Crystallized V 2 O 5 as Oxidized Phase for Unexpected Multi- Color Electrochromism in V 2 O 3 thick film

Transcription

1 SUPPORTING INFORMATION Crystallized V 2 O 5 as Oxidized Phase for Unexpected Multi- Color Electrochromism in V 2 O 3 thick film Issam Mjejri, Manuel Gaudon, Giljoo Song, Christine Labrugère^ and Aline Rougier * CNRS, ICMCB, UMR 5026, F Pessac, France Univ. Bordeaux, ICMCB, UMR 5026, F Pessac, France ^CNRS, Université de Bordeaux, PLACAMAT UMS 3626, F Pessac, France *Corresponding Author: aline.rougier@icmcb.cnrs.fr, ICMCB-CNRS, 87 avenue du Dr Albert Schweitzer, Pessac cedex, France S-1-

2 FIGURE S1. XRD of (a) V 2 O 3 powders, (b) V 2 O 3 film and (c) ITO. S-2

3 FIGURE S2. Coulombic efficiency and its evolution during cycling for V 2 O 3 film (a) and V 2 O 5 film (b) cycled in ITO/V 2 O 3 (V 2 O 5 )/LiTFSI-EMITFSI/Pt vs SCE cell. S-3

4 TABLE S1. The L*a*b* parameters in the blue-reduced state and orange-oxidized state of V 2 O 3 at initial state and after 30 days. Initial After 30 days L* a* b* L* a* b* (-0.9V) (+1.9V) TABLE S2. The L*a*b* parameters in the blue-reduced state and orange-oxidized state of V 2 O 5 at initial state and after 30 days. Initial After 30 days L* a* b* L* a* b* (-0.9V) (+1.9V) S-4

5 FIGURE S3. ex-situ XRD of V 2 O 3 film before cycling (a), after 5 cycles in oxidized state (b), after 50 cycles in oxidized state (c). IV. EXPERIMENTAL DETAILS IV.1. Powder from polyol synthesis and film elaboration All of the chemical reagents were purchased from Acros Organics and used without further purification steps. Ammonium metavanadate (NH 4 VO 3 ) was used as vanadium source and ethylene glycol (H 6 C 2 O 2 ) as template. In a typical synthesis, NH 4 VO 3 (2.924 g) was added to 250 ml H 6 C 2 O 2. The resulting mixture was heated to 110 C under continuous stirring to obtain a yellow sol refluxed at 160 C for 1 h. At the end of the reaction, a vanadylglycolate (VEG) precipitate was obtained. The precipitate was centrifuged and washed several times with ethanol to remove the organic product and dried in an oven at 80 C. To synthesize the final V 2 O 3 and V 2 O 5 powders, the VEG precursor was annealed at 500 C for 2 hrs under a 95%Ar/5%H 2 gas mixture and air, respectively. V 2 O 3 and V 2 O 5 films were deposited on In 2 O 3 :Sn/glass, ITO/glass, by Doctor Blade from the powder synthesized by the polyol method. Firstly, 80 mg of powder was dispersed into 3 ml distilled water. The resulting dilute was stirred at room temperature and after aliquots of the as-prepared colloidal solution was deposited on the ITO coated glass. The thickness of the two films, measured using a Dektak mechanical profilometer, was of about 910 nm, and 830 nm, for vanadium sesquioxide and di-vanadium pentoxide films, respectively. S-5

6 IV.2. Characterization tools on V x O y powder/films The powders structure was characterized by X-ray diffraction analysis (Philips PW 1820, PANalytical X Pert instrument, 2θ range from 8 to 60 and λcukα1= Å). The unit cell parameters were refined by structural pattern matching using the Fullprof program package. The powder patterns were firstly analyzed using the Caglioti function (function N 5), i.e. the isotropic peak profile function for which the u, v, w and shape parameters are refined; the powder patterns as well as the V 2 O 5 thick films were also refined using anisotropic peak profile (function N 7) that allows the crystallite size determination for each (hkl) crystallographic directions. Grazing incidence X-ray analyses, on films were carried out with a high resolution diffractometer Bruker D8 Discover (films, grazing incidence, and textures), with Cu radiation. Transmission electron microscopy (TEM) images were recorded with JEOL JSM-6700F (operating at 5 kv) microscope. The diffuse reflectance of V 2 O 3 and V 2 O 5 films were ex situ recorded after application of various potentials using a Varian Cary 5000 UV-Vis-NIR spectrophotometer. From the diffuse reflectance spectra, the determination of colorimetric parameters in the CIE L*a*b* colorimetric space for each films was made using x(λ);y(λ);z(λ) color matching functions which are the numerical description of the chromatic response of the observer (herein, CIE 1931 Standard Observer function). The angle is 10. The optical contrast ( E*) between two color states was calculated using the equation: E* = [(L* 1 -L* 2 ) 2 +(a* 1 -a* 2 ) 2 +(b* 1 -b* 2 ) 2 ] 1/2 Surface composition of the films, and especially the oxidation number of the vanadium cations, as obtained, after different potential states were applied upon the electrochemical measurements, by ex-situ X-ray photoelectron spectroscopy (XPS). The VG ESCALAB 220i-XL apparatus allows an analysis of the 5 nm first nanometers in depth with a lateral resolution of 150 µm. A ThermoFisher Scientific K-Alpha spectrometer was used for surface XPS analysis of thin films. The monochromatized AlKα source (hν=1486.6ev) was activated with a spot size 200 µm in diameter. The full spectra (0-1320eV) were obtained with a constant pass energy of 200 ev and high resolution spectra with a constant pass energy of 40eV. High resolution XPS spectra were quantified and fitted using the AVANTAGE software provided by ThermoFisher Scientific. IV.3. Electrochromic measurements of vanadium oxides thick films Electrochemical measurements were carried out in a three electrodes cell configuration using a BioLogic SP50 potentiostat/galvanostat apparatus and V x O y films on ITO/glass as working electrode. The counter-electrode and reference electrode consisted of a platinum foil and Saturated Calomel Electrode, SCE (ESCE = V/ENH), respectively. The operating voltage was controlled between -1.2 V/-0.9 V and +1.9 V at 20 mv/s in lithium based electrolyte, namely lithium bis-trifluoromethanesulfonimide (LiTFSI, Solvionic, purity > 99.99%) in ethylimidazoliumbis-(trifluoromethane-sulfonyl)-imide (EMITFSI). All the electrochemical measurements were performed at room temperature. S-6