1. 1 Solid oxide membranes for hydrogen separation and isolation Aurelija Martišiūtė

2. 2 Membrane permeation mechanisms; Review of different types conductivity; Experimental data; Results (XRD, SEM,Water permeability test); Conclusion. Outline of the presentation:

3. 3 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.

4. 4 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

5. 5 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

6. 6 Hydrogen separation from mix gases during catalysis CH4 → CH ● 3 + H ● H ● → H + + e - 2H + + 2e - → H 2

7. 7 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.

8. 8 Pulse DC: Experiment : t U

9. 9 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. 10 Cross – section of chromium oxide film PNSi5: p=2Pa, I=1A, U=345V, U Bias =100V, I Bias =0.01A, thickness=2.47 µm, t=3h Cross – section image (SEM)

11. 11 Si substrate and chromium oxide film on it(PNSi5) SEM RESULTS PNSi5: p=2Pa, I=1A, U=345V, U Bias =100V, I Bias =0.01A, thickness=2.47µm, t=3h

12. 12 Cross – section of chromium oxide film Cross – section image (SEM) PNSi6: p=5.3Pa, I=1A, U=360V, U Bias =100V, I Bias =0.01A, thickness=1.47µm, t=3h

13. 13 Si substrate and chromium oxide film on it(PNSi6) SEM RESULTS PNSi6: p=5.3Pa, I=1A, U=360V, U Bias =100V, I Bias =0.01A, thickness=1.47µm, t=3h

14. 14 Cross – section image (SEM) Cross – section of chromium oxide film PNSi8: p=2Pa, I=1A, U=345V, thickness=2.38 µm, t=3h

15. 15 Si substrate and chromium oxide film on it(PNSi8) SEM RESULTS PNSi8: p=2Pa, I=1A, U=345V, thickness=2.38µm, t=3h

16. 16 XRD RESULTS MOTTCr20: p=2Pa, I=1A, U=345V, U Bias =100V, I Bias =0.01A, thickness=2.31µm, t=3h MOTTCr21: p=5.3Pa, I=1A, U=360V, U Bias =100V, I Bias =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

17. 17 SEM RESULTS MOTTCr20: p=2Pa, I=1A, U=345V, U Bias =100V, I Bias =0.01A, thickness=2.31µm, t=3h MOTT substrate and chromium oxide film on it(MOTTCr20)

18. 18 MOTT substrate and chromium oxide film on it(MOTTCr21) SEM RESULTS MOTTCr21: p=5.3Pa, I=1A, U=360V, U Bias =100V, I Bias =0.01A, thicknes=2.2µm, t=3h

19. 19 MOTT substrate and chromium oxide film on it(MOTTCr22) SEM RESULTS MOTTCr22: p=5.3Pa, I=1A, U=365V, thickness =?µm, t=3h

20. 20 MOTT substrate and chromium oxide film on it(MOTTCr23) SEM RESULTS MOTTCr23: p=2Pa, I=1A, U=345V, thicknes=2.55µm, t=3h

21. 21 Water permeability test SampleR 1, Ω R 2, Ω R 3, Ω MOTTCr200.0515 ×10 6 4 ×10 6 MOTTCr210.0510 6 2.8 ×10 6 MOTTCr220.0510 ×10 6 3.5 ×10 6 MOTTCr234010 6 13 ×10 4 SampleR1, ΩR2, ΩR3, Ω PNSi58 ×106411 ×106 PNSi68 ×1066.513 ×106 PNSi88 ×10655 ×106

22. 22 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.