Science Advances

Supplementary Materials

This PDF file includes:

  • Experimental Section
  • fig. S1. Molecular structures of precursors.
  • fig. S2. Temperature and time profile of pyrolysis and carbonization process.
  • fig. S3. FESEM images of the sample after pyrolysis at different temperatures.
  • fig. S4. Low-magnification FESEM image of the N-GRW.
  • fig. S5. FESEM images of samples prepared with different melamine–to–L-cysteine ratios.
  • fig. S6. XPS spectra of C3N4 and S-doped C3N4.
  • fig. S7. TEM and FESEM images of C3N4 and S-doped C3N4.
  • fig. S8. Nitrogen adsorption isotherms of C3N4 and S-doped C3N4.
  • fig. S9. TGA and heat flow curves of S-doped C3N4.
  • fig. S10. XPS spectra of S-doped C3N4 and S-doped C3N4 carbonized at 800°C.
  • fig. S11. Nitrogen adsorption isotherms of S-doped C3N4 and S-doped C3N4 carbonized at 800°C.
  • fig. S12. S2p core XPS spectra of S-doped C3N4 and S-doped C3N4 carbonized at 800° to 1000°C.
  • fig. S13. FESEM and TEM images of N-HGS and N-GS.
  • fig. S14. Nitrogen adsorption isotherms and pore size distribution of N-doped graphene samples.
  • fig. S15. C1s, N1s, and O1s core level high-resolution XPS spectra of the N-GRW, N-HGS, and N-GS.
  • fig. S16. XRD patterns and Raman spectra of the N-GRW, N-HGS, and N-GS.
  • fig. S17. LSV of N-doped graphene samples at different rotation speeds in the ORR region.
  • fig. S18. Linear sweeping voltammograms and Koutecky-Levich plots of different catalysts in the ORR region.
  • fig. S19. Cyclic voltammograms of N-doped graphene catalysts and Pt/C (20%) in Ar- and O2-saturated 1 M KOH.
  • fig. S20. Peroxide yield and electron transfer number of N-doped graphene catalysts.
  • fig. S21. Tafel plots of N-doped graphene catalysts in ORR region.
  • fig. S22. Cyclic voltammograms of Pt/C and the N-GRW electrode in O2-saturated 0.1 M KOH filled with methanol.
  • fig. S23. Current-time response of Pt/C and N-GRW for ORR with/without introducing CO into the electrolyte.
  • fig. S24. Cycling durability of Pt/C and N-GRW.
  • fig. S25. Linear sweeping voltammograms and Tafel plots of N-doped graphene catalysts in the OER region.
  • fig. S26. RRDE measurements for the detection of H2O2 and O2 generated during the OER process.
  • fig. S27. OER Tafel plots of N-doped graphene catalysts.
  • fig. S28. Cyclic voltammograms of the N-GRW in the OER region at different scan rates.
  • fig. S29. Faraday efficiency of OER measurement.
  • fig. S30. Mott-Schottky plots of N-doped graphene catalysts in two potential regions.
  • fig. S31. XPS valence band spectra of the N-GRW.
  • fig. S32. Nyquist plots of N-doped graphene samples in the ORR and OER regions.
  • fig. S33. The assembly processes for preparation of hybrid air cathode.
  • fig. S34. The assembly processes for the fabrication of a rechargeable zinc-air battery.
  • fig. S35. ORR and OER performances of air cathode tested in half-cell configuration.
  • fig. S36. Charge/discharge profiles and power density curves of zinc-air batteries assembled from mixed Pt/C + Ir/C air electrode.
  • fig. S37. Open-circuit voltage profiles of zinc-air batteries.
  • fig. S38. Charging/discharging cycling curves of the N-GRW–loaded electrode at charging/discharging current densities of 2 mA cm−2.
  • fig. S39. Charging/discharging cycling curves of Pt/C and Ir/C electrodes at charging/discharging current densities of 20 mA cm−2.
  • fig. S40. XRD patterns of materials detached from Ti foil after long time charging.
  • note S1. XPS study of C3N4 and S-doped C3N4 samples.
  • note S2. Deconvolution of C1s, N1s, and O1s XPS spectra of N-doped graphene samples.
  • note S3. Average crystallite size of the sp2 domains of N-doped graphene samples from Raman spectra.
  • note S4. Brief explanation of ac impedance of N-doped graphene samples.
  • table S1. Structural and compositional parameters of nitrogen-doped graphene catalysts.
  • table S2. Surface nitrogen and oxygen species concentrations of nitrogen-doped graphene catalysts.
  • table S3. Comparison of ORR and OER performances of our N-doped graphene nanoribbon networks with the recently reported highly active bifunctional catalysts.
  • Legends for videos S1 to S3

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Other Supplementary Material for this manuscript includes the following:

  • video S1 (.mp4 format). The evolution of O2 bubbles at potentials from 1.6 to 1.8 V versus RHE.
  • videos S2 and S3 (.mp4 format). The demonstration of water splitting driven by a single zinc-air battery.

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