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Issue 47, 2014
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Electrochemical and Raman spectroscopy identification of morphological and phase transformations in nanostructured TiO2(B)

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Abstract

TiO2(B) exhibits unique electrochemical lithiation behavior where two closely spaced reduction and oxidation peaks, referred to as “double peaks,” are observed for 3-D forms of bulk and nanostructured TiO2(B) while a single broad redox peak is observed for 2-D nanosheet architectures. In this study, we have used a combination of transmission electron microscopy (TEM), powder X-ray diffraction (XRD), Raman spectroscopy and cyclic voltammetry on TiO2(B) nanosheets as well as a series of thermally annealed nanosheets to map the morphological and phase transformation pathways that help clarify the structure-dependent lithiation behavior. We found that the double peak redox behavior only arises once a three dimensional nanocrystalline structure of TiO2(B) exists by observing nanoparticle growth on the TiO2(B) nanosheet surface via TEM at temperatures above 150 °C. This morphological transformation was also verified by Raman spectroscopy. The appearance of low-energy torsional modes at temperatures above 150 °C which are not observed in 2-D morphologies of TiO2(B) agrees well with TEM evidence of 3-D nanoparticle formation. Using scan rate dependent cyclic voltammetry we also verified that all lithiation behavior associated with TiO2(B) (either nanosheet or nanoparticle) is due primarily to a surface redox (pseudocapacitive) mechanism. The thermal annealing study also shows the phase transformation of surface nucleated TiO2(B) nanoparticles to anatase nanoparticles at temperatures above 200 °C. These studies clearly show how nano-morphological control can influence electrochemical lithiation behavior and help identify a possible mechanism to explain the double peak phenomenon observed for TiO2(B).

Graphical abstract: Electrochemical and Raman spectroscopy identification of morphological and phase transformations in nanostructured TiO2(B)

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Publication details

The article was received on 25 Aug 2014, accepted on 20 Oct 2014 and first published on 20 Oct 2014


Article type: Paper
DOI: 10.1039/C4TA04394D
Citation: J. Mater. Chem. A, 2014,2, 20331-20337
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    Electrochemical and Raman spectroscopy identification of morphological and phase transformations in nanostructured TiO2(B)

    A. G. Dylla and K. J. Stevenson, J. Mater. Chem. A, 2014, 2, 20331
    DOI: 10.1039/C4TA04394D

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