<p> Supporting Information</p><p>Facile synthesis of N-doped carbon nanosheets encased cobalt nanoparticles as efficient oxygen reduction catalysts in alkaline and acidic media</p><p>Qiuping Zhaoa b c, Qin Mab, Fuping Pand, Junhong Guoc , Junyan Zhangd﹡</p><p>Figure S1. TGA characterization of corn starch</p><p>Figure S2 . Typical SEM (a,b), TEM (c,d) images of NCN. Figure S3. Typical SEM (a,b), TEM (c,d) images of NCN-Co-0.1</p><p>Figure S4. Energy dispersive X-ray spectroscopy(EDX) of (a) NCN and (b) NCN-Co- 0.1</p><p> a b</p><p>Figure S5. Nitrogen adsorption/desorption isotherm plot of (a) NCN, (b) NCN-Co- 0.1, with an inset showing the pore distribution. Table S1. Textural properties of the NCN and NCN-Co-0.1 BET surface area Pore volume(cm3/g) Average pore size Sample (m2/g) （BJH D） (nm) (BJH D) NCN 603.42 2.84 16.52 NCN-Co-0.1 345.82 1.40 14.20</p><p>Table S2. Surface composition concentration of NCN and NCN-Co-0.1 Samples Carbon Cobalt Oxygen N total (at.%) (at.%) (at.%) (at.%) NCN 91.89 0 3.3 4.81 NCN-Co-0.1 92.1 0.23 5.3 2.37</p><p> a b</p><p>Figure S6. （a）XPS survey spectrum ; (b) High-resolution C 1s XPS spectra of NCN-Co-0.1</p><p> a b</p><p>Figure S7. (a) LSV curves with various rotation rates of Pt/C electrode, (b) Koutecky– Levich (K-L) plots of Pt/C electrode in O2-saturated 0.1 M KOH electrolyte with a sweep rate of 5 mV s−1.</p><p> a b Figure S8. (a) LSV curves with various rotation rates of Pt/C electrode, (b) K–L plots of Pt/C electrode in O2-saturated 0.5 M H2SO4 electrolyte with a sweep rate of 5 mV s−1.</p><p>Figure S9. Tafel plots of the NCN-Co-0.1(a) in 0.1 M KOH, (b) in 0.5 M H2SO4.</p><p>Table S3 Comparison of the ORR performance of some non-precious metal catalysts reported in literature</p><p>ORR activity (V vs. Ag/AgCl)a Ref. Catalysts medium Onset potentialb Half-wave potentialb NCN-Co-0.1 -0.03 #5 mv s-1 -0.14 This work Fe/N/G 0.08 #10mv s-1 -0.11 [1] Fe-N/C-900 0.04 #50mv s-1 -0.07 [2] Co,N-CNF -0.08 #10 mv s-1 -0.16 [3] Alkaline CoO/C -0.14 #50mv s-1 -0.20 [4] solution Co/N-C -0.14 #10 mv s-1 -0.23 [5] 0.1 M KOH Co/CoO/CoFeO4/ -0.20 #10 mv s-1 -0.28 [6] G Co-N-CAs -0.13 #10 mv s-1 -0.19 [7] Co-N-rGO -0.06 #10 mv s-1 -0.20 [8] NCN-1000 -0.03 #5 mv s-1 -0.15 [9] NCN-Co-0.1 0.55 #5 mv s-1 0.42 This work Fe/N/G c 0.62 #10 mv s-1 0.44 [1] Acidic Fe-N/C-900 c 0.52 #50 mv s-1 0.40 [2] solution Co,N-CNF 0.50 #10 mv s-1 0.42 [3] 0.5 M H SO FeNG-900 2 4 0.58 #5 mv s-1 0.50 [10] FeCo-N-rGO 0.50 #50 mv s-1 0.36 [11] NCN-900 0.62 #5 mv s-1 0.42 [9] a Conversions of Hg/HgO electrode, RHE electrode, and SCE into Ag/AgCl scale were achieved by adopting the calibration results. b Onset potential and Half-wave potential were obtained from linear sweep voltammetry performed on RDE in O2-saturated 0.1 M KOH solution(Alkaline) or 0.5 M H2SO4 (Acidic) with a rotation rate of 1600 rpm unless otherwise noted. c Onset potential and Half-wave potential were obtained from linear sweep voltammetry performed on RDE in O2-saturated 0.1 M HClO4 solution (Acidic)</p><p>References:</p><p>1. 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