Support Information. Porous Boron Carbon Nitride Nanosheets as Efficient Metal-free. Catalysts for the Oxygen Reduction Reaction in Both Alkaline and

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1 Support Information Porous Boron Carbon Nitride Nanosheets as Efficient Metal-free Catalysts for the Oxygen Reduction Reaction in Both Alkaline and Acidic Solutions Jiemin Wang, Jian Hao,, Dan Liu,*, Si Qin, David Portehault, Yinwei Li, Ying Chen and Weiwei Lei*, Institute for Frontier Materials, Deakin University, 75 Pigdons Road, Waurn Ponds, 3216, VIC, Australia s: School of Physics and Electronic Engineering, Jiangsu Normal University, Xuzhou,Jiangsu, , China Sorbonne Universités, UPMC Université Paris 06, CNRS, Collège de France, Laboratoire de Chimie de la Matière Condensée de Paris (LCMCP), 11 place Marcelin Berthelot, F Paris, France

2 Contents: 1. Experimental details. 2. Figure S1. XPS Survey Spectra of the porous BCN nanosheets. 3. Figures S2-S4. TEM, SEM and AFM of the porous BCN nanosheets. 4. Figures S5-S6. Nitrogen adsorption/desorption isotherms and TEM images of BCN nanosheets synthesized without adding P Figures S7. CV curves of BCN nanosheets in N 2 and O 2 saturated solution, (a) in solution, (b) in HClO 4 solution. 6. Figure S8. RDE linear sweep voltammograms (LSV) curves of graphite+bn (mole ratios=6.7:1), pure graphite and BCN at a rotation rate of 1600 rpm and a scan rate of 5mV/s in solution. 7. Table S1-S2. Table S1: comparison of several reported B,N-doped graphene and borocarbonitride nanosheets as ORR catalysts in alkaline conditions. Table S2: Comparison of latest reported carbon materials (metal free and Fe containing) with high ORR performances in acid solutions. 1. Experimental sections (1) Synthesis of BCN nanosheets: All reagents, unless otherwise stated, were obtained from commercial sources (Sigma Aldrich) and were used without further purification. In a typical synthesis, 1g polyving akohol (PVA) was dissolved in 80 C deionized water at first. After it was fully dissolved, 0.46g guanidine carbonate salt was next added in the PVA solution, followed by adding 0.23g boric acid under magnetic stirring to yield gelation. Afterwards, 0.3g poly (ethylene oxide-co-propylene oxide) P123 was introduced as soft template to further crosslink in the polymer gelation. The gel was then cooled to room temperature, dried and grinded. Subsequently, the resultant precursors were loaded in a

3 quartz boat and then annealed at 900 C at a ramp rate of 5 C/min for 3h under N 2 flow. Finally, the fluffy and black BCN powders were collected. (2) Characterization: X-ray powder diffraction (XRD) (PANalytical X'Pert PRO system) was performed with Cu Kα radiation with 2θ ranging from 15 to 60. Fourier Transform Infrared (FTIR) was performed on a Bruker Vertex 70 FTIR with range of 4000 cm cm -1. X-ray photoelectron spectroscopy (XPS) was carried out on an ESCALAB 250 instrument equipped with using non-monochromatised Mg-Ka X-rays as the excitation source. Raman tests were processed on a Renishaw Raman spectrometer with a laser wavelength of nm at room temperature. The sample morphology was characterized by using a Zeiss Supra 55 VP Scanning electron microscopy (SEM). Transmission electron microscopy (TEM) and energydispersive X-ray spectroscopy (EDS) mapping were performed on a JEOL 2100F (operating at 200 kv) apparatus. Nitrogen adsorption and desorption isotherms were processed in a Tristar 3000 apparatus at 77 K. (3) Electrochemical Measurement: The ORR performances of the catalysts were conducted on an electrochemical workstation (Solartron 1470E) with a three-electrode cell. The as-prepared sample was used as work electrode. And the fabrication process could be referenced by our previous work. 1 Generally, 5 mg of BCN powders were dispersed in a solution containing 900 µl ethanol and 100 µl Nafion. Then the mixture solution was further ultrasonicated to achieve a homogenous dark ink. Afterwards, the working electrodes were assembled by dropping a certain amount of ink on a glassy carbon rotating disk electrode (5mm in diameter, from PINE Instruments, USA). The catalyst loading was around 0.30mg/cm 2 on the electrode. In contrast, 1 mg commercial Pt/C (20wt% Pt) catalyst was dispersed in 900 µl ethanol and 100 µl Nafion as well. The electrode was fabricated by the same procedure described above, resulting in a mass loading

4 of 0.1 mg/cm 2. In the alkaline test, was used as electrolyte. And the counter and referenced electrodes were a platinum wire and an Hg/HgO (MMO) electrode, respectively. Cyclic voltammetry (CV) was performed from 0 to 1.2V (vs. RHE) at 50mV/s under N 2 and O 2 atmosphere for 1h separately. Linear-scan-voltammetry (LSV) was measured via RDE at different rotating speeds from 100 to 2500 rpm in an O 2 -saturated electrolyte from 0 to 1.2V (vs. RHE) at a sweep rate of 5 mv/s. Afterwards, the electrode was then scanned in an N 2 - saturated electrolyte under the same conditions for subtracting the background capacitance current. As for the acid tests, the measurement was referenced according to pertinent literature. 2 HClO 4 was employed for both Pt/C and our sample as electrolyte instead of 0.5M H 2 SO 4, which may cause bisulfate adsorption in Pt. And Ag/AgCl electrode was employed as reference electrode. Other procedures in HClO 4 were the same as it was measured in. The converted equation was listed as below: 3 E (vs. RHE) =E (vs. Hg/HgO) pH+0.098, E (vs. RHE) = E (vs. Ag/AgCl) pH The electron-transfer numbers (n) of all the samples at different potentials were calculated according to the Koutecky-Levich equation: 4,5 J -1 =J -1 L +J -1 K =Bω -1/2-1 +J K B=0.2nF C 0 (D 0 ) 2/3 ν -1/6 Where J is the measured current density, J K and J L are the kinetic- and diffusion-limited current densities the ORR, n is the overall number of electrons transferred during the oxygen reduction, F is the Faraday constant (96485C/mol), C 0 is the bulk concentration of oxygen, D 0 is the molecular diffusion coefficient of oxygen. ν is the kinematic viscosity of the electrolyte. The coefficient 0.2 is adopted when the rotating speed is expressed in rpm. (In, C 0 =1.2x10 3 mol/l, D 0 =1.9x10-5 cm 2 /s, ν=0.01cm 2 /s. In HClO 4, C 0 =1.6x10 3 mol/l, D 0 =1.1x10-5 cm 2 /s, ν=0.01cm 2 /s.)

5 Rotating ring-disk electrode (RRDE) measurements were carried out to investigate the electron number path (n) and the hydrogen peroxide yield (%H 2 O 2 ). The disk electrode was scanned at a rate of 5 mv s -1, and the ring electrode potential was set to 1.2 V vs. RHE. The electron transfer number (n) and the hydrogen peroxide yield (%H 2 O 2 ) were achieved by the following equations below: 6 n=4 i d i d +i r /N H 2 O 2 (%) =200 i r /N i d +i r /N x 100% Where id and ir are the disk and ring currents, respectively. N is the ring collection efficiency (~20 %) Figure S1. XPS Survey Spectra of BCN nanosheets.

6 Figure S2. TEM image of the porous BCN nanosheets, the micropores and mesopores could be clearly observed, corresponding to AFM image and the profile of BJH pore size distributions in BET test. Figure S3. Low-magnification SEM image of the porous BCN nanosheets.

7 Figure S4. (a) Lower magnification AFM images of the porous BCN nanosheets, (b) Higher magnification AFM images of the porous BCN nanosheets,(c) The height profiles of BCN nanosheets in Figure S4(b) (black line mark). 4. Figure S5. Nitrogen adsorption/desorption isotherms of BCN nanosheets synthesized without adding P123, the inset shows the corresponding pore size distributions. (BET surface area: 612m 2 g -1, pore volume: 0.37cm 3 g -1 ) Figure S6. TEM images of BCN nanosheets with synthesized without adding P123, (a) Magnification of 200nm, (b) Magnification of 50nm, (c) Magnification of 2nm.

8 5. Figure S7. CV curves of BCN nanosheets in N 2 and O 2 saturated solution, (a) in solution, (b) in HClO 4 solution. 6. The graphite+bn composites are fabricated by uniformly mixing and grinding them with the mole ration of 6.7:1 to mimic the ratio in our BCN sample (B 1 C 6.66 N 1.09 ). Therefore, the results from these materials can distinguish the different effects of isolated BN domains (in graphite+bn) and C-N-B (in BCN nanosheets) on the ORR catalytic performance. The results in Figure S8 indicate that the ORR catalytic performance of pure graphite is better than that of graphite+bn (mole ratio=6.7:1). However, our sample B 1 C 6.66 N 1.09 shows superior catalytic activity indicating that there are many active B-N-C edges in our sample rather than those BN domains which do not form bonding with carbon atoms in the sample of graphite+bn.

9 Figure S8. RDE linear sweep voltammograms (LSV) curves of graphite+bn (mole ratio=6.7:1), pure graphite and BCN at a rotation rate of 1600 rpm and a scan rate of 5mV/s in solution. 7. Table S1. Comparison of several reported B,N-doped graphene and borocarbonitride nanosheets as ORR catalysts in alkaline conditions. Electrocatalysts Electrolyte ORR activity performance /V(vs RHE) Electron transfer RHE) Mass Loading of catalysts Ref. Porous BCN nanosheets E onset E 1/2 : @0.364 ~0.30mg/cm 2 This work BCN graphene E onset: ~0.95 # E 1/2 : # 3.8@ mg Angew.Chem., Int. Ed., 2012, 51, 4209 Two-step B,N doped graphene E onset: ~0.86 # E 1/2 :0.714 # 3.97@0.364 # 0.28mg/cm 2 Angew.Chem., Int. Ed., 2013, 52, 3110 B,N doped-graphene foams E onset: # E 1/2:~0.757 # 3.8@0.464 # Not mentioned Phys.Chem. Chem.Phys.,2013, 15, 1222 One-step B,N selfdoped graphene sheets E onset :0.95 E 1/2: ~0.80 # 4@ mg/cm 2 J. Mater. Chem. A, 2013, 1, 14700

10 N,P,B doped porous nanocarbon-2 E onset: # E 1/2:~0.704 # 3.6@0.364 # ~0.1mg/cm 2 ACS Appl. Mater. Interfaces, 2014, 6, B,N doped graphene frameworks E onset:0.794 # E 1/2 :~0.70 # 4@0.364 # ~0.1mg/cm 2 RSC Adv.,2014, 4, Crumpled B, Nitrogen doped graphite layers E onset:~0.95 # E 1/2 :0.817 # 3.97@0.714 # 0.283mg/cm 2 ACS Nano, 2014,8,3313 B,N-doped graphitic nanosheets E onset :0.95 E 1/2 :~0.80 4@0.7 ~0.2mg/cm 2 Sci.Rep.,2014,4,5 184 ZnO/h-BNC E onset: E 1/2: # 3.8@0.45 Not mentioned RSC Adv., 2015, 5, N,B doped 3D graphene network E onset : # E 1/2:~0.804 # 3.8@0.364 # ~0.1mg/cm 2 Nanoscale,2015, 7, 9394 B,N doped CNF web E onset:0.896 # E 1/2 :0.683 # 3.86@0.064 # ~0.1mg/cm 2 Curr.Appli.Phys., 2015, B,N doped hollow graphene microspheres E onset : ~0.91 E 1/2 :~0.84 4@ mg/cm 2 ACS Appl. Mater. Interfaces, 2015, 7, B,N doped-graphitic carbon/nanodiamond E onset: E 1/2:~ @0.364 # 0.76mg/cm 2 Electrochim.Acta, 2016,194,161 Few-layered Borocarbonitride-1 E onset :~0.9 E 1/2:~ ~4@0.364 # Not mentioned Chem. Asian J., 2014, 9, 838 Mark The approximate potential values referred in the literature, # RHE potentials conversion from the original potentials in the reference. E (vs. RHE) =E (vs. Hg/HgO) pH+0.098, E (vs. RHE) = E (vs. Ag/AgCl) pH+0.24, E (vs. RHE) = E (vs. SCE) pH+0.197,

11 E (vs. RHE) = E (vs. NHE) pH. Table S2. Comparison of latest reported carbon materials (metal-free and Fe-containing) with high ORR performances in acid solutions. Electrocatalysts Electrolyte ORR activity performance /V(vs RHE) Electron transfer RHE)) Mass Loading of catalysts Ref. BCN nanosheets HClO 4 E onset :0.84 E 1/2 : @0.364 ~0.30mg/cm 2 This work N,P doped CNT/graphene nanospheres HClO 4 E onset :0.90 E 1/2 : @0.364 ~0.60mg/cm 2 Adv.Mater.,2016, 23,4606 N,P doped mesoporous carbon foam HClO 4 E onset :0.83 E 1/2 :0.62 ~4@ mg/cm 2 Nature Nanotech., 2015, 10,444 N doped CNT/graphene HClO 4 E onset :~0.81 E 1/2 :~0.61 ~4@ mg/cm 2 Sci.Adv.,2015,1, N doped Carbon Nanosheets 0.5M H 2 SO 4 E onset :0.72 E 1/2 : @ mg Angew.Chem., Int. Ed., 2014, 126, 1596 N doped hierarchically porous carbon 0.5M H 2 SO 4 E onset :0.84 E 1/2 :0.72 ~3.99@ mg/cm 2 Nat. Commun., 2014, 5,4973 S,N co-doped CNT 1M HClO 4 E onset :~0.77 E 1/2 :~ @ mg/cm 2 J. Mater. Chem. A, 2013, 1,14853 N doped CNT/graphene (Containing Fe impurities) HClO 4 E onset :0.89 E 1/2 :0.76 Not mentioned Not mentioned Nature Nanotech., 2012,7, 394 Fe/N doped CNF 0.5M H 2 SO4 E onset :0.84 E 1/2 : @ mg/cm 2 Angew.Chem., Int. Ed., 2015, 54, 8179

12 CNT/FeC Nanoparticle 0.5M H 2 SO4 E onset : E 1/2 :~0.66 ~3.99@ mg/cm J.Am.Chem. Soc., 2015, 137, 1436 Mark The approximate potential values referred in the literature. Reference: (1) Liu, D.; Lei, W.; Portehault, D.; Qin,S.; Chen, Y. J. Mater. Chem. A, 2015, 3, 1682 (2) Garsany, Y.; Baturina,O.A.; Swider,L.; Kocha,S. Anal. Chem., 2010, 82, (3) Yang, W.; Liu, X.; Yue, X,; Jia, J.; Guo, S. J. Am. Chem.Soc. 2015, 137, (4) Liu, X.; Antonietti, M. Adv. Mater. 2013, 25, (5) Shi, Q.; Peng, F.; Liao, S.; Wang, H.; Yu, H.; Liu, Z.; Zhang, B.; Su, D. J. Mater. Chem. A 2013, 1, (6) Yang, J.; Sun, H.; Liang, H.; Ji, H.; Song, L.; Gao, C.; Xu, H. Adv. mater. 2016, 28,