Hydrogen Doped Metal Oxide Semiconductors with Exceptional and Tunable Localized Surface Plasmon Resonances

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1 Supporting Information for Hydrogen Doped Metal Oxide Semiconductors with Exceptional and Tunable Localized Surface Plasmon Resonances Hefeng Cheng,, Meicheng Wen,, Xiangchao Ma, Yasutaka Kuwahara,, Kohsuke Mori,, Ying Dai, Baibiao Huang, *, and Hiromi Yamashita, *,, Division of Materials and Manufacturing Science, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka , Japan Unit of Elements Strategy Initiative for Catalysts & Batteries (ESICB), Kyoto University, Katsura, Kyoto , Japan School of Physics, Shandong University, Jinan , China State Key Laboratory of Crystal Materials, Shandong University, Jinan , China S1

2 Figure S1. Basic structural information of commercial MoO 3 and WO 3 samples. (a and b) (a) XRD pattern, (c) SEM image and (e) typical TEM image of the commercial MoO 3. (b) XRD pattern, (d) SEM image and (f) typical TEM image of the commercial WO 3 sample. Commercial MoO 3 sample belongs to orthorhombic phase (PDF#5-0508). SEM and TEM images reveal its plate morphology, of which the width ranges from around 0.6 to 4.0 µm and thickness of about 200 nm. Additionally, commercial WO 3 is well indexed to monoclinic phase (PDF# ). SEM and TEM images display the particulate morphology of commercial WO 3 in sub-micron scale, and the size starts from one hundred to several hundreds of nanometers. The Brunauer-Emmett-Teller (BET) surface area of MoO 3 and WO 3 are determined to be 1.7 and 4.6 m 2 /g, respectively. S2

3 Figure S2. H 2 TPR plots of (a) the Pd/MoO 3, Au/MoO 3 hybrids and pristine MoO 3, (b) the Pd/WO 3 hybrid and pristine WO 3, (c) the Pd/MoO 3, Pd/WO 3 and Pd/SiO 2 hybrids, and (d) Au/MoO 3 and Au/SiO 2 (without calcination) hybrids. As drawn from the H 2 uptake that is reflected by the TCD signal, pristine MoO 3 and WO 3 react hardly with H 2 below 400 C and 550 C, respectively. The introduction of metals such as Pd is able to decrease the reduction temperature of both MoO 3 and WO 3, of which the reduction peaks shift to lower temperatures in contrast to ones without metals. In the case of MoO 3, Pd and Au metal facilitates the reduction of the MoO 3 support, with two clear reduction peak maxima at around 260 C and 430 C, respectively. These two peaks are attributed to the reduction of MoO 3 to the corresponding MoO 2 sub-oxide, 1 which starts at around 200 C and 240 C, respectively, for Pd/MoO 3 and Au/MoO 3. For WO 3, the TPR reduction peaks shift to lower temperatures in the presence of Pd metal compared to that without Pd. The first TPR peak of Pd/WO 3, which starts around 340 C and reach a maximum at 390 C, is assigned to the reduction of WO 3 to WO 2.9 phase. 2 In order to obtain hydrogen bronzes (H x MoO 3 and H x WO 3 ) and avoid the further reduction into their sub-oxides, S3

4 reduction temperature of Pd/MoO 3 and Au/MoO 3 were kept ranging from RT to 200 C, while it was kept from RT to 300 C for Pd/WO 3. To check the supports effect in the H-spillover process, the Pd/SiO 2 and Au/SiO 2 hybrids were also prepared. In the Pd/SiO 2 hybrid, only a negative peak at 56 C due to the β-pdh decomposition 3 is observed. As Au ions species are easily reduced to Au 0 metal with calcination in air at 300 C, the Au/SiO 2 was not calcined in air prior to H 2 TPR measurement. The TPR peaks at 114 and 140 C in the Au/SiO 2 are attributed the reduction of Au 3+ to Au +, and Au + to Au 0, respectively. No TPR peaks are found in the SiO 2 support, even in the presence of Pd and Au NPs, suggesting the neglectable interplay between noble metal NPs and non-reducible supports. S4

5 Figure S3. (a) UV/vis NIR diffuse reflectance spectra and (b) XRD patterns of the MoO 3 before and after H 2 reduction at 300 C. (c) UV/vis NIR diffuse reflectance spectra and (d) XRD patterns of the WO 3 before and after H 2 reduction at 300 C. S5

6 Figure S4. (a) XRD pattern of the Pd/MoO 3 hybrids upon H 2 reduction at RT. The drop lines show the standard pattern of monoclinic H 1.68 MoO 3 (black, PDF# ). (b) SEM and (c) TEM images of the as-prepared Pd/MoO 3 hybrids upon H 2 reduction at RT. (d) The particle size distribution of Pd NPs in (c). S6

7 Figure S5. (a) UV/vis NIR diffuse reflectance spectra of the Pd/MoO 3 and Pd/SiO 2 hybrids before and after H 2 reduction at room temperature. (b) The absorbance difference between the Pd/MoO 3 and Pd/SiO 2 hybrids after H 2 reduction at room temperature through subtraction of their corresponding UV/vis NIR diffuse reflectance spectra in (a). S7

8 Table S1. Summary of the reported plasmonic doped-semiconductors. Plasmonic Materials Morphology LSPR wavelength (nm) H 1.68 MoO 3 Micro-plates 565 This work Ref. TiO 2-x Nanocrystals ~3400 J. Am. Chem. Soc. 2012, 134, Cu 2-x S Quantum dots 1800 Nat. Mater. 2011, 10, 361. Cu 2-x S Nanodisks 1800 J. Am. Chem. Soc. 2011, 133, Cu 2-x Se Nanocrystals J. Am. Chem. Soc. 2011, 133, CuTe Nanocubes 900 J. Am. Chem. Soc. 2013, 135, Cu x In y S 2 Quantum dots ~1500 Nano Lett. 2014, 14, Cu 3 P Nanoplatelets ~1800 Angew. Chem. Int. Ed. 2013, 52, GeTe Nanoparticles ~2500 Phys. Rev. Lett. 2013, 111, ITO Nanoparticles 1618 >2200 J. Am. Chem. Soc. 2009, 131, Al-doped Nanocrystals >2500 Nano Lett. 2011, 11, ZnO P-doped Si Nanocrystals >2500 Nano Lett. 2013, 13, WO 3-x Nanorods ~900 J. Am. Chem. Soc. 2012, 134, MoO 3-x Nanosheets 900 Chem. Eur. J. 2012, 18, MoO 3-x Nanoflakes 700 Adv. Mater. 2014, 26, MoO 3-x Nanosheets 680 Angew. Chem. Int. Ed. 2014, 53, MoO 3-x Nanoplates 640 Adv. Mater. 2015, 27, S8

9 Table S2. Summary of some reported plasmonic noble metals. Plasmonic Materials Morphology LSPR wavelength (nm) Ref. Au Nanoparticles J. Phys. Chem. B 1999, 103, Au Nanoparticles 550 J. Am. Chem. Soc. 2012, 134, Au Nanorods 760 J. Am. Chem. Soc. 2013, 135, Ag Nanoprisms Nature 2013, 425, 487. Ag Triangular Adv. Mater. 2006, 18, nanoplates Ag Nanocubes Nat. Mater. 2011, 10, 911. Cu Nanoparticles ~565 nm Science 2013, 339, Pd Nanosheets Nat. Nanotechnol. 2011, 6, 28. Au-Ag Nanocages J. Am. Chem. Soc. 2004, 126, Au-Cu Pentacle nanocrystals Nat. Commun. 2014, 5, S9

10 Figure S6. Pd 3d XPS spectra of the Pd/MoO 3 products before and after H 2 reduction at RT. Prior to H 2 reduction, the prepared Pd/MoO 3 hybrid shows less structured peaks, which consists of both Pd 2+ and Pd 0 species. The predominant peaks located at and ev are assigned to Pd 2+ ions, while the peaks at and ev are attributed to metallic Pd 0 species. 4 On the basis of peak area, Pd 2+ accounts the predominant proportion (90%). After H 2 reduction at room temperature, the Pd 3d XPS core level displays well-defined spin-orbit doublet and shifts to lower binding energies (335.2 and ev), which correlates well with metallic Pd 0 species. The results demonstrate that upon H 2 reduction, the Pd 2+ ions were fully reduced to metallic Pd 0 nanoparticles, facilitating H 2 reduction of the MoO 3 support through hydrogen spillover process. S10

11 Figure S7. (a) Pd K-edge XANES and (b) FT-EXAFS spectra for the Pd/MoO 3 products before and after H 2 reduction and the reference materials (Pd foil and H 2 PdCl 4 ). From Figure S5a, the line shape of Pd/MoO 3 resembles that of the H 2 PdCl 4 reference, while the line shape of the Pd/MoO 3 H 2 -RT resembles that of Pd foil reference. It indicated that before H 2 reduction, the Pd species in the Pd/MoO 3 were mainly in the form of Pd 2+, while after H 2 reduction, Pd 2+ was completely transformed into Pd 0. Furthermore, after H 2 reduction, the main peak of the product locates around 2.5 Å in the FT-EXAFS spectra assigned to Pd-Pd bonding 5 is identical to that of Pd foil reference. However, in the product Pd/MoO 3 before H 2 reduction, the predominant peak at around 1.8 Å due to Pd-Cl bonding 6 resemble that of the H 2 PdCl 4 reference, while slight peak at 2.5 Å assigned to Pd-Pd accounts for a small proportion. S11

12 Figure S8. (a) UV/vis NIR diffuse reflectance spectra of Pd/MoO 3 products before and after H 2 reduction at different temperatures. (b) XRD pattern of the Pd/MoO 3 H C product. The drop lines show the standard pattern of monoclinic MoO 2 (black, PDF# ). S12

13 Figure S9. (a) XRD pattern of the Au/MoO 3 H C product. The drop line shows the standard pattern of monoclinic H 1.68 MoO 3 (black, PDF# ). (b) TEM image of the Au/MoO 3 H C product and (inset) the corresponding particle size distribution of Au NPs. (c) Au L III -edge XANES and (d) FT-EXAFS spectra for the Au/MoO 3 products before and after H 2 reduction at 200 C and the reference materials (Au foil and HAuCl 4 ). XRD pattern of the Au/MoO 3 H C product is predominantly assigned to monoclinic H 1.68 MoO 3, and TEM image shows Au NPs with mean sizes of 28 nm on the support material. From Au L III -edge XANES spectra, the line shapes of Au/MoO 3 before and after H 2 at 200 C resemble that of Au foil reference, but differ from that of HAuCl 4. In addition, the main peak of the Au/MoO 3 products before and after H 2 at 200 C locates around 2.5 Å in the FT-EXAFS spectra (Figure S7d) assigned to Au-Au bonding 7 is identical to that of Au foil reference, and no Au-Cl bonding 8 at 2.0 Å in HAuCl 4 reference material is observed. These results confirm that before and after H 2 reduction at 200 C, only metallic Au 0 are present in the Au/MoO 3 products. S13

14 Figure S10. Au 4f XPS spectra of the Au/MoO 3 products before and after H 2 reduction at 200 C. The Au 4f XPS core levels display symmetric doublet in the Au/MoO 3 hybrids before (binding energies at 84.1 and 87.7 ev) and after (binding energies at 84.2 and 87.8 ev) H 2 reduction at 200 C, which correlate well with metallic Au 0 species. 4 The XPS result shows that in both cases of the Au/MoO 3 hybrids before and after H 2 reduction, Au exists in the form of metallic Au NPs. S14

15 Figure S11. (a) UV/vis NIR diffuse reflectance spectra of Au/MoO 3 products before and after H 2 reduction at different temperatures. (b) XRD pattern of the Au/MoO 3 H 2 -RT. The drop line is orthorhombic MoO 3 (PDF#5-0508). (c) XRD pattern of the Au/MoO 3 H C. The drop lines are H 0.34 MoO 3 (PDF# ) and H 0.9 MoO 3 (PDF# ) is orthorhombic MoO 3 (PDF#5-0508). (d) XRD pattern of the Au/MoO 3 H C. The drop line is MoO 2 (PDF# ). Temperature dependence of the plamonic absorption was also observed in the Au/MoO 3 products upon H 2 reduction. Different from Pd/MoO 3, H 2 reduction of Au/MoO 3 at room temperature only leads to an absorption tail lift in the product without structural change of the support. As H 2 reduction temperature increases to 100 C, the Au/MoO 3 H C product shows the wide plasmonic absorption with the peak pinning at around 590 nm. XRD pattern reveals that both orthorhombic H 0.34 MoO 3 (PDF# ) and monoclinic H 0.9 MoO 3 (PDF# ) are present in the products. However, further increase of H 2 reduction temperature to 300 C causes the emergence of MoO 2, thereby leading to the quenching of the plasmonic absorption. S15

16 Figure S12. (a) TEM image of the Pd/WO 3 H 2 -RT product and (inset) the corresponding particle size distribution of Pd NPs. (b) XRD pattern of the Pd/WO 3 product after H 2 reduction at room temperature. The drop line shows the standard pattern for tetragonal H 0.33 WO 3 (PDF# ). S16

17 Figure S13. (a) XRD patterns and (b) UV/vis NIR diffuse reflectance spectra of the Pd/WO 3 products after H 2 reduction at different temperatures. The increase of H 2 reduction temperature from room temperature to as high as 300 C does not change the crystal structure of the support material, which remains the same as H 0.33 WO 3. As no obvious structural variation takes place, plasmonic absorption of H 0.33 WO 3 is thus maintained almost at the same peak wavelength. S17

18 Figure S14. UV/vis NIR diffuse reflectance spectra of the Pd/MoO 3 hybrids using (a) commercial MoO 3 and (b) MoO 3 nanosheets before and after H 2 reduction at different temperatures. (c) SEM image of MoO 3 nanosheets. (d) XRD pattern of the Pd/MoO 3 nanosheets product after H 2 reduction at 200 C for 1 h. The drop line is MoO 2 (PDF# ). Upon H 2 reduction, the Pd/MoO 3 nanosheets H 2 -RT and Pd/MoO 3 nanosheets H C products showed plasmonic absorption at 750 and 675 nm, respectively. However, further increase of H 2 reduction temperature to 200 C caused the emergence of MoO 2. S18

19 Figure S15. (a) The evolution of the optical response of Pd/WO 3 H C product exposed to air for different time periods. (b) XRD pattern of the Pd/WO 3 H C products after exposure in air for 4 h. The drop line shows the standard XRD pattern of monoclinic WO 3 (PDF# ). Upon exposure to ambient air, the hydrogen tungsten bronzes undergo gradual oxidation, with the plasmon bands red shifting to the longer wavelength. After oxidation for 4 h in air condition, plasmon bands disappeared, and XRD pattern shows that the support material was transformed into WO 3 completely. S19

20 Figure S16. (a) The optical response spectra of Pd/MoO 3 H 2 -RT product before and after exposure in air for 24 h. (b) XRD pattern of the Pd/MoO 3 H 2 -RT products after exposure in air for 24 h. The drop line shows the standard XRD pattern of orthorhombic H 0.34 MoO 3 (PDF# ). Upon exposure to ambient air, the hydrogen molybdenum bronzes also undergo gradual oxidation and red-shift of the plasmon band, but at rather lower rate as compared to hydrogen tungsten bronzes. After exposure to air for 24 h, the Pd/MoO 3 H 2 -RT product still shows strong plasmon band in the visible light region, with the peak pinning at around 620 nm. XRD patterns revealed the structure of the support material to be H 0.34 MoO 3 phase, which was transformed from the original H 1.68 MoO 3 after air exposure for 24 h. S20

21 Figure S17. UV/vis NIR diffuse reflectance spectrum of the Pd/MoO 3 sample after H 2 reduction at room temperature. The surface plasmon resonance peak is located at about 565 nm, with a typical line width of 212 nm. S21

22 Figure S18. Top views of the crystal structure configuration of (a) orthorhombic MoO 3 (001) and (b) H 1.68 MoO 3 (001) surface. S22

23 Figure S19. Top views of the crystal structure configuration of (a,b) monoclinic WO 3 (010) and (c,d) H 0.5 WO 3 (001) surface. Figure S20. TDOS and PDOS of (a) pure WO 3 and (b) H 0.5 WO 3. S23

24 Figure S21. Top views of the crystal structure configuration of (a,b) orthorhombic V 2 O 5 (010) and (c,d) H 0.5 V 2 O 5 (010) surface. Figure S22. TDOS and PDOS of (a) pure V 2 O 5 and (b) H 0.5 V 2 O 5. S24

25 Figure S23. (a) XRD pattern of the Pd/V 2 O 5 hybrid upon H 2 reduction at room temperature. The drop lines indicates the standard XRD pattern of hydrogen vanadium oxide bronze (PDF# ). (b) UV/vis NIR diffuse reflectance spectra of Pd/V 2 O 5 products before and after H 2 reduction at room temperature. S25

26 Figure S24. Time-dependent evolution of UV-Vis absorption spectra of reaction solutions without catalysts (a) in the dark and (b) under visible light irradiation (λ > 420 nm). S26

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