Elsevier

Materials Letters

Volume 268, 1 June 2020, 127334
Materials Letters

Synergistic effects in N-K2Ti4O9/ZIF-8 composite and its photocatalysis degradation of Bisphenol A

https://doi.org/10.1016/j.matlet.2020.127334Get rights and content

Highlights

  • The N-K2Ti4O9/ZIF-8 composites were synthesized via in-situ heterogeneous deposition method.

  • Composite exhibited enhanced visible light photocatalytic activity.

  • N-K2Ti4O9/ZIF-8 completely degraded Bisphenol A in water.

  • Adsorption-photocatalytic synergistic effects played a vital role in improving photocatalytic activity.

Abstract

N-K2Ti4O9 and metal organic frameworks (MOFs) have a wide range of application in the field of photocatalysis and adsorption. Here, N-K2Ti4O9/ZIF-8 as visible-light-driven photocatalysts was successfully synthesized by a simple in-situ heterogeneous deposition method. The synthesized samples were characterized by XRD, SEM, TEM(SAED), EDS, Mapping, BET, PL spectra and UV–vis DRS. The photocatalytic performance was investigated through the degradation of Bisphenol A (BPA) under visible-light irradiation within 90 min. The composite exhibited higher photocatalytic activity, as the rate constant (k) for BPA degradation was almost 9 times that of N-K2Ti4O9. The improved photocatalytic activity was mostly caused by the great adsorption capacity of ZIF-8 and high separation efficiency of photogenerated electron-hole pairs through interfaces between N-K2Ti4O9 and ZIF-8. The work is expected to provide new insight into the photocatalytic mechanism for composites, and rationally design and synthesis of highly efficient photocatalysts for environmental application.

Introduction

N-K2Ti4O9 has been known as an excellent photocatalyst due to its physical and chemical stability, nontoxicity, low cost [1]. However, pure N-K2Ti4O9 tend to aggregate with low surface area and rapid electron–holes recombination, reducing adsorption and photocatalytic activity [2]. So far, some solutions have been proposed to improve photocatalytic properties [3], [4]. However, it is rarely reported that the adsorption-photocatalytic synergistic performance of N-K2Ti4O9-based catalysts are significantly improved. Metal–organic frameworks (MOFs) are crystalline synthetic porous materials formed by binding organic linkers to metal nodes [5]. They have a high internal surface area and widely tunable composition, which makes them widely used in adsorption and catalysis [6]. Combining N-K2Ti4O9 with MOFs could promote photoelectrons and holes transfer and enhance adsorption performance [7]. Zeolitic imidazolate framework-8 (ZIF-8), which is constructed by Zn(II) ions and imidazolate organic ligands, exhibits high thermal and chemical stability. Taking advantage of its outstanding adsorption ability, ZIF-8 can be used as an excellent porous support in composite photocatalysts [8]. Therefore, the combination of N-K2TI4O9 and ZIF-8 may be a viable method to improve adsorption-photocatalytic performance.

Here, a novel semiconductor–MOF hybrid structure was designed by wrapping N-K2TI4O9 in ZIF-8 homogeneously via a simple in-situ heterogeneous deposition method. The adsorption and photocatalytic properties of N-K2TI4O9/ZIF-8 composites were studied by degrading BPA. Moreover, the photocatalytic and adsorption mechanisms were proposed.

Section snippets

Experimental

The detailed preparation method and processing parameters of N-K2Ti4O9/ZIF-8 are described in Text S1 of the Supplementary Material.

The crystal morphology of these materials was characterized by XRD (D/MAX2500 diffractometer). The morphological analysis of the samples was done using a FESEM (SUPRA55) equipped with an energy dispersive X-ray spectrometer (EDS) and FETEM(Jeol 2100F). Ultravivlet-visible (UV–vis) spectra were recorded on a DUV-3700 spectrometer. The Brunauer-Emmett-Teller (BET)

Results and discussion

Fig. 1a showed the SEM image of N-K2Ti4O9. It had the feature of rod-shaped microcrystals with the diameter between 100 nm and 350 nm, and the length of a few micrometers. In Fig. 1b, the ZIF-8 nanocrystals exhibit a well-defined polyhedral shape. Fig. 1c displayed that ZIF-8 was loaded on the surface of the rod-like N-K2Ti4O9 microcrystallines. The TEM analysis of the samples was carried out for clearer observation of the compositions (Fig. 1d,e). It could be seen that ZIF-8 exhibited a

Conclusion

N-K2Ti4O9/ZIF-8 was successfully synthesized via simple in-situ heterogeneous deposition method. The prepared photocatalyst exhibited alomost 9 times higher photocatalytic activity for BPA degradation than N-K2Ti4O9 under visible-light. The material characterizations showed that ZIF-8 was well dispersed on the highly porous N-K2Ti4O9 and retained large surface area (>500 m2/g). The large surface area of the material facilitated adsorption of organic pollutants and provided abundant

CRediT authorship contribution statement

Cong Shao: Software, Formal analysis, Data curation, Writing - original draft, Writing - review & editing. Sheng Feng: Conceptualization, Methodology, Resources, Funding acquisition. Guiliang Zhu: Validation. Wei Zheng: Visualization. Jiajia Sun: Project administration. Xianglin Huang: Investigation. Ziqiu Ni: Supervision.

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgements

The authors sincerely acknowledged financial supports from the National Natural Science Foundation of China (No. 41371446 and No. 41271498) and the Chinese National Funding of Social Sciences (No. 16BJL074).

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