Mechanism of Electrochemical Deposition and Coloration of Electrochromic V2O5 Nano Thin Films: an In Situ X-Ray Spectroscopy Study
© Lu et al. 2015
Received: 22 August 2015
Accepted: 27 September 2015
Published: 5 October 2015
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.
The recent years have witnessed growing environmental concerns and increasing energy demands . In the USA, up to 40 % energy is used for primary energy consumption of buildings, which contribute over 30 % CO2 emissions . Thus, the effective use of energy has increasingly become an important issue. Smart windows can change optical properties by using an applied electric field or current, thereby avoiding excessive solar heating while taking advantage of heating mechanisms when necessary. Vanadium oxide systems comprise many oxide phases, including VO, V2O3, VO2, V6O13, V3O7, and V2O5. In particular, vanadium pentoxide is the most stable oxide in such systems. V2O5 exhibits an energy gap of approximately 2.2 eV and undergoes semiconductor–metal transition at around 250 °C. V2O5 materials demonstrate a color change when lithium ions are injected into or extracted from the layer spaces. Hence, V2O5 materials provide significant potential for applications in energy-saving devices, such as catalysts, sensors, electronic materials, and battery electrodes [3–5]. V2O5 films have been fabricated by various methods, such as reactive DC magnetron sputtering , vacuum-evaporated deposition , chemical vapor deposition , sol–gel method , spray pyrolysis technique , and electrodeposition . Electrochemical method is greatly advantageous over other methods in terms of economics and flexibility; typically, this method can also be used to fabricate mesostructured thin films . The high surface area of the mesoporous structure of V2O5 thin films provides porous channels, which facilitate fast ion diffusion and effective strain relaxation upon cycling of Li ion intercalation and deintercalation. Numerous studies on the application of V2O5 in energy-saving (smart windows ) or energy storage devices (batteries/supercapacitors ) have reported various synthesis methods , electrochemical properties, and photocatalytic performances . Several studies have also demonstrated the importance of electronic structure characterization [17–19]. Eyert et al.  indicated that octahedral distortions enhance the optical band gap. Willinger et al.  compared the basic structural VO5 units in α-V2O5 and γ-V2O5 with regard to the differences in their geometric and electronic structures. The relation between geometric and electronic structures is critical because the basic structural unit is also common to industrial vanadium phosphorus oxide (VPO) catalysts . However, the detail determination of the local atomic/electronic structure during growth of such electrochemically deposited film and during electrochromic coloration has not been thoroughly examined because of the lack of proper characterization tools. In the current study, an in situ electrochemical liquid cell was built, and in situ synchrotron hard X-ray absorption spectroscopy (XAS) was performed to monitor the electronic and atomic structures during the electrochemical deposition of V2O5 nano thin films. Changes in atomic/electronic structure upon coloration were determined. This approach is critical in determining the electrochemical growth and coloration mechanism, providing a great opportunity to further understand and improve the electrochemical properties of electrochromic materials.
Characterization and Measurement of Electrochemical Properties
Scanning electron microscopy (SEM, model PHILIPS S-4300) was used to examine the surface morphology. Electrodeposition was performed on a potentiostat/galvanostat (Princeton Applied Research, Versa STAT 4). A conventional three-electrode cell was utilized with an ITO substrate. V2O5 thin films were electrodeposited to a 1:1 mixture of deionized water and ethanol, which contained 1 M VOSO4·xH2O. Electrodepositions were performed at −0.7 V against the reference electrode for 20, 40, and 60 s. The lithium-ion intercalation/deintercalation properties of the V2O5 material were investigated in 1 M LiClO4 solution containing propylene carbonate. Cyclic voltammetry was performed between −1 and +1.25 V (versus Pt) at a scanning rate of 0.025 V s−1 using a potentiostat/galvanostat (Princeton Applied Research, Versa STAT 4). Chronoamperometric measurements were obtained at a constant voltage of +0.5 V, and the current change was monitored for 45 s at room temperature.
Measurement of Electronic Structure
Results and Discussion
Electrochromic switching devices have been widely investigated because such switching can control the throughput of visible light and solar radiation into buildings by applying electrical voltage, thereby imparting energy efficiency. Electrochemical in situ XAS studies indicated that the electrodeposition of V2O5 under constant 0.7 V conditions produced V2O5 thin films with different local electronic and atomic structures along with variation of film thickness. Given the increasing film thickness, the local geometrical symmetry of V2O5 thin films varies from V5+ with octahedral symmetry to V5+ with pyramid symmetry. In situ XAS was performed in the present study to monitor the effects of delithiation/lithiation on the vanadium oxidation states and the local atomic structures of the V2O5 thin films. Color switching upon the intercalation of hydrogen is caused by the valence change of the cations. Such effect is accompanied by structural rearrangement. This in situ XAS electrochemical cell setup allows real-time monitoring of the element-specific electronic structural changes in a system at all stages of electrochemical reaction. It is anticipated that using this technique, the growth parameters of V2O5 thin films can be fine-tuned, achieving optimization.
This study was financially supported by the National Science Council of Taiwan under contract nos. MOST 104-2112-M-032-008-MY3 and 102-2112-M-001-004-MY3.
Open AccessThis article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.
- Luo J, Im JH, Mayer MT, Schreier M, Nazeeruddin MK, Park NG et al. (2014) Water photolysis at 12.3 % efficiency via perovskite photovoltaics and Earth-abundant catalysts. Science 345:1593View ArticleGoogle Scholar
- Yang L, Yan H, Lam Joseph C (2014) Thermal comfort and building energy consumption implications–a review. Appl Energy 115:164View ArticleGoogle Scholar
- Fujita Y, Miyazaki K, Tatsuyama C (1985) On the electrochromism of evaporated V2O5 films. Jpn J Appl Phys 24:1082View ArticleGoogle Scholar
- Wang Z, Chen J, Hu X (2000) Electrochromic properties of aqueous sol-gel derived vanadium oxide films with different thickness. Thin Solid Films 375:238View ArticleGoogle Scholar
- Karimov KS, Saleem M, Mahroof-Tahir M, Akram R, Saeed Chanee MT, Niaz AK (2014) Resistive humidity sensor based on vanadium complex films. J Semicond 9:094001View ArticleGoogle Scholar
- Baddour-Hadjean R, Pereira-Ramos JP, Navone C, Smirnov M (2008) Raman microspectrometry study of electrochemical lithium intercalation into sputtered crystalline V2O5 thin films. Chem Mater 20:1916View ArticleGoogle Scholar
- Rajendra Kumar RT, Karunagaran B, Venkatachalam S, Mangalaraj D, Narayandass SK, Kesavamoorthy R (2003) Influence of deposition temperature on the growth of vacuum evaporated V2O5 thin films. Mater Lett 57:3820View ArticleGoogle Scholar
- Davide B, Lidia A, Federico C, Vito Di N, Andrea G, Gian Andrea R et al (2000) Highly oriented V2O5 nanocrystalline thin films by plasma-enhanced chemical vapor deposition. Chem Mater 12:98View ArticleGoogle Scholar
- Patrissi Charles J, Martin Charles R (1999) Sol-gel-based template synthesis and li-insertion rate performance of nanostructured vanadium pentoxide. J Electrochem Soc 146:3176View ArticleGoogle Scholar
- Mousavi M, Kompany A, Shahtahmasebi N, Bagheri-Mohagheghi MM (2013) The effect of solution concentration on the physical and electrochemical properties of vanadium oxide films deposited by spray pyrolysis. J Semicond 10:103001View ArticleGoogle Scholar
- Arunabha G, Eun Ju R, Meihua J, Hae-Kyung J, Tae Hyung K, Chandan B et al. (2011) High pseudocapacitance from ultrathin V2O5 films electrodeposited on self‐standing carbon‐nanofiber paper. Adv Funct Mater 21:2541View ArticleGoogle Scholar
- Liu P, Lee S-H, Tracy CE, Yan Y, Turner JA (2002) Preparation and lithium insertion properties of mesoporous vanadium oxide. Adv Mater 14:27View ArticleGoogle Scholar
- Takahashi K, Wang Y, Cao G (2005) Growth and electrochromic properties of single-crystal V2O5 nanorod arrays. Appl Phys Lett 86:053102View ArticleGoogle Scholar
- Wei D, Scherer MR, Bower C, Andrew P, Ryhänen T, Steiner U (2012) A nanostructured electrochromic supercapacitor. Nano Lett 12:1857View ArticleGoogle Scholar
- Zhu J, Cao L, Wu Y, Gong Y, Liu Z, Hoster HE et al (2013) Building 3D structures of vanadium pentoxide nanosheets and application as electrodes in supercapacitors. Nano Lett 13:5408View ArticleGoogle Scholar
- Amano F, Tanaka T, Funabiki T (2004) Steady-state photocatalytic epoxidation of propene by O2 over V2O5/SiO2 photocatalysts. Langmuir 20:4236View ArticleGoogle Scholar
- Eyert V, Höck K-H (1998) Electronic structure of V2O5: role of octahedral deformations. Phys Review B 57:12727View ArticleGoogle Scholar
- Willinger MG, Pinna N, Su DS, Schlögl R (2004) Geometric and electronic structure of γ−V2O5: comparison between α−V2O5 and γ−V2O5. Phys Review B 69:155114View ArticleGoogle Scholar
- Jang WL, Lu YM, Chen CL, Lu YR, Dong CL, Hsieh PH et al (2014) Local geometric and electronic structures of gasochromic VOx films. Phys Chem Chem Phys 16:4699View ArticleGoogle Scholar
- Wei-Luen J, Yang-Ming L, Ying-Rui L, Chi-Liang C, Chung-Li D, Wu-Ching C et al. (2013) Effects of oxygen partial pressure on structural and gasochromic properties of sputtered VOx thin films. Thin Solid Films 544:448View ArticleGoogle Scholar
- Wong J, Lytle FW, Messmer RP, Maylotte DH (1984) K-edge absorption spectra of selected vanadium compounds. Phys Review B 30:5596View ArticleGoogle Scholar
- Yamamoto T (2008) Assignment of pre-edge peaks in K-edge x-ray absorption spectra of 3d transition metal compounds: electric dipole or quadrupole? X‐Ray Spectrom 37:572View ArticleGoogle Scholar
- Marco G, Stefano P, Smyrla WH, Sanjeev M, Yangb XQ, James MB (1999) In situ X‐ray absorption spectroscopy characterization of V2O5 xerogel cathodes upon lithium intercalation. J Electrochem Soc 146:2387View ArticleGoogle Scholar
- Chaurand P, Rose J, Briois V, Salome M, Proux O, Nassif V et al (2007) New methodological approach for the vanadium K-edge X-ray absorption near-edge structure interpretation: application to the speciation of vanadium in oxide phases from steel slag. J Phys Chem B 111:5101View ArticleGoogle Scholar
- Stizza S, Mancini G, Benfatto M, Natoli CR, Garcia J, Bianconi A (1989) Structure of oriented V2O5 gel studied by polarized x-ray-absorption spectroscopy at the vanadium K edge. Phys Review B 40:12229View ArticleGoogle Scholar
- Chen Z, Augustyn V, Wen J, Zhang Y, Shen M, Dunn B et al (2011) High-performance supercapacitors based on intertwined CNT/V2O5 nanowire nanocomposites. Adv Mater 23:791View ArticleGoogle Scholar