Facile synthesis of porous nitrogen-doped holey graphene as an efficient metal-free catalyst for the oxygen reduction reaction

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1 Electronic Supplementary Material Facile synthesis of porous nitrogen-doped holey graphene as an efficient metal-free catalyst for the oxygen reduction reaction Li Qin 1,2,5, Ruimin Ding 1,2, Huixiang Wang 1,2,5, Jianghong Wu 1,2,5, Conghui Wang 1,2,5, Chenghua Zhang 1,3, Yao Xu 4, Liancheng Wang 1,2 (), and Baoliang Lv 1,2 () 1 State Key Laboratory of Coal Conversion, Institute of Coal Chemistry, Chinese Academy of Sciences, Taiyuan , China 2 Key Laboratory of Carbon Materials, Institute of Coal Chemistry, Chinese Academy of Sciences, Taiyuan , China 3 Synfuels China Technology Co. Ltd., Beijing , China 4 State Key Laboratory of Transient Optics and Photonics, Xi'an Institute of Optics and Precision Mechanics, Chinese Academy of Sciences, Xi an , China 5 University of Chinese Academy of Sciences, Beijing , China Supporting information to DOI /s TG-MS Measurement The temperature programmed mass spectra were performed using a quadrupole mass spectrometer (OMIstar GSD 301 O3; Pfeiffer Vacuum D Asslar) coupled to a thermogravimetric analysis (TG, SETARAM SETSYS EVOLUTIO TGA 16/18). 15 mg of fully grinded urea and magnesium acetate tetrahydrate was loaded into the crucible, and then it was transferred into thermogravimetric analysis. Before heating up, high purity Ar gas was fed over 30 min to exhaust oxygen. Then, the thermogravimetric analysis was heated from room temperature to 1,000 C at a heating rate of 5 C min 1 under argon atmosphere (with a constant flow rate of 30 ml min 1 ). A mass range between m/z = 1 64 was monitored by scan mode. A portion of the evolved products was introduced into the mass spectrometer operating in the electron impact ionization mode at 70 ev electron energy. The signals of 18 and 44 in MS spectrums shown in Fig. 5(b) are identified as the released components of H 2 O and CO 2, respectively, while the ion signals of 17 and 28 in MS spectrums can be identified as the released H 3 and CO as they have eliminated the ion fragment current caused by H 2 O and CO 2. Electrochemical equations Equations for the Koutecky Levich plots Address correspondence to Liancheng Wang, wanglc@sxicc.ac.cn; Baoliang Lv, lbl604@sxicc.ac.cn

2 (1) 1/2 J J J J B( ) K D K J nfk ( E) C (2) K f 0 B 0.62nFC D v (3) 2/3 1/6 0 0 where J is the measured current density, J K and J D are the kinetic- and diffusion-limiting current densities, ω is the angular velocity of the rotating disk electrode, n is the number of electrons that is exchanged during the reaction, F is the Faraday constant (96,485 C mol 1 e 1 ), k f is the electron transfer rate constant (at a certain potential E), C 0 is the bulk concentration of O 2, is the kinematic viscosity of the electrolyte and D 0 is the diffusion coefficient of O 2. J K and n can be determined from the intercept and the slope of the plot of J 1 versus ω 1/2, respectively. Since the electrolyte was O 2 saturated 0.1 M KOH in this report, C 0, D 0 and were used as M, cm 2 s 1 and 0.01 cm 2 s 1 [S1]. Equation for four electron selectivity 4ID n ID 200 HO% 2 2 ID (4) (5) where = 0.37 is the current collection efficiency of Pt ring [S2]. Figure S1 (a) and (b) SEM images of PHG.

3 ano Res. Figure S2 (a) (c) TEM images of PHG-600 (a), PHG-800 (b) and PHG-1000 (c), respectively; (d) HRTEM image of PHG Figure S3 (a) and (b) 2 adsorption desorption isotherms and corresponding pore-size distribution of PHG, PHG-800 and PHG Figure S4 (a) C, and O atomic percent of PHG, PHG-600, PHG-800 and PHG (b) Quaternary, pyridinic, pyrrolic, and oxidized contents of different samples. ano Research

4 Figure S5 RRDE tests of the ORR on PHG, PHG-600, PHG-800, PHG-1000 and Pt/C in O 2 -saturated 0.1 M KOH at a rotation speed of 1,600 rpm with a scan rate of 10 mv s 1. Table S1 ORR performances of various -doped carbon metal-free catalysts in 0.1 M KOH Catalysts Loading (mg cm 2 ) E 0 (V) E 1/2 (V) Electron-transfer number n References PHG This work Pt/C This work DC [S2] -MCs T [S3] Meso/micro-PoPD [S4] C-A [S5] G/CF [S6] HP-CFs [S7] CC700/ [S8] AG [S9] G [S10] CM [S11] rgo [S12] G-H 3 H 2 O [S13] G [S14] -graphene [S15] a All potentials initially measured vs. Ag/AgCl electrode were converted to a reversible hydrogen electrode (RHE) scale by adding V [S3]. References [S1] Zhang, Y. J.; Fugane, K.; Mori, T.; iu, L.; Ye, J. H. Wet chemical synthesis of nitrogen-doped graphene towards oxygen reduction electrocatalysts without high-temperature pyrolysis. J. Mater. Chem. 2012, 22, [S2] Wei, W.; Liang, H. W.; Parvez, K.; Zhuang, X. D.; Feng, X. L.; Müllen, K. itrogen-doped carbon nanosheets with size-defined mesopores as highly efficient metal-free catalyst for the oxygen reduction reaction. Angew. Chem., Int. Ed. 2014, 53,

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