Porous BN/TiO2 hybrid nanosheets as highly efficient visible-light-driven photocatalysts

doi:10.1016/j.apcatb.2017.02.011

Applied Catalysis B: Environmental

Volume 207, 15 June 2017, Pages 72-78

https://doi.org/10.1016/j.apcatb.2017.02.011 Get rights and content

Highlights

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TiO₂ nanoparticles are uniformly grown on porous BN nanosheets to prepare a novel photocatalyst (porous BN/TiO₂ hybrid nanosheets), where BOTi bonds were formed.
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The superior photocatalytic activity of porous BN/TiO₂ hybrid nanosheets to commercial P25 in both simulated solar light (λ > 300 nm) and visible light (λ > 420 nm) suggests their competitive advantages.
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The excellent recyclability of these porous BN/TiO₂ hybrid nanosheets in visible light irradiation was demonstrated, implicating their potentials in water cleaning and up-scale practical applications.

Abstract

Porous boron nitride (BN) nanosheets, which possess extreme large surface areas, high thermal conductivity and special chemical activities, have demonstrated advantages in water cleaning and energy storage. However, they are usually considered as an underachieving catalytic material for photocatalysis and other photovoltaic conversion applications due to their wide bad gap of 5.5 eV. Here, we report a novel porous BN/TiO₂ hybrid nanosheets with the formation of new B single bond OTi bondings between the boron dangling bonds at the open edges of pores of porous BN nanosheets and nanosized TiO₂ particles. Such highly active bondings make the hybrid nanosheets responsive to an extended wavelength range from UV to visible light (λ > 420 nm) spectrum and also substantially enhance the photocatalytic effect (up to 99%) for degradation of organic molecules. In addition, the porous BN/TiO₂ hybrid nanosheets exhibit excellent cycling stability up to 5 cycles maintaining high visible-light photocatalytic activity (97%). These results provide new insights for design of advanced hybrid photocatalysts with actively chemical bonding species, which can be applied in environmental protection, water splitting, and photo-electrochemical conversion.

Graphical abstract

Introduction

Porous two-dimensional (2D) nanomaterials with unique structural advantages have led to their intriguing properties, attractive applications, as well as industrial and environmental benefits [1], [2], [3], [4]. Several porous 2D nanomaterials, including ZnO nanosheets [5], In₂O₃ nanosheets [6], graphene [7], and BN nanosheets [4] were successfully produced and they exhibit significantly new properties in oil adsorption, gas sensing, biological probes, water cleaning, and electrochemical energy storage and conversion. One of the most attractive functionalities of the porous 2D nanomaterials is that they can interact with various organic or inorganic species not only on the surfaces but also at the edges of pores due to a large number of exposed and active radicals [8], [9], [10]. Therefore, the design and fabrication of unconventional porous nanosheet structures with highly active edges is an appealing endeavor for new properties and applications.

Among various 2D nanomaterials, boron nitride nanosheets (BNNSs), so−called “white graphene” due to the similarity to graphene, consist of a honeycomb structure of covalently bound boron and nitrogen atoms [11]. It has unique electronic features with a wide bandgap of up to 5.5 eV, and some important applications such as a deep-ultraviolet-light emitter and perfect substrates for graphene based devices [12], [13]. Although BNNSs are not commonly considered as a catalytic material for photocatalysis and other photovoltaic conversion applications because of the strong optical absorption within the ultraviolet-visible region, they could be a promising support material for catalysts due to its remarkable properties, including extremely high resistance to oxidation and good chemical inertness, high thermal conductivity, high melting point and high surface area, especially under relatively harsh conditions, as it could avoid the sintering of the supported catalysts on hot spots [14], [15], [16], [17], [18], [19], [20]. Besides of the intrinsic properties of BNNSs, porous BNNSs with plentiful pores and large surface areas are showing some innovative applications in hydrogen storage and water cleaning treatment [21], [22], [23], [24], [25], [26].

In this work, we demonstrated a rationally design of porous BN/TiO₂ hybrid nanosheets with a large number of new B single bond OTi chemical bonds. The synthesized porous BN/TiO₂ hybrid nanosheets possess much higher photocatalytic activity and regeneration ability for degradation of organic molecules in both UV and visible light (λ > 420 nm). A mechanism on their highly efficient visible-light-driven characteristic was also proposed based on the experimental results. All the results implicated the great potentials of the developed porous BN/TiO₂ hybrid nanosheets and inspired the further design of the BN-based photocatalytic materials.

Section snippets

Synthesis of samples

Porous boron nitride nanosheets were produced by a dynamic templating approach using boron trioxide and guanidine hydrochloride [4]. In a typical experimental run, boron trioxide and guanidine hydrochloride with 1:5 molar ratio were mixed in 10 mL methanol under stirring to form a clear, colorless solution. After 24 h fast stirring, a white crystalline powder (a complex between the boron trioxide and guanidine chloride) as precursors was formed. After that, the precursors were put into a quartz

Characterizations of porous BN/TiO₂ hybrid nanosheets

The porous BNNSs were produced using a dynamic templating approach with boron trioxide and guanidine hydrochloride as the starting materials and N₂/H₂ gas as nitrogen source [4]. The TEM and high-resolution TEM (HRTEM) images of as-prepared porous BNNSs are shown in Figs. 1 b and S1, respectively. One can see clearly that porous BNNSs have a layer structure composed of several stacking layers with a large number of pores with diameters ranging from 20 nm to several hundred nanometers. Porous

Conclusion

We demonstrate that, for the first time, porous BN/TiO₂ hybrid nanosheets with new actively chemical bonding specie B single bond OTi were successfully prepared using a solvothermal process. This exotic specie benefits from the richly exposed edges of pores and edges of the unique porous BNNS structures, which endow the hybrid material with capability being responsive to both UV and visible lights. As expected, the hybrid material, especially for the porous BN/TiO₂ hybrid nanosheets (38 wt%), shows the

Acknowledgements

Financial support from the Australian Research Council Discovery Early Career Researcher Award scheme (DE150101617 and DE140100716), the National Natural Science Foundation of China (NSFC 51302197) and Deakin University, Central Research Grant Scheme are acknowledged.

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¹: These authors contributed equally.

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Porous BN/TiO2 hybrid nanosheets as highly efficient visible-light-driven photocatalysts

Highlights

Abstract

Graphical abstract

Introduction

Section snippets

Synthesis of samples

Characterizations of porous BN/TiO2 hybrid nanosheets

Conclusion

Acknowledgements

Sens. Actuators B: Chem.

J. Catal.

J. Catal.

Thermochim. Acta

Nano Energy

Nano Energy

J. Photochem. Photobiol. A: Chem.

J. Adv. Oxid. Technol.

Bioresour. Technol.

Angew. Chem.

Chem. Mater.

Chem. Mater.

Nat. Commun.

Small

Adv. Mater.

J. Phys. Chem. Lett.

Adv. Funct. Mater.

Nat. Commun.

Adv. Mater. Interfaces

Adv. Mater.

Nat. Commun.

Chem.–Asian J.

Porous BN/TiO₂ hybrid nanosheets as highly efficient visible-light-driven photocatalysts

Characterizations of porous BN/TiO₂ hybrid nanosheets