Supporting Information

Transcription

1 Supporting Information Sinmyung Yoon,, Kyunghwan Oh,, Fudong Liu,, Ji Hui Seo, Gabor A. Somorjai,, Jun Hee Lee,, * and Kwangjin An, * School of Energy and hemical Engineering, Ulsan National Institute of Science and Technology(UNIST), Ulsan 44919, Republic of Korea Department of hemistry, University of alifornia, Berkeley, A 947, United States hemical Sciences and Materials Sciences Divisions, Lawrence Berkeley National Laboratory, Berkeley, A 947, United States *To whom correspondence should be addressed ( junhee@unist.ac.kr and kjan@unist.ac.kr) 1

2 Preparation of nanoparticles, 15 MnO, Fe3O4, o3o4, 25 u2o, 26 ZnO, 27 TiO2, 28 Fe, 29 and o 29 nanoparticles (NPs) were prepared by reported methods. For the synthesis of NPs via the polyol reduction approach,.4 g of H2l6 xh2o (.1 mmol, Sigma-Aldrich, >99.9%) and.1 g of poly(vinylpyrrolidone) (PVP, MW = 55,) were dissolved into 1 ml of ethylene glycol (EG, Sigma-Aldrich, >99%) in a 5 ml three-neck round bottom flask. 15 The solution was heated to 5 and evacuated at this temperature for min to remove water and oxygen under vigorous magnetic stirring. The flask was then heated to and maintained at this temperature for 1 min under Ar atmosphere. The solution was then cooled to room temperature and an excess of acetone was poured into the solution. Bimetallic Fe and o NPs were synthesized via the same polyol reduction. 29 For example, 4 mg of platinum acetylacetonate ((acac)2, Sigma-Aldrich, >99%) and 26.6 mg of cobalt acetylacetonate (o(acac)2, Sigma-Aldrich, >99%) were mixed with 55 mg of PVP in 5 ml of EG. The reaction proceeded at for 1 min. MnO, Fe3O4, and ZnO NPs were synthesized via the thermal decomposition of metal-oleate complex, The metal-oleate complex was prepared by mixing 4 mmol of metal chloride (1.8 g of Fel3 6H2O, 7.92 g of Mnl2 4H2O, or 5.42 g Znl2) and 1 mmol (36.5 g for Fe(III)-oleate) or 8 mmol (24.36 g for Mn(II)-oleate and Zn(II)-oleate) of sodium oleate (TI 97%) in 8 ml of ethanol, 14 ml of n-hexane, and 6 ml of D.I. water at 6. The upper organic layer containing metal-oleate complex was separated from the bottom water layer containing Nal. The metal-oleate complex was obtained by evaporating solvent by a rotary evaporator. MnO NPs with an average diameter of 6.5 nm were synthesized with 1.24 g of Mn(II)-oleate in 1 g of 1-hexadecane at 28 for 1 h. Fe3O4 NPs with an average diameter of 6. nm were synthesized with 1.8 g of Fe(III)-oleate and.57 g of oleic acid in 1 g of 1-hexadecane (Sigma-Aldrich, >98.5%) at 28 for 1 h. Pyramidal shaped ZnO NPs were synthesized with 1.8 g of Zn(II)-oleate and 9 ml of oleic acid and 3 ml of oleylamine (Sigma-Aldrich, 7%) at 3 for 1 h. 27 o3o4 NPs were synthesized through the hot injection of dicobaltoctacarbonyl (o2(o)8, Sigma-Aldrich, >9%) into hot oleic acid solution. 25 Briefly, 2 ml of o2(o)8 dissolved in dichlorobenzene (Sigma-Aldrich, 99%) was injected into 8 ml of dichlorobenzene in the presence of 2 ml of oleic acid (Sigma-Aldrich, 9%) at 168 and subsequent reaction at the same temperature proceeded for 1 h. o NPs with an average diameter of 6.5 nm was 2

3 produced after washing and centrifugation. When the colloidal o NPs were exposed in air for more than 3 days, o was oxidized to become o3o4 NPs preserving the original size. For u2o NPs with an average diameter of 7.2 nm, 3.7 mm of copper acetate (u(oac)2, Sigma-Aldrich, 98%) was dissolved into 1 ml of 1-butanol (Sigma-Aldrich, 99.4%) in the presence of mm of oleylamine and 23 mm of NaOH, and the mixture was maintained at 14 for 1 h. 26 In order to synthesize TiO2 NPs with controlled shapes, stainless steel autoclave reactor was used for solvothermal reaction. 21,43,48 For typical synthesis of TiO2 with a truncated rhombic shape, 1.7 ml (5 mmol) of titanium n-butoxide (Ti(n-BuO)4, Sigma-Aldrich 97%) was added with 7.1 g (25 mmol) of oleic acid, 6.7 g (25 mmol) oleylamine into 5 ml (1 mmol) of absolute ethanol. After stirring for 1 min, the mixture solution in a 4 ml Teflon cup was transferred into a 1 ml Teflon-lined stainless steel autoclave containing ml of a mixture of ethanol and water. After heating at 18 for 18 h, TiO2 NPs were generated after washing with ethanol. The shape of TiO2 NPs was changed by different molar ratio of Ti(n- BuO)4:oleic acid:oleylamine. When 1:8:2, 1:5:5, and 1:4:6 of Ti(n-BuO)4:oleic acid:oleylamine ratio were introduced, spherical-, concave cube-, and truncated rhombicshaped TiO2 NPs were produced, respectively. 48 TiO2 nanowires with a dimension of approximately 3.4 X 26 nm were prepared by the hot-injection and subsequent thermal decomposition. 43 A stock solution was prepared separately by dissolving.2 M titanium(iv) chloride (Til4, Aldrich, 99. %) and 1. M oleic acid in 1-octadecene. 3 mmol of oleylamine,.48 ml of oleic acid, and 1.2 ml of 1-octadecene were degassed at 1 o for 1 h. Then the pre-heated Til4 stock solution at 6 o was added to the solution and maintained the solution at 29 o for 1 min. Table S1 summarizes the synthetic factors of various NPs. 3

4 Table S1. Detailed information for the synthesis of NPs. Type Size (nm) 2.97 MnO 6.48 Fe 3 O o 3 O u 2 O 7.21 ZnO Fe 2.49 o 6.57 Method Polyol Reduction Thermal Decomposition Thermal Decomposition Thermal Decomposition Thermal Decomposition Thermal Decomposition Polyol Reduction Polyol Reduction Precursor Surfactan t Solvent Reacti on Temp. ( o ) Reacti on Time (min) Solvent for dispersion H2l6 PVP EG 1 ethanol Mn(II)-oleate OA 1-HDE 28 6 n-hexane Fe(III)-oleate OA 1-HDE 28 6 n-hexane o2(o)8 OA ODB n-hexane u(oac)2 OAM butanol 14 6 n-hexane Zn(II)-oleate OA OAM 3 6 n-hexane Fe(acac)2 and (acac)2 o(acac)2 and (acac)2 TiO 2 (Spheres) 4.74 Solvothermal Ti(n-BuO)4 TiO 2 (Rhombuse Solvothermal Ti(n-BuO)4 s) TiO 2 (Wires) 3.4 X 26. Thermal Decomposition TiO 2 (oncave Solvothermal Ti(n-BuO)4 ubes) PVP OA 1 ethanol PVP OA 1 ethanol OA/OA M OA/OA M EtOH n-hexane EtOH n-hexane Til4 OA 1-ODE 29 1 n-hexane OA/OA M EtOH n-hexane Nanoparticle atalysts BN Heater Batch Reactor (1L chamber) O 2 Air He Methanol Turbo Pump G irculation Pump Figure S1. A scheme of a batch-mode gas reactor for catalytic methanol oxidation on layered NP catalysts. 4

5 Atomic Fraction : N: UV treatment time (min) Figure S2. XPS results showing the relative fraction of : and N: for /TiO2 layered catalysts. Results indicate removal of organic surfactants from the NP catalysts by UV photodecomposition as a function of UV treatment time. (a) (b) /ZnO /TiO 2 nm 1 nm Figure S3. TEM images of /oxide layered catalysts: (a) /ZnO and (d) /TiO2. NPs are dispersed on top of pyramidal-shaped ZnO and rod-shaped TiO2 NPs, respectively. 5

6 (a) ±.7 nm (b) 3 MnO 6.48±.9 nm (c) 3 Fe 3 O 4 6.4±.7 nm (d) 3 o 3 O ±.6 nm (e) u 2 O 7.21±1.1 nm (f) ZnO 17.58±1.7 nm (g) (h) (i) 3 Fe 6.57±.6 nm 4 3 o 2.49±.5 nm 3 TiO 2 (Spheres) 4.74±.7 nm (j) TiO 2 (Rhombuses) 13.34±1.7 nm (k) TiO 2 (Wires) 3.4 x 26. nm 4 (l) TiO 2 (oncave ubes) 15.97±2.3 nm Thickness Lengths (nm) Figure S4. Particle size histograms of as-synthesized NPs. Average particle sizes and standard deviations are provided (insets): (a), (b) MnO, (c) Fe3O4, (d) o3o4, (e) u2o, (f) ZnO, (g) Fe, (h) o, (i) TiO2 (Spheres), (j) TiO2 (Rhombuses), (k) TiO2 (Wires), and (l) TiO2 (oncave ubes). 6

7 Intensity (a) MnO (111) () (2) (b) Fe 3 O 4 (2) (311) (4) (422) (511) (44) (311) (222) (533) (c) o 3 O 4 (311) (4) (511) (4) (d) u 2 O (111) () (111) () (e) ZnO (11) (1) (2) (12) (11) (13) (112) () (1) (4) θ Figure S5. XRD patterns of as-synthesized NPs: (a) MnO, (b) Fe3O4, (c) o3o4, (d) u2o, and (e) ZnO. 7

8 Selectivity Table S2. atalytic TOFs and selectivities over /oxide layered NP catalysts in methanol oxidation (1 Torr of MeOH and 5 Torr of O2 with balanced He at 6 o ). For all /oxide catalysts used, the amount of NP colloids was same. TOFs were calculated by the number of sites based on ethylene hydrogenation (11.7 molecules site 1 s 1 ). atalysts TOF (S -1 ) Selectivity (%) O 2 HHO HOOH /MnO /Fe 3 O /o 3 O /u 2 O /ZnO Fe o /TiO 2 (Spheres) /TiO 2 (Rhombuses) /TiO 2 (Wires) /TiO 2 (oncave ubes) % 8% 6% O2 HHO HOOH3 4% % % /Fe Fe3O4 3 O 4 /o oox 3 O 4 Fe o Figure S6. Product selectivity of methanol oxidation over /Fe3O4, /o3o4, Fe, and o NP catalysts, measured in 1 Torr of MeOH and 5 Torr of O2 with balanced He at 6 o. 8

9 TOF(s -1 ) (a) Fe (b) o 1 nm nm (c) (d) :o = 79.8:.2 (wt%) :Fe = 8.4:19.96 (wt%) Figure S7. TEM images (a-b) and EDS mapping data (c-d) of bimetallic (a-c) Fe and (b-d) o NPs. 1 8 O2 HHO HOOH μl 1 μl TiO 2 3 μl TiO 2 1 μl TiO 2 on 1 μl on 1 μl Figure S8. TOFs and selectivities of methanol oxidation over /TiO2 NPs catalysts with different layered structures. The shape of TiO2 NPs is a sphere. 9

10 Intensity (11) (4) () (15) (4) (a) Spheres (b) Rhombuses (c) Wires (d) oncave ubes θ Figure S9. XRD patterns of as-synthesized TiO2 NPs with controlled shapes: (a) spheres, (b) rhombuses, (c) wires, and (d) concave cubes. Figure S1. High-resolution TEM images of NPs attached to either (11) or (1) facet of rhombic TiO2 NPs. 1

11 (a.u.) (a.u.) (a.u.) (a.u.) (a.u.) (a.u.) (a.u.) (a.u.) (a.u.) (a.u.) (a.u.) (a) /MnO : 51% 2+ : 29% 4+ : % (b) /Fe 3 O 4 : 45% 2+ : 32% 4+ : 23% (c) /o 3 O 4 : 46% 2+ : 28% 4+ : 27% (d) /u 2 O : 48% 2+ : 34% 4+ : 18% (e) /ZnO : 5% 2+ : 26% 4+ : 24% (f) Fe : 51% 2+ : 25% 4+ : 24% (g) o : 44% 2+ : 27% 4+ : 29% (h) /TiO 2 (Spheres) : 52% 2+ : 28% 4+ : % (i) /TiO 2 (Rhobuses) : 52% 2+ : 27% 4+ : 21% (j) /TiO 2 (Wires) : 57% 2+ : 26% 4+ : 17% (k) /TiO 2 (oncave ubes) : 51% 2+ : 33% 4+ : 16% Figure S11. XPS of 4f of /oxide NP catalysts: (a) /MnO, (b) /Fe3O4, (c) /o3o4, (d) /u2o, (e) /ZnO, (f) Fe, (g) o, (h) /TiO2 (Spheres), (i) /TiO2 (Rhombuses), (j) /TiO2 (Wires), and (k) /TiO2 (oncave ubes). 11

12 (a) (b) (c) 3.167Å H O 2.17Å H H O O 2.236Å 3.136Å 2.178Å 2.71Å HHO on (111) 2-H : Å, 1-O: 2.17 Å ΔE = E(/HHO) E() E(HHO) HOOH on (111) HOOH 3 on (111) 2-H : Å, 1-O: Å 2-H : Å, 1-O: 2.71 Å, ΔE = E(/HOOH) E() E(HOOH) ΔE = E (/HOOH 3 ) E() E(HOOH 3 ) = ( ) - ( ) = ev = ( ) - ( ) = -.55 ev = ( ) - (-46.9) = -.76 ev Figure S12. Structures of adsorbed (a) HHO, (b) HOOH, and (c) HOOH3 on (111) surfaces and corresponding binding energies. (a) (b) (c) O O2 O1 O2 O1 Ti Ti1 Ti2 Ti1 Ti2 HHO on /TiO 2 (11) HOOH on /TiO 2 (11) HOOH 3 on /TiO 2 (11) Ti-O : 1.871Å, -1: 2.67Å ΔE = E(/TiO 2 -HHO) - E(/TiO 2 ) E(HHO) = ( ) - ( ) = ev Ti1-O2 : 2.258Å, -: 2.5Å, Ti2-O1: 1.955Å ΔE = E(/TiO 2 -HOOH) - E(/TiO 2 ) E(HOOH) = ( ) - ( ) = ev Ti1-O2 : 2.237, -: 2.51, Ti2-O1: ΔE = E(/TiO 2 -HOOH 3 ) - E(/TiO 2 ) E(HOOH 3 ) = ( ) - ( ) = ev Figure S13. Structures of adsorbed (a) HHO, (b) HOOH, and (c) HOOH3 on /TiO2(11) surfaces and corresponding binding energies. 12

13 (a) (b) (c) O O2 O1 O2 1 O1 Ti Ti1 Ti2 Ti1 Ti2 HHO on /TiO 2 (1) HOOH on /TiO 2 (1) HOOH 3 on /TiO 2 (1) Ti-O : 1.834Å, -: 2.31Å ΔE = E(/TiO 2 -HHO) - E(/TiO 2 ) E(HHO) Ti1-O2 : 2.311Å, Ti2-O1: 1.884Å, -: 2.22Å Ti1-O2 : 2.145Å, Ti2-O1: 1.887Å, -: 2.15Å ΔE = E(/TiO 2 -HOOH) - E(/TiO 2 ) E(HOOH) ΔE = E(/TiO 2 -HOOH 3 ) - E(/TiO 2 ) E(HOOH 3 ) E= (-629.2) - ( ) = ev E= (-629.2) - ( ) = -2.3 ev E= (-629.2) - (-45.9) = ev Figure S14. Structures of adsorbed (a) HHO, (b) HOOH, and (c) HOOH3 on /TiO2(1) surfaces and corresponding binding energies. HHO HOOH ΔE = E (-HOOH) - E (-HHO) E(HOOH) + E(HHO) = ( ) ( ) + ( ) (111) E = ev = ev HHO HOOH 3 ΔE = E (-HOOH 3 ) - E (-HHO) E(HOOH 3 ) + E(HHO) = ( ) (-46.9) + ( ) E =.246 ev =.246 ev HOOH HOOH 3 ΔE = E (-HOOH 3 ) - E (-HOOH) E(HOOH 3 ) + E(HOOH) = ( ) (-46.9) + ( ) =.429 ev E =.429 ev Figure S15. alculated formation energies obtained from the difference of the binding energies of HHO, HOOH, and HOOH3 on (111) surface. 13

14 HHO HOOH ΔE = E(/TiO 2 (11)-HOOH) - E(/TiO 2 (11)-HHO) E(HOOH) + E(HHO) = ( ) ( ) + ( ) =.564 ev /TiO 2 (11) E =.564 ev HHO HOOH 3 ΔE = E(/TiO 2 (11)-HOOH 3 ) - E(/TiO 2 (11)-HHO) E(HOOH 3 ) + E(HHO) = ( ) ( ) + ( ) =.47 ev E =.47 ev HOOH HOOH 3 ΔE = E(/TiO 2 (11)-HOOH 3 ) - E(/TiO 2 (11)-HOOH) E(HOOH 3 ) + E(HOOH) = ( ) ( ) + ( ) = -.94 ev E = -.94 ev Figure S16. alculated formation energies obtained from the difference of the binding energies of HHO, HOOH, and HOOH3 on /TiO2(11) surface. HHO HOOH ΔE = E(/TiO 2 (1)-HOOH) - E(/TiO 2 (1)-HHO) E(HOOH) +E(HHO) /TiO 2 (1) = ( ) ( ) + ( ) =.77 ev E =.77 ev HHO HOOH 3 ΔE = E(/TiO 2 (1)-HOOH 3 ) - E(/TiO 2 (1)-HHO) E(HOOH 3 ) +E(HHO) = ( ) (-45.9) + ( ) =.572 ev E =.572 ev HOOH HOOH 3 ΔE = E(/TiO 2 (1)-HOOH 3 ) - E(/TiO 2 (1)-HOOH) E(HOOH 3 ) + E(HOOH) = ( ) (-45.9)+ ( ) = ev E = ev Figure S17. alculated formation energies obtained from the difference of the binding energies of HHO, HOOH, and HOOH3 on /TiO2(1) surface. 14

15 +.437e (a) +.472e (b) H1 (c) H e H e O2 H e +.562e H2 -.21e O -.392e e e H2 O e O e -.558e e +.329e e O e 3.167Å 2.17Å 2.236Å 2.178Å 3.136Å 2.71Å +.153e -.168e -.97e -.9e +.92e -.9e HHO on (111) HOOH on (111) HOOH 3 on (111) HHO HHO on (111) HOOH HOOH on (111) HOOH 3 HOOH 3 on (111) Atom harge Atom harge Atom harge Atom harge Atom harge Atom harge H1.921 H H1.954 H H1.921 H H H H2.44 H H H O O O O H H O O H H O O O O Total Total Total Total Total Total harge Transfer.433 harge Transfer.778 harge Transfer.394 Figure S18. alculated charge transfer from catalyst surfaces to HHO, HOOH, and HOOH3 on (111) surface by the Bader method. 15

16 .4479e.546e H2 (a).494e (b) (c) H1 H1.5371e.7524e.5629e H4 H1 H2 H e.5695e.8388e H e.4942e O e e O e.736 O1 1 O2 O e e Ti e e -.33e Ti2 Ti1 Ti e Ti e -.535e -.695e HHO on /TiO 2 (11) HOOH on /TiO 2 (11) HOOH 3 on /TiO 2 (11) HHO HHO on /TiO 2(11) HOOH HOOH on /TiO 2(11) HOOH 3 HOOH 3 on /TiO 2(11) Atom harge Atom harge Atom harge Atom harge Atom harge Atom harge H1.996 H H1.971 H H1.936 H H2.964 H H2.61 H H2.976 H O O 6.56 O O H3.948 H O O H4.889 H O O O O Total Total Total Total Total Total harge Transfer.719 harge Transfer.799 harge Transfer.818 Figure S19. alculated charge transfer from catalyst surfaces to HHO, HOOH, and HOOH3 on /TiO2(11) surface by the Bader method. 16

17 (a) (b) (c) e +.574e H2 H e H e e e e H e H2 2 H4 H e H e +.656e e O e -.257e O -.156e e O e O2 O e e -.536e -.932e -.417e -.582e -.431e Ti Ti1 Ti2 Ti1 Ti2 HHO on /TiO 2 (1) HOOH on /TiO 2 (1) HOOH 3 on /TiO 2 (1) HHO HHO on /TiO 2(1) HOOH HOOH on /TiO 2(1) HOOH 3 HOOH 3 on /TiO 2(1) Atom harge Atom harge Atom harge Atom harge Atom harge Atom harge H1.97 H H1.943 H H1.948 H H2.935 H H H H H O 6.88 O O O H3.943 H O O H4.949 H O O O O Total Total Total Total Total Total 24.8 harge Transfer.752 harge Transfer.81 harge Transfer.838 Figure S. alculated charge transfer from catalyst surfaces to HHO, HOOH, and HOOH3 on /TiO2(1) surface by the Bader method. 17