Supplementary Information

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1 Supplementary Information Two-Dimensional Corrugated Porous Carbon-, Nitrogen-Framework/Metal Heterojunction for Efficient Multi-Electron Transfer Processes with Controlled Kinetics Ken Sakaushi,*,, Andrey Lyalin, Satoshi Tominaka, Tetsuya Taketsugu,, Kohei Uosaki,, Center for Green Research on Energy and Environmental Materials, Global Research Center for Environment and Energy based on Nanomaterials Science (GREEN), and WPI International Center for Materials Nanoarchitectonics (MANA), National Institute for Materials Science, 1-1 Namiki, Tsukuba , Japan Department of Chemistry, Faculty of Science, Hokkaido University, Sapporo , Japan *Correspondence should be addressed to K.S. S1

2 Standard Analytical Methods and Details about DFT Figure S1. SEM image of 2DCN on Au Figure S2. Tyndall effect of 2DCN Figure S3. FT-IR spectrum for the bulk C 3 N 4 and 2DCN Figure S4. X-ray diffractometry for the bulk C 3 N 4 with Rietveld analysis Figure S5. Reproduced structures based on a PDF-RMC method Figure S6. The corrugated 2DCN structure and (7 7) unit of Au(111) Figure S7. SEM image of 2DCN/Au after electrochemical measurement Figure S8. Loading dependence of the HER activity Figure S9. Structure of the typical pore in 2DCN on Au(111) Figure S10. LSV curves with different rotating speeds, and KL Plot of Au electrode S3-S5 S6 S7 S8 S9 S10 S11 S12 S13 S14 S15 Figure S11. LSV curves with different rotating speeds and KL Plot of 2DCN/Au electrode S16 Figure S12. Optimized geometry of O * 2 adsorbed on 2DCN/Au(111) Figure S13. Optimized geometry of OOH * adsorbed on 2DCN/Au(111) Figure S14. Optimized geometry of OH * adsorbed on 2DCN/Au(111) Figure S15. Optimized geometry of O * adsorbed on 2DCN/Au(111) Figure S16. C1s XPS spectrum of 2DCN Figure S17. N1s XPS spectrum of bulk g-c 3 N 4 Figure S18. HER Tafel data in a steady state condition Figure S19. Stability test of 2DCN/Au electrode on ORR S17 S18 S19 S20 S21 S22 S23 S24 S2

3 Standard analytical methods The SEM observation was carried out on a field-emission SEM SU8000 (Hitachi) with an accelerating voltage of 5 kv. The X-ray diffractometry was performed on an Altima III (Rigaku) with Cu K α1 radiation source. FT-IR spectrometry was performed on Nicolet Nexsus 4700 (Thermo). AFM observation was carried out on an Agilent 5500 AFM/SPM microscope (Agilent Technologies) with a silicon nitride cantilever (PPP-FM, typical spring constant 2.8 N/m, resonance frequency = 75 khz; Nanosensors). We used Au or HOPG substrate and we dropped 2DCN solution (1 g/l, solvent is MilliQ water) on the substrates. Then, these samples are dried very slowly at 20 degree Celcius. Several illustrations were drawn by VESTA: K. Momma and F. Izumi, "VESTA 3 for three-dimensional visualization of crystal, volumetric and morphology data," J. Appl. Crystallogr., 44, (2011). TEM observation was carried on an atomic resolution analytical electron microscopy JEM-ARM200F (JEOL) with a STEM Cs corrector. The accelerating voltage was 80 kv. The first principle calculations on HER and ORR The calculations are performed using Density Functional Theory (DFT) with the gradient-corrected exchangecorrelation functional of Wu and Cohen (WC) [Z. Wu, R. E. Cohen, Phys. Rev. B: Condens. Matter Mater. Phys. 73, (2006)] as implemented in the SIESTA package [J. M. Soler, E. Artacho, J. D. Gale, A. García, J. Junquera, P. Ordejón, D. Sánchez-Portal, J. Phys.: Condens. Matter 14, (2002)]. The WC functional provides an adequate description of the lattice constants, structures, and surface energies of solids and layered systems such as graphene or hexagonal boron-nitride (h-bn) monolayers deposited on 3d, 4d, and 5d transition-metal surfaces [F. Tran, R. S3

4 Laskowski, P. Blaha, K. Schwarz, Phys. Rev. B: Condens. Matter Mater. Phys. 75, (2007); R. Laskowski, P. Blaha, K. Schwarz, Phys. Rev. B: Condens. Matter Mater. Phys. 78, (2008)]. Double-ζ plus polarization function (DZP) basis sets were used to treat the valence electrons of all atoms, while the core electrons were represented by Troullier-Martins norm-conserving pseudopotentials [N. Troullier, J. L. Martins, Phys. Rev. B: Condens. Matter Mater. Phys. 43, (1991)] Periodic boundary conditions were used for all systems, including free molecules. The Au fcc lattice was optimized using the Monkhorst-Pack [H. J. Monkhorst, J. D. Pack, Special Points for Brillouin-Zone Integrations. Phys. Rev. B 13, 5188 (1976)] 10x10x10 k-point mesh for Brillouin zone sampling. The calculated Au lattice parameter, a = Å, is in excellent agreement with the experimental value of a = Å [A. Maeland, T. B. Flanagan, Can. J. Phys. 42, (1964)]. Optimized lattice of bulk Au was used to construct a four-layer 7 x 7 slab for Au(111), where the bottom two layers were fixed. The periodically replicated slab was separated by a vacuum region of 20 Å. Only the Γ point was used for sampling the Brillouin zone of the slabs because of the large size of the supercell. An energy cutoff of 200 Ry was chosen to guarantee convergence of the total energies and forces. A common energy shift of 10 mev was applied. Self-consistency of the density matrix was achieved with a tolerance of For geometry optimization, the conjugate-gradient approach was used with a threshold of 0.02 ev Å. Further details can be found in our recent works [A. Lyalin, A. Nakayama, K. Uosaki, and T. Taketsugu, Theoretical predictions for hexagonal BN based nanomaterials as electrocatalysts for the oxygen reduction reaction, Phys. Chem. Chem. Phys. 15, (2013); A. Lyalin, A. Nakayama, K. Uosaki, and T. Taketsugu, Functionalization of Monolayer h BN by a Metal Support for the Oxygen Reduction Reaction, J. Phys. Chem. C 117, (2013)] and references therein. In order to model HER we have calculated the free energy diagram for the reaction at equilibrium over 2DCN/Au system. At this condition the initial and the final states of the reaction H + S4

5 + e - ½H 2 remain the same, while energy of the adsorbed intermediate state H * depends on the catalyst. Here, the asterisk denotes that a hydrogen atom adsorbed on the surface. Change in free energy, G * H, is calculated in respect to ½H 2 and includes corrections for the change in zero-point energy (ZPE), E ZPE, and entropy S H of the system as follows: * G H = H f + E ZPE - TS H, where H f is the heat of formation in respect to ½H 2, obtained from our DFT calculations and T = K is the temperature. Details of calculations of E ZPE and S H can be found in our recent work [A. Lyalin, A. Nakayama, K. Uosaki, and T. Taketsugu, Theoretical predictions for hexagonal BN based nanomaterials as electrocatalysts for the oxygen reduction reaction, Phys. Chem. Chem. Phys. 15, (2013); A. Lyalin, A. Nakayama, K. Uosaki, and T. Taketsugu, Functionalization of Monolayer h BN by a Metal Support for the Oxygen Reduction Reaction, J. Phys. Chem. C 117, (2013)] and references therein. As it was discussed in [J. K. Nørskov, T. Bligaard, A. Logadottir, J. R. Kitchin, J. G. Chen, S. Pandelov, and U. Stimming, Trends in the Exchange Current for Hydrogen Evolution, J. Electrochem. Soc (3), J23-J26] and references therein, the HER over the best catalyst should be essentially termo-neutral, i.e. the value * of G H should be as close to zero as possible. Theoretical approaches to model the ORR are described in our recent works [A. Lyalin, A. Nakayama, K. Uosaki, and T. Taketsugu, Theoretical predictions for hexagonal BN based nanomaterials as electrocatalysts for the oxygen reduction reaction, Phys. Chem. Chem. Phys. 15, (2013); A. Lyalin, A. Nakayama, K. Uosaki, and T. Taketsugu, Functionalization of Monolayer h BN by a Metal Support for the Oxygen Reduction Reaction, J. Phys. Chem. C 117, (2013)] and references therein S5

6 Supplementary Figure S1. SEM image of 2DCN on Au S6

7 Supplementary Figure S2. Tyndall effect of 2DCN S7

8 Supplementary Figure S3. FT-IR spectrometry for bulk C 3 N 4 and 2DCN. The Fourier-transform infrared spectrum (FT-IR) confirms the formation of cyameluric nucleus (C 6 N 7 ), which has absorption bands at 1640(vs), 1560(vs), 1450(s), 1410(s), 1320(vs) and 810(vs) cm -1, and the absence of N-H stretching bands around 3500 cm -1 confirms the polymerization. S8

9 Supplementary Figure S4. X-ray diffractometry for bulk C 3 N 4 compared with a simulated pattern based on a hexagonal unit cell. The powder X-ray diffraction pattern shows a small broad peak at 13.1 (d = 6.74 Å), a large broad peak at 27.4 (d = 3.26 Å) and featureless intensities between these peaks. As found in the crystals of C 6 N 7 (NH 2 ) 3 molecules where the spacing between cyameluric rings is 3.21 Å along the stacking direction, the large peak is assignable to intermolecular spacing between stacked cyameluric rings. The first small peak is attributable to the periodicity in the two-dimensional network, because its distance is almost equal to the distance between two amino groups in C 6 N 7 (NH 2 ) 3 molecules, 6.78 Å. The two peaks indicates the stacked two-dimensional networks composed of hexagonally connected cyameluric nucleus, the presence of diffuse pattern between peaks indicate non-hexagonal lattice, namely a lower symmetry. S9

10 Supplementary Figure S5. Reproduced structure of graphitic carbon nitride based on a PDF-RMC method. S10

11 Supplementary Figure S6. Optimized 2DCN structure on the Au(111) surface 7x7 four-layer slab computed with DFT. Carbon atoms are yellow-colored, nitrogen atoms are dark blue and gold atoms are pink. Only the first layer of Au atoms is shown in top view for clarity. Figure A shows optimized structure of 2DCN on Au(111) surface computed within DFT. As can be seen from Figure A1 2DCN on Au(111) remains strongly corrugated. S11

12 Supplementary Figure S7. SEM image of 2DCN/Au after electrochemical measurement. The electrode was treated by CV (from -0.3 to 1.0 V vs. RHE: covering both HER and ORR reactions region) in O 2 -saturated 0.05M H 2 SO 4. S12

13 Supplementary Figure S8. 2DCN loading dependence of HER activity of 2DCN/Au. S13

14 Supplementary Figure S9. Structure of the typical pore in 2DCN on Au(111). This figure shows 3 groups of pyridinic-nitrogen atoms located at the short (1), intermediate (2) and large (3) distances from the metal surface. Blue, yellow, pink balls indicate nitrogen, carbon and Au atoms, respectively. S14

15 Supplementary Figure S10. LSV curves with different rotating speeds (a) and Koutecky-Levich Plot of Au electrode (b). S15

16 Supplementary Figure S11. LSV curves with different rotating speeds (a) and Koutecky-Levich Plot of 2DCN/Au electrode (b). S16

17 Supplementary Figure S12. Optimized geometry of O 2 * adsorbed on 2DCN/Au(111). Distances are given in Angstroms. S17

18 Supplementary Figure S13. Optimized geometries of OOH * adsorbed on 2DCN/Au(111) heterojunction on top of 2DCN layer (a) and on Au(111) surface (b) with G OOH = 1.54 and 1.46 ev, respectively. S18

19 Supplementary Figure S14. Optimized geometry of OH * adsorbed on 2DCN/Au(111) S19

20 Supplementary Figure S15. Optimized geometry of O * adsorbed on 2DCN/Au(111) S20

21 Figure S16. C1s XPS spectrum of 2DCN S21

22 Figure S17. N1s XPS spectrum of Bulk g-c3n4. N1: pyridinic-n. N2: graphitic-n. S22

23 Figure S18. HER Tafel data in a steady state condition. S23

24 Figure S19. Stability test for 2DCN/Au electrode on ORR. We measured ORR with CV with RDE configuration (1600rpm, 50 mv/s) in O2-saturated 0.05 M H2SO4 solution. S24