Supplemental Materials

(1)

Supplemental Materials

Zirconia Overcoats as On-Board Strontium Getters for Improved

Solid Oxide Fuel Cell Nano-Composite Cathode Durability

Yubo Zhanga_{, Yeting Wen}b_{, Dr. Kevin Huang}b_{and Dr. Jason D. Nicholas}a*

a _{Chemical Engineering and Materials Science Department, Michigan State University, 2100}

Engineering Building, 428 S. Shaw Lane, East Lansing, MI, 48824, USA

b _{Department of Mechanical Engineering, University of South Carolina, 300 Main St, Columbia,}

SC, 29208, USA

(2)

Figure S1. TEM images taken in the same spot for FIB-SEM sectioned 5nm ZrO2 coated standard

12 vol% LSCF-GDC NCCs taken after 1000 hours of 650o_{C aging and approximately (a) three}

weeks after high temperature exposure and several days after FIB-SEM liftout, and (b) two more additional of unprotected exposure to room-temperature air. Note that the ALD coating amorphized and expanded (perhaps due to atmospheric water attack) after FIB-SEM sectioning and multiple months of unprotected, room-temperature exposure to air.

(3)

Figure S2. TEM images taken (a) near the cathode surface and (b) near the cathode/electrolyte interface for the sample shown in Figure S1b.

(4)

Figure S3. Normalized 650o_{C (a) polarization resistance and (b) ohmic resistance aging behavior}

for 0, 1, 3 and 5 nm ZrO2 coated standard 12 vol% LSCF-GDC NCCs collected at the University

(5)

Figure S4. Long term polarization resistance tests for standard 12 vol% LSCF-GDC NCCs with 0 (#11, 21 and 31), 1 (#15, 16 and 17) and 2 nm (#18, 19 and 20) ZrO2 overcoats collected at the

University of South Carolina using silver paste as a current collector. As can be seen through comparison with Figures S3 and 6, switching from silver to gold current collectors removed the cell to cell variation encountered with silver current collectors and produced systematic electrical

(6)

performance trends with overcoat thickness that matched those independently collected at Michigan State on identically-produced cells.

(7)

Figure S5. Scanning electron microscopy (a-c) and the associated Energy Dispersive X-ray Spectropscopy scans (d-f) taken near the cathode-electrolyte interface for standard 12 vol% LSCF-GDC NCCs with (a,d) 0 (#11), (b,e) 1 (#15) and (c,f) 2 nm (#18) ZrO2 overcoats after 1000-hours

(8)

(9)

Figure S7. X-ray diffractograms for an as-produced, uncoated LSCF pellet infiltrated with LSCF. The reference LSCF and SrCO3 XRD patterns are from JCPDS 00-048-0124 and JCPDS

(10)

Figure S8. A quartz crystal microbalance analysis for ALD ZrO2 overcoats on gold coated crystal

(11)

Table S1. Microstructural Characteristics of LSCF-GDC NCCs with Different Overcoat Thicknesses ± the Standard Deviation Between At Least Three Identically-Prepared Samples

Overcoat Thickness (nm) LSCF Loading Level (vol %) Cathode Thickness (m) Electrolyte Thickness (m) GDC Scaffold Porosity (%) Scaffold Surface Roughness (m) 0 12.0 ± 0.1 30.8 ± 1.1 533 ± 25 41 ± 2 2.7 ± 0.4 1 12.0 ± 0.1 31.6 ± 1.0 533 ± 25 41 ± 2 3.1 ± 0.3 2 12.0 ± 0.1 32.3 ± 0.5 533 ± 25 41 ± 2 2.5 ± 0.6 5 12.0 ± 0.1 32.9 ± 1.9 508 ± 25 41 ± 2 2.8 ± 0.3 10 12.0 ± 0.1 31.8 ± 1.9 508 ± 25 41 ± 2 2.3 ± 0.5

(12)

Table S2. Relative atomic concentration for relevant elements for standard 12 vol% LSCF-GDC NCCs with different ZrO2 thicknesses before and after 1000-hour 650oC Ageing

C O La Sr Co Fe Zr Uncoated 18.85 52.73 5.29 15.60 4.04 3.47 0.00 1nm ZrO2 Coated 31.34 40.23 2.64 6.99 3.02 2.49 13.29 2nm ZrO2 Coated 27.44 41.89 1.21 4.76 2.57 1.42 20.71 5nm ZrO2 Coated 29.02 38.53 0.40 1.62 1.48 0.95 27.99 10nm ZrO2 Coated 30.10 38.00 0.36 1.41 1.35 0.83 27.95 Aged Uncoated 23.65 47.36 7.76 9.20 6.70 5.33 0.00

Aged 1nm ZrO2 Coated 21.40 44.44 4.13 10.60 3.21 3.50 12.71

(13)

Table S3. Binding Energy (BE), Full Width Half Max (FWHM) and Relative Integrated Area (RA) for 0, 1 nm and 2 nm ZrO2 Coated standard 12 vol% LSCF-GDC NCCs Before and After

Aging BE (eV) FWHM (eV) RA (%) Lattice Sr 3d 5/2 131.82 1.2 22.90 Lattice Sr 3d 3/2 133.61 1.2 15.34 Surface Sr 3d 5/2 133.26 1.7 36.98 Before Ageing Surface Sr 3d 3/2 135.05 1.7 24.78 Lattice Sr 3d 5/2 132.26 1.7 26.25 Lattice Sr 3d 3/2 134.05 1.7 24.29 Surface Sr 3d 5/2 133.97 1.2 23.63 Uncoated LSCF-GDC NCC After Ageing Surface Sr 3d 3/2 135.76 1.2 15.83 Lattice Sr 3d 5/2 131.83 1.5 24.21 Lattice Sr 3d 3/2 133.62 1.5 16.22 Surface Sr 3d 5/2 133.29 1.7 35.67 Before Ageing Surface Sr 3d 3/2 135.08 1.7 23.90 Lattice Sr 3d 5/2 132.77 1.7 55.67 Lattice Sr 3d 3/2 134.56 1.7 37.30 Surface Sr 3d 5/2 134.21 1.2 4.21 1 nm ZrO2 Coated LSCF-GDC NCC After Ageing Surface Sr 3d 3/2 136.0 1.2 2.82

(14)

Lattice Sr 3d 5/2 131.71 1.3 14.81 Lattice Sr 3d 3/2 133.50 1.3 9.92 Surface Sr 3d 5/2 133.38 1.6 45.07 Before Ageing Surface Sr 3d 3/2 135.17 1.6 30.20 Lattice Sr 3d 5/2 133.37 1.6 54.00 Lattice Sr 3d 3/2 135.16 1.6 36.18 Surface Sr 3d 5/2 134.92 1.3 5.88 2 nm ZrO2 Coated LSCF-GDC NCC After Ageing Surface Sr 3d 3/2 136.71 1.3 3.94