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Scalable water splitting on particulate photocatalyst sheets with a

solar-to-hydrogen energy conversion efficiency exceeding 1%

List of authors

Qian WANG,1,2 Takashi HISATOMI,1,2 Qingxin JIA,1,2 Hiromasa TOKUDOME,2,3

Miao ZHONG,1,2 Chizhong WANG,1 Zhenhua PAN,1 Tsuyoshi TAKATA,4 Mamiko

NAKABAYASHI,5 Naoya SHIBATA,5 Yanbo LI,6 Ian D. SHARP,6 Akihiko KUDO,7

Taro YAMADA,1,2 Kazunari DOMEN1,2,*

Affiliation and full postal address

1 Department of Chemical System Engineering, School of Engineering, The University

of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan

2 Japan Technological Research Association of Artificial Photosynthetic Chemical

Process (ARPChem), 5-1-5 Kashiwanoha, Kashiwa-shi, Chiba 277-8589, Japan

3 Research Institute, TOTO Ltd., 2-8-1 Honson, Chigasaki, Kanagawa 253-8577, Japan

4 Global Research Center for Environment and Energy Based on Nanomaterials

Science (GREEN), National Institute for Materials Science (NIMS), 1-1 Namiki,

Tsukuba-shi, Ibaraki 305-0044, Japan

Scalable water splitting on particulatephotocatalyst sheets with a solar-to-hydrogen

energy conversion efficiency exceeding 1%

SUPPLEMENTARY INFORMATIONDOI: 10.1038/NMAT4589

NATURE MATERIALS | www.nature.com/naturematerials 1

© 2016 Macmillan Publishers Limited. All rights reserved.

http://dx.doi.org/10.1038/nmat4589

2

5 Institute of Engineering Innovation, The University of Tokyo, 2-11-16 Yayoi,

Bunkyo-ku, Tokyo 113-8656, Japan

6 Joint Center for Artificial Photosynthesis, Lawrence Berkeley National Laboratory, 1

Cyclotron Road, Berkeley, CA 94720, United States

7 Department of Applied Chemistry, Tokyo University of Science, 1-3 Kagurazaka,

Shinjuku-ku, Tokyo 162-8601, Japan

*Corresponding author

Professor Kazunari DOMEN

Department of Chemical System Engineering, School of Engineering, The University of

Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan

Tel: +81-3-5841-1148

Fax: +81-3-5841-8838

E-mail: [email protected]


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Supplementary Figure S1 | SEM images for (a) SrTiO3:La,Rh photocatalyst

powder, (b) BiVO4:Mo photocatalyst powder, and (c) Ru-modified

SrTiO3:La,Rh/Au/BiVO4:Mo sheet (top-view). SrTiO3:La,Rh consisted of particles

0.3-0.7 μm in size and BiVO4:Mo consisted of plate-like particles with the clear crystal

habit reflecting the high crystallinity.


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Supplementary Figure S2 | Ru 3p3/2 XPS spectra for SrTiO3:La,Rh powder,

BiVO4:Mo powder, and SrTiO3:La,Rh/Au/BiVO4:Mo sheet. The Ru species were

photodeposited on SrTiO3:La,Rh powder (100 mg) and BiVO4:Mo powder (100 mg) in

aqueous methanol (10 vol%) and NaIO3 (4 mM)1 solutions, respectively, containing 10

μmol of RuCl3·3H2O under Xe lamp (λ > 420 nm). The SrTiO3:La,Rh/Au/BiVO4:Mo

sheet was irradiated using the same light source in a distilled water containing 0.4 μmol

RuCl3·3H2O. The XPS signal of the Ru species deposited on SrTiO3:La,Rh was

deconvoluted into a major peak at 462.2 eV and a small peak at 464.2 eV. These peaks

were attributable to metallic Ru and tetravalent RuO2, respectively.2 The XPS signal of

the Ru species deposited on BiVO4:Mo was deconvoluted into a major peak of

tetravalent RuO2 at 464.2 eV and two peaks at 462.2 eV and 466.5 eV attributable to

metallic Ru and hydrous ruthenium oxide (RuOxHy), respectively.2 The peak

deconvolution suggests that the Ru species deposited on the

SrTiO3:La,Rh/Au/BiVO4:Mo sheet were likely attributable to metallic Ru on

SrTiO3:La,Rh and RuOx on BiVO4:Mo although the difference in the deposition

conditions of the Ru species on the photocatalyst sheet and powders needs to be taken

into account.


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Supplementary Figure S3 | Dependence of overall water splitting activity of

Ru-modified SrTiO3:La,Rh/Au/BiVO4:Mo photocatalyst sheets on annealing

duration. All samples were annealed at 573 K. “w/o” stands for the pristine sample.

The error bars show the standard deviations. The reactions were carried out under Xe

lamp (300 W) illumination (λ > 420 nm) at 288 K and 5 kPa.


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Supplementary Figure S4 | Time courses for overall water splitting on Ru-modified

SrTiO3:La,Rh/Au/BiVO4:Mo sheets without heat treatment (red circles), with

pre-annealing (blue squares), and with annealing at 573 K for 20 min (green

triangles). The reactions were carried out under Xe lamp (300 W) illumination (λ > 420

nm) at 288 K and 5 kPa.


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Supplementary Figure S5 | Effect of annealing on the PEC properties. a,b,

Current-potential curves for (a) SrTiO3:La,Rh/Au and (b) BiVO4:Mo/Au

photoelectrodes before and after annealing at 573 K for 20 min acquired under Xe lamp

(300 W) illumination (λ > 420 nm). SrTiO3:La,Rh/Au electrodes showed a cathodic

photocurrent with an onset potential at +1.2 V vs. reversible hydrogen electrode (RHE).

Compared with the unannealed SrTiO3:La,Rh/Au electrode, the sample annealed at 573

K for 20 min generated almost twice the photocurrent at the water reduction potential (0

V vs. RHE). On the other hand, BiVO4:Mo/Au electrodes showed an anodic

photocurrent. The magnitude of the photocurrent of the BiVO4:Mo/Au electrode is not

comparable to that of previously reported BiVO4 electrodes3,4 because gold has a large

work function and will not form an ohmic contact with n-type semiconductors.5 Note

that the current-potential profiles of SrTiO3:La,Rh/Au and BiVO4:Mo/Au

photoelectrodes were dependent on the scan directions to some extent presumably

because of redox reactions involving the dopants.


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Supplementary Figure S6 | Appearance of gold-deposited SrTiO3:La,Rh and

BiVO4:Mo after annealing. a,b, Photographs of gold-deposited SrTiO3:La,Rh and

BiVO4:Mo after annealing (a) at various temperatures for 20 min and (b) at 573 K for

different times. “w/o” stands for the pristine sample.


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SrTiO3:La,Rh/Au/BiVO4:Mo sheets upon the amounts of RuCl3. The reactions were

carried out under Xe lamp (300 W) illumination (λ > 420 nm) at 288 K and 5 kPa.


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Supplementary Figure S8 | Time course of the water spitting reaction on a

Ru-modified SrTiO3:La,Rh/Au/BiVO4:Mo sheet under simulated sunlight (AM

1.5G). The reaction was carried out at 288 K and 5 kPa.


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Supplementary Figure S9 | Effect of background pressure on photocatalytic water

splitting rate of the SrTiO3:La,Rh/Au/BiVO4:Mo sheets. a-c, Dependence of gas

evolution rates on (a) Ru-loaded, (b) Cr2O3/Ru-loaded, and (c) a-TiO2/Cr2O3/Ru-loaded

SrTiO3:La,Rh/Au/BiVO4:Mo sheets upon the background pressure in the reaction

system. Photodeposition from RuCl3·3H2O (0.2 μmol), K2CrO4 (0.2 μmol), Ti peroxide

(1.3 μmol) and the overall water splitting reaction were carried out under Xe lamp (300

W) illumination (λ > 420 nm) at 288 K.


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Ru-modified SrTiO3:La,Rh/Au/BiVO4:Mo sheets upon the amounts of K2CrO4

added. The reactions were carried out under Xe lamp (300 W) illumination (λ > 420

nm) at 288 K and 5 kPa.


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Supplementary Figure S11 | A top-view SEM image of a printed SrTiO3:La,Rh/Au

colloid (10 wt%)/BiVO4:Mo photocatalyst sheet.


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Supplementary Figure S12 | Structure of a printed SrTiO3:La,Rh/Au colloid (40

wt%)/BiVO4:Mo photocatalyst sheet. a-e, Top-view SEM-EDX elemental mapping

images showing (a) an SEM image with back-scattered electrons, (b) Sr distribution, (c)

Bi distribution, (d) Au distribution, and (e) superimposition of (b-d).


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SrTiO3:La,Rh/Au colloid/BiVO4:Mo printed photocatalyst sheets (6.25 cm2) upon

the weight fraction of gold colloid. The reactions were carried out under Xe lamp (300

W) illumination (λ > 420 nm) at 288 K and 5 kPa.


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Supplementary Figure S14 | XRD patterns for photocatalyst powders. a,

SrTiO3:La,Rh and the reference SrTiO3. b, BiVO4:Mo and the reference BiVO4.

Production of single-phase SrTiO3:La,Rh in the SrTiO3-type structure

(JCPDS-ICDD:35-0734) and BiVO4:Mo in the monoclinic BiVO4 phase

(JCPDS-ICDD:14-0688) was confirmed.


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Supplementary Figure S15 | Diffuse-reflectance spectra for SrTiO3:La,Rh and

BiVO4:Mo powders. SrTiO3:La,Rh had a steep absorption edge intrinsic to SrTiO3 at

around 390 nm and shoulder absorption extending to the visible light region owing to

the impurity levels of trivalent Rh species,6 whilst BiVO4:Mo had a steep absorption

edge typical to monoclinic BiVO4 at 520 nm.7


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SrTiO3:La,Rh/Au/BiVO4:Mo upon the mass ratio of SrTiO3:La,Rh to BiVO4:Mo.

The reactions were carried out under Xe lamp (300 W) illumination (λ > 420 nm) at 288

K and 5 kPa.


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Supplementary Figure S17 | Spatial distribution of the power spectra of the Xe

lamp used. a,b, A 300 W Xe lamp equipped with (a) a cut-off filter ( > 420 nm) and

(b) a band-pass filter ( = 418.6 nm, full width half maximum = 9.5 nm). The spectra

were acquired with the spatial interval of 2 mm from the centre of illumination.


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Supplementary Figure S18 | Power spectra of the standard AM 1.5G (ASTMG 173)

and the solar simulator used.


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Supplementary Table S1 | EDX analysis of BiVO4:Mo with and without annealing.

Samples Molar ratio of Bi/V

Pristine 1.0

Annealed (773 K, 20 min) 1.2

Annealed (573 K, 30 min) 1.1

The turnover number (TON) of the water splitting reaction using a

Cr2O3/Ru-modified SrTiO3:La,Rh/Au/BiVO4:Mo sheet (this discussion refers to

Figure 2 in the main text)

The TON of the water splitting reaction was estimated by the following equation:

TON = the number of reacted electrons in 10 h / the number of chosen atom in the

materials

Assuming that the amount of the SrTiO3:La,Rh and BiVO4:Mo powders on the

photocatalyst sheet is 10 mg each, the TONs for SrTiO3:La,Rh, BiVO4:Mo, Cr, Ru, Rh

and Mo are calculated to be 54, 96, 2.9×104, 1.5×104, 1.4×103 and 1.9×105 at 331 K, by

far higher than unity, which attests the stability of the photocatalyst sheet. The TONs

estimated here are the lower bounds because not all of the atoms are exposed to the

reaction solution and not all of the photocatalyst particles remain on the photocatalyst

sheet.

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