Oxygen vacancies induced exciton dissociation of flexible BiOCl nanosheets for effective photocatalytic CO <sub>2</sub> conversion

Author(s): Zhaoyu Ma ¹ ^, ² ^, ³ ^, ⁴ ^, ⁵ , Penghui Li ⁶ ^, ⁷ ^, ⁸ ^, ⁵ ^, ⁹ , Liqun Ye ¹ ^, ² ^, ³ ^, ⁴ ^, ⁵ , Ying Zhou ⁶ ^, ⁷ ^, ⁸ ^, ⁵ ^, ⁹ , Fengyun Su ¹ ^, ² ^, ³ ^, ⁴ ^, ⁵ , Chenghua Ding ¹ ^, ² ^, ³ ^, ⁴ ^, ⁵ , Haiquan Xie ¹ ^, ² ^, ³ ^, ⁴ ^, ⁵ , Yang Bai ⁶ ^, ⁷ ^, ⁸ ^, ⁵ , Po Keung Wong ¹⁰ ^, ¹¹ ^, ¹² ^, ⁵

Publication date (Electronic): 2017

Journal: Journal of Materials Chemistry A

Publisher: Royal Society of Chemistry (RSC)

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Abstract

Oxygen vacancies induced exciton dissociation of flexible BiOCl nanosheets for effective photocatalytic CO ₂ conversion via the CO ₂ hydrogenation pathway.

Abstract

Layered bismuth oxychloride (BOC) exhibits highly efficient activity for photocatalytic environmental remediation due to the confinement effect induced excitonic photocatalytic process. However, the strong excitonic process suppresses catalytic reactions with photo-induced electrons, such as hydrogen generation, CO ₂ conversion and nitrogen fixation. Moreover, the wide band gap of BiOCl limits its application under visible light. In this study, flexible BiOCl nanosheets with oxygen vacancies (BOC-OV) were successfully prepared. Molecular oxygen activation, electronic spin resonance (ESR), transient photocurrent, transient absorption spectroscopy, and transient fluorescence spectroscopy indicated that oxygen vacancies induced exciton dissociation of flexible BiOCl nanosheets. Moreover, oxygen vacancies induced wide spectrum (UV-Vis) absorption. The enhanced exciton dissociation resulted in the superior CO ₂ conversion of BOC-OV under UV-Vis light irradiation, where the light to carbon monoxide (LTCO) conversion efficiency reached up to 26.5 × 10 ⁻⁶. Theoretical calculations and in situ Fourier transform infrared spectrometry (FT-IR) analysis revealed that the mechanism of oxygen vacancies improves the photocatalytic CO ₂ conversion with BOC-OV via the CO ₂ hydrogenation pathway. This study indicates that oxygen vacancies have a great influence on photocatalytic CO ₂ reduction due to their special surface and electron structure properties.

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A metal-free polymeric photocatalyst for hydrogen production from water under visible light.

Xinchen Wang, Kazuhiko Maeda, Arne Thomas … (2009)

The production of hydrogen from water using a catalyst and solar energy is an ideal future energy source, independent of fossil reserves. For an economical use of water and solar energy, catalysts that are sufficiently efficient, stable, inexpensive and capable of harvesting light are required. Here, we show that an abundant material, polymeric carbon nitride, can produce hydrogen from water under visible-light irradiation in the presence of a sacrificial donor. Contrary to other conducting polymer semiconductors, carbon nitride is chemically and thermally stable and does not rely on complicated device manufacturing. The results represent an important first step towards photosynthesis in general where artificial conjugated polymer semiconductors can be used as energy transducers.

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Efficient Visible Light Nitrogen Fixation with BiOBr Nanosheets of Oxygen Vacancies on the Exposed {001} Facets.

Hao Li, Jian-Hua Shang, Zhihui Ai … (2015)

Even though the well-established Haber-Bosch process has been the major artificial way to "fertilize" the earth, its energy-intensive nature has been motivating people to learn from nitrogenase, which can fix atmospheric N2 to NH3 in vivo under mild conditions with its precisely arranged proteins. Here we demonstrate that efficient fixation of N2 to NH3 can proceed under room temperature and atmospheric pressure in water using visible light illuminated BiOBr nanosheets of oxygen vacancies in the absence of any organic scavengers and precious-metal cocatalysts. The designed catalytic oxygen vacancies of BiOBr nanosheets on the exposed {001} facets, with the availability of localized electrons for π-back-donation, have the ability to activate the adsorbed N2, which can thus be efficiently reduced to NH3 by the interfacial electrons transferred from the excited BiOBr nanosheets. This study might open up a new vista to fix atmospheric N2 to NH3 through the less energy-demanding photochemical process.