Supporting Information Oxygen Reduction Electrocatalyst Based on Strongly Coupled Cobalt Oxide Nanocrystals and Carbon Nanotubes
Yongye Liang,1§ Hailiang Wang,1§Peng Diao,1§ Wesley Chang,1 Guosong Hong1, Yanguang Li,1 Ming Gong,1 Liming Xie,1 Jigang Zhou,2 Jian Wang,2 Tom Z. Regier,2 Fei Wei3 and Hongjie Dai1*
1 2
Department of Chemistry, Stanford University, Stanford, CA 94305, USA. Canadian Light Source Inc., Saskatoon, SK S7N 0X4, Canada.
3
Department of Chemical Engineering, Tsinghua University, Beijing 100084, China
*Correspondence to:
[email protected] Supplementary figures: Figures S1 – S8
S1
Figure S1. Low magnification SEM (a) and TEM (b) images of the Co3O4/NCNT hybrid prepared by hydrothermal method. Inset in (b) showed the electron diffraction pattern. (c) . High magnification TEM images of the Co3O4/NCNT hybrid. (d) XRD spectra of compacted films of the Co3O4/NCNT (red) and CoO/NCNT (black) hybrids.
Figure S2. (a) Rotating ring-disk electrode voltammogram of the Co3O4/NCNT and CoO/NCNT hybrids in O2-saturated 1 M KOH at 1600 rpm. The disk potential was scanned at 5 mV/s and the ring potential was constant at 1.3 V vs RHE. (b) Peroxide yield (bottom) and the electron transfer number (n) (top) of Co3O4/NCNT and CoO/NCNT hybrids at various potentials based on the corresponding RRDE data in (a). Catalyst loading was 0.10 mg/cm2 for all samples.
S2
Figure S3. Impedance spectra of the Co3O4/NCNT and Co3O4/N-rmGO hybrids at 0.8 V vs. RHE in 1M KOH.
Figure S4. Electron diffraction patterns of the hydrothermally derived Co3O4/NCNT, the gas phase derived CoO/NCNT hybrids before and after ORR cycling test from 1-0.4 V vs. RHE for 2000 cycles in 1 M KOH.
S3
Figure S5. Nitrogen K-edge XANES of the CoO/NCNT hybrid (red curve) and NCNT (black curve).
Figure S6. Oxygen reduction polarization curves of the NCNT hybrids prepared by gas phase annealing method with Ar (black) and NH3 red at 00 . and r at 650 .C (blue). Catalyst loading was ~0.24 mg/cm2 for all samples.
S4
Figure S7. a M ima e o the T h rids prepared as phase annealin method with r at 00 C. (b). spectra o compacted ilms o the T h rids prepared as phase annealin method with r lue at 00 C, the CoO/NCNT (red) and Co3O4/NCNT hybrids (black).
Figure S8. Oxygen reduction currents of the CoO/NCNT hybrids with various CoO contents loaded on carbon fiber paper in O2-saturated 1 M KOH (loading was 0.24 mg/cm2 for all samples).
S5
