Supporting information for

Transcription

1 Supporting information for Highly Active, Selective and Stable Direct H 2 O 2 Generation by Monodispersive PdAg Nanoalloy Jin Zhang, Bolong Huang, *# Qi Shao, and Xiaoqing Huang * College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Jiangsu, , China. hxq006@suda.edu.cn # Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong SAR, China. bhuang@polyu.edu.hk S1

2 Supplementary Figures Figure S1. TEM images of (a) PdAgS NPs, (b) PdAgM NPs, and (c) PdAgL NPs with corresponding statistics of particle size. Figure S2. XRD patterns of PdAg NPs with different sizes. S2

3 Figure S3. EDS patterns of (a) PdAgS NPs, (b) PdAgM NPs and (c) PdAgL NPs. Figure S4. (ab) STEM images and (c) HRTEM image of PdAgL NPs. (de) STEM images and (f) HRTEM image of PdAgS NPs. S3

4 Figure S5. (a) TEM image and (c) EDS pattern of PdAg1.5 NPs. (b) TEM image and (d) EDS pattern of Pd1.5Ag NPs. (e) XRD patterns of PdAg NPs with different ratios of Pd and Ag. Figure S6. (ab) STEM images and (c) HRTEM image of PdAg1.5 NPs. (de) STEM images and (f) HRTEM image of Pd1.5Ag NPs. S4

5 Figure S7. TEM images of PdAgM NPs/TiO2. Figure S8. TEM images of (a) PdAgM NPs/Al2O3, (b) PdAgM NPs/CeO2, (c) PdAgM NPs/SiO2, and (d) PdAgM NPs/ZrO2. Figure S9. TEM images of (a) PdAgS NPs/TiO2, (b) PdAgM NPs/TiO2, and (c) PdAgL NPs/TiO2. S5

6 Figure S10. TEM images of (a) PdAg1.5 NPs/TiO2 and (b) Pd1.5Ag NPs/TiO2. Figure S11. TEM images of (a) the commercial Pd/C, (b) Ag NPs, and (c) Pd NPs. Figure S12. (a)tem image and (b) SEMEDS pattern of PdAgM/TiO2 after six reaction rounds. Figure S13. XPS curves of (a) Ag 3d for Ag NPs and (b) Pd 3d for Pd NPs. S6

7 Figure S14. Obtained values of U out1 and U out2 for (a) 4d orbital of Pd on the (100) surface of PdAg within fcc lattice. (b) 4d orbital of Ag on the (100) of fccpdag. The crossover feature indicates U out1 U out2 = 0 denotes the fully occupied orbitals of 4d in both Pd and Ag sites on the (100) surface of fcc PdAg. Table S1. Productivity, hydrogenation, and selectivity of H 2 O 2 of different catalysts. Catalyst 20 wt% Pd/C Pertreatment H 2 O 2 Productivity 1 (mol kg cat h 1 ) 3.4 H 2 Conversion (%) H 2 O 2 Hydrogenation 1 (mol kg cat h 1 ) H 2 O 2 Selectivity (%) wt% Ag/TiO wt% Pd/TiO wt%pdags /TiO wt%pdagl /TiO wt%pdagm /TiO wt%pdagm /TiO wt%pdagm /TiO wt%pdag 1.5 M /TiO wt%pd 1.5 AgM /TiO S7

8 Table S2. XPS data of the five different PdAg NPs. Catalysts Ag 3d 5/2 Ag 3d 3/2 Pd 0 3d 5/2 Pd 2+ 3d 5/2 Pd 0 3d 3/2 Pd 2+ 3d 3/2 Pd 0 /at% Pd 2+ /at% Ag/Pd /at% Ag NPs/TiO Pd NPs/TiO PdAgS NPs/TiO PdAgM NPs /TiO PdAgL NPs /TiO Pd 1.5 AgM NPs /TiO PdAg 1.5 M NPs /TiO S8

9 Computational methods: We used the CASTEP code to perform our DFT+U calculations. 1 In this framework, we use the rotationally invariant (Anisimov type) DFT+U functional 2 and the Hubbard U parameter selfconsistently determined for the pseudized Pd4d and Ag4d orbital by our new linear response method when using DFT+U. 38 The geometry optimization used the BroydenFletcherGoldfarb Shannon (BFGS) algorithm through all calculations. The PBE functional was chosen for PBE+U calculations with a kinetic cutoff energy of 750 ev, with the valence electron states expressed in a planewave basis set. The ensemble DFT (EDFT) method of Marzari et al. is used for convergence. 9 The supercell of fccpdag (100) surface model is chosen as with sizes of 108 atoms (i.e. Pd 54 Ag 54 ), and is established with 6layer thick. The vacuum thickness is set to be 15 Å. We only allow the top two layers to be varied freely. The reciprocal space integration was performed using the mesh of with Gammacenteroff, 10 which was selfconsistently selected for total energy minimization. With these special kpoints, the total energy is converged to less than 5.0x10 7 ev per atom. The HellmannFeynman forces on the atom were converged to less than ev/å. As to the pseudopotentials, we know that the normconserving pseudopotentials can reflect allelectron behavior for outer shell valence electrons for Smatrix =1, unlike the ultrasoft pseudopotentials. 11,12 Therefore, the nonlinear core corrected normconserving pseudopotential can provide a better response in DFT+U calculations, especially for the calculations of defects. 4 We note that our method actually provides almost identical values of the U parameter for both normconserving and ultrasoft pseudopotentials. This means that the obtained value has an intrinsic physical meaning for the studied materials. Meanwhile, this will help us to reflect allelectron behavior of the valence electrons especially for the subtle effect of the 4d electrons and outer 5s electrons. The Pd and Ag normconserving pseudopotentials are generated using the OPIUM code in the KleinmanBylander projector form, 13 and the nonlinear partial core correction 14 and a scalar relativistic averaging scheme 15 are used to treat the spinorbital coupling effect. For this treatment, we actually similarly choose nonlinear core correction technique for correcting the valencecore charge density overlapping in such heavy fermions elements. In particular, we treated the (4d, 5s, 5p) states as the valence states of both Pd and Ag atoms. The RRKJ S9

10 method is chosen for the optimization of the pseudopotentials. 16 Prior to abinitio predictions of the Hubbard U on orbitals, the geometries and lattice parameters of all PdAg structural models were optimized using PBE functional calculations. This procedure reduces the computational cost and ensures the reliability of the Hubbard U value obtained by our selfconsistent iterative calculations. We use this procedure before the Hubbard U determination because DFT has been already verified to be reliable for the structural optimization of compound solids even with 4f or 5f orbitals, 17 even with ultrasoft pseudopotentials. This may be due to the welldeveloped pseudopotential technique 4,5,17 and, more importantly, to the fact that the electrons on semicore orbitals have a small influence on the lattice parameters when treated as valence electrons, as shown by the small difference of 35, 18, 19 the DFT and DFT+U calculated lattice parameters. Nevertheless, 35, 18, 19 determined more carefully. the U parameter must be With the above preliminary structure determination, the corresponding electronic structure is further estimated with anisimovtype rotational invariant DFT+U method with CASTEP code. 2 We previously devised a method to abinitially determine the semicore d/f orbital energy in order to further selfconsistently correct the electronic structures from routine firstprinciples calculations. 3, 20 Our work shows that the method is particularly valid for those materials synthesized via the extremely physical or chemical conditions. 3, 20 The Hubbard U parameter has been selfconsistently determined based on our previous developed method. 3, 20 For the all of the electronic states calculations in PdAg models, we use the selfconsistent determination for the U correction on the localized 4d orbitals to correct the onsite Coulomb energy of the electron spurious selfenergy. By that method, the Hubbard U parameters on the halffilled shell of 4d 10 orbitals of Pd is selfconsistently determined to be U d =4.04 ev, and U d =5.58 ev for Ag4d 10. The detail process was refered to the previous work. With our selfconsistently determination process, the onsite Hubbard U parameters for 4d of Pd and Ag sites are obtained respectively. The Hubbard potentials for the Pd4d and Ag4d orbitals have been determined in following Figure S14. Here in the simulation, we define the direction synthesis route is only the (H 2 and O 2 ) or (H and O), without H 2 O participated reactions. To interpret the performance for the experimentally observed direct S10

11 synthesis of H 2 O 2, we simulate the typical reactions towards H 2 O 2, as follows: (H 2 + O 2 ) ( ) free (H 2 + O 2 ) ( ) adsorption 2H + O ( ) 2 2H + 2 ( ) + (O 2 ) H 2 O 2 References 1. S. J. Clark, M. D. Segall, C. J. Pickard, P. J. Hasnip, M. I. J. Probert, K. Refson, and M. C. Payne, Zeitschrift Fur Kristallographie 2005, 220, I. A. Vladimir, F. Aryasetiawan, and A. I. Lichtenstein, J. Phys. Condens. Matter 1997, 9, B. Huang, J. Comput. Chem. 2016, 37, B. Huang, R. Gillen, and J. Robertson, J. Phys. Chem. C 2014, 118, B. Huang, Philosophical Magazine 2014, 94, B. Huang, Solid State Commun. 2016, 230, B. Huang, Solid State Commun. 2016, , B. Huang, Phys. Chem. Chem. Phys. 2016, 18, N. Marzari, D. Vanderbilt, and M. C. Payne, Phys. Rev. Lett. 1997, 79, M. I. J. Probert and M. C. Payne, Phys. Rev. B 2003, 67, P. J. Hasnip and C. J. Pickard, Comput. Phys. Commun. 2006, 174, K. Laasonen, A. Pasquarello, R. Car, C. Lee, and D. Vanderbilt, Phys. Rev. B 1993, 47, L. Kleinman and D. M. Bylander, Phys. Rev. Lett. 1982, 48, S. G. Louie, S. Froyen, and M. L. Cohen, Phys. Rev. B 1982, 26, I. Grinberg, N. J. Ramer, and A. M. Rappe, Phys. Rev. B 2000, 62, A. M. Rappe, K. M. Rabe, E. Kaxiras, and J. D. Joannopoulos, Phys. Rev. B 1990, 41, C. J. Pickard, B. Winkler, R. K. Chen, M. C. Payne, M. H. Lee, J. S. Lin, J. A. White, V. Milman, and D. Vanderbilt, Phys. Rev. Lett. 2000, 85, T. Zacherle, A. Schriever, R. A. De Souza, and M. Martin, Phys. Rev. B 2013, 87, P. R. L. Keating, D. O. Scanlon, B. J. Morgan, N. M. Galea, and G. W. Watson, J. Phys. Chem. C 2011, 116, B. Huang, Phys. Chem. Chem. Phys. 2017, 19, S11