Chao Chen1, Zexu Sun2, Yueping Li3, Liyuan Yi4, Haoming Hu5

Supporting Information

Self-assembly of N Doped 3D Porous Carbon Frameworks from Carbon

Quantum Dots and its application for Oxygen Reduction Reaction

1 School of Computing Science, Sichuan University of Science & Engineering,

Zigong, 643000, China. E-mail: [email protected]; Fax: +86-813-5505878;

Tel: +86-813-5505878.

2 Powder Metallurgy Research Institute, Central South University, Changsha, 410083,

China.

3 Primary School of Jiantangpin, Yiyang, 413412, China.

4 The Seventh High School of TaoJiang, Yiyang, 413400, China.

5 Primary School of Niutian, Yiyang, 413412, China.

*Corresponding author. Tel./fax: +86-813-5505878.

E-mail address: [email protected]

Supplemental Table and Figures Figure S1. the UV-vis absorption spectrum of CQDs. Inset: photograph of CQDs ethanol solution taken under visible and UV light.

Table S1. BET results of NCF-700, NCF-800 and NCF-900. specific surface pore volume Samples area (cm2 g-1) (cm3 g-1) NCF-700 76.75 0.243 NCF-800 171.21 0.542 NCF-900 154.38 0.416 Table S2. Elemental composition of the NCF samples obtained from XPS results. Samples C (at.%) O (at.%) N (at.%) NCF-700 90.31 3.28 6.42 NCF-800 90.68 4.09 5.23 NCF-900 90.99 4.40 4.62

Table S3. Atomic concentrations (at.%) of heterocyclic N components of NCF samples in the N 1s binding energy region. Pyridinic N Pyrrolic N Graphitic N Oxidated N Samples ~398.4 eV ~400 eV ~401.5 eV ~402-406 eV NCF-700 41.32 % 33.85 % 14.54 % 10.29 % NCF-800 34.70 % 19.73 % 28.86 % 20.71 % NCF-900 27.62 % 21.42 % 29.17 % 21.79 % Figure S2. CV curves of NCF-800 in N2-saturated (black line) and O2-saturated (red line) 0.1 M KOH electrolytes at a scan rate of 50 mV s-1. Figure S3. CV curves of Pt/C (20 wt.%) in N2-saturated (black line) and O2-saturated (red line) 0.1 M KOH electrolytes at a scan rate of 50 mV s-1. Figure S4. CV curves of CQDs in N2-saturated (black line) and O2-saturated (red line) 0.1 M KOH electrolytes at a scan rate of 50 mV s-1.

Table S1 Comparison of the ORR performance of NCF-800 and other metal-free catalysts reported in literatures under the same conditions.

Catalyst EP (V Eonset (V E1/2 (V Limiting current n Ref. vs.RHE vs.RHE) vs.RHE) density (mA cm-2) ) This NCF-800 0.78 0.87 0.74 5.46 3.90 work NDoped Carbon 0.75 0.78 0.68 3.82 3.50 [1] Aerogels N, P co-doped porous carbon 0.78 0.84 0.72 5.12 3.64 [2] networks N, As co- doped 0.60 1.1 0.63 5.42 3.58 [3] CNT N, P co-doped 0.77 0.86 0.76 4.71 3.50 [4] Graphene N doped 0.74 0.88 0.70 3.01 3.80 [5] Graphene N, S, P co-doped 0.73 0.85 0.72 5.35 3.58 [6] CNT Figure S5. The durability test of Pt/C (20 %) performed in O2-saturated 0.1 M KOH electrolyte before and after 5000 extensive cycles.

Supplementary References 1. J. L. Zhang, G. L. Chen, Q. Zhang, F. Kang, B. You, Self-assembly synthesis of N- doped carbon aerogels for supercapacitor and electrocatalytic oxygen reduction. ACS Appl. Mater. Interfaces 7 12760-12766 (2015). 2. B. You, F. Kang, P. Q. Yin, Q. Zhang, Hydrogel-derived heteroatom-doped porous carbon networks for supercapacitor and electrocatalytic oxygen reduction. Carbon 103 9-15 (2016). 3. Z. W. Liu, M. Li, F. Wang, Q. D. Wang, Novel As-doped, As and N-codoped carbon nanotubes as highly active and durable electrocatalysts for O2 reduction in alkaline medium. J. Power Sources 306 535-540 (2016). 4. X. C. Qiao, S. J. Liao, C. H. You, R. Chen, Phosphorus and nitrogen dual doped and simultaneously reduced graphene oxide with high surface area as efficient metal- free electrocatalyst for oxygen reduction. Catalysts 5 981-991 (2015). 5. L. T. Soo, K. S. Loh, A. B. Mohamad, W. R. W. Daud, W. Y. Wong, Effect of nitrogen precursors on the electrochemical performance of nitrogen-doped reduced graphene oxide towards oxygen reduction reaction. J. Alloys Compd. 677 112-120 (2016). 6. Z. W. Liu, F. Wang, M. Li, Z. H. Ni, N, S and P-ternary doped carbon nano- pore/tube composites derived from natural chemicals in waste sweet osmanthus fruit with superior activity for oxygen reduction in acidic and alkaline media. RSC Adv 6 37500-37505 (2016).