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Solid oxide membranes for Solid oxide membranes for

hydrogen separation and isolationhydrogen separation and isolation

Aurelija MartiAurelija Martišiūtėšiūtė

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Membrane permeation mechanisms;

Review of different types conductivity;

Experimental data;Results (XRD, SEM,Water

permeability test); Conclusion.

Outline of the presentation:

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There are two main membrane permeation mechanisms:

• Through the bulk of the material (dense membranes). A gas molecule is adsorbed on one side of the membrane, dissolves in the membrane material, diffuses through the membrane and desorbs on the other side of the membrane.

• Through pores (porous membranes). The separation factor for these mechanisms depends strongly on pore size distribution, temperature, pressure and interactions between gases being separated and the membrane surfaces.

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Chromium oxide Chromium oxide has characteristic of protonic – electronic conductivity, so it can be used as electrolyte where hydrogen can go toward cathode during electrolysis

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Schematic of the use of mixed oxygen ion – electronic conductor for oxygen separation with direct reforming of methane, followed by the use of mixed protonic – electronic conductor for hydrogen extraction. The products are thus pure hydrogen and synthesis gas with reduced hydrogen content

Oxygen ion – electronic & Protonic - electronic conductivity

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Hydrogen separation from mix gases during catalysis

CH4 → CH●3 + H●

H● → H+ + e -

2H+ + 2e- → H2

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There are different types of conductivity:

Polymer based proton exchange materials (PEMs);

Mixed oxygen ion – electronic conductors;

High temperature, acceptor – doped system with mixed protonic – p – type or n – type electronic conduction;

Reduced materials with mixed protonic and n – type electronic disorder;

Materials with water or crystallographic protons;

Hydrogen insertion compound.

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Pulse DC:Experiment :

t

U

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XRD RESULTS

PNSi5: p=2Pa, I=1A, U=345V, UBias=100V, IBias=0.01A, thickness=2.47µm, t=3h

PNSi6: p=5.3Pa, I=1A, U=360V, UBias=100V, IBias=0.01A, thickness=1.47µm, t=3h

PNSi8: p=2Pa, I=1A, U=345V, thickness=2.38µm, t=3h

10 20 30 40 50 60 70

0

500

1000

1500

2000

2500

3000

3500

4000

4500

PNSi6

PNSi8

r-Cr2O

3(110) r-Cr

2O

3(116)

r-Cr2O

3(300)

PNSi5

Si substrate

Inte

nsi

ty, a

rb.u

.

difraction angle,2 theta

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Cross – section of chromium oxide film

PNSi5: p=2Pa, I=1A, U=345V, UBias=100V, IBias=0.01A, thickness=2.47µm, t=3h

Cross – section image (SEM)

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Si substrate and chromium oxide film on it(PNSi5)

SEM RESULTS

PNSi5: p=2Pa, I=1A, U=345V, UBias=100V, IBias=0.01A, thickness=2.47µm, t=3h

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Cross – section of chromium oxide film

Cross – section image (SEM)

PNSi6: p=5.3Pa, I=1A, U=360V, UBias=100V, IBias=0.01A, thickness=1.47µm, t=3h

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Si substrate and chromium oxide film on it(PNSi6)

SEM RESULTS

PNSi6: p=5.3Pa, I=1A, U=360V, UBias=100V, IBias=0.01A, thickness=1.47µm, t=3h

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Cross – section image (SEM)

Cross – section of chromium oxide film

PNSi8: p=2Pa,

I=1A,

U=345V, thickness=2.38µm, t=3h

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Si substrate and chromium oxide film on it(PNSi8)

SEM RESULTS

PNSi8: p=2Pa,

I=1A,

U=345V, thickness=2.38µm, t=3h

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10 20 30 40 50 60 700

200

400

600

800

1000

1200

1400

1600

1800

2000

MOTTCr23

r-Cr2O

3(300)

r-Cr2O

3(113)

r-Cr2O

3(110)

MOTTCr22r-Cr

2O

3(300)

r-Cr2O

3(110)

MOTTCr21

MOTT substrate

MOTTCr20

r-Cr2O

3(110)

Substrate

Inte

nsity

, arb

.u.

difraction angle, 2 theta

  XRD RESULTS

MOTTCr20: p=2Pa, I=1A, U=345V, UBias=100V, IBias=0.01A, thickness=2.31µm, t=3h

MOTTCr21: p=5.3Pa, I=1A, U=360V, UBias=100V, IBias=0.01A, thickness=2.2µm, t=3h

MOTTCr22: p=5.3Pa, I=1A, U=365V, thickness = ?µm, t=3h

MOTTCr23: p=2Pa, I=1A, U=345V, thickness=2.55µm, t=3h

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SEM RESULTS

MOTTCr20: p=2Pa, I=1A, U=345V, UBias=100V, IBias=0.01A, thickness=2.31µm, t=3h

MOTT substrate and chromium oxide film on it(MOTTCr20)

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MOTT substrate and chromium oxide film on it(MOTTCr21)

SEM RESULTS

MOTTCr21: p=5.3Pa, I=1A, U=360V, UBias=100V, IBias=0.01A, thicknes=2.2µm, t=3h

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MOTT substrate and chromium oxide film on it(MOTTCr22)

SEM RESULTS

MOTTCr22: p=5.3Pa, I=1A, U=365V, thickness =?µm, t=3h

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MOTT substrate and chromium oxide film on it(MOTTCr23)

SEM RESULTS

MOTTCr23: p=2Pa, I=1A, U=345V, thicknes=2.55µm, t=3h

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Water permeability test

Sample R1, Ω R2, Ω R3, Ω

MOTTCr20 0.05 15 ×106 4 ×106

MOTTCr21 0.05 106 2.8 ×106

MOTTCr22 0.05 10 ×106 3.5 ×106

MOTTCr23 40 106 13 ×104

Sample R1, Ω R2, Ω R3, Ω

PNSi5 8 ×106 4 11 ×106

PNSi6 8 ×106 6.5 13 ×106

PNSi8 8 ×106 5 5 ×106

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CONCLUSIONS:

Chromium oxide has mixed protonic – electronic conductivity, so it can be used as membrane for hydrogen separation from other gases.

Thin chromium oxide films were deposited on plains silicon substrates and porous substrates. On silicon substrates we detected amorphous phase practically in all films;

XRD analysis shows that when chromium oxide film is deposited on porous substrate, dominates rombohedric phase of Cr2O3.

SEM analysis shows that chromium oxide films are porous and characterize island grow.

It was done water permeability test. Results are negative, water leak through chromium oxide membranes.