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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.


Vanadium K-edge XAS spectra of V2O5 electrodes deposited for 20, 40, and 60 s. The inset magnifies the pre-edge region
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Fig3: Vanadium K-edge XAS spectra of V2O5 electrodes deposited for 20, 40, and 60 s. The inset magnifies the pre-edge region

Mentions: In situ K-edge XAS was employed to investigate the electrochemical growth of the V2O5 thin films in both local electronic and atomic structures as a function of time. Figure 3 shows a comparison of the normalized V K-edge spectra for the V2O5 films deposited at different times (20, 40, and 60 s). Numerous reports dealing with XAS spectra of V2O5 have already been published. The first feature shown in the spectra is the pre-edge peak (a). The intensity and energy position of the pre-edge may be used qualitatively to derive structural and chemical information. Pre-edge absorption is associated with dipole forbidden s → d transitions, which become allowed in the vanadium 3D states mixed with oxygen p states arising from the noncentrosymmetric environment of the slightly distorted octahedral [20]. Hence, the pre-edge peak intensity is very sensitive to alterations in the local geometrical symmetry [21]. Features b and c originate from the 1s core-electron excitation to the 4p orbital. The above features are highly sensitive to the effective valence state of the vanadium and the chemical environment surrounding the vanadium site [22, 23]. The V2O5 thin films deposited for 20 s are most likely in the form of V5+ with octahedral symmetry [19, 23]. Examination of the spectra with deposition time reveals that the edge energy shifted to increased values (inset of Fig. 3a), suggesting that vanadium is most likely in the form of V5+ with pyramid symmetry in the V2O5 electrode deposited for 40 and 60 s [19, 24]. In addition to the shift in edge energy, the intensity of the pre-edge peak also increases, suggesting an increase in the distortion of the VO5 square pyramid with increasing deposition time [25].Fig. 3


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)

Vanadium K-edge XAS spectra of V2O5 electrodes deposited for 20, 40, and 60 s. The inset magnifies the pre-edge region
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4593985&req=5

Fig3: Vanadium K-edge XAS spectra of V2O5 electrodes deposited for 20, 40, and 60 s. The inset magnifies the pre-edge region
Mentions: In situ K-edge XAS was employed to investigate the electrochemical growth of the V2O5 thin films in both local electronic and atomic structures as a function of time. Figure 3 shows a comparison of the normalized V K-edge spectra for the V2O5 films deposited at different times (20, 40, and 60 s). Numerous reports dealing with XAS spectra of V2O5 have already been published. The first feature shown in the spectra is the pre-edge peak (a). The intensity and energy position of the pre-edge may be used qualitatively to derive structural and chemical information. Pre-edge absorption is associated with dipole forbidden s → d transitions, which become allowed in the vanadium 3D states mixed with oxygen p states arising from the noncentrosymmetric environment of the slightly distorted octahedral [20]. Hence, the pre-edge peak intensity is very sensitive to alterations in the local geometrical symmetry [21]. Features b and c originate from the 1s core-electron excitation to the 4p orbital. The above features are highly sensitive to the effective valence state of the vanadium and the chemical environment surrounding the vanadium site [22, 23]. The V2O5 thin films deposited for 20 s are most likely in the form of V5+ with octahedral symmetry [19, 23]. Examination of the spectra with deposition time reveals that the edge energy shifted to increased values (inset of Fig. 3a), suggesting that vanadium is most likely in the form of V5+ with pyramid symmetry in the V2O5 electrode deposited for 40 and 60 s [19, 24]. In addition to the shift in edge energy, the intensity of the pre-edge peak also increases, suggesting an increase in the distortion of the VO5 square pyramid with increasing deposition time [25].Fig. 3

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.