Hydrothermal synthesis and photocatalytic properties of layered La2Ti2O7 nanosheets

I NSTITUTE OF P HYSICS P UBLISHING N ANOTECHNOLOGY Nanotechnology17(2006)4863–4867doi:10.1088/0957-4484/17/19/014

Hydrothermal synthesis and photocatalytic properties of layered

La2Ti2O7nanosheets

KunWei Li,Yan Wang,Hao Wang1,Mankang Zhu and Hui Yan

The College of Materials Science and Engineering,Beijing University of Technology,

Beijing100022,People’s Republic of China

E-mail:haowang@

Received17July2006,infinal form1August2006

Published11September2006

Online at /Nano/17/4863

Abstract

Layered La2Ti2O7nanosheets were prepared through a one-step hydrothermal

method at low temperature.The concentration of NaOH mineralizer plays an

important role in the synthesis.The scanning electron microscopy(SEM)and

transmission electron microscopy(TEM)images show that the thickness of

every nanosheet is about5–10nm,while the planar dimension is more than

1μm.The photo-catalytic activities of the nanosheets were characterized by the

decolourization of methyl orange solution and the evolution rate of H2.The

results demonstrated that the La2Ti2O7nanosheets possess significantly

improved photocatalytic properties in water purification and evolution rate of

H2from water–ethanol solution compared with those of samples prepared by

conventional solid-state reaction.

1.Introduction

Lanthanide titanate(La2Ti2O7),as one of the layered compounds,has attracted widespread attention[1,2]in the photocatalytic domain due to its unique layered structure and chemical activity[3].Hwang et al have reported that La2Ti2O7 loaded with Ni–NiO has good photocatalytic activity in the water-splitting reaction[4]and the destruction of volatile organic compounds(CH3Cl)[5].However,they obtained La2Ti2O7through the conventional solid-state reaction(SSR) or the polymerizable complex method[6].Both of these methods need high temperatures and produce materials with low specific surface areas,nonuniform particle sizes and low phase purity,which lead to a relatively low photocatalytic activity.Zhang et al[7]obtained nanopowders of La2Ti2O7 by a metallorganic decomposition method.However,no photocatalytic properties were reported in their study.The desired catalyst should have high specific surface area,uniform particle sizes and pure phase.Therefore,if we control the experimental parameters to synthesize the layered compounds with a few layers,that is to say,nanosheets,the products will better answer our desire for a catalyst.

The use of solution-based soft chemical methods to prepare nanocrystalline materials is expected to result in 1Author to whom any correspondence should be addressed.chemically homogeneous and phase-pure specimens,a narrow particle size distribution,and low crystallization temperatures of the materials.Among many methods,hydrothermal synthesis is particularly promising for low-cost production of advanced catalysts on a large scale.Because crystalline powders are directly produced in a hydrothermal process, the needs for high-temperature calcination and milling procedures are eliminated.Chen and Xu[8]have prepared La2Ti2O7powders through the hydrothermal treatment of La2O3·2TiO2·n H2O coprecipitation,but this method needs two steps to get thefinal product,and they did not get the La2Ti2O7 nanosheets.

Here,we report the simple hydrothermal synthesis of La2Ti2O7two-dimensional(2D)nanosheets.The products were used as photocatalysts for the decolourization of methyl orange solution and the evolution of H2from water–ethanol solution.

2.Experimental details

2.1.Synthesis

All reagents were of analytical grade and purchased from Beijing Chemical Reagent Ltd without further purification. The exact quantity of La in the lanthanum nitrate hydrate,

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