Facile synthesis of 2D Bi4O5Br2/2D thin layer-Ti3C2 for improved visible-light photocatalytic hydrogen evolution

https://doi.org/10.1016/j.jssc.2020.121470Get rights and content

Highlights

  • Bi4O5Br2/Thin layer-Ti3C2 was prepared by in-situ synthesis at room temperature.

  • Bi4O5Br2/Thin layer-Ti3C2 manifests better photocatalytic H2 evolution than Bi4O5Br2.

  • The enhanced activity was mainly attributed to the rapidly charge transfer.

  • An electron transfer channel was established in Bi4O5Br2/Thin layer-Ti3C2.

  • The possible H2 evolution mechanism of Bi4O5Br2/Thin layer-Ti3C2 was proposed.

Abstract

Photocatalytic hydrogen evolution via water splitting was considered as a promising way of solar energy conversion and storage in the past decades. However, the weak visible-light response and fast recombination of electron-hole pairs are still main obstacles to overcome. Herein, a novel 2D/2D Bi4O5Br2/TL-Ti3C2 (Thin layer-Ti3C2) visible-light photocatalyst was successfully prepared by in-situ synthesis of Bi4O5Br2 nanosheets on the surface of TL-Ti3C2 at room temperature. The resulting Bi4O5Br2/TL-Ti3C2 exhibits a higher hydrogen evolution activity (83.5 ​μmol·g−1·h−1) than that of pristine Bi4O5Br2 (44.9 ​μmol·g−1·h−1) under visible-light irradiation. The enhanced hydrogen evolution activity of as-prepared photocatalyst mainly attributes to the increased visible light responsiveness and rapid transfer of photo-induced electrons. The strong interaction between TL-Ti3C2 and Bi3+ in Bi4O5Br2 nanosheets establishes a good electron transfer channel and close contact, which accelerates the transfer of photo-induced electrons from Bi4O5Br2 to Ti3C2 and promotes the separation of photo-generated charge carriers, thereby increasing the number of effective photo-induced electrons involved in the hydrogen evolution. This work provides a new insight into the construction of BixOyBrz/MXene photocatalyst system, and demonstrated that Ti3C2 has excellent application potential in promoting the photocatalytic performance of bismuth-rich bismuth oxyhalides (BixOyXz X ​= ​Cl, Br, I).

Graphical abstract

Benefiting from the rapidly transfers photo-induced electrons and increases the visible light responsiveness, the resulting 2D Bi4O5Br2/2D TL-Ti3C2 manifests more significant photocatalytic hydrogen evolution activity (83.5 ​μmol·g−1·h−1) than that of pristine Bi4O5Br2 (44.9 ​μmol·g−1·h−1). This work provides a new insight into the construction of BixOyBrz/MXene photocatalyst system, and demonstrated that Ti3C2 has excellent application potential in promoting the photocatalytic performance of bismuth-rich bismuth oxyhalides (BixOyXz X ​= ​Cl, Br, I).

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Introduction

Since 1972, Fujishima and Honda reported TiO2 as photocatalyst splitting water into oxygen and hydrogen [1], the application of photocatalysis has been considered as a promising strategy in the field of clean energy to solve the increasing energy crisis and environmental issues. Various new photocatalysts have been extensively developed and investigated, such as metal oxide [2], sulfide [3], graphite carbon nitride (g-C3N4) [4], metal-organic frameworks (MOFs) [[5], [6], [7]], Ag-based photocatalysts [8], Bi-based material [9,10]. However, most of these photocatalysts only can absorb UV light (only 3–5% of the total sunlight) and usually suffer from high recombination of photo-generated charge and stability problem, which greatly hinder the performance in industrial applications. Therefore, it is essential to design and develop the preparation of the environmentally benign and exceptionally stable photocatalysts, especially visible light sensitive photocatalysts to efficiently utilize solar energy.

Bismuth-rich bismuth oxybromide (BixOyBrz), as a typical 2D layered photocatalyst, has attracted wide attention due to their open layered crystalline structure and indirect transition, which can generate an internal static electric field, ultimately promoting the separation of electrons and holes effectively to obtain good photocatalytic activity [[11], [12], [13]]. Moreover, the band structure of BixOyBrz can be regulated from 2.0 to 3.13 ​eV through the bismuth rich strategy, so that it not only meets the requirements of water splitting, but also makes the most use of visible light, such as Hao et al. firstly discovered Bi24O31Br10 can produce hydrogen by water splitting under visible light with an activity of 0.07 ​mmol·g−1·h−1 in 2014 [14]. Ye et al. reported that Bi4O5Br2 prepared by solvothermal method has H2 evolution properties under visible light with an activity of 6.81 ​μmol·g−1·h−1 [15]. Nevertheless, the single-phase BixOyBrz photocatalysts still exist the awkward situation of low light-harvesting ability and high photo-generated electron-hole pairs recombination rate, which result in low photo-generated electrons utilization and low photocatalytic activity. Hence, it is significant that the introduction of a conductive material into BixOyBrz-based photocatalytic structure would establish a charge transport channel from the catalyst to the substrate [16], then leading to the fast separation of photo-generated charge carriers and improving the photocatalytic activity of catalyst. For instance, Zhang et al. prepared [Cl2]-[Bi12O17]-[MoS2] double-layer heterojunction photocatalyst, and found that its activity reached 33 ​mmol·g−1·h−1 under visible light in 2016 [17].

Recently, MXenes has increasingly became one of the hot spots in the field of photocatalysis due to its excellent electrical conductivity, anisotropy, hydrophilicity and high carrier mobility [[18], [19], [20]]. The recent studies show the presence of highly electronegative group (-O, –OH, –F) on the surface of these MXenes series, which can form a strong binding force with Bi3+ by chemical bonds, then promoting the in-situ synthesis of Bi4O5Br2 on the Ti3C2 substrate. The in-situ synthesis is quite helpful in the formation of homogeneous mixture, and the tighter interface between Bi4O5Br2 and Ti3C2 with stronger interaction, would ultimately cause the high interfacial charge-transfer and low self-agglomeration [21]. Meanwhile, Thin layer-Ti3C2 (TL-Ti3C2), as a typical 2D MXene material, can form 2D/2D structure with Bi4O5Br2, which can provide higher charge mobility and larger interface contact area while retaining the advantage of the low charge recombination rates of 1D/2D structure (line-to-face contact) and 0D/2D structure (point-to-face contact), thus leading to more surface active sites and then improving the photocatalytic reaction rate [22,23]. Therefore, derived from abundant surface groups, large surface area and good electrical conductivity, MXene should be an excellent model for constructing 2D/2D BixOyBrz/MXene. However, to the best of our knowledge, there were no reports about the introduction of MXene into the BixOyBrz photocatalyst system.

In this work, we constructed a novel 2D/2D Bi4O5Br2/TL-Ti3C2 composite at room temperature. Benefiting from the superior visible-light response, effective electron-hole separation rate, low interfacial charge-transfer resistance and strong reduction ability of the electrons, Bi4O5Br2/TL-Ti3C2 increases visible light absorption performance of Bi4O5Br2 and improves its effective electron utilization in the reaction, thus significantly enhancing hydrogen evolution in comparison to pristine Bi4O5Br2. The physical properties, electronic structure, optical, photophysical and photoelectrochemical property and band structure were fully characterized. The potential mechanism for Bi4O5Br2/TL-Ti3C2 to improve hydrogen production was described in detail.

Section snippets

Reagents and materials

Ti3AlC2 (98%, 200 mesh) was purchased from the Forsman Scientific Co., Ltd. (Beijing, China). Lithium fluoride (LiF, AR, 99%) and Chloroplatinic acid (H2PtCl6·6H2O) were purchased from Aladdin Co., Ltd. (Shanghai, China). Hydrochloric acid (HCl, AR grade, 36–38%) was purchased from Kelon Chemical (Chengdu, China). Bismuth nitrate (Bi(NO3)3·5H2O, AR, ≥ 99%), Methanol (CH3OH, AR) and Ethylene glycol (EG, AR) were purchased from Sinopharm Chemical Co., Ltd. Potassium bromide (KBr, AR, ≥ 99%) and

Synthesis and characterizations of Bi4O5Br2/TL-Ti3C2

The synthetic process of the Bi4O5Br2/TL-Ti3C2 was illustrated in Scheme 1. Firstly, Ti3AlC2 was etched by LiF–HCl mixed solution to prepared Multilayer-Ti3C2, and then delaminated to produce TL-Ti3C2 by ultrasonic method. Secondly, Bi3+ and Br were uniformly dispersed in the EG solution, after that a solution containing TL-Ti3C2 and NH3·H2O was added for the reaction. Due to the negatively charged of the terminal group (-OH, –O, –F) on the surface of Ti3C2, Bi3+ can be easily adsorbed onto

Conclusions

In summary, Bi4O5Br2 on the surface of TL-Ti3C2 was successfully synthesized in-situ via a facile alcoholysis method. The morphology and structure of as-prepared samples were characterized by XRD, AFM, TEM, Raman and XPS analysis, and the optical and electrochemical properties were determined by DRS, PL, TRPL, PC and EIS analysis. Benefiting from the rapid transfers photo-induced electrons and increases the visible light responsiveness, the resulting 2D Bi4O5Br2/2D TL-Ti3C2 manifests more

Credit authorship contribution statement

Qing Xi: Conceptualization, Investigation, Methodology, Writing - original draft, Writing - review & editing. Xiuping Yue: Investigation. Junqiang Feng: Resources. Jianxin Liu: Software. Xiaochao Zhang: Methodology. Changming Zhang: Resources. Yawen Wang: Data curation. Yunfang Wang: Methodology. Zhiping Lv: Investigation. Rui Li: Methodology, Supervision, Data curation. Caimei Fan: Supervision, Project administration, Data curation.

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

This work is financially supported by the National Natural Science Foundation of China (No. 21808151, No. 21676178, No. 21978187 and No 21978196), Science and Technology Innovation Project of Higher Education Institutions in Shanxi (2019L0138) and Natural Science Foundation for Young Scientists of Shanxi Province (201901D211100).

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