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Mechanism of Electrochemical Deposition and Coloration of Electrochromic V2O5 Nano Thin Films: an In Situ X-Ray Spectroscopy Study.

Lu YR, Wu TZ, Chen CL, Wei DH, Chen JL, Chou WC, Dong CL - Nanoscale Res Lett (2015)

Bottom Line: Chronoamperometric analyses have indicated that the thin V2O5 film demonstrates faster intercalation and deintercalation of lithium ions than those of the thick V2O5 film, benefiting the coloration rate.Despite substantial research on the synthesis of vanadium oxides, the monitoring of electronic and atomic structures during growth and coloration of such material has not been thoroughly examined.This study improves our understanding of the electronic and atomic properties of the vanadium oxide system grown by electrochemical deposition and enhances the design of electrochromic materials for potential energy-saving applications.

View Article: PubMed Central - PubMed

Affiliation: Department of Physics, Tamkang University, New Taipei, 25137, Taiwan. porsche911959@hotmail.com.

ABSTRACT
Electrochromic switching devices have elicited considerable attention because these thin films are among the most promising materials for energy-saving applications. The vanadium oxide system is simple and inexpensive because only a single-layer film of this material is sufficient for coloration. Vanadium dioxide thin films are fabricated by electrochemical deposition and cyclic voltammetry. Chronoamperometric analyses have indicated that the thin V2O5 film demonstrates faster intercalation and deintercalation of lithium ions than those of the thick V2O5 film, benefiting the coloration rate. Despite substantial research on the synthesis of vanadium oxides, the monitoring of electronic and atomic structures during growth and coloration of such material has not been thoroughly examined. In the present study, in situ X-ray absorption spectroscopy (XAS) is employed to determine the electronic and atomic structures of V2O5 thin films during electrochemical growth and then electrochromic coloration. In situ XAS results demonstrate the growth mechanism of the electrodeposited V2O5 thin film and suggest that its electrochromic performance strongly depends on the local atomic structure. This study improves our understanding of the electronic and atomic properties of the vanadium oxide system grown by electrochemical deposition and enhances the design of electrochromic materials for potential energy-saving applications.

No MeSH data available.


a Cyclic voltammograms of electrodeposited vanadium oxide films for lithium intercalation/deintercalation. b The average voltage difference between the cathodic and the corresponding anodic double peak of the redox reactions. c Chronoamperometry of vanadium oxide films
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Fig4: a Cyclic voltammograms of electrodeposited vanadium oxide films for lithium intercalation/deintercalation. b The average voltage difference between the cathodic and the corresponding anodic double peak of the redox reactions. c Chronoamperometry of vanadium oxide films

Mentions: The electrochemical behavior of the V2O5 material was investigated using the three-electrode system, in which Pt foils were used as the counter and reference electrodes. Cyclic voltammetry and chronoamperometry were adopted to investigate the Li insertion/extraction behavior in 1 M LiClO4 propylene carbonate solution with a scan rate of 0.25 V s−1. Figure 4a shows typical cyclic voltammograms of V2O5 electrodes with different deposition times in the potential range of −1 to 1.25 V. The electrochemical Li+ insertion process occurring at V2O5 electrodes can be expressed by V2O5 + x Li+ + xe− ↔ LixV2O5 [14, 26], which is accompanied by color changes. These processes lead to film coloration [yellow → green → blue (inset of Fig. 4c)]. The V2O5 electrode shows two sets of broad, symmetric, and well-separated redox peaks, indicating sluggish lithium ion insertion/deinsertion kinetics. Moreover, compared with the V2O5 electrode at 40 and 60 s deposition times, all the peaks from the V2O5 electrode at 20 s deposition time shifted to decreased potentials (Fig. 4a). The average voltage difference between the cathodic and the corresponding anodic double peaks of the redox reactions (Fig. 4b) decreases from 350 mV at 60 s deposition time to 175 mV at 20 s deposition time, indicating easier intercalation and deintercalation of lithium ions. To compare the coloration efficiencies directly, the V2O5 electrodes at different deposition times were first biased at −0.5 V versus a Pt reference electrode for 45 s to facilitate lithium intercalation. The polarity was then switched immediately to +0.5 V to initiate lithium deintercalation, recording the change in current (Fig. 4b). Compared with the V2O5 electrode deposited for 20 s, the V2O5 electrode deposited for 40 and 60 s showed a very slow current decay, indicating that the charge characteristics, such as deposition times, are much slower in cation deintercalation. In the case of the V2O5 electrode deposited for 20 s, the initial increase in current was much higher than that of the V2O5 electrodes deposited for 40 and 60 s. This finding implies that the V2O5 electrode deposited for 20 s indicates faster intercalation and deintercalation of lithium ions. The higher kinetics of lithium insertion/extraction in the V2O5 electrode deposited for 20 s depends not only on the film thickness of the electrode but also on the electronic and atomic structures, as revealed in greater detail by the in situ K-edge XAS discussed later.Fig. 4


Mechanism of Electrochemical Deposition and Coloration of Electrochromic V2O5 Nano Thin Films: an In Situ X-Ray Spectroscopy Study.

Lu YR, Wu TZ, Chen CL, Wei DH, Chen JL, Chou WC, Dong CL - Nanoscale Res Lett (2015)

a Cyclic voltammograms of electrodeposited vanadium oxide films for lithium intercalation/deintercalation. b The average voltage difference between the cathodic and the corresponding anodic double peak of the redox reactions. c Chronoamperometry of vanadium oxide films
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

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Fig4: a Cyclic voltammograms of electrodeposited vanadium oxide films for lithium intercalation/deintercalation. b The average voltage difference between the cathodic and the corresponding anodic double peak of the redox reactions. c Chronoamperometry of vanadium oxide films
Mentions: The electrochemical behavior of the V2O5 material was investigated using the three-electrode system, in which Pt foils were used as the counter and reference electrodes. Cyclic voltammetry and chronoamperometry were adopted to investigate the Li insertion/extraction behavior in 1 M LiClO4 propylene carbonate solution with a scan rate of 0.25 V s−1. Figure 4a shows typical cyclic voltammograms of V2O5 electrodes with different deposition times in the potential range of −1 to 1.25 V. The electrochemical Li+ insertion process occurring at V2O5 electrodes can be expressed by V2O5 + x Li+ + xe− ↔ LixV2O5 [14, 26], which is accompanied by color changes. These processes lead to film coloration [yellow → green → blue (inset of Fig. 4c)]. The V2O5 electrode shows two sets of broad, symmetric, and well-separated redox peaks, indicating sluggish lithium ion insertion/deinsertion kinetics. Moreover, compared with the V2O5 electrode at 40 and 60 s deposition times, all the peaks from the V2O5 electrode at 20 s deposition time shifted to decreased potentials (Fig. 4a). The average voltage difference between the cathodic and the corresponding anodic double peaks of the redox reactions (Fig. 4b) decreases from 350 mV at 60 s deposition time to 175 mV at 20 s deposition time, indicating easier intercalation and deintercalation of lithium ions. To compare the coloration efficiencies directly, the V2O5 electrodes at different deposition times were first biased at −0.5 V versus a Pt reference electrode for 45 s to facilitate lithium intercalation. The polarity was then switched immediately to +0.5 V to initiate lithium deintercalation, recording the change in current (Fig. 4b). Compared with the V2O5 electrode deposited for 20 s, the V2O5 electrode deposited for 40 and 60 s showed a very slow current decay, indicating that the charge characteristics, such as deposition times, are much slower in cation deintercalation. In the case of the V2O5 electrode deposited for 20 s, the initial increase in current was much higher than that of the V2O5 electrodes deposited for 40 and 60 s. This finding implies that the V2O5 electrode deposited for 20 s indicates faster intercalation and deintercalation of lithium ions. The higher kinetics of lithium insertion/extraction in the V2O5 electrode deposited for 20 s depends not only on the film thickness of the electrode but also on the electronic and atomic structures, as revealed in greater detail by the in situ K-edge XAS discussed later.Fig. 4

Bottom Line: Chronoamperometric analyses have indicated that the thin V2O5 film demonstrates faster intercalation and deintercalation of lithium ions than those of the thick V2O5 film, benefiting the coloration rate.Despite substantial research on the synthesis of vanadium oxides, the monitoring of electronic and atomic structures during growth and coloration of such material has not been thoroughly examined.This study improves our understanding of the electronic and atomic properties of the vanadium oxide system grown by electrochemical deposition and enhances the design of electrochromic materials for potential energy-saving applications.

View Article: PubMed Central - PubMed

Affiliation: Department of Physics, Tamkang University, New Taipei, 25137, Taiwan. porsche911959@hotmail.com.

ABSTRACT
Electrochromic switching devices have elicited considerable attention because these thin films are among the most promising materials for energy-saving applications. The vanadium oxide system is simple and inexpensive because only a single-layer film of this material is sufficient for coloration. Vanadium dioxide thin films are fabricated by electrochemical deposition and cyclic voltammetry. Chronoamperometric analyses have indicated that the thin V2O5 film demonstrates faster intercalation and deintercalation of lithium ions than those of the thick V2O5 film, benefiting the coloration rate. Despite substantial research on the synthesis of vanadium oxides, the monitoring of electronic and atomic structures during growth and coloration of such material has not been thoroughly examined. In the present study, in situ X-ray absorption spectroscopy (XAS) is employed to determine the electronic and atomic structures of V2O5 thin films during electrochemical growth and then electrochromic coloration. In situ XAS results demonstrate the growth mechanism of the electrodeposited V2O5 thin film and suggest that its electrochromic performance strongly depends on the local atomic structure. This study improves our understanding of the electronic and atomic properties of the vanadium oxide system grown by electrochemical deposition and enhances the design of electrochromic materials for potential energy-saving applications.

No MeSH data available.