光催化产氢操作

Highly Selective Ammonia Synthesis from Nitrate with Photocatalytically Generated
Hydrogen on CuPd/TiO2
Miho Yamauchi,1, 2, 3, 4* Ryu Abe,1, 2, 3,Tatsuya Tsukuda,1 Kenichi Kato,3, 4, 5 Masaki Takata 4, 5 1CRC, Hokkaido University, Nishi 10, Kita 21, Kita-ku, Sapporo 001-0021, Japan, 2JST-PRESTO, Sanbancho 5, Chiyoda-ku, Tokyo 102-0075, 3JST-CREST, Sanbancho 5, Chiyoda-ku, Tokyo
102-0075, 4RIKEN SPring-8 Center, 1-1-1 Kouto, Sayo-gn, Hyogo 679-5148, Japan, 5Japan
Synchrotron Radiation Research Institute, 1-1-1 Kouto, Sayo-gun, Hyogo 679-5198, Japan
RECEIVED DATE (automatically inserted by publisher);
yamauchi@cat.hokudai.ac.jp
Experimental details
1. Sample preparation
2. TEM images of CuPd nanoalloys and Pd nanoparticles
3. XRD patterns of CuPd nanoalloys
4. IR spectra of CO adsorbed on CuPd nanoalloys and Pd nanoparticles
5. Photocatalytic hydrogen evolution over CuPd/TiO2, Pd/TiO2 and TiO2
6. Photocatalytic nitrate reduction over CuPd/TiO2 and Pd/TiO2
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Experimental Details
1.Sample preparation
[CuPd nanoalloy]
Copper(II) acetate monohydrate (98%, Sigma-Aldrich) and palladium (II) acetate (99.0%, Wako) were used as purchased. 1.5 mmol of copper acetate and 1.5 mmol palladium acetate were dissolved into a solution containing 250 ml water and 50 ml acetone. 150 mmol of polyvinylpyrrolidone (K30, Wako) was added into the solution and stirred vigorously. 7.5 mmol sodium tetrahydroborate (Wako) dissolved into 5 ml water was poured into the mixed solution which was warmed to 303 K. After addition of the aqueous NaBH4solution, the color of the solution immediately changed to dark brown. Stirring of the solution was continued for 1 hour at the same temperature. The resultant dark brawn colloid was collected by reprecipitation using acetone. The precipitate was washed 3 times with a mixture of 5 ml water and 30 ml acetone. ICP-AES measurement was made using an ICPE-9000 at the OPEN FACILITY, Hokkaido University Sousei Hall. The alloy composition and content were determined to be Cu:Pd = 52:48 and 7.2 wt.%, respectively.
[Pd nanoparticle]
Palladium nanoparticles were synthesized with palladium(II) chloride by ethanol reduction.1 50 ml of a 2 mM aqueous solution of palladium chloride, 1 mmol polyvinylpyrrolidone and 350 ml water were mixed and stirred for 15 min. After sufficient mixing of the metal ion and polyvinylpyrrolidone, 100 ml ethanol was added and the solution refluxed for 3 hours to yield a colloidal solution of Pd nanoparticles. The prepared nanoparticles were collected by evaporating the solvents. The metal content was calculated from the weight balance of starting materials.
[CuPd/TiO2, Pd/TiO2]
Photocatalysts were produced as follows. TiO2(AEROXIDE®, TiO2P25) kindly gifted by Nippon AEROSIL” was used as the oxide support. An aqueous solution of the CuPd nanoalloy containing 45µmol metal atoms was blended into 1 g TiO2P25 powder, to yield a catalyst containing a metal percentage of metal to whole catalyst was 0.37 wt. %. After 15 minutes of ultrasonification and filtration of the mixture, a gray paste was obtained. This paste was dried under vacuum at room temperature. A TiO2 supported catalyst containing palladium nanoparticles was prepared in a similar manner such that the molar content of palladium was the same as the CuPd/TiO2 catalyst, i.e., 0.46 wt. %.
[n-Cu-Pd/TiO2]
1.5 mmol of palladium acetate was dissolved into 10 ml acetone and 1g TiO2 added. The mixture was heated in a water bath and stirred until the acetone completely evaporated. The resultant residue was mixed with 10 ml aqueous 1.5 mmol copper acetate solution and again stirred while heating in a water bath until a powdery sample was obtained. This powder was calcined at 623 K for 6 hours and reduced under an H2 gas flow at 723 K for 2 hours.
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2. TEM images of CuPd nanoalloys and Pd nanoparticles
TEM images of the CuPd nanoalloys and Pd nanoparticles were taken with a JEM 2000FX and a JEM 2100, respectively and are shown in Figures S1(a) and (d). The size distributions of the samples were obtained by counting particles. From the TEM image shown in Figure S1(a), CuPd nanoalloys were found to have a moniliform structure. The largest width of each bulge in the sample was taken for the static values of their sizes. Average sizes of the CuPd nanoalloys and Pd nanoparticles were determined to be 5.6±1.7 and 4.3±0.7 nm, respectively. TEM images of the CuPd nanoalloy taken using high magnification are shown in Figures S1(b) and (c). TEM image (b) indicates that the crystallinity of the CuPd nanoalloy is quite low. The image (c) was taken along the [001] zone axis of the center part of the field of vision. The d -spacing of {001} was estimated from 0.61 nm of double d -spacing to be 0.305 nm.
Figure S1. TEM images of the (a) CuPd nanoalloys and (d) Pd nanoparticles with size distributions at the right of the images. TEM images of the CuPd nanoalloys taken under high magnifications are shown in (b) and (c).
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20 nm
(a) 20 nm (d) 2 nm (b) (c)
1 nm
3. XRD patterns of the CuPd nanoalloy
The structure of the CuPd nanoalloy was investigated by XRD using a wavelength of 0.57975(1)Åa t the beam line BL44B2 in the Super Photon Ring (SPring-8). The CuPd nanoalloy was sealed into a φ0.5 of capillary made from borosilicate (W. Muller). Powder XRD patterns were obtained with a 0.01°step in the parallel beam optical system. In Figure S2, the measured patterns of the CuPd nanoalloy sample and of the borosilicate capillary are shown. The borosilicate showed the diffraction intensities in the 2 theta range of 8-35, which agrees with the calculated background curve in the Rietveldt analysis as indicated in Figure 1. Calculated patterns of 2 nm CuPd nanoparticles assuming ordered-B2, disordered-bcc and disordered-fcc type structures are also given in Figure S2. Among the calculated patterns, both the ordered-B2 and disordered-bcc lattices were found to correspond with the observed one.
Figure S2.(a) Powder XRD patterns of the CuPd nanoalloy and (b) the borosilicate capillary. The patterns calculated for 2 nm of CuPd nanoparticles assuming (c) ordered-B2 (lattice const. = 3.05 Å) , (d) disordered-bcc (lattice const. = 3 Å) and (e) disordered-fcc type structures (lattice const. = 3.783 Å)
structures are also described.
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4. IR spectra of CO adsorbed on CuPd nanoalloys and Pd nanoparticles
FTIR spectra of CO molecules adsorbed on the CuPd nanoalloy and Pd nanoparticles in CH2Cl2 solution were measured using an FTIR-4200 system (JASCO) and are shown below. We observed a CO stretching band at the bridging sites of the Pd nanoparticles at 1907 cm-1. On the other hand, stretching bands for CO both at the bridging and on-top sites of CuPd/TiO2 were detected at 1937 and 2100 cm-1, respectively. It was reported that stretching of CO adsorbed at the on-top sites of Cu surface is observed above 2070 cm-1.2 These results suggest that the surface structure of the CuPd nanoalloy is modified from the pure Pd surface and that both metals are homogeneously mixed on the surface.
Figure S4. IR spectra of CO adsorbed on (a) CuPd/TiO2 and (b) Pd/TiO2 in CH2Cl2 solution.
(2) Ghiotti, G; Boccuzzi, F; Chiorino, A, Surf. Sci., 1986, 178, 553-564; Bradley, J. S; Via, G. H; Bonneviot, L; Hill, E. W, Chem. Mater, 1996, 8, 1895-1903.
5. Photocatalytic hydrogen evolution over CuPd/TiO2, Pd/TiO2 and TiO2
The activity of CuPd/TiO2, Pd/TiO2 and TiO2 for photocatalytic hydrogen evolution was studied. 100 mg of the catalyst was suspended in 250 ml of a 10 vol. % aqueous methanol solution using a magnetic stirrer in a Pyrex side-irradiation reaction vessel connected to a closed glass gas circulation system (Makuharirika). The reaction mixtures were evacuated several times to remove air prior to irradiation under a 300 W xenon lamp. The irradiation wavelength was controlled by a cold mirror. The generated hydrogen gas was collected by an automatic gas collecting system and successively quantified by GC-8A gas chromatography (Shimazu).
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6. Photocatalytic nitrate reduction over CuPd/TiO2, Pd/TiO2
The photocatalytic nitrate reduction over CuPd/TiO2, Pd/TiO2and TiO2was studied. 100 mg of the catalyst and 12 or 60 mg of potassium nitrate were added to the in 250 ml of a 10 vol. % aqueous methanol solution, which corresponds to 470 or 2353 µM NO3- solutions, and stirred by magnetic stirrer in a Pyrex side-irradiation reaction vessel connected to a closed glass gas circulation system (Makuharirika). The reaction mixtures were evacuated several times to remove air prior to irradiation under a 300 W xenon lamp. The irradiation wavelength was controlled by a cold mirror. The generated hydrogen and nitrogen gases were detected similarly to the hydrogen evolution experiment. The concentrations of nitrate ions, nitrite ions and ammonia in the resultant solution were investigated by IC-2001 ion chromatography (TOSO) .
Table S1.Reduced concentrations of nitrate ions, [NO3-] int-[NO3-], and concentrations of generated nitrite ions, [NO2-] and ammonia, [NH3], in the reaction solution for 3 hours under UV irradiation and in the dark are tabulated for (a) initial nitrate concentration of 29 and (b) initial nitrate concentration of 145 ppm. Ratios of these amounts obtained under UV irradiation and the dark condition are shown in (c).
(a)
[NO3-] int - [NO3-] / µM [NO2-] / µM [NH3] / µM
dark 402 386 39
UV 470 79 314
(b)
[NO3-] int- [NO3-] / µM [NO2-] / µM [NH3] / µM
dark 1638 1367 71
UV 2216 1201 618
(c)
[NO3-] initial NO3-NO2-NH3
29 ppm (470 µM) 1.2 0.2 8.1
145 ppm (2353 µM) 1.4 0.9 8.7
Reference
1.(a) Teranishi, T; Miyake, M Chem. Mater. 1998, 10, 594-600. (b)Teranishi, T.; Miyake, M. Hyomen
1997, 35, 439.
2.Ghiotti, G; Boccuzzi, F; Chiorino, A, Surf. Sci., 1986, 178, 553-564; Bradley, J. S; Via, G. H;
Bonneviot, L; Hill, E. W, Chem. Mater, 1996, 8, 1895-1903.
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