Mesoporous N-Doped Carbons Prepared with Thermally Removable Nanoparticle Templates: an Efficient Electrocatalyst for Oxygen Reduction Reaction

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1 Supporting Information Mesoporous N-Doped Carons Prepared with Thermally Removale Nanoparticle Templates: an Efficient Electrocatalyst for Oxygen Reduction Reaction Wenhan Niu, a Ligui Li,* a Xiaojun Liu, a Nan Wang, a Ji Liu, a Weijia Zhou, a Zhenghua Tang a and Shaowei Chen* a, a New Energy Research Institute, School of Environment and Energy, South China University of Technology, Guangzhou Higher Education Mega Centre, Guangzhou 516, China Department of Chemistry and Biochemistry, University of California, 1156 High Street, Santa Cruz, California 9564, United States s: esguili@scut.edu.cn; shaowei@ucsc.edu Tale S1 Summary of Fe and nitrogen concentrations and BET surface area of Fe-N/C-precursor and Fe-N/C-T (T=6, 7, 8, 9) Fe-N/C precusor Fe-N/C-6 Fe-N/C-7 Fe-N/C-8 Fe-N/C-9 Pyridinic N (at.%) Pyrrolic N (at.%) graphitic N (at.%) Total N (at.%) Fe (at.%) BET surface area (m 2 /g) The content of Fe in Fe-N/C-precursor might e underestimated in XPS measurements ecause most of the FeO(OH) nanocrystals were emedded in the P2FANI matrix. To quantify the content of FeO(OH), Fe-N/C-precursor was washed with a copious amount of acetone and ethanol until the color of the filtrate changed from purplish red to colorless, signifying the removal of P2FANI (ecause P2FANI is solule in organic solvents such as acetone, ethanol etc.). Then the solid residues were collected and dried in a vacuum oven at 5 C for 8 h, affording dried FeO(OH) powders which were then weighed. The results showed that FeO(OH) accounted for aout 75 wt% of Fe-N/C-precursor. SI

2 Tale S2. Summary of ORR catalytic activities of Fe-N/C-8 and relevant leading catalysts reported in recent literature of transition metal/caron materials in.1 M KOH (electrode rotating speed 16 rpm) Materials Catalyst loading (mg/cm2) Onset potential (V vs RHE) Current density at (.45 V vs RHE) (ma/cm2) Electron transfer numer or H 2 O 2 yield% (at.7v vs RHE) Reference Fe-N/C This work (N-Fe-co-doped caron lack) Adv. Mater. 213, 25, PDMC J. Am. Chem. Soc. 213, 135, 7823 Fe-N/C J. Am. Chem. Soc. 214, 136, GNC-Co.4 55 mv negative to Pt/C Angew. Chem. Int. Ed. 213, 52, CoP-CMP Adv. Mater. 214, 26, Fe3C/C Ca. 3.8 Unknow Angew. Chem. Int. Ed. 214, 53, N-doped Fe/Fe3C@C/RGO.7.91 Ca ~3.52 Adv. Energy Mater. 214, SI

3 5 nm Figure S1. Representative SEM image of Fe-N/C-precursor showing the sheet-like morphology. Figure S2. (a) TEM image of Fe-N/C precursor and () EDS analysis of the area indicated y a red cycle in panel (a). SI

4 Intensity Figure S3. (a) TEM image of Fe-N/C-8, and (-d) EDS analyses on the corresponding areas indicated in panel (a). Fe element can only e oserved on the dark-contrast spots 2 and 3 ut totally asent on spot 1. The signal of Cu originated from the copper grid. Fe-N/C-6 D G I D /I G =.84 Fe-N/C-7 I D /I G =.94 Fe-N/C-8 I D /I G =.91 Fe-N/C-9 I D /I G = Raman shift (cm ) Figure S4. Raman spectra of Fe-N/C-T (T = 6, 7, 8 and 9). SI

5 Intensity (a.u.) Quantity adsored (cm 3 /g STP) (a) (c) 15 Fe-N/C precusor 14 Fe-N/C-6 Fe-N/C () (d) Fe-N/C-9 2 Relative Pressure (P/P ) Figure S5. N 2 adsorption/desorption isotherms of Fe-N/C-precursor, Fe-N/C-6, Fe-N/C-7 and Fe-N/C-9. Fe-N/C-6 Pyrrolic N Graphitic N Pyridinic N Fe-N/C-7 Fe-N/C Binding Energy (ev) Figure S6. High-resolution XPS spectra of the N1s electrons of Fe-N/C-6, Fe-N/C-7 and Fe-N/C-9. The spectra in the three samples can e deconvoluted into three individual peaks at 398. ev, ev and 4.9 ev, which are assigned to pyridinic N, pyrrolic N and graphitic N, respectively. SI

6 Current Density N2 O2 Fe-N/C-6 Fe-N/C-7 2 ma/cm 2 Fe-N/C-8 Fe-N/C-9 Pt/C 1.2 Figure S7. CV curves of Fe-N/C-6, Fe-N/C-7, Fe-N/C-8, Fe-N/C-9 and Pt/C in N 2 -saturated (lack line) and O 2 -saturated (red line).1 M KOH solution at a potential sweep rate of 5 m/s. SI-6

7 a c e g i Fe-N/C-6 Fe-N/C-7 4 rpm 625 rpm 9 rpm 16 rpm 225 rpm Fe-N/C-8 4 rpm 625 rpm 9 rpm 16 rpm 225 rpm Fe-N/C-9 Pt/C 4 rpm 625 rpm 9 rpm 16 rpm 225 rpm 4 rpm 625 rpm 9 rpm 16 rpm 225 rpm 4 rpm 625 prm 9 rpm 16 rpm 225 rpm j /cm 2 ma j /cm 2 ma j /cm 2 ma j /cm 2 ma d j /cm 2 ma f h j /2 /s 1/2 rad / V.2.54 V V.64 V.2.69 V /2 /s 1/2 rad / V.54 V.59 V.64 V.69 V.49 V.54 V.59 V.64 V /2 /s 1/2 rad / /2 /s 1/2 rad / /2 /s 1/2 rad /2.49 V.54 V.59 V.64 V.69 V.49 V.54 V.59 V.64 V.69 V SI-7

8 Figure S8. RRDE curves and K-L plots of (a, ) Fe-N/C-6, (c, d) Fe-N/C-7, (e, f) Fe-N/C-8, (g, h) Fe-N/C-9 and (i, j) commercial Pt/C in O 2 -saturated.1 M KOH at a potential sweep rate of 1 mv/s and electrode-rotation speeds of 4 to 225 rpm. Electron Transfer Numer (n) Electron Transfer Numer (n) a Pt/C Fe-N/C Figure S9. (a) LSV curves of Fe-N/C-8 and Pt/C in an O 2 -saturated.1 M HClO 4 aqueous solution at a potential sweep rate of 1 mv/s and electrode rotation speed of 16 rpm. Catalyst loading 79.6 g/cm 2. () Variation of numer of electron transfer of Fe-N/C-8 and Pt/C with electrode potential. It can e seen that the Fe-N/C-8 catalyst also demonstrated remarkale catalytic activity for ORR in acidic electrolyte solution, with the numer of electron transfer even slightly higher than that of the state-of-art Pt/C catalyst Pt/C Fe-N/C-8 1 a Fe-N/C-8 (.5) Fe-N/C-8 (1.) Fe-N/C-8 (2.) Fe-N/C-8 (5.) Figure S1. (a) LSV curves of Fe-N/C-8 catalysts derived from Fe-N/C-precursors at various FeCl 3 to 2FANI molar ratios (.5, 1., 2. and 5.) in an O 2 -saturated.1 M KOH aqueous solution at a scan rate of 1 mv/s and electrode rotation speed of 16 rpm. () Variation of the numer of electron transfer of corresponding catalysts with electrode potential. One can see that the Fe-N/C-8 catalyst derived from a Fe-N/C-precursor at the FeCl 3 :2FANI ratio of 2. demonstrated the est electrocatalytic activity for ORR in terms of onset potential, diffusion-limiting current density and corresponding electron transfer numer. 4 3 Fe-N/C-8 (1.) Fe-N/C-8 (2.) Fe-N/C-8 (.5) Fe-N/C-8 (5.) SI-8

Traditionally Fe-N/C catalysts are usually prepared y using nitrogen-containing polymers such as polyaniline and polypyrrole as a nitrogen source.

9 Quantity adsored (cm 3 /g STP) dv/dd (cm 3 g nm ) Intensity (a.u.) Intensity (a.u.) Figure S11. (left) A stale solution was formed when 2-fluoroaniline was mixed FeCl 3 in deionized water after 1 min stirring. (Right) A suspension was formed instead with aniline mixed with FeCl 3. Traditionally Fe-N/C catalysts are usually prepared y using nitrogen-containing polymers such as polyaniline and polypyrrole as a nitrogen source. To etter understand the effect of 2-fluoroaniline on the formation of special mesoporous structure in Fe-N/C-8, a comparative experiment was performed. Experimentally, Fe-PANi-precursor (Figure S11) was prepared y following the same protocol for the synthesis of Fe-N/C-precusor except that aniline was used instead of 2-fluoroaniline. The precursor was then suject to pyrolysis at 8 C y following the same method used for the preparation of Fe-N/C-8. The resulting sample was denoted as Fe-PANI-8. a Fe-PANi-8 Fe 3 O 4 PDF#6517 2μm degree) c Adsorpotion Desorption Pore diameter / nm Relative Pressure(P/P ) Binding Energy (ev) Figure S12. (a) SEM image showing the formation of polyaniline fiers (red dashed cycle), () XRD patterns, (c) N 2 adsorption/desorption isotherms and pore size distriution (insert), (d) XPS d C1s N1s O1s Fe2p Fe-PANi-8 SI-9

10 survey of Fe-PANI-8. SEM measurements (Figure S12a) show sheet-like and fier-like structures of Fe-PANI-8 catalyst. XRD analysis (Fig S12) indicates Fe 3 O 4 crystals were formed in Fe-PANI-8. N 2 adsorption/desorption isotherm (Fig S12c) display a BET surface area of m 2 /g with pore diameters in the range of 25 to 5 nm. XPS measurements (Figure S12d) shows that the elemental contents are at% of C, 2.17 at% of N, and.36 at% of Fe in Fe-PANi-8 sample a N O Fe-PANi Fe-N/C-8 Fe-PANi Fe-PANi-8 4 rpm 625 rpm 9 rpm 16 rpm 225 rpm c Figure S13. Cyclic voltammetry curves of (a) Fe-PANI-8 in nitrogen- and oxygen-saturated.1m KOH aqueous solution. The scan rate is 5 mv/s. () RRDE curves of () Fe-PANI-8 in oxygen-saturated.1m KOH aqueous solution at different electrode-rotation rates with a scan rate of 1 mv/s. As shown aove (Figure S13a), an ovious peak of O 2 reduction is oserved at +.54 V for Fe-PANI-8 in O 2 -saturated.1 M KOH solution, in comparison to a featureless profile when the solution as saturated with N2. Figure S13 shows the LSVs of Fe-PANI-8 at various rotating speeds. The ORR activity of Fe-PANI-8 was apparently lower than that of Fe-N/C-8 in terms of onset potential and limiting current. Note that the Fe contents in Fe-PANI-8 and Fe-N/C-8 were almost identical at at%, while the nitrogen concentration in Fe-PANI-8 was only 1.77 at%, much lower than that of Fe-N/C-8 (5.79 at%, Tale S1). The BET surface area of Fe-PANI-8 (377.9 m 2 /g) was also much lower than that of Fe-N/C-8 ( m 2 /g). Oviously, Figure S13 shows that whereas the two catalysts were prepared y the same way other than using aniline to replace 2-fluoroaniline, the ORR activity of Fe-PANI-8 was markedly lower than that of Fe-N/C-8 in terms of onset potential and limiting current. SI

Nitrogen and sulfur co-doped porous carbon derived from human hair as. highly efficient metal-free electrocatalyst for hydrogen evolution reaction

Electronic Supplementary Material (ESI) for Journal of Materials Chemistry A. This journal is The Royal Society of Chemistry 2015 Electronic Supplementary Information Nitrogen and sulfur co-doped porous