Nitrogen Doped Carbon Nanomaterials as Non-metal. Electrocatalysts for Water Oxidation

Transcription

1 Supplementary online materials for Nitrogen Doped Carbon Nanomaterials as Non-metal Electrocatalysts for Water Oxidation Yong Zhao, Ryuhei Nakamura, Kazuhide Kamiya, Shuji Nakanishi *, Kazuhito Hashimoto Corresponding

2 Supplementary Figure S1 SEM image of IrO 2 /C materials. The size of IrO 2 /C is nm in diameter with aggregation.

3 Supplementary Figure S2 The full circle of the OER activity of the N/C materials. With the employed sweep rate (5 mv s -1 ), the forward and backward scans almost overlapped, indicating a low capacitive current.

4 Supplementary Figure S3 Tafel plot of OER activity from (1) the N/C and (2) N/C-NiOx materials. Based on the actual active surface area (EASA), the calculated OER activity of N/C-NiOx is comparable to that of the N/C materials

5 Supplementary Figure S4 RRDE data showing the Pt ring currents (detected H 2 O 2 production) in OER process for N/C electrode at KOH medium (ph13). (catalysts, 0.2 mg cm -1, rotation speed, 1500 rpm) The poisoned potential on the Pt ring is 1.51 V vs RHE.

6 Supplementary Figure S5 XRD spectra of the pyrolyzed (1) N/C and (2) N/C-NiO x materials. For the N/C-NiO x sample, it is hybrid of Ni metal and NiO x based on the references. 41,42

7 a) b) C N C N O Ni O Ni Supplementary Figure S6 TEM images of a) N/C catalyst and b) N/C-NiO x catalysts and EDS C, N, O, Ni maps of a) N/C catalyst and b) N/C-NiO x catalysts. Nickel species are not detected in the N/C catalysts, while nickel oxide was enriched in N/C-NiO x samples. We marked a cycle in the TEM image, in which no N/C sample was localized in that area. The elements, C, N and O, cannot be detected in such area, while some signal noise (the red points) was found and distributed in the nickel mapping. The red points were signal noise in Figure S6a.

8 Supplementary Figure S7 The elemental contents of a) N/C sample and b) N/C-NiO x sample analyzed from EDS-TEM measurement. No nickel species was detected in the N/C samples and large amount of nickel oxide are existed in the N/C-NiO x samples (N/C-NiOx sample is synthesized from pyrolyzing the melamine/formaldehyde polymer and nickel nitrate without acid leaching. The nickel species are remained in the N/C-NiOx samples.). a) b)

9 Supplementary Figure S8 The Ni 2p XPS of a) N/C and b) N/C-NiO x materials. It shows that no nickel specie is existed in the N/C sample, while the NiO x was included in the N/C-NiO x material based on their binding energy (The peaks at ev and ev are assigned to the nickel oxide. 41,43 ).

10 a) b) Supplementary Figure S9 a) SEM images of the pyrolyzed graphene/pdps (900 o C/ 5 min.); b) the deconvoluted XPS N1s of the pyrolyzed graphene/pdps. The pyridinic (N1) and quanterary (N2) nitrogen are the dominant N species.

11 a) b) Supplementary Figure S10 a) The measured CV diagrams of different amounts of N/C catalysts on the glassy carbon electrode; b) the relationship between capacitors and loaded amounts of N/C catalysts. (scan rate: 10 mv s -1, electrolyte: ph13 KOH medium, room temperature.)

12 Supplementary Figure S11 The deconvoluted N1s XPS of N/C materials pyrolyzed at different temperatures.

13 Supplementary Figure S12 The OER Stability of the N/C electrodes. (Nafion-to-catalyst 1:2 wt:wt)

14 Supplementary Table S1 The BET surface area of different materials used in this study and the electrochemical active surface area (EASA) calculated from their capacitor current.

15 Supplementary Table S2 The surface elemental contents of N/C materials pyrolyzed at different temperatures and N/C-NiO x pyrolyzed at 700 o C (analyzed from XPS).

16 Supplementary Table S3 The surface elemental contents of pyrolyzed graphene/pdps (900 o C/5 min.) materials (analyzed from XPS).

17 Supplementary Table S4 The percentages of surface nitrogen species contents in N/C materials pyrolyzed at different temperatures (analyzed from deconvoluted N 1s XPS).

18 Supplementary Table S5 The surface nitrogen species concentrations in N/C materials pyrolyzed at different temperatures (analyzed from deconvoluted N 1s XPS).

19 Supplementary references [41] Chigane, M., & Ishikawa, M. XRD and XPS characterization of electrochromic nickel oxide thin films prepared by electrolysis-chemical deposition, J. Chem. Soc., Faraday Trans. 94, (1998) [42] Wu, M. S., Huang, C. Y. & Lin, K. H. Electrophoretic deposition of nickel oxide electrode for high-rate electrochemical capacitors Electrophoretic deposition of nickel oxide electrode for high-rate electrochemical capacitors, J. Power Sources 186, (2009) [43] Grosvenor, A. P. et al. New interpretations of XPS spectra of nickel metal and oxides. Surf. Sci. 600, (2006)