Remarkably and stable catalytic activity in reduction of 4-nitrophenol by sodium sesquicarbonate-supporting Fe₂O₃@Pt

Abstract

Reasonable design of bimetallic nanomaterials with support is beneficial to improve catalytic performance. This work reports a new kind of sodium sesquicarbonate-supporting Fe₂O₃@Pt via etching Fe₃O₄@Pt@SiO₂, which exhibits highly efficient and stable catalytic reduction performance towards 4-NP. Sodium sesquicarbonate-supporting Fe₂O₃@Pt has an interconnected one-dimensional network structure that provides sufficient channels for mass transfer. At the same time, a large amount of Fe₂O₃@Pt is exposed on its surface, which hinders the aggregation of pt clusters and Fe₂O₃ nanoparticles, and facilitates the direct contact of Fe₂O₃@Pt reaction sites with reactant molecules, thus improving the catalytic rate of 4-NP reduction reaction. Moreover, the introduction of non-metallic Fe can not only reduce the consumption of precious metal Pt, but also improve the catalytic efficiency due to the synergistic effect. This study opens up a new avenue to develop robust catalysts for heterogeneous catalytic reactions.

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Introduction

In recent decades, environmental pollution and the energy crisis are threatening human life, leading to a variety of deteriorative consequences. Nitrophenol and its derivatives are some of the most refractory pollutants that occur in industrial wastewater, synthetic dyes, pharmaceuticals and other industries.^1,2 Among them, 4-nitrophenol (4-NP) is regarded by the U.S. government as one of the toxic and refractory priority pollutants endangering the human central nervous system.^3–5 Nevertheless, aminophenol with low toxicity is an important chemical intermediate in the synthesis of drugs, dyes, pesticides and imaging agents.⁶ Therefore, it is of great environmental and energy significance to eliminate nitro groups in toxic phenolic compounds or convert them into amino groups. Additionally, the conversion of nitrophenol to aminophenol has considerable industrial relevance for aniline and paracetamol production.⁷

Among various methods, the reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) using reducing agents (such as NaBH₄) is one of the simplest and cost-effective methods.^8,9 This process requires E₀ (4-NP/4-AP) = −0.76 V, which is thermodynamically appropriate, but there is a high kinetic barrier among the 4-NP and BH₄⁻ ions. Therefore, it is particularly important to select a suitable catalyst for the catalytic reduction of 4-NP to 4-AP. Noble metal nanoparticles have attracted attention due to their distinctive physicochemical properties.^10–14 The catalytic reduction of 4-NP by noble metal nanostructures has been extensively investigated, including Au,^15,16 Pd,^17,18 Ag,^19,20 Pt,^21,22 Ag-Pt,²³ Au-Pt,²⁴ etc. These catalysts exhibit good catalytic reduction effect toward 4-NP. However, noble metal nanoparticles have small size, large specific surface area and high specific surface energy, so there is a trend of aggregation, which will lead to the gradual decline of the catalytic activity. Therefore, insufficient catalyst utilization coefficient, low mass transfer rate and unstable deactivation of noble metal catalysts are still some common problems that limit their application.²⁵

To maximize the catalytic activity of noble metal nanoparticles, it is necessary to choose appropriate carrier materials to disperse them. Some oxides are used as carriers to disperse noble metal nanoparticles, such as Fe₂O₃,²⁶ Al₂O₃,²⁷ SiO₂,²⁸ and CeO₂.²⁹ As the carrier of noble metal nanoparticles, two-dimensional membrane materials have more advantages, which can not only improve the catalytic activity, but also improve the stability of the catalyst. Zhang's group loaded Au–Pt alloy nanoparticles on α-Co(OH)₂ nanosheets to improve the catalytic performance for the 4-NP reduction reaction.³⁰ Han's group used Pd nanospheres decorated reduced graphene oxide for highly efficient catalytic reduction of the hazardous 4-nitrophenol pollutant.³¹ Our research group has also published a study on the high efficiency reduction of p-nitrophenol (4-NP) by Au atomic cluster decorated Fe(OH)₃/Fe₂O₃ nanosheets.³² In addition, relevant literature reports that inorganic salt materials can also be used as carriers. Yang's group describe the synthesis of Au nanoparticles coated chicken eggshell composites (defined as Au/CaCO₃ nanocomposite), which can also be used as a sensor and catalyst for the efficient detection and treatment of 4-NP.³³

On the other hand, due to the high cost and scarcity of noble metals, their wide application has been severely hampered. Relevant literature reports that transition metals can also be used as catalysts for the catalytic reduction of 4-NP. CuFe₂O₄ magnetic nanoparticles prepared by Chen's group exhibited several advantages such as stability, monodispersity, low-cost, simplicity and rapid separation performance over other catalysts for the reduction of nitrophenol.³⁴ Chiaki Terashima's group use nanoflakes-like NiCo₂O₄ samples as catalysts for rapid reduction of 4-nitrophenol.³⁵ In addition, Cu/graphdiyne material prepared by Li's group also exhibits high catalytic ability for rapid reduction of 4-NP within 3 min.³⁶ These literature show that the transition metal nanomaterials also have a good catalytic effect on the 4-NP reduction reaction.

Furthermore, the reasonable design of bimetallic catalysts, based on alloying of noble metal with other transition metal (such as Cu, Co), is not only crucial to reduce costs, but even more importantly, to improve the physical and chemical properties of alloys.³⁷ Li's group reported a clean and composition-tunable PdCu and AuCu monolithic aerogels with 3D nanowire-based network for enhanced catalytic reduction of 4-nitrophenol, the introduction of nonprecious Cu not only drastically cuts down the cost but also attains the excellent catalytic activity due to the bimetallic intrinsic synergetic effect.^38,39 However, there are few reports on the catalytic reduction of 4-NP by bimetallic catalysts based on the alloying of noble metals with other easily oxidized transition metals.

Herein, Fe₃O₄@Pt were prepared. Although the synergistic effect between Pt and Fe greatly improves the catalytic rate for 4-NP reduction reactions, Fe₃O₄/Pt is easily separated and aggregated during use or storage, resulting in a worsening catalytic rate. Therefore, Fe₂O₃@Pt was designed to be loaded onto the surface of sodium sesquicarbonate crystals. The prepared sodium sesquicarbonate structure can not only prevent the aggregation of Pt cluster and Fe₂O₃ nanoparticle, but also ensure the synergistic effect between Pt and Fe, and improve the catalytic activity for 4-NP reduction.

Experimental

Materials

Chloroplatinic acid hexahydrate (H₂PtCl₆·6H₂O), 2-morpholinoethanesulfonic acid (MES), hexadecyl trimethyl ammonium bromide (CTAB), polyvinylpyrrolidone (PVP) and p-nitrophenol (4-NP) were obtained from Aladdin reagent (Shanghai) Co., Ltd. Tetraethyl orthosilicate (TEOS) were obtained from Shanghai Zhongqin Chemical Reagent Co., Ltd. Ethanol and aqueous ammonia were obtained from Beijing Chemical Reagent. FeSO₄ and Na₂CO₃ were obtained from Sinopharm Chemical Reagent Co., Ltd. NaBH₄ was obtained from Jinan Yuxin Chemical Co., Ltd. All reagents used in this study are analytically pure and have not been purified in any way except for special labels. All experiments used deionized water.

Synthesis of Fe₃O₄@Pt

First, 5 mL distilled water and 4 mg FeSO₄ were added into a 50 mL beaker for ultrasonic dispersion. Then add 5 mL ethanol and 0.2 mL H₂PtCl₆ aqueous solution (1 g/100 mL). After fully stirring, 5 mg NaBH₄ was added into the mixed system. Centrifuge after stirring for ten minutes, discard the supernatant, wash the sediment with distilled water before dispersing the sediment in 2 mL distilled water for standby.

Synthesis of Fe₃O₄@Pt@SiO₂

First, 5 mL distilled water, 4 mg FeSO₄ and 100 mg MES were added into a 50 mL beaker for ultrasonic dispersion. Then add 5 mL ethanol, 0.2 mL H₂PtCl₆ aqueous solution (1 g/100 mL) and 45 μL TEOS. After fully stirring, 5 mg NaBH₄ and 0.7 mL ammonia water were added into the mixed system at the same time. Centrifuge after stirring for ten minutes, discard the supernatant and wash the sediment with distilled water. Mark the prepared sample as Fe₃O₄@Pt@SiO₂.

The synthesis method of the Fe₃O₄@Pt@SiO₂ with different experimental condition was the same as the above, except that without MES or with 100 mg MES and 100 mg PVP or with 100 mg MES and 100 mg CTAB.

Synthesis of sodium sesquicarbonate-supporting Fe₂O₃@Pt

Wheat spike shaped sodium sesquicarbonate-supporting Fe₂O₃@Pt could be obtained by etching the Fe₃O₄@Pt@SiO₂. The etching method is as follows: Fe₃O₄@Pt@SiO₂ obtained by the above method was ultrasonically dispersed in 10 mL distilled water. Then add 0.035 g CTAB and 1.06 g Na₂CO₃ successively, and stir in a constant temperature oil bath at 80 °C. 100 μL mixed solution was taken from the system every 3 hours to monitor the change of catalytic performance. Centrifuge after etching for 9 hours. The product was centrifuged at hot time, and washed with hot water five times, then dispersed in 2 mL distilled water for standby.

The catalytic performance test for 4-NP reduction reaction

The catalytic performance test was carried out at room temperature with a 4 mL quartz colorimetric dish as the reaction vessel. The absorbance performance during reaction was monitored by 722N visible spectrophotometer or UV-vis spectra. The specific operation steps are as follows: 3 mL H₂O, 20 μL 4-NP (0.01 mol L⁻¹), and 20 μL catalyst solution (Pt nanoparticles, Fe₃O₄ nanoparticles or sesquicarbonate-supporting Fe₂O₃@Pt solution take from 2 mL spare solution) were successively added into a 4 mL quartz colorimetric dish. After the solution was completely dispersed evenly, 100 μL fresh NaBH₄ (0.2 mol L⁻¹) aqueous solution is dropped into the above solution. Then continue to record the absorbance value at λ = 400 nm or scan the UV-vis spectrum in the range of 250–500 nm immediately.

Characterizations

The powder X-ray diffraction (XRD) patterns were performed on a Panaco X′ Pert PRO X-ray diffractometer with Cu Kα radiation (l = 0.15406 nm) with the operation voltage and current maintained at 45 kV and 40 mA. Scanning speed: 1° min⁻¹, test range: 10° ≤ 2θ ≤ 70°. Fourier transform infrared spectroscopy (FT-IR) analysis was carried out on a PerkinElmer FT-IR spectrometer. The scanning electron microscope (SEM) images were determined by Zeiss MERLIN Compact SEM-EDX microanalysis. TEM images and elemental mapping analysis of the samples were obtained on a FEI Talos F200S transmission electron microscope operating at 200 kV. The chemical states of different elements were determined by Thermo ESCALAB 250XI X-ray photoelectron spectroscopy (XPS). The UV-vis absorption spectra of the samples were measured on Shimadzu UV-1780 UV-vis-NIR spectrophotometer. The absorbance of the solution during the reaction was monitored by a 722N visible spectrophotometer.

Results and discussions

The catalytic performance of Fe₃O₄@Pt for 4-NP reduction reaction

4-NP solution has an obvious absorption peak at 400 nm. The reduction of 4-NP to 4-AP using reducing agents NaBH₄ is thermodynamically appropriate, but there is a high kinetic barrier among the 4-NP and BH₄⁻ ions. Therefore, precious metal nanoparticles are the first choice for catalytic reduction of 4-NP. Fig. S1† shows the reaction process and time-dependent absorption spectrum of the reaction mixture in the wavelength range of 250–500 nm for the catalytic reduction of 4-NP by Pt nanoparticles at room temperature. The decrease in the 400 nm peak indicates the disappearance of 4-NP, whereas the formation of a new peak at 300 nm indicates the formation of 4-AP. Therefore, the absorbance value A at 400 nm could represent the concentration C of 4-NP in the solution. Since the amount of NaBH₄ is excessive compared with that of 4-NP, the reaction kinetics follows the pseudo-first-order law, the apparent kinetic rate constant k_app can be obtained according to eqn (1)where t is the reaction time, A_t and A₀ stand for the absorbance at time t and the initial absorbance of 4-NP, C_t and C₀ is the concentration at time t and the initial concentration of 4-NP.

It can be seen from the Fig. 1a that the catalytic rate of Pt nanoparticles is not very ideal. In order to reduce the consumption of precious metals and solve the problems of insufficient utilization coefficient, low mass transfer rate and unstable deactivation, Fe₃O₄@Pt were designed and prepared. Fig. S2† shows the XRD result of Fe₃O₄@Pt, the diffraction peak at about 40° is attributed to Pt nanoparticles. The fine XPS spectrum of Fe element (as shown in Fig. S3†) indicates that Fe exists in the form of divalent and trivalent. The catalytic reduction effect of Fe₃O₄@Pt on 4-NP reduction reaction is much better than that of Pt, and Fe₃O₄ nanoparticles has no catalytic reduction effect (Fig. S4†). Therefore, it is speculated that the excellent catalytic performance of Fe₃O₄@Pt on the reduction of 4-NP was attributed to the synergistic effect between Pt and Fe. However, with the extension of the sample storage time, the catalytic performance of Fe₃O₄@Pt gradually weakened. When stored in aqueous solution for 3 hours, its catalytic rate decreases to half of the original one, and becomes worse after 6 hours.

Fig. 1 Plots of −ln(A_t/A₀) versus the reaction time t for the reduction of 4-NP catalyzed by: (a) Pt and Fe₃O₄@Pt, (b) Fe₃O₄@Pt 0 h, 3 h, and 6 h, as well as the XPS fine spectra of (c) Pt 4f, (d) Fe 2p.

The reasons for the poor catalytic effect of Fe₃O₄@Pt were characterized by XPS and TEM. As shown in Fig. 1c, the high-resolution Pt 4f peaks near the binding energies of 71.0 and 74.5 eV are attributed to Pt 4f_7/2 and 4f_5/2, respectively. Notably, the Fe₃O₄@Pt (0 h) peak shows 0.2 eV negative shift compared to the Fe₃O₄@Pt (3 h), indicating the charge transfer from Fe to Pt in Fe₃O₄@Pt (0 h) and lead to the excellent catalytic effect of Fe₃O₄@Pt (0 h).^41,42 In Fig. 1d, the peak at 710.0 and 724.2 eV were originated from Fe 2p_3/2 and Fe 2p_1/2, respectively. The TEM results of Fe₃O₄@Pt (0 h) and Fe₃O₄@Pt (3 h) were shown in Fig. 2. In Fe₃O₄@Pt (0 h), the dispersion and homogeneity of Pt and Fe₃O₄ are particularly good. Pt clusters of about 2 nm is evenly distributed on the surface of Fe₃O₄. After the sample is dispersed in aqueous solution for 3 h, Pt and Fe₃O₄ are separated from each other and agglomerated. Therefore, the interaction between Pt and Fe is reduced, and the catalytic reduction effect becomes worse. Combined with XPS and TEM results, Fe₃O₄@Pt (0 h) has a good catalytic effect on 4-NP reduction due to the synergistic effect between Pt and Fe.

Fig. 2 The TEM images of (a) Fe₃O₄@Pt 0 h and (b) Fe₃O₄@Pt 3 h at same magnifications.

Preparation and characterization of sodium sesquicarbonate-supporting Fe₂O₃@Pt

In order to prevent the separation of Pt and Fe₃O₄ and the agglomeration of Pt nanoparticles, newly prepared Fe₃O₄@Pt were encapsulated in SiO₂ nanospheres (labeled as Fe₃O₄@Pt@SiO₂), and then SiO₂ was etched away by Na₂CO₃ to prepare sodium sesquicarbonate-supporting Fe₂O₃@Pt. As SEM results shown in Fig. 3, Fe₃O₄@Pt@SiO₂ nanoparticles present irregular polyhedron and adhere to each other, which is attributed to the rapid polymerization of TEOS under alkaline conditions, and the Fe₃O₄@Pt nanoparticles are basically encapsulated in SiO₂ polyhedron. After etching with Na₂CO₃ solution at 80 °C for 9 hours, irregular Fe₃O₄@Pt@SiO₂ polyhedron are transformed into wheat ear like one-dimensional materials, as shown in Fig. 3c and d.

Fig. 3 The scanning electron microscope (SEM) images of (a and b) Fe₃O₄@Pt@SiO₂, (c and d) sodium sesquicarbonate-supporting Fe₂O₃@Pt at different magnifications.

XRD and FT-IR spectra verified the composition, crystal phase and surface characteristics of samples before and after Na₂CO₃ etching. According to X-ray diffraction results (Fig. 4), only a strong SiO₂ (JCPDS#29-0085) diffraction peak at 20–30° is observed before Na₂CO₃ etching. However, a series of strong diffraction peaks were observed after Na₂CO₃ etching, the diffraction peaks at 18.17°, 27.90°, 29.12°, 29.21°, 33.91°, 36.83° and 40.09° correspond to (400), (111), (402), (3̄11), (5̄11), (800) and (204) crystal planes of sodium sesquicarbonate (JCPDS#72-1152), respectively. The FT-IR spectra also reflect the evolution of surface functional groups before and after etching. As shown in Fig. S5,† before etching, the strong and wide absorption band at 1077 cm⁻¹ can be classified as Si–O–Si antisymmetric stretching vibration, and the wide peak at 3128 cm⁻¹ is –OH antisymmetric stretching vibration on the SiO₂ surface. After etching by Na₂CO₃, the above two characteristic peaks disappeared, and a new characteristic absorption peak appeared at 1457 cm⁻¹, which was attributed to the stretching vibration of CO₃²⁻. The XRD and FT-IR results are consistent with SEM results. Before etching, Fe₃O₄@Pt were encapsulated in SiO₂, only the diffraction peak of SiO₂ and the absorption band of Si–O–Si antisymmetric stretching vibration could be detected. And after Na₂CO₃ etching, the SiO₂ disappeared and there was a large amount of CO₃²⁻ on the surface. Therefore, SEM, XRD and FT-IR spectra confirmed the formation of wheat spike shaped sodium sesquicarbonate crystals.

Fig. 4 X-ray powder diffraction (XRD) patterns of Fe₃O₄@Pt@SiO₂ (before etching) and wheat spike shaped sodium sesquicarbonate-supporting Fe₂O₃@Pt (after etching).

Due to the strong crystallinity of sodium sesquicarbonate crystals, the presence of Fe in the etched sample cannot be determined from XRD results. Therefore, the XPS fine spectrum of Fe was characterized. As shown in Fig. 5, the Fe 2p fine spectrum showed a significant shift after etching, and Fe exists in a trivalent form. Therefore, we speculate that Fe₃O₄ has transformed into Fe₂O₃.

Fig. 5 The Fe 2p XPS fine spectra of (a) Fe₃O₄@Pt and sodium sesquicarbonate-supporting Fe₂O₃@Pt, (b) sodium sesquicarbonate-supporting Fe₂O₃@Pt.

In order to further verify the composition of sodium sesquicarbonate crystal and the distribution of Fe₂O₃@Pt, the TEM images and the EDX elemental mapping patterns were characterized. As can be seen from Fig. 6, the residual SiO₂ after etching is mixed with Fe₂O₃@Pt and uniformly adheres to the surface of sodium sesquicarbonate crystal (marked as sodium sesquicarbonate-supporting Fe₂O₃@Pt). Pt nanoparticles are uniform in size, with an average diameter of 2–3 nm. Due to natural self-assembly, they are in a disordered state. The HRTEM images of Pt nanoparticles presented all-pervading lattice fringes with a spacing of 0.23 nm, which corresponding to (111) interplane distance of cubic Pt (Fig. 6c and d). The chemical composition of sodium sesquicarbonate-supporting Fe₂O₃@Pt was also revealed by energy-dispersive X-ray (EDX) analysis. The EDX spectrum shown in Fig. S6† verified that the as-prepared sodium sesquicarbonate supporting Fe₂O₃@Pt is indeed doped with some Si. The EDX elemental mapping patterns further demonstrated the detailed composition distribution of sodium sesquicarbonate-supporting Fe₂O₃@Pt, indicating the homogeneous distribution of Pt and Fe elements (Fig. 6e–l).

Fig. 6 (a–d) TEM image of wheat spike shaped sodium sesquicarbonate-supporting Fe₂O₃@Pt, (e–l) corresponding elemental mappings of Fe, Pt, Na, O, C and Si according to the image in (e).

Catalytic performance of sodium sesquicarbonate-supporting Fe₂O₃@Pt for 4-NP reduction

The catalytic performances of Fe₃O₄@Pt@SiO₂ (before etching) and sodium sesquicarbonate-supporting Fe₂O₃@Pt (after etching) on 4-NP reduction reaction with different conditions were investigated. As shown in Fig. 7a, the catalytic activity of Fe₃O₄@Pt@SiO₂ prepared under different conditions (without MES, MES, MES + PVP and MES + CTAB) are similar, and the catalytic rate are very slow due to the encapsulation of SiO₂. During the etching process (Fig. 7b–e), the catalytic rate becomes slower and slower. When the excess Na₂CO₃ is washed away after 9 hours of etching, the catalytic rate is significantly higher than that before etching. It is believed that the rate determining step of the reaction is the reaction between the adsorbed 4-NP and the surface hydrogen species released from NaBH₄ on the catalyst. Wheat spike shaped sodium sesquicarbonate-supporting Fe₂O₃@Pt has an interconnected network structure to provide sufficient channels for mass transfer. At the same time, a large amount of Fe₂O₃@Pt is exposed on its surface, which is conducive to the direct contact between Fe₂O₃@Pt reaction sites and reactant molecules, thus improving the catalytic rate of 4-NP reduction reaction.

Fig. 7 Plots of −ln(A_t/A₀) versus the reaction time t for the reduction of 4-NP catalyzed by: (a) Fe₃O₄@Pt@SiO₂, (b–f) sodium sesquicarbonate-supporting Fe₂O₃@Pt under different preparation conditions.

The sodium sesquicarbonate-supporting Fe₂O₃@Pt prepared under different conditions (without MES, MES, MES + PVP and MES + CTAB) showed great differences in their catalytic properties (Fig. 7f). Owing to the hindrance of PVP and CTAB, the etched sodium sesquicarbonate-supporting Fe₂O₃@Pt with PVP or CTAB showed the lower catalytic rate. However, sodium sesquicarbonate-supporting Fe₂O₃@Pt with MES showed the best catalytic performance due to the reduction protection characteristics of MES.^32,40 The rate constants k_app was calculated to be 13.98 × 10⁻³ s⁻¹ from the slope of the plots (Fig. S7†). Another significant parameter turnover frequency (TOF), defined as moles of reactant reduced through per mole of catalyst per second, was calculated to be 78 h⁻¹. The comparison of the kinetic parameter of sodium sesquicarbonate-supporting Fe₂O₃@Pt with that of previous work was shown in Table S1.†

To further verify the synergistic effect between Fe and Pt, the catalytic effects of sodium sesquicarbonate-supporting Fe₂O₃@Pt and sodium sesquicarbonate-supporting Pt and Fe₂O₃ alone on 4-NP reduction were compared. It can be seen from Fig. S8† that the catalytic effect of sodium sesquicarbonate-supporting Fe₂O₃@Pt is much better than that of sodium sesquicarbonate-supporting Pt and Fe₂O₃ alone. And the conversion of 4-NP was up to 90% in 4 min (Fig. S9†), which is much better than loading Pt and Fe separately. Therefore, the introduction of non-metallic Fe can not only reduce the consumption of precious metal Pt, but also improve the catalytic efficiency due to the synergistic effect.

In conclusion, the prepared sodium sesquicarbonate structure can not only prevent the aggregation of Pt and Fe₂O₃, but also ensure the interaction between Pt and Fe, and improve the catalytic activity for 4-NP reduction. The material could be used in heterogeneous catalysis, water treatment and green chemistry.

Conclusions

In summary, the sodium sesquicarbonate-supporting Fe₂O₃@Pt with interconnected one-dimensional network structure is developed via etching Fe₃O₄@Pt@SiO₂. The supporting role of sodium sesquicarbonate is not only prevent the aggregation of pt clusters and Fe₂O₃ nanoparticles, but also provide sufficient channels for mass transfer. At the same time, due to the synergistic effect between Pt and Fe, sodium sesquicarbonate-supporting Fe₂O₃@Pt shows good catalytic activity for 4-NP reduction. Moreover, the introduction of non-metallic Fe can not only reduce the consumption of precious metal Pt, but also improve the catalytic efficiency due to the synergistic effect. In conclusion, we believe the one-dimensional sodium sesquicarbonate-supporting Fe₂O₃@Pt will be attractive for broad applications in heterogeneous catalysis, water treatment and green chemistry.

Author contributions

Xia Xu: methodology, writing – original draft. Liming Yang: characterization of the TEM and collected the data performed the analysis. Mingqiang Li: synthesis nanomaterials collected the data. Bing Hu: writing – review & editing, funding acquisition. Xia Xu: designed the experiment and wrote the revised the paper.

Conflicts of interest

There are no conflicts to declare

Acknowledgements

The authors are grateful for the financial aid from the National Natural Science Foundation of China (Grant Nos. 21961001), Natural Science Foundation of Gansu Province (21JR7RA829), Innovation fund of Gansu Provincial Department of Education (2021B-121) and the Scientific research start-up funds for openly-recuited doctors provided by Gansu Agricultural University (GAU-KYQD-2018-14).

Notes and references

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Footnote

† Electronic supplementary information (ESI) available. See DOI: https://doi.org/10.1039/d3ra01930f

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