Z. Cui et al. / Journal of Alloys and Compounds 549 (2013) 70–76
75
for BOC-110, as was displayed in Fig. 6(c) and (d). Generally,
hydroxyl radicals were formed through the oxidation reaction of
photogenerated electrons and holes with water molecules. BiOCl
has a semiconductor band gap of 3.4 eV and thus can only be
excited by UV light [31]. It is interesting to see that the formation
of hydroxyl radicals with low concentration were detected for
BOC-110 under visible light irradiation. This could be ascribed to
the dangling groups of Bi–Cl and Bi–OH on the facets of {110},
which created mid-band states in BiOCl and possibly contributed
to the response in the visible light range [32].
the surface of BiOCl solids. Since the MO dyes in the aqueous solu-
tion was anodic, they tended to adsorbed on the surfaces which
were positively charged. With regard to BiOCl with exposed facets
of {110}, the existence of surface atomic structure with exposed
positively charged [Bi–Cl] layers could facilitate the adsorption of
MO dyes to BiOCl, also allowing the efficient photosensitization
process and thus giving rise to the high photodegradation effi-
ciency of BiOCl under visible light irradiation.
4. Conclusions
Moreover, Jiang recently reported the facet-dependent photore-
activity of BiOCl nanosheets with {001} and {010} facets and sim-
ilar effect was also observed in ZnS and Fe2O3 [18,33,34]. In this
case, the exposed facets of BiOCl were {110} planes, the synthe-
sized sample exhibited high photodegradation efficiency either un-
der UV light irradiation or visible light irradiation. For {110}
planes, the negatively charged [O] layer and positively charged
[Bi–Cl] layer were arranged alternatively in the crystal structure,
as shown in Fig. 7. The resultant local internal electrostatic field
could benefit the separation of photoinduced electrons and holes
and thus help improve the photocatalytic activity of BiOCl under
UV light irradiation [35,36]. When the sample was irradiated under
visible light irradiation, the photosensitization process occurred on
the interface between the exposed facets and the dye molecules.
The process was followed by the transfer of electrons from dyes
to adjacent semiconductor side, leading to the generation of free
radicals and thereby the photodegradation of the dyes. The
prerequisite of this process was the adsorption of MO dyes on
In conclusion, the crystal growth of BiOCl nanosheets in EG
based solvothermal system was investigated through time series
experiments. It was found experimentally that the BiOCl nano-
sheets slowly transformed from polycrystalline nanoparticles to
single crystalline nanosheets via oriented attachment mechanism.
The photocatalytic activity tests revealed that the synthesized BiO-
Cl nanostructures with {110} facets could efficiently photodegrade
MO dyes under either UV light irradiation or visible light irradia-
tion. The atomic structure along {110} planes could generate local
internal electrostatic field and benefit the separation of photoin-
duced electrons and holes under UV light irradiation, while the
existence of exposed positively charged [Bi–Cl] layers on the sur-
face of BiOCl solids was thought to facilitate the adsorption of
MO dyes and thus promote the photosensitization process under
visible light irradiation. The experimental observations and the
corresponding results reported here are expected to help realize
the morphology control and benefit the understanding of the
facet-dependent photocatalytic property of BiOCl.
Acknowledgements
This work was financially supported by the National Basic Re-
search Program of China (Grant Nos. 2009CB939705 and
2009CB939702), Nature Science Foundation of China (Nos.
50772040 and 50927201), the Opening Research Foundation of
State Key Laboratory of Advanced Technology for Materials Syn-
thesis and Processing (Wuhan University of Technology) and the
Program for Innovative Research Team (in Science and Technology)
in University of Henan Province (IRTSTHN). Also, the technology
was supported by the Analytic Testing Center of Huazhong Univer-
sity of Science and Technology (HUST) for carrying out XRD and
FESEM characterization and the Center for Electron Microscopy
of Wuhan University (WHU) for conducting (HR)TEM analysis.
References
[1] K. Zhang, D. Zhang, J. Liu, K. Ren, H. Luo, Y. Peng, G. Li, X. Yu, Cryst. Eng.
Commun. 14 (2011) 700.
[2] S. Liu, J. Yu, M. Jaroniec, J. Am. Chem. Soc. 132 (2010) 11914.
[3] L. Zhou, W. Wang, H. Xu, S. Sun, M. Shang, Chem.-Eur. J. 15 (2009) 1776.
[4] R. Yuan, C. Lin, B. Wu, X. Fu, Eur. J. Inorg. Chem. 2009 (2009) 3537.
[5] G. Pfaff, P. Reynders, Chem. Rev. 99 (1999) 1963.
[6] Z. Deng, F. Tang, A.J. Muscat, Nanotechnology 19 (2008) 295705.
[7] S. Cao, C. Guo, Y. Lv, Y. Guo, Q. Liu, Nanotechnology 20 (2009) 275702.
[8] K.L. Zhang, C.M. Liu, F.Q. Huang, C. Zheng, W.D. Wang, Appl. Catal. B 68 (2006)
125.
[9] M. Shang, W. Wang, H. Xu, Cryst. Growth Des. 9 (2009) 991.
[10] H. Zhou, T. Fan, T. Han, X. Li, J. Ding, D. Zhang, Q. Guo, H. Ogawa,
Nanotechnology 20 (2009) 085603.
[11] H. Peng, C.K. Chan, S. Meister, X.F. Zhang, Y. Cui, Chem. Mater. 21 (2009) 247.
[12] L. Armelao, G. Bottaro, C. Maccato, E. Tondello, Dalton Trans. 41 (2012) 5480.
[13] X. Zhang, Z. Ai, F. Jia, L. Zhang, J. Phys. Chem. C 112 (2008) 747.
[14] L. Zhu, G. Liao, N. Bing, L. Wang, Y. Yang, H. Xie, Cryst. Eng. Commun. 12 (2010)
3791.
[15] H. Zhang, J. Huang, X. Zhou, X. Zhong, Inorg. Chem. 50 (2011) 7729.
[16] S. Pruneanu, L. Olenic, S.A.F. Al-Said, G. Borodi, A. Houlton, B.R. Horrocks, J.
Mater. Sci. 45 (2010) 3151.
[17] Y. Lei, G. Wang, S. Song, W. Fan, M. Pang, J. Tang, H. Zhang, Dalton Trans. 39
(2010) 3273.
Fig. 7. A (110) plane located in the unit cell of the BiOCl crystal structure (a) and
the possible mechanism for the enhancement of photocatalytic efficiency under
either UV light irradiation or visible light irradiation (b).
[18] J. Jiang, K. Zhao, X. Xiao, L. Zhang, J. Am. Chem. Soc. 134 (2012) 4473.