DIP -COATED AND ELECTRODEPOSITED MESOPOROUS WO 3 THIN FILMS FOR - - PowerPoint PPT Presentation

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DIP -COATED AND ELECTRODEPOSITED MESOPOROUS WO 3 THIN FILMS FOR - - PowerPoint PPT Presentation

Jul 07, 2023 281 likes •487 views

DIP -COATED AND ELECTRODEPOSITED MESOPOROUS WO 3 THIN FILMS FOR ELECTROCHROMIC APPLICATIONS Speaker: Chatzikyriakou Dafni Supervisors: Dr. Henrist Catherine, Prof. Cloots Rudi 16th International Conference on Thin Films 13-16 October,

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SLIDE 1

‘’DIP-COATED AND ELECTRODEPOSITED MESOPOROUS WO3 THIN FILMS FOR ELECTROCHROMIC APPLICATIONS’’

16th International Conference on Thin Films 13-16 October, Dubrovnik, Croatia

Speaker: Chatzikyriakou Dafni Supervisors: Dr. Henrist Catherine, Prof. Cloots Rudi

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SLIDE 2

WO3 (PROPERTIES/APPLICATIONS)

 n-type semiconductor (2.6-3.25eV)

  • Photocatalyst
  • Gas sensing applications
  • Dye-Sensitized Solar Cells (DSSC)

 Optical properties/Chromism

  • Gasochromism
  • Electrochromism
  • Thermochromism
  • Photochromism

W(VI) (transparent) W(V) (blue)

2

e- e-

Li+ Li+ Li+

e-

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SLIDE 3

WO3(ELECTROCHROMISM/APPLICATIONS)

  • Electrochromic displays
  • Auto-dimming car mirrors
  • Smart windows

WO3 + xLi++ xe- LixWO3

3

Bleached state Coloured state

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SLIDE 4

SMART WINDOWS

  • Control heat, glare, fading
  • Reduce the need for air-conditioning
  • Better management of natural light
  • Require less than 5V (DC)

Reduce energy demands

PROBLEM!!! HIGH COST (3x)  SMALL MARKET

NEED FOR A MORE COST-EFFECTIVE BUT EFFICIENT PRODUCTION ROUTE

4

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SLIDE 5

GOAL OF THIS WORK

COST

  • No vacuum techniques
  • Cheap materials

EFFICIENCY

  • Cyclic stability
  • Reversibility
  • Optical modulation
  • Color/Bleach time
  • Charge density
  • Coloration efficiency
  • Increased surface area  increase of ‘’active’’ material
  • Reduces the diffusion length of cations

5

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SLIDE 6

POROUS FILMS THROUGH TEMPLATING

condensation Removal of the template hydrolysis

6

template Hydrophobic part Hydrophilic part metal precursor

  • Acc. Chem. Res. 2007, 40, 784-792
  • Chem. Soc. Rev., 2013, 42, 4198-4216
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SLIDE 7

TECHNIQUES

7

  • Chem. Mater. 2008, 20, 682-737
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SLIDE 8

EXPERIMENTAL PROCEDURE OF THE DIP-COATING

TECHNIQUE

Wx(H2O2)y(acetic acid)z in EtOH/H2O Calcination at elevated temperatures Porous amorphous films Controlled speed Evaporation Induced Self-Assembly (EISA)

8

Brij-56 in EtOH/H2O Superior electrochromic properties Controlled RH%

Crystalline films

  • Robust and rigid materials
  • Less absorption of visible light
  • D. Chatzikyriakou et al., Electrochimica Acta 137 (2014), 75-82
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SLIDE 9

STRUCTURAL CHARACTERIZATION OF THE DIP-

COATED FILMS

dense film porous film

  • Regular porosity
  • Pores diameter: 2-3nm
  • Pore-pore distance: 6nm
  • Wall thickness: 3-4nm

9

Compact and smooth surface

Without template With template

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SLIDE 10

ELECTROCHROMIC CHARACTERIZATION OF THE

DIP-COATED FILMS: CYCLIC VOLTAMMETRY

10

dense film

E (V) vs. Li/Li+ I (A.cm-2)

porous film

E (V) vs. Li/Li+ I (A.cm-2)

Reversibility % 1stcycle 20th cycle Dense film 54% 94% Porous film 93% 98%

Permanent coloration

reduction

  • xidation
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SLIDE 11

11

ELECTROCHROMIC CHARACTERIZATION FOR THE DIP-

COATED FILMS: CHRONOAMPEROMETRIC MEASUREMENTS

Sample Time for attaining the 10%

  • f total current capacity

(20th cycle) Coloration time (s) Bleaching time (s) Dense film 48 11 Porous film 100 32 Charge capacity (mC.cm-2) Intercalation (20th cycle) De- intercalation (20th cycle) 3.3 3.1 18.0 17.4

time (s)

100 200 300 400

I (mA.cm-2)

  • 0,4
  • 0,2

0,0 0,2 0,4 0,6 dense film mesoporous film

2.225V vs. Li/Li+

coloration 4.225V vs. Li/Li+ bleaching

Dense film  faster inter-/de-intercalation

Charge capacity (mC.cm-2) Sample Intercalation (20th cycle) De- intercalation (20th cycle) Dense film 3.3 3.1 Porous film 8.0 7.8

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SLIDE 12

ELECTROCHROMIC CHARACTERIZATION OF

THE DIP-COATED FILMS

12

wavelength (nm)

400 500 600 700 800 900 1000

T%

20 30 40 50 60 70 80 90 virgin film colored film bleached film

wavelength (nm)

400 500 600 700 800 900 1000

T (%)

10 20 30 40 50 60 70 80 90 virgin film colored film bleached film

Sample ΔT% (550/750nm) Optical Efficiency (cm-2/C) 20th cycle (550/750nm) log (Tb/Tc) C Dense film 4.6/5.6 12/17 Porous film 27.2/40.4 33/60

dense film porous film

Coloured state Bleached state Coloured state Bleached state Virgin state Virgin state

η =

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SLIDE 13

SUMMARIZING FOR THE DIP-COATED FILMS

13

Mesoporous film Dense film Switching kinetics Worse Better Charge capacity (mC.cm-2) Better Worse Reversibility Better Worse ΔΤ% Better Worse Coloration efficiency Better Worse

Porous film has better properties than the dense film

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SLIDE 14

EXPERIMENTAL PROCEDURE FOR THE

ELECTRODEPOSITION

14

  • Reduction of H2O2 (W(H2O2)x(CH3COO)y) to OH-
  • Precipitation of MOx(OH)y on the surface of the electrode
  • Framework’s built-up around the template
  • Calcination (350oC/2h or 400oC/1h)

PSS-Na

Counter electrode (Pt) Working electrode (glass/FTO) Reference electrode (Calomel)

350mC.cm-2

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SLIDE 15

Uncalcined films

STRUCTURAL

CHARACTERIZATION OF THE ELECTRODEPOSITED FILMS CALCINED AT 350OC

15

  • 0.5V

dense

  • 0.6V

dense

  • 0.4V

porous Not homogeneous coating!!

  • 0.4V

Less PSS-Na

Balance between condensation and co-assembly formation

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SLIDE 16

16

STRUCTURAL

CHARACTERIZATION OF THE ELECTRODEPOSITED FILMS

400oC/1h 400oC/1h

CRYSTALLINE FILMS

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SLIDE 17

STRUCTURAL

CHARACTERIZATION OF THE ELECTRODEPOSITED FILMS

17

  • 0.5V

dense films

  • 0.6V
  • 0.4V

porous Not adequate coating!!

  • 0.4V

Less PSS-Na Porous films

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SLIDE 18

18

Porous film Dense film Partial deterioration Dense Porous

Reversibility % 1st cycle 20th cycle Dense film 83% (54%) Porous film 91% (77%)

ELECTROCHROMIC CHARACTERIZATION OF THE

ELECTRODEPOSITED FILMS: CYCLIC VOLTAMMETRY

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SLIDE 19

19

Sample Time for attaining the 10%

  • f total current capacity

(20th cycle) Coloration time (s) Bleaching time (s) Dense film 26 10 Porous film 20 9 Charge capacity (mC.cm-2) Sample Intercalation (20th cycle) De-intercalation (20th cycle) Dense film 1.8 1.5 Porous film 3.8 3.5

Thickness and relative amount of W have not been adjusted yet

ELECTROCHROMIC CHARACTERIZATION FOR THE

ELECTRODEPOSITED FILMS: CHRONOAMPEROMETRIC MEASUREMENTS

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SLIDE 20

 Porous films at -0.4V but not at -0.5V/-0.6V  Calcination at 400oC gives porous but crystalline films  Deterioration of the porous film upon cycling (porous are still

filled with polymer)

 Film at -0.5V (dense film) similar behavior with the dense film

  • f the dip-coating technique

 Higher charge capacity for the films at -0.4V (porous films) 20

SUMMARIZING FOR THE ELECTRODEPOSITED FILMS Thank you for your attention!