Origin of enhanced photocatalytic activity and photoconduction in high aspect ratio ZnO nanorods

Leelavathi, A and Madras, Giridhar and Ravishankar, N (2013) Origin of enhanced photocatalytic activity and photoconduction in high aspect ratio ZnO nanorods. In: Physical Chemistry Chemical Physics, 15 (26). pp. 10795-10802.

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Abstract

Faceted ZnO nanorods with different aspect ratios were synthesized by a solvothermal method by tuning the reaction time. Increased reaction leads to the formation of high aspect ratio ZnO nanorods largely bound by the prism planes. The high aspect ratio rods showed significantly higher visible light photocatalytic activity when compared to the lower aspect ratio structures. It is proposed that the higher activity is due to better charge separation in the elongated 1D structure. In addition, the fraction of unsaturated Zn2+ sites is higher on the {10 (1) over bar0} facets, leading to better adsorption of oxygen-containing species. These species enhance the production of reactive radicals that are responsible for photodegradation. The photocurrent for these ZnO nanostructures under solar light was measured and a direct correlation between photocurrent and aspect ratio was observed. Since the underlying mechanisms for photodegradation and photocurrent generation are directly related to the efficiency of electron-hole creation and separation, this observation corroborates that the charge separation processes are indeed enhanced in the high aspect ratio structures. The efficiency of photoconduction (electron-hole pair separation) could be further improved by attaching Au nanoparticles on ZnO, which can act as a sink for the electrons. This heterostructure exhibits a high chemisorption of oxygen, which facilitates the production of highly reactive radicals contributing to the high photoreactivity. The suggested mechanisms are applicable to other n-type semiconductor nanostructures with important implications for applications relating to energy and the environment.

Item Type:	Journal Article
Publication:	Physical Chemistry Chemical Physics
Publisher:	Royal Society of Chemistry
Additional Information:	Copyright of this article belongs to Royal Society of Chemistry.
Department/Centre:	Division of Chemical Sciences > Materials Research Centre Division of Interdisciplinary Sciences > Centre for Nano Science and Engineering
Date Deposited:	30 Jul 2013 12:01
Last Modified:	30 Jul 2013 12:01
URI:	http://eprints.iisc.ac.in/id/eprint/46922

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