene in TiO₂ matrix can significantly enhance the surface and optical response of the designed nanocomposites and thereby allowing it to be an efficient ternary photocatalyst for many applications.

In this context, the main purpose of this work is to prepare a ternary system based on titanium dioxide (TiO₂) nanoparticles with excellent light absorption and high photocatalytic efficiency. In recent years, iron oxide more precisely the hematite phase (α-Fe₂O₃) was found to be an ideal metal oxide to expand the photo response of TiO₂ and therefore enhance its photocatalytic performance [16–19]. On the other side, silver nanoparticles (AgNPs) are a plasmonic metal nanoparticles with their intrinsic plasmonic properties can increase the electrons activity over the surface of TiO₂ NPs and slows down the recombination of e-/h+ pairs. Consequently, the loading of both hematite iron oxide (α-Fe₂O₃) and silver nanoparticles (AgNPs) at the TiO₂ surface can subsequently boost the photocatalytic activity of the final nanocomposite. The present paper develop a simple one pot solvothermal protocol to synthesize ternary Ag@TiO₂/α-Fe₂O₃ nanocomposite using N,N-dimethylformamide (DMF) as solvent and reducing agent without recourse to use any capping agent or surfactant. The photodegradation reaction against MB dyes prove the efficiency of this ternary system compared to bare TiO₂ or α-Fe₂O₃ NPs.

2.1. Measurement and Characterizations

Powder X-ray diffraction (D8 Advance Bruker, USA) technique was performed to study the obtained crystalline phase. Shape and size of the photocatalyst was examined using transmission electron microscope (Philips Tecnai F-20 SACTEM working at 200 kV). X-ray photoelectron spectrometry (XPS, Kratos Axis Ultra DLD) was recorded for further elemental analysis. Optical response was investigated via UV–Visible Perkin-Elmer Lambda 11 spectrophotometer. To study the charge recombination process, Photoluminescence (PL) measurements were adopted using Jobin Yvon Flurolog-3-11 instrument equipped with 450 W xenon lamp. Photocatalytic test were evaluated at room temperature for removal of MB molecules dyes under visible light illumination (lamp of 400 W Metal Halide. The solution pH was fixed at 7. The photocatalyst amoun was fixed to 7 mg during the photocatalytic test. The initial MB concentration solution was 3.0 .10⁻⁵ mol/L.

2.2. Synthesis of Ag@TiO₂/α-Fe₂O₃ Photocatalyst

Iron oxide was first synthesized using the hydrothermal process [21] by mixing iron chloride and ammonium dihydrogen phosphate. After that, the mixture was transferred into a Teflon-lined autoclave and heated at 220℃ for 48 h. Ag@TiO₂/α-Fe₂O₃ photocatalyst was prepared as follows: Titanium(IV) butoxide (5 ml) and silver nitrate (100 mg) were first dissolved in 50 ml of N,N-dimethylformamide (DMF) at room temperature. The resulting mixture was magnetically stirred, and an adequate amount of as-prepared iron oxide nanoparticles (10 mg) was added. Then the obtained final mixture was heated at 153 ℃ for 2 h. The recuperated powder was then calcinated in air at 400℃ for 2 h to produce the desired ternary Ag@TiO₂/α-Fe₂O₃ nanocomposite.

Powder X-ray diffraction patterns of TiO₂, α-Fe₂O₃ and ternary Ag@TiO₂/α-Fe₂O₃ photocatalyst are shown in Figure 1. As can be observed, in the diffractogram of the ternary nanocomposite, all diffractions peaks characteristic of titanium dioxide, silver and iron oxide are detected. No other peaks or impurities can be detected which prove the purity of the obtained sample. Based on the XRD data, we can assume the successful fabrication of the ternary Ag@TiO₂/α-Fe₂O₃ heterojunction. Figure 2 displays the morphology of the ternary photocatalyst. As shown, we can detect the deposition of both AgNPs and α-Fe₂O₃ NPs on the TiO₂ surface. Furthermore, the HRTEM image confirms the ternary heterojunction by the presence of (111), (003) and (101) lattice spacing characteristic of Ag, α-Fe₂O₃ and TiO₂ NPs, respectively. The SAED pattern further confirms the presence of the three system by the detection of all characteristic electron diffraction responses. To further confirm the successful synthesis of Ag@TiO₂/α-Fe₂O₃ nanocomposites, XPS mesearement was performed to study the chemical composition and their corresponding valence states (Figure 3). The XPS spectra of the asprepared sample are shown in Figure 3. In the Ti 2p spectrum, two peaks at 458 eV, and 465 eV were assigned to Ti 2p3/2 et Ti 2p1/2, respectively. Values agree well with the Ti⁴⁺ state in TiO₂. The spectrum of Fe which exhibites also two peaks at 711 eV and 725 eV can be ascribed to the Fe 2p element of hematite α-Fe₂O₃. In the case of O 1s, it can be detected the presence of asymmetrical peak located at 529.9 eV which can be attributed to lattice oxygen and surface oxygen. For Ag element, two characteristic peaks are located at 273.6 and 367.8 eV which can be assigned to Ag 3d3/2 et Ag 3d5/2 respectively. Values agree well with Ag⁰ metal. The deconvolution of the XPS peaks of Ag (Figure S1) revealed the presence of peaks characteristic of Ag-O bonds. As mentioned above, HRTEM results showed the deposotion of AgNPs on both TiO₂ and α-Fe₂O₃ surfaces. The XPS data agree well with the HRTEM observation. However, the presence of XPS peaks characteristic of Ag-O bonds confirmed the the adsorption processes of AgNPs on TiO₂ and α-Fe₂O₃ surfaces, through chemical oxygen bonds. This chemisorption between AgNPs and metals oxide ensures the formation of .he ternary heterojunction and avoiding metal desorption [12, 13]. The optical properties of Ag@TiO₂/α-Fe₂O₃ nanocomposite, hybrid Ag@TiO₂ and as well as bare TiO₂ and α-Fe₂O₃ were investigated using UV-visible absorption spectroscopy (Figure 4-a). Regarding the TiO₂, Ag@TiO₂ and Ag@TiO₂/α-Fe₂O₃ spectra, each spectrum shows an absorption edge at 346 nm that corresponds to a band gab energy of 3.85 eV. Result agree well agreement with the band gap energy reported in the literature. On the other hand, for Ag@TiO₂ and Ag@TiO₂/α-Fe₂O_3, an additional absorption band located between 435 and 480 nm which can be attributed to the surface plasmon resonance of silver nanoparticles. On the other side, iron oxide is generally reported to absorb strongly in the ultraviolet (UV) region. However, regarding the α-Fe₂O₃ and Ag@TiO₂/α-Fe₂O₃ spectra, effectively an absorption edge located at 245 nm can clearly detected and can be assigned to the electronic transition in the hematite 𝛼-Fe₂O₃ structure. The change of the absorption behaviour of Ag@TiO₂/α-Fe₂O₃ compared to bare TiO₂ and α-Fe₂O_3, implies that the charge-transfer transition between the three materials occurs while loading Ag to TiO₂ and α-Fe₂O₃. This observation was further supported by PL measurements (Figure 4-b). Indeed, as can be seen, the PL spectrum of all samples exhibited blue emission located at 445 nm. It has been reported that the visible luminescence, related to deep level emissions, mainly results from defects such as interstitials and oxygen vacancies. On the other hand, as can be seen in Figure 4-b, a considerable PL emission quenching of Ag@TiO₂/α-Fe₂O₃ nanocomposite was observed which indicated that a lower recombination rate of the photogenerated carrier could be efficiently achieved resulting from the synergistic effects between Ag, TiO₂ and α-Fe₂O₃. This result implying that the intimate contact between Ag, TiO₂ and α-Fe₂O₃ could make for the vectorial migrate of charge carriers among the nanocomposite, enhancing the photogenerated carrier’s separation and therefore improving the photocatalytic efficiency.

The photocatalytic efficiencies of Ag@TiO₂/α-Fe₂O₃ nanocomposites were evaluated using MB dyes as a model pollutant. Photocatalytic activities of hybrid Ag@TiO₂, bare TiO₂ and α-Fe₂O₃ were also measured for comparison. As shown in Figure 5-a, the photodegradation rate of MB was found to be the highest using the ternary Ag@TiO₂/α-Fe₂O₃ photocatalyst. On the other side, the photodegradation rate using pristine α-Fe₂O₃ photocatalyst is the lowest. However, the photocatalytic performance of hematite α-Fe₂O₃ is limited due to the charge carrier recombination. On the other hand, the hybrid Ag@TiO₂ photocatalyst exhibited interesting photodegradation rate due to the presence of plasmonic AgNPs which can generate more electrons and therefore boost the photocatalytic activity of TiO₂. It can be seen that ternary Ag@TiO₂/α-Fe₂O₃ photocatalyst exhibits much higher photodegradation activities than that of hybrid Ag@TiO₂ may be due to the support given by α-Fe₂O₃ NPs which increases the surface are of the photocatalyst and also increases the light absorption which generates more electron-hole pairs for dye photodegradation and consequently enhances the photocatalytic activity of the ternary nanocomposite. To examine the reaction kinetics of photocatalysts, experimental data were fitted by a first-order kinetic equation (Ln(C₀/C) = k_apt) using the Langmuir–Hinshelwood model. It can be seen from the curves displayed in Figure 5-b that the photodegradation process followed first order kinetics. A proposed possible photocatalytic mechanism is illustrated in Figure 5-c. After excitation the VB electrons of both TiO₂ and α-Fe₂O₃ were excited to the CB, creating holes in the VB. These photogenerated electrons-holes recombined rapidly, leading to a low photocatalytic performance of the photocatalyst. However, after loading the AgNPs, the photogenerated electrons could be continuously transported from TiO₂ and α-Fe₂O₃ to AgNPs. Those vector transfers led to spatial separation of the photogenerated carries with an electron transferred to AgNPs while the holes remain trapped at the TiO₂ and α-Fe₂O₃ surface. Subsequently, the adsorbed oxygen molecule (O₂) can after that react with electrons produce therefore reactive oxygen species (such asO₂.⁻, .O²⁻) that could oxidize and destruct MB dyes.

In summary, the synthesis of ternary Ag@TiO₂/α-Fe₂O₃ nanocomposite using modified solvothermal protocol was reported. Physicochemical properties of the designed photocatalyst are found by means of various modern techniques such as XRD, TEM/HRTEM, XPS and UV-visible. The designed photocatalyst exhibited the highest photocatalytic activity. The performance of the ternary nanocomposite could be attributed to the synergistic effects of co-loading α-Fe₂O₃ and Au cocatalyst with TiO₂ which expand the separation efficiency of photogenerated electron-hole carriers and consequently boost the photodegradation rate.

AUTHOR INFORMATION

Corresponding Authors

*[email protected] [email protected]

Phone number: 00966582735533, ORCID: 0000-0002-2915-4834

Notes

The authors declare no competing financial interest.

ACKNOWLEDGMENTS

Taif University Researchers Supporting Project number (TURSP-2020/28), Taif University, Taif, Saudi Arabia.

[1] Omar Fawzi, Suleiman Khasawneh, Puganeshwary Palaniandy, Mohsen Ahmadipour, Hossein Mohammadi, Mohammad Razak Bin Hamdan. Removal of acetaminophen using Fe2O3-TiO2 nanocomposites by photocatalysis under simulated solar irradiation: Optimization study. Journal of Environmental Chemical Engineering Volume 9, Issue 1, February 2021, 104921

[2] Sahu, K., Dhonde, M. & Murty, V.V.S. Preparation of copper/TiO2/ graphene oxide ternary nanocomposites and their structural, surface morphology, and optical properties. J Mater Sci: Mater Electron 32, 15971–15980 (2021).

[3] Yi-Chi Zhang, Ya You, Sen Xin,Ya-XiaYin, Juan Zhang, Ping Wang, Xin-sheng Zheng, Fei-Fei Cao, Yu-GuoGuo. Rice husk-derived hierarchical silicon/nitrogen-doped carbon/carbon nanotube spheres as low-cost and high-capacity anodes for lithium-ion batteries. Nano Energy Volume 25, July 2016, Pages 120-127

[4] Zixun Fang, Ming Xu, Qing Li, Man Qi, Tongtong Xu, Zhimin Niu, Nianrui Qu, Jianmin Gu, Jidong Wang, and Desong Wang. Over-Reduction-Controlled Mixed-Valent Manganese Oxide with Tunable Mn²⁺/Mn³⁺ Ratio for High-Performance Asymmetric Supercapacitor with Enhanced Cycling Stability. Langmuir 2021, 37, 8, 2816–2825

[5] Yanhui Ge, Hao Luo,Juanru Huang, Zhiming Zhang. Visible-light-active TiO2 photocatalyst for efficient photodegradation of organic dyes. Optical Materials Volume 115, May 2021, 111058

[6] A. Temir, K. Sh Zhumadilov, М.V. Zdorovets, A. Kozlovskiy, A.V. Trukhanov. Study of the effect of doping CeO2 in TeO2–MoO–Bi2O3 ceramics on the phase composition, optical properties and shielding efficiency of gamma radiation. Optical Materials, Volume 115, 2021, 111037

[7] Zhang, Y., Zhao, SM., Su, QW. et al. Visible light response ZnO–C3N4 thin film photocatalyst. Rare Met. 40, 96–104 (2021).

[8] He Wang, Xuan Liu, Ping Niu. Porous Two-Dimensional Materials for Photocatalytic and Electrocatalytic Applications. June 2020 Matter 2(6):1377-1413

[9] Xu, T., Liu, X., Wang, S. et al. Ferroelectric Oxide Nanocomposites with Trimodal Pore Structure for High Photocatalytic Performance. Nano-Micro Lett. 11, 37 (2019).

[10] Mahesh Dhonde, Kirti Sahu Dhonde, · V. V. S. Murty. Novel sol–gel synthesis of Al/N co-doped TiO2 nanoparticles and their structural, optical and photocatalytic properties Journal of Materials Science: Materials in Electronics https://doi.org/10.1007/s10854-018-9962-7

[11] Guang Cong Zhang, Jinling Zhong, Ming Xu, You Yang, Yu Li, Zixun Fang, Shoufeng Tang, Deling Yuan, Bin Wen, Jianmin Gu. Ternary BiVO4/NiS/Au nanocomposites with efficient charge separations for enhanced visible light photocatalytic performance. Chemical Engineering Journal 375 (2019) 122093

[12] Todorka Vladkova, Orlin Angelov, Dragomira Stoyanova, Dilyana Gospodinova, Luciana Gomese, Alexandra Soarese, Filipe Mergulhaoe, Iliana Ivanovac. Magnetron co-sputtered TiO2/SiO2/Ag nanocomposite thin coatings inhibiting bacterial adhesion and biofilm formation. Surface & Coatings Technology 384 (2020) 125322

[13] M.Jayapriy and M.Arulmozhi. Beta vulgaris peel extract mediated synthesis of Ag/TiO2 nanocomposite: Characterization, evaluation of antibacterial and catalytic degradation of textile dyes-an electron relay effect.
Inorganic Chemistry Communications Volume 128, June 2021, 108529

[14] Mezni A, Ibrahim MM, El-Kemary M, Shaltout AA, Mostafa NY, Ryl J, et al. Cathodically activated Au/TiO2 nanocomposite synthesized by a new facile solvothermal method: an efficient electrocatalyst with Pt-like activity for hydrogen generation. Electrochim Acta 2018;290:404-18.

[15] Mezni A, Ben Saber N, Ibrahim MM, Hamdaoui N, Alrooqi A,Mlayah A, et al. Photocatalytic activity of hybrid gold-titania nanocomposites. Mater Chem Phys 2019;221:118e24.

[16] Mezni A, Ben Saber N, Bukhari A, Ibrahim MM, Al-Talhi H, Alshehri NA, et al. Plasmonic hybrid platinumtitaniananocomposites as highly active photocatalysts:selfcleaning

of cotton fiber under solar light. J Mater Res Technol 2020;9:1447e56.

[17] Mezni A, Ben Saber N, Ibrahim MM, El-Kemary M,Aldalbahi A, Feng P, et al. Facile synthesis of highly thermally stable TiO2 photocatalysts. J Chem 2017;41:5021

[18] Omar Fawzi Suleiman Khasawneh, Puganeshwary Palaniandy. Removal of organic pollutants from water by Fe2O3/TiO2 based photocatalytic degradation: A review Environmental Technology & Innovation Volume 21, February 2021, 101230

[19] Yongxia Li, Binsheng Yang, Bin Liu. MOF assisted synthesis of TiO2/Au/Fe2O3 hybrids with enhanced photocatalytic hydrogen production and simultaneous removal of toxic phenolic compounds. Journal of Molecular Liquids Volume 322, 15 January 2021, 114815

[20] Yanming Fu, Chung-Li Dong, Wu Zhou, Ying-Rui Lu, Yu-Cheng Huang, Ya Liu, Penghui Guo, Liang Zhao, Wu-Ching Chou, Shaohua Shen. A ternary nanostructured Fe2O3/Au/TiO2 photoanode with reconstructed interfaces for efficient photoelectrocatalytic water splitting. Applied Catalysis B: Environmental Volume 260, January 2020, 118206

[21] Yudong Xue and Yunting Wang. A review of the α-Fe2O3 (hematite) nanotube structure: recent advances in synthesis, characterization, and applications.
Nanoscale, 2020,12, 10912-10932

SI1.docx
Figure S1

Download PDF

Version 1

posted

You are reading this latest preprint version

Solar Energy as Renewable Energy for the Degradation of Pollutants using High Active Ag@TiO₂/α-Fe₂O₃ Ternary Nanocomposite Photocatalyst

Status:

Version 1

Abstract

Figures

1. Introduction

2. Materials And Methods

2.1. Measurement and Characterizations

2.2. Synthesis of Ag@TiO₂/α-Fe₂O₃ Photocatalyst

3. Results And Discussion

4. Conclusion

Declarations

References

Supplementary Files

Status:

Version 1

Solar Energy as Renewable Energy for the Degradation of Pollutants using High Active Ag@TiO2/α-Fe2O3 Ternary Nanocomposite Photocatalyst

Status:

Version 1

Abstract

Figures

1. Introduction

2. Materials And Methods

2.1. Measurement and Characterizations

2.2. Synthesis of Ag@TiO2/α-Fe2O3 Photocatalyst

3. Results And Discussion

4. Conclusion

Declarations

References

Supplementary Files

Status:

Version 1

Solar Energy as Renewable Energy for the Degradation of Pollutants using High Active Ag@TiO₂/α-Fe₂O₃ Ternary Nanocomposite Photocatalyst

2.2. Synthesis of Ag@TiO₂/α-Fe₂O₃ Photocatalyst