Supporting Information

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1 Supporting Information Wiley-VCH Weinheim, Germany Surfactant-Free Nonaqueous Synthesis of Plasmonic Molybdenum Oxide Nanosheets with Enhanced Catalytic Activity for Hydrogen Generation from Ammonia Borane under Visible Light** Hefeng Cheng, Takashi Kamegawa, Kohsuke Mori, and Hiromi Yamashita* anie_ _sm_miscellaneous_information.pdf

2 Experimental Section 1.1 Materials Molybdenum metal powder, hydrogen peroxide (H 2 O 2, 30 wt%), ethanol, 1-butanol, 2-propanol, and acetonitrile were purchased from Nacalai Tesque Inc. Commercial MoO 3 was purchased from Wako Pure Chemical Industries. Ammonia borane (NH 3 BH 3 ) was obtained from Sigma-Aldrich Co. All chemical reagents were used without any further purification. 1.2 Synthesis of the plasmonic MoO 3-x nanosheets In a typical synthetic procedure, 2 mmol of molybdenum metal powder was added to a Teflon vessel (45 ml) containing 24 ml of ethanol. Then 3 ml of H 2 O 2 was introduced and magnetically stirred for about 30 min to obtain the transparent yellow solution. The Teflon vessel was then sealed in stainless steel autoclave, heated and maintained at 160 C for 12 h. After cooling down to room temperature naturally, the product was collected by centrifugation, rinsed with ethanol for three times and finally dried at vacuum. Instead of ethanol, some other solvents such as 1-butanol, 2-propanol, and acetonitrile were also used as the solvents to prepare MoO 3-x nanostructures. 1.3 Samples characterization XRD patterns were recorded on a Rigaku RINT2500 diffractometer with Cu Kα radiation (λ = Å). SEM images were obtained on a JSM-6500 field emission microscope (JEOL). TEM images were measured with a Hitachi H-800 electron microscope equipped with an energy dispersive X-ray detector operated at 200 kv. UV Vis NIR diffuse reflectance spectra were collected on a Shimadzu UV 2600 recording spectrophotometer equipped with an integrating sphere at room temperature. The reference was BaSO4 and the absorption spectra were obtained using the Kubelka Munk function. XPS measurements were carried out using a Shimadzu ESCA 3200 photoelectron spectrometer with Mg Kα radiation, and C 1s (284.6 ev) was used to calibrate the peak positions of the elements. Mo K-edge XAFS spectra were measured at room temperature in fluorescence mode at the beam line 01B1 station with an attached Si (311) monochromator at SPring-8, JASRI, Harima, Japan (prop. No. 2013B1041). Normalization and background subtraction of the data was carried out using the Athena software package. Fourier transforms (FT) of k 3 -weighted normalized EXAFS data was performed over the 2.0 Å < k/å 1 < 13 Å range for Mo K-edge sample to obtain the radial structure function. 1.4 Catalytic performances evaluation The catalytic performances of the plasmonic molybdenum oxide nanostructures were measured by dehydrogenation of NH 3 BH 3 in aqueous suspensions at room temperature (25 C). MoO 3-x sample (20 mg) was firstly suspended in 5 ml of distilled water in a test tube. After bubbling with Argon gas for 30 min, NH 3 BH 3 (20 μmol) solution was injected into the suspension through a rubber septum. The reaction was carried out with magnetically stirred in the dark condition, under visible light irradiation (λ > 420 nm, λ > 450 nm) with cutoff filter, by monochromatic light (λ = 440, 480 nm) with band-pass filter, or by red LED lamp illumination (λ max = 650 nm). The amount of H 2 in gas phase was determined on a Shimadzu GC-8A gas chromatograph with MS-5A column by TCD detector.

3 Scheme S1. Schematic illustration of the plausible growth process of the MoO 3-x nanosheets. To understand the growth process of the MoO 3-x nanosheets, a plausible schematic illustration based on intrinsic growth was proposed (Scheme 1). Firstly, pure Mo powder was added the ethanol solution containing 3 ml of H 2 O 2 (30 wt%). After magnetic stirring for about 30 min, the Mo powder was dissolved to result in a transparent yellow solution, with the formation of the solution-soluble precursor compound 1 MoO 2 (OH)(OOH). In this synthetic process, the use of ethanol as the solvent has two important functions: (i) ethanol performs as the reducing agents to reduce MoO 3 into blue MoO 3-x at higher solvothermal temperatures, and (ii) ethanol could abate the violent reaction speed between Mo powder and H 2 O 2 in a mild rate. Then under solvothermal treatments at elevated temperature (160 C), the dissolved yellow Mo-complex would give birth to tiny MoO 3 nuclei by dehydration. In the subsequent growth stage, the crystal structure played a crucial role in determining the morphology of the products. 2 Due to the layered crystal structure of orthorhombic MoO 3, which is comprised of MoO 6 octahedra by sharing edges and corners, the intrinsic anisotropic crystal growth led to the preferential formation of 2D MoO 3 nanosheets. In addition, the stronger reducibility of ethanol enabled MoO 3 to be reduced for the formation of MoO 3-x. Therefore, upon solvothermal treatments for 12 h, well-defined 2D MoO 3-x nanosheets were obtained.

4 Table S1. Influences of solvents, H 2 O 2 volumes and solvothermal temperatures in the tailoring the phase structures, color and the corresponding LSPR peak wavelength of molybdenum oxide nanostructures.

5 Figure S1. (a) XRD patterns and (b d) typical SEM images of the products synthesized under different conditions: (b) 160 C for 12 h with 1 ml of H 2 O 2, (c) 140 C for 12 h with 3 ml of H 2 O 2 and (d) 180 C for 12 h with 3 ml of H 2 O 2. When the amount of H 2 O 2 in the starting materials was reduced to 1 ml while keeping other parameters unchanged (160 C), however, only cubic Mo metal (JCPDS No ) in the shape of micro-sized octahedral and microspheres was obtained after the solvothermal reaction (Figure S1). On the basis of the control experiments, it indicates that the synergistic effect of synthetic temperature and H 2 O 2 amount is crucial to the plasmonic MoO 3-x nanostructures, while too high temperature and too little H 2 O 2 amount are disadvantageous to the formation of plasmonic resonances.

6 Figure S2. (a) XRD patterns and (b) UV Vis NIR diffuse reflectance spectra and (c,d) typical SEM images of the products synthesized in the presence of 1-butanol and 2-propanol, respectively.

7 Figure S3. (a) XRD, (b) SEM image, (c) UV Vis NIR diffuse reflectance spectrum and (d) plots of (αhν) 1/2 versus energy for the hexagonal MoO 3 sample prepared under solvothermal treatment using acetonitrile as the solvent. When the solvent was replaced by acetonitrile, however, only hexagonal MoO 3 (JCPDS No ) micro-rods with length up to 10 μm were obtained. In addition, no LSPR was found on the h-moo 3 micro-rods, which showed strong UV response with the band gap of about 2.94 ev.

8 Figure S4. The average valence states of MoO 3-x and Mo oxide references as a function of the Mo K-edge position and (inset) the feature used to determine the K-edge position. Figure S5. FT-EXAFS spectra for the as-prepared MoO 3-x sample and the Mo oxides references (commercial MoO 3 and MoO 2 ).

9 Figure S6. Comparison of the as-prepared MoO 3-x and reference materials (Ag/SBA-15) 3 for H 2 yield time course from NH 3 BH 3 solution a) in the dark condition and b) under visible light irradiaton (λ > 420 nm). Figure S7. Time course of H 2 evolution from NH 3 BH 3 aqueous solution at room temperature over different samples under visible light irradiation (λ > 450 nm) using Y45 cutoff filter (AGC Asahi Glass Co., Ltd., Japan).

10 Figure S8. The comparison of the initial H 2 yied rate on MoO 3-x in dark conditions (25 and 40 C) and under visible light irradiation (λ > 420 nm). Figure S9. Wavelength-dependent initial H 2 yield rate enhancement of MoO 3-x sample upon irradiation by monochromatic light (λ = 440, 9.5 mw cm 2 and 480 nm, 10.6 mw cm 2 ) and red LED light with λ max = 650 nm (20.5 mw cm 2 ).

11 Figure S10. The comparison of H 2 production activity from NH 3 BH 3 solution in the dark condition and under light irradiation with or without NaHCO 3 (100 μmol) as positive charge scavenger over MoO 3-x samples. Figure S11. Photographs of the commercial MoO 3 suspension in the test tubes: (a) before injection of NH 3 BH 3, (b) after NH 3 BH 3 experiment in the dark condition, and (c) after NH 3 BH 3 experiment under visible light irradiation condition.

12 Figure S12. The three recycling experiments for NH 3 BH 3 dehydrogenation under visible light irradiation over MoO 3-x sample. Figure S13. XRD patterns of (a) fresh prepared and (b) reused MoO 3-x samples after three repeated NH 3 BH 3 dehydrogenation experiments.

13 Figure S14. UV Vis NIR diffuse reflectance spectra of (a) fresh prepared and (b) reused MoO 3-x samples after the recycling NH 3 BH 3 dehydrogenation experiments. References: 1. K. Segawa, K. Ooga, Y. Kurusu, Bull. Chem. Soc. Jpn. 1984, 57, a) S. H. Yu, B. Liu, M. S. Mo, J. H. Huang, X. M. Liu, Y. T. Qian, Adv. Funct. Mater. 2003, 13, 639; b) Z. T. Deng, D. Chen, B. Peng, F. Q. Tang, Cryst. Growth Des. 2008, 8, K. Fuku, R. Hayashi, S. Takakura, T. Kamegawa, K. Mori, H. Yamashita, Angew. Chem. 2013, 125, 7594; Angew. Chem. Int. Ed. 2013, 52, 7446.