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1 Copyright WILEY-VCH Verlg GmH & Co. KGA, Weinheim, Germny, 216. Supporting Informtion for Adv. Mter., DOI: 1.12/dm A Highly Efficient Metl-Free Oxygen Reduction Electroctlyst Assemled from Cron Nnotues nd Grphene Ji Yng, Hiyn Sun, Hiyi Ling, Hengxing Ji, Li Song, Cho Go,* nd Hngxun Xu*

2 Supporting Informtion A Highly Efficient Metl-Free Oxygen Reduction Electroctlyst Assemled from Cron Nnotues nd Grphene Ji Yng, Hiyn Sun, Hiyi Ling, Hengxing Ji, Li Song, Cho Go,* nd Hngxun Xu* J. Yng, Prof. H. Ling, Prof. H. Ji, Prof. L. Song, Prof. H. Xu CAS Key Lortory of Soft Mtter Chemistry Deprtment of Polymer Science nd Engineering Deprtment of Modern Mechnics Deprtment of Mterils Science nd Engineering Ntionl Synchrotron Rdition Lortory University of Science nd Technology of Chin Hefei, Anhui 2326, Chin E-mil: hxu@ustc.edu.cn Dr. H. Sun, Prof. C. Go MOE Key Lortory of Mcromoleculr Synthesis nd Functionliztion Deprtment of Polymer Science nd Engineering Zhejing University Hngzhou, Zhejing 3127, Chin E-mil: chogo@zju.edu.cn

3 Experimentl Section Mterils. Grphite powder (5 um) ws purchsed from Qingdo Henglide Grphite Co., Ltd. Multiwlled Cron Nnotue ws purchsed from Chengdu Orgnic Chemicls Co., Ltd. (Chinese Acdemy of Science). Concentrted H 2 SO 4 (98%), KMnO 4, hydrogen peroxide (3%), concentrted HNO 3 (65%) were purchsed from Sinophrm Chemicl Regent Co., Ltd., nd used s received. Triphenylphosphine (99%) ws purchsed from Sigm-Aldrich. Commercil Pt/C (2 wt%, Johnson Mtthey Compny, HiSPEC 3) ws used in this work for comprison. Argon gs nd NH 3 gs (1% in Ar) were purchsed from Nnjing Specil Gs Fctory Co., Ltd. Synthesis of GOs. Grphene oxides were synthesized ccording to our previous report (Z. Xu, H. Sun, X. Zho, C. Go, Adv. Mter. 213, 25, 188.). Purifiction nd oxidtion of CNTs. Multiwlled CNTs were purified nd oxidized y refluxing in the mixture of concentrted H 2 SO 4 nd HNO 3 (3:1 y volume) for out 2 hours to remove metl residues, nd then collected y repeted centrifuging nd wshing with deionized wter. Assemly of CNTs nd grphene into CGHNs. Aqueous dispersions of oxidized CNTs nd GOs with different mss rtios (totl concentrtion ws 2 mg/ml) were erosolized nd pssed through tue furnce preheted t 35 C to otin CGHNs. Argon ws used s crrier gs nd the flow rte ws set t.8 L/min. A PVDF filter ws plced t the exhust to collect the products. Nitrogen nd phosphorus doping of CGHNs. Nitrogen doping ws ccomplished y nneling s otined CGHNs under NH 3 (1% in Argon) t 5 C for 2 hours. 1 mg of nitrogen doped CGHNs were then immersed into 1 ml triphenylphosphine (2 mg/ml) methnol solution for 24 hours. After drying under vcuum for 3 hours, the dried powder ws nneled under Ar flow in tue furnnce t 8 C for 2 hours to otin the.

4 Chrcteriztion. Scnning electron microscopy (SEM) ws performed on FEI SIRION2 microscope. High-resolution trnsmission electron microscopy (HRTEM) ws conducted on JEM-ARM 2F Atomic Resolution Anlyticl Microscope operting t n ccelerting voltge of 2 kv. Elementl mppings were collected using Gtn GIF Quntum 965 instrument. Powder X-ry diffrction (PXRD) ptterns were otined using Jpn Rigku DMx-γA rottion node X-ry diffrctometer equipped with grphite monochromtized Cu Kα rdition (λ = Å). The N 2 dsorption-desorption experiments were crried out using Micromeritics ASAP 22 instrument. X-ry photoelectron spectroscopy (XPS) mesurements were performed on n X-ry photoelectron spectrometer (Thermo ESCALAB 25). Rmn spectr were tken y LRAM HR spectrometer (HORIBA Scientific) with nm lser excittion. Electrochemicl Mesurements. All electrochemicl mesurements were performed in three-electrode system on PGSTAT32N electrochemicl worksttion (Metrohm Autol). A 5. mm glssy cron rotting disk electrode (PINE Reserch Instrumenttion, USA) served s the sustrte for working electrode. A pltinum foil nd Ag/AgCl (3.5 M KCl) served s the counter nd reference electrodes, respectively. The glssy cron electrode ws polished using.5 um lumin slurry, rinsed with distilled wter, nd then ultrsoniclly treted in wter for 3 s nd wshed with distilled wter efore ech test. To prepre the working electrode, 2 mg of the ctlyst ws dispersed in 1 ml ethnol nd sonicted to get homogeneous ink, followed y dding 1 ul 5% Nfion solution. A certin mount of the ctlyst ink ws drop-csted on the glssy cron electrode nd dried t room temperture (~.3 mg/cm 2 in lkline nd ~.6 mg/cm 2 in cidic solutions, respectively). Electrolyte ws sturted with Ar/O 2 y uling Ar/O 2 prior to the strt of ech experiment for 3 min. A flow of O 2 ws mintined over the electrolyte during the mesurement in order to ensure O 2 sturtion. The cyclic voltmmetry experiments were performed in Ar/O 2 sturted.1 M KOH nd.1 M HClO 4 t room temperture with scn rte of 1 mv/s. RDE tests were performed in O 2 sturted.1 M KOH nd.1 M HClO 4 t room

5 temperture with scn rte of 1 mv/s nd different rottion speeds. For comprison, Pt/C (2 wt%, Johnson Mtthey) ws conducted on the sme electrochemicl tests with loding mount of.1 mg/cm 2. The electron trnsfer numer during ORR ws clculted y Koutecky-Levich eqution: J = J J K = J K B=.62nFC D 2/3 v -1/6 where J is the mesured current density, J K nd J L re the kinetic nd diffusion-limiting current densities, is the ngulr velocity, n is trnsferred electron numer, F is Frdy constnt (96485 C mol -1 ), C is the ulk concentrtion of O 2 (1.2 1 mol cm ), D is the diffusion coefficient of O 2 in.1m KOH nd.1m HClO 4 (1.9 1 cm 2 s -1 ), nd v is the kinetic viscosity of the electrolyte (.1 cm 2 s -1 ). Rotting ring-disk electrode (RRDE) mesurements were crried out to determine the four-electron selectivity. The disk electrode ws scnned t rte of 1 mv s -1, nd the ring electrode potentil ws set to 1.2 V vs. RHE. The hydrogen peroxide yield (%H 2 O 2 ) nd the electron trnsfer numer (n) were clculted y the following equtions: %H = i r i d i r n= i d i d i r where i d nd i r re the disk nd ring currents, respectively. N is the ring current collection efficiency which ws determined to e ~37 %. Zn-ir tteries were tested in home-uilt electrochemicl cell, where ctlysts loded on cron pper (.5 mg/cm 2 ) s the ir cthode nd Zn foil s node in 6 M KOH. Pt/C (2 wt%, Johnson Mtthey) were used for comprison with the sme mss loding. Mesurements were crried out on the s-fricted cell t room temperture with PGSTAT32N (Metrohm Autol) electrochemicl worksttion.

6 Furnce Precursor Argon 1.7MHz Exhust Ultrsonic neulizer Figure S1. Schemtic illustrtion of experimentl setup used in this work. Figure S2. SEM nd HRTEM imges of pure CNT nnospheres (,c,e) nd crumpled

7 grphene nnospheres (,d,f) otined y erosoliztion of oxidized CNTs nd GOs respectively. C 1S O 1S Rw Totl ev C=C ev C-O 288 ev C=O 289 ev O-C=O c Binding Energy (ev) C 1S O 1S d Binding Energy (ev) Rw Totl ev C=C 286 ev C-O 288 ev C=O 289 ev O-C=O Binding Energy (ev) Binding Energy (ev) Figure S3. XPS full scn nd high-resolution C 1s spectr of CGHNs prepred from 1:1 mss rtio of CNT/grphene efore (,) nd fter (c,d) erosol processing. 1-1 s otined H 2 reduced P doped N doped N,P doped M KOH s otined H 2 reduced P doped N doped N,P doped.1 M HClO Figure S4. LSV curves of s-otined CGHNs, H 2 -reduced CGHNs, N-CGHNs, P-CGHNs, nd in ().1 M KOH nd ().1 M HClO 4, respectively. All tests were performed using CGHNs prepred from 1:1 mss rtio of CNT/grphene. Electrode rottion speed, 16 rpm; scn rte, 1 mv/s.

8 Figure S5. SEM imges of synthesized using different mss rtios of CNT/grphene: () :1, () 1:5, (c) 1:1, (d) 5:1, nd (e) 1:. Oxidized CNT/GO mixture CGHNs Oxidized CNT/GO mixture CGHNs c Oxidized CNT/GO mixture CGHNs Thet (degree) d Oxidized CNT/GO mixture CGHNs Thet (degree) e Oxidized CNT/GO mixture CGHNs Thet (degree) Thet (degree) Thet (degree) Figure S6. Powder X-ry diffrction (PXRD) ptterns of the mixtures of oxidized CNTs nd GOs efore erosol processing, CGHNs, nd prepred from different mss rtios of CNT/grphene: () 1:, () 5:1, (c) 1:1, (d) 1:5, nd (e) :1. Figure S7. SEM imges of synthesized using different mss rtios of CNT/grphene fter 3 min soniction in wter: () :1, () 1:5, (c) 1:1, (d) 5:1, nd (e) 1:.

9 c Oxidized CNT/GO mixture CGHNs N,P-CGHNS Oxidized CNT/GO mixture CGHNs Oxidized CNT/GO mixture CGHNs ID/IG=1.4 ID/IG=1.4 ID/IG=1.7 ID/IG=1.2 ID/IG=1.2 ID/IG=1.12 ID/IG=.99 ID/IG=1. ID/IG= Rmn shift (cm -1 ) d Oxidized CNT/GO mixture CGHNs Rmn shift (cm -1 ) e Oxidized CNT/GO mixture CGHNs Rmn shift (cm -1 ) ID/IG=1.3 ID/IG=1.1 ID/IG=1.9 ID/IG=.95 ID/IG=.96 ID/IG= Rmn shift (cm -1 ) Rmn shift (cm -1 ) Figure S8. Rmn spectr of the mixtures of oxidized CNTs nd GOs efore erosol processing, CGHNs, nd prepred from different mss rtios of CNT/grphene: () 1:, () 5:1, (c) 1:1, (d) 1:5, nd (e) :1. C 1S N 1S O 1S C 1S Rw Totl ev C=C 286 ev C-O ev C-N ev C=N 288 ev C=O 289 ev O-C=O 291 ev - * Binding Energy(eV) c N 1S Rw Totl ev pyridinic N ev mine group 4.1 ev pyrrolic N 41.4 ev grphitic N d Binding Energy (ev) P 2p Rw Totl 133 ev P-C 134 ev P-O Binding Energy (ev) Binding Energy (ev) Figure S9. () XPS full scn, () high-resolution C 1s, (c) N 1s, nd (d) P 2p spectr of prepred from 1:1 mss rtio of CNT/grphene.

10 Figure S1. () HRTEM imge of hyrid nnosphere prepred from 1:1 mss rtio of CNT/grphene fter doping with nitrogen nd phosphorus, () corresponding SAED pttern, nd (c-f) corresponding elementl mpping of cron, oxygen, nitrogen nd phosphorus. 15 N,P doped N doped P doped H 2 reduced 4 3 N,P doped N doped P doped H 2 reduced -Z'' (W) 1 -Z'' (W) M KOH Z' (W) Z' (W) Figure S11. High-frequency region of the electrochemicl impednce spectr of CGHNs prepred from 1:1 mss rtio of CNT/grphene t different stges of doping in ().1 M KOH nd ().1 M HClO 4..1 M HClO 4

11 Volume Adsored (cm 3 /g STP) Differentil pore volume (cm 3 /g/nm) Volume dsored (cm 3 /g STP) Differentil pore volume (cm 3 /g/nm) Volume dsored (cm 3 /g STP) Differentil Pore Volume (cm 3 /g/nm) Volume dsored (cm 3 /g STP) Differentil pore volume (cm 3 /g/nm) Volume dsored (cm 3 /g STP) Differentil pore volume (cm 3 /g/nm) CNT/grphene :1 CNT/grphene 1:5-1 CNT/grphene 1:1 CNT/grphene 5:1 CNT/grphene 1: M HClO 4.1 M KOH Figure S12. LSV curves of the prepred from different mss rtios of CNT/grphene in ().1 M KOH nd ().1 M HClO 4. Electrode rottion speed, 16 rpm; scn rte, 1 mv/s. -7 CNT/grphene :1 CNT/grphene 1:5 CNT/grphene 1:1 CNT/grphene 5:1 CNT/grphene 1: 25 2 surfce re=163 m 2 /g c Reltive pressure (P/P) 25 surfce re=189 m 2 /g 2 d Pore dimeter (nm) e Reltive pressure (P/P ) 2 surfce re=194 m 2 /g f Pore dimeter (nm) g Reltive pressure (P/P) 1 surfce re=58 m 2 /g 8 h. 5 1 Pore dimeter (nm) i Reltive pressure (P/P ) 1 surfce re=61 m 2 /g j Pore dimeter (nm) Reltive Pressure (P/P ) Pore dimeter (nm) Figure S13. Nitrogen dsorption-desorption isotherms nd corresponding BJH pore size distriutions of prepred using different mss rtios of CNT/grphene: (,) 1:, (c,d) 5:1, (e,f) 1:1, (g,h) 1:5, nd (i,j) :1..

12 CNT/grphene :1 CNT/grphene 1:5 CNT/grphene 1:1 CNT/grphene 5:1 CNT/grphene 1: CNT/Grphene :1 CNT/grphene 1:5 CNT/grphene 1:1 CNT/grphene 5:1 CNT/grphene 1: -Z'' (W) 6 -Z'' (W) M KOH Z' (W).1 M HClO Z' (W) Figure S14. High-frequency region of the electrochemicl impednce spectr of the prepred from different mss rtios of CNT/grphene in ().1 M KOH nd ().1 M HClO 4..4 O 2 Ar.2 Pt/C O 2 Ar Figure S15. CV curves of () nd () Pt/C in.1 M KOH sturted with Ar nd O 2 respectively Pt/C initil fter 5cycles.1 M KOH

13 Figure S16. Endurnce test of the commercil Pt/C ctlyst for 5 cycles in O 2 -sturted.1 M KOH. Electrode rottion speed, 16 rpm; scn rte, 1 mv/s..5.1 M KOH.1 M KOH + 1 M MeOH M KOH.1 M KOH + 1 M MeOH Pt/C Figure S17. CV curves of () nd () commercil Pt/C ctlyst efore nd fter dding 1 M methnol in.1 M KOH M KOH.1 M KOH + 1 M MeOH Figure S18. LSV curves of the commercil Pt/C ctlyst efore nd fter dding 1 M methnol into.1 M KOH. Electrode rottion speed, 16 rpm; scn rte, 1 mv/s.

14 .4. O 2 Ar.2. Pt/C O 2 Ar M HClO M HClO Figure S19. CV curves of () nd () Pt/C in.1 M HClO 4 sturted with Ar nd O 2 respectively Pt/C initil fter 5 cycles Figure S2. Endurnce test of the commercil Pt/C ctlyst for 5 cycles in O 2 -sturted.1 M HClO 4. Electrode rottion speed, 16 rpm; scn rte, 1 mv/s. 1-1 Pt/C Figure S21. LSV curves of nd the commercil Pt/C ctlyst fter 5

15 cycles in.1 M HClO 4. Electrode rottion speed, 16 rpm; scn rte, 1 mv/s M HClO 4.1 M HClO M MeOH M HClO 4.1 M HClO M MeOH Pt/C Figure S22. CV curves of () nd () commercil Pt/C ctlyst efore nd fter dding 1 M methnol in.1 M HClO M HClO 4.1 M HClO mm KSCN Figure S23. LSV curves of efore nd fter dding 5 mm KSCN into.1 M HClO 4. Electrode rottion speed, 16 rpm; scn rte, 1 mv/s.

16 Voltge (V) 1-1 sol-cryo method hydrotherml method erosol method 1-1 sol-cryo method hydrotherml method erosol method.1 M KOH.1 M HClO Figure S24. LSV curves of N,P-doped CNT/grphene hyrid mterils prepred from 1:1 mss rtio of CNT/grphene using different methods in ().1 M KOH nd ().1 M HClO 4. Electrode rottion speed, 16 rpm; scn rte, 1 mv/s erosol hydrotherml sol-cryo 25 2 erosol hydrotherml sol-cryo Z'' (W) 1 -Z'' (W) Z' (W) Z' (W) Figure S25. Electrochemicl impednce spectr (high-frequency region) of N,P-doped CNT/grphene hyrid mterils prepred from 1:1 mss rtio of CNT/grphene using different methods in ().1 M KOH nd ().1 M HClO Pt/C Time (min) Figure S26. Open circuit voltge mesurements of the Zn-Air tteries with

17 nd commercil Pt/C s the cthode ctlysts.

18 Tle S1. XPS results of the CGHNs efore nd fter erosol processing. CNT : grphene mss rtio efore erosol processing C tom % O tom % 1: : : : : CNT : grphene mss rtio fter erosol processing C tom % O tom % 1: : : : :1 8 2 Tle S2. XPS results of the CGHNs fter doping with N nd P. CNT : grphene mss rtio C tom % O tom % N tom % P tom % 1: : : : :

19 Tle S3. Summry of the reported ORR performnce of metl-free electroctlysts. All ctlysts were tested in.1 M KOH. Ctlyst Ctlyst loding mount (mg/cm 2 ) Onset potentil (Vvs. RHE) Hlf-wve potentil (V vs. RHE) Current density t.2 V(vs. RHE) (ma/cm 2 ) Refs P-doped grphite lyers Angew. Chem. Int. Ed. 211, 5, 3257 P-doped ordered mesoporous crons J. Am. Chem. Soc. 212, 134, N-doped ordered mesoporous cron Angew. Chem. Int. Ed. 21, 49, N-doped cron nnosheets Angew. Chem. Int. Ed. 214, 53, 157 N,S-doped grphene Adv. Mter. 214, 26, 6186 N,P-mesoporous nnocron Nture Nnotech. 215, 1, 444 N-hierrchiclly porous cron Nture Commun. 214, 5, 4973 N-grphene/cron nnotue Smll 214, 1, 2251 Porous cron nnofier J. Am. Chem. Soc. 214, 136, N-grphene quntum dots J. Am. Chem. Soc. 212, 134, 15 B,N-grphene Angew. Chem. Int. Ed. 213, 52, 311 C 3 N 3.7 J. Am. Chem. Soc. 211, 133, 2116 N-holey grphitic cron Adv. Mter. 214, 26, 3315 S-grphene nnopltelets Adv. Mter. 213, 25, 6138 N-cron nnotue rry Science 29, 323, This work

20 Tle S4. Summry of the reported ORR performnce of metl-free nd severl high-performnce Fe-N/C electroctlysts in cidic medi. Ctlyst Ctlyst loding mount (mg/cm 2 ) Medi Onset potentil (V vs. RHE) Hlf-wve potentil (V vs. RHE) Current density t.2 V (vs. RHE) (ma/cm 2 ) Refs N-hierrchiclly porous cron.5.5 M H 2SO Nture Commun. 214, 5, 4973 N-cron spheres.25.5 M H 2SO Adv. Mter. 213, 25, 998 N-mesoporous cron.8.1 M HClO J. Am. Chem. Soc. 211, 133, 26 N-doped cron nnosheets.6.5 M H 2SO Angew. Chem. Int. Ed. 214, 53, 157 N,P-mesoporous nnocron.45.1 M HClO Nture Nnotech. 215, 1, 444 N-CNTs unknown.5 M H 2SO J. Am. Chem. Soc. 21, 132, N-ordered mesoporous cron.31.5 M H 2SO Chem. Mter. 21, 22, 2178 N-doped cron lck (Ketjen).6.5 M H 2SO 4 < J. Phys. Chem. B. 26, 11, 1787 N-doped grphene.5.5 M H 2SO ACS Nno 212, 6, 9541 N-doped cron lck (Ketjen).6.5 M H 2SO J. Power Sources 28, 183, 34 Fe-N-C.1.1 M HClO J. Am. Chem. Soc. 214, 136, 1127 Fe-N-CNF.6.5 M H 2SO Angew. Chem. Int. Ed. 215, 54, M HClO This work