Optimization of Absorption/Desorption Parameters of ... - ePrints@IISc

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S1

Optimization of Absorption/Desorption Parameters of Brownmillerite SrCoO

2.5

for Oxygen Storage

Aswathy M. Narayanan, Arun M. Umarji

Materials Research Centre, Indian Institute of Science, Bengaluru, India

Supplementary Material

10 30 50 70 90

(e) Abs@723 (d) Abs@693 (c) Abs@673 (b) Abs@648 (a) Abs@623

Intensity (arb. units)

SrCoO3-

Space group P4/mmm SrCoO3-

Space group P4/mmm BM-SrCoO_2.5 Space group Ima2

2 (^/Cu K_)

y_obs y_calc y_bkg Difference Phase

Figure S 1 Refined XRD patterns of the samples after absorption at different temperatures (a) 623 K (b) 648 K (c) 673 K (d) 693 K and (e) 723 K.

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S2

30 35 40 45 50 55 60

Offset Intensity (arb. units)

2 (^/Cu K)

(a) As synthesized BM SrCoO_2.5 (b) Desorbed-abs@623

(c) Desorbed-abs@648 (d) Desorbed-abs@673 (e) Desorbed-abs@693 (f) Desorbed-abs@723

(411), (020)

(510),

(022) (420) (611) (321), (312)

(800

) (022), (521)

(031), (811), (330), (422)

(820), (431), (530), (802) (413

)

Figure S 2 Comparison of XRD patterns of (a) as synthesized BM SrCoO2.5 and (b-f) samples after desorption.

0 1000 2000

0.0 0.2 0.4 0.6 0.8 1.0

Des @ 673 K Fit

Extent of conversion ()

Time (s)

0 500 1000

0.0 0.2 0.4 0.6 0.8 1.0

Des @ 693 K Fit

Time (s) 0.00 500 1000

0.2 0.4 0.6 0.8 1.0

Des @ 723 K Fit

Time (s)

0.0 0.5 1.0

0.00 0.05 0.10

Contracting Sphere model

d/dt

Nucleation and growth model

0 500 1000

0.0 0.5 1.0

Nucleation and growth model

Contracting Sphere model

Extent of Conversion ()

Time (Seconds)

(c) (d)

(e) (f) (g)

Oxidized form Oxidized form Reduced form

(a) (b)

Figure S 3 Schematic representation of reduction through (a) contracting sphere model (b) nucleation and growth model (adapted from ref 1). Comparison of (c) extent of conversion () vs time (d) d/dt vs  for contracting sphere and nucleation and growth models (adapted from ref 1). (e-g) Desorption curves fitted with the equation given in table S3.

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S3

0.001 0.002 0.003

833 455 313

2 4 6 8 10

Adj.R² = 0.995 E_a=0.19 0.05 eV

Temperature (K)

ln (T)

1/T (K^-1)

Adj.R² = 0.997 E_a=0.67 0.05 eV

0.0015 0.0020 0.0025 0.0030

667 500 400 333

10 11 12

Adj.R² = 0.996 E_a=0.06 0.05 eV

Temperature (K)

ln (T)

1/T (K^-1)

(a) (b)

Figure S 5 Plots of ln (T) vs inverse of temperature (From DC conductivity measurements) of (a) BM SrCoO2.5 sample and (b) the sample absorbed at 673 K

0 200 400 600 800

Normalized Intensity

Binding Energy (eV)

BM SrCoO_2.5

Sr 3d Abs @ 673 K

Co 2p O 1s

Sr 3s C 1s Sr 3p

0 20 40 60 80

Binding Energy (eV)

BM SrCoO_2.5 Sr loss

Co 3d Sr 4p Abs @ 673 K

Co 3p

O 2sSr 4s

275 280 285 290 295 0.0

0.5

1.0 C 1s adventitious C 1s carbonate

Binding Energy (eV)

BM SrCoO_2.5 Abs @ 673 K Sr 3p

(c)

(b) (a)

Figure S 4 (a) XPS wide spectra of BM SrCoO2.5 and the sample absorbed at 673 K, (b) zoomed version of the spectra in (a) up to 80 eV and (c) C 1s region of BM and absorbed sample showing an increased contribution of carbonate carbon in absorbed sample.

Abs@673 Abs@673

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S4 10^-2 10^-1 10⁰ 10¹ 10²

0.0 0.2 0.4 0.6 0.8

1.0 ^{373 K}_{413 K}

433 K 443 K 446 K 448 K 453 K 458 K 463 K 468 K 473 K

Z"/Z" max

f/f_max 0 10² 10³ 10⁴ 10⁵ 10⁶ 200

400

600 ^{373 K}_{413 K}

433 K 443 K 446 K 448 K 453 K 458 K 463 K 468 K 473 K

Z' ()

Frequency (Hz)

(a) (b)

10² 10³ 10⁴ 10⁵ 10⁶ 0

1x10^-4 2x10^-4

373 K 413 K 433 K 443 K 446 K 448 K 453 K 458 K 463 K 468 K 473 K

M"

Frequency (Hz)

(c)

10⁴ 10⁵ 10⁶ 0

1x10^-4

2x10^-4 _{373 K}

413 K 433 K 443 K 446 K 448 K 453 K 458 K 463 K 468 K 473 K

M'

Frequency (Hz)

(d)

(e)

2.1x10^-3 2.2x10^-3

476 455

13.0 13.5 14.0

Temperature (K)

ln (f max)

1/T (K^-1)

W_H = 0.44 0.05 eV

(f)

0.0021 0.0024 0.0027

476 417 370

-2 0 2

Temperature (K)

ln (T)

1/T (K^-1)

E_a=0.25 0.05 eV E_a=0.56 0.05 eV

Figure S 6 BM SrCoO2.5 (a) normalized impedance plots (b) variation of real part of impedance with frequency at different temperatures (c) Imaginary part of modulus versus frequency (d) variation of real part of modulus with frequency, Arrhenius plots of (e) conductivity and (f) frequency maximum

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S5 Table S1: Lattice parameter values obtained from Rietveld refinement for different absorbed samples

Table S2: Oxygen stored and delta value from desorption experiments and Iodometric titration

Absorption temperature

(K)

From desorption experiment From Iodometric titration

Pressure change (m bar)

O2

evolved cm³/g of SrCoO3-

Delta

Composition after absorption

Composition after desorption

Delta

723 41.1 13.24 0.22 SrCoO2.650.02 SrCoO2.410.02 0.24 693 43.9 14.16 0.23 SrCoO2.650.01 SrCoO2.380.01 0.27 673 47.1 15.28 0.26 SrCoO2.670.02 SrCoO2.400.01 0.27 648 36.5 11.76 0.19 SrCoO2.680.01 SrCoO2.430.01 0.25

623 1 0.14 0 SrCoO2.430.01 SrCoO2.430.01 0

Table S3: Fitting results for desorption kinetics study Temperature

(K)

Equation used for

fitting A1 1 (s) A2 2 (s) Adj. R

square

673  = 1-exp(-t/) - 444.2(3) - 0.9989

693  = A1*exp(-t/1) + A2*exp(-t/2) + 1

-0.93(3) 53.8(3) -0.06(3) 287(12) 0.9979

723 -0.85(3) 13.8(1) -0.15(2) 165(2) 0.9936

References

1. N. W. Hurst, S. J. Gentry, A. Jones, B. D. McNicol, Temperature programmed reduction, Catalysis Reviews Science and Engineering 24 (2) (1982) 233-309

Absorption Temperature

(K)

Space group

Lattice Parameters (Å) Cell Volume (Å³)

Cell formul a units

Normalized Cell Volume

(Å³)

a b c

623 Ima2 15.707(8) 5.557(8) 5.456(9) 476.405 8 59.550 648 P4/mmm 3.385(5) 3.385(5) 7.696(9) 113.230 2 56.615 673 P4/mmm 3.830(8) 3.830(8) 7.691(6) 112.868 2 56.434 693 P4/mmm 3.833(1) 3.833(1) 7.693(8) 113.045 2 56.522 723 P4/mmm 3.833(3) 3.833(3) 7.692(2) 113.033 2 56.517