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
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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