Electronic Supplementary Information (SI)

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an Ag/AgCl (saturated KCl solution) reference electrode in an oxygen-free 0.5 M NaClO4 (A) and. Na2SO4 (B) solution. 0. 600 1200 1800 2400 3000 3600. 0. 2.
Electronic Supplementary Information (SI) Exceptional performance of photoelectrochemical water oxidation of single-crystal rutile TiO2 nanorods dependent on the hole trapping of modified chloride Xuliang Zhang, Haiqin Cui, Muhammad Humayun, Yang Qu, Xiaojun Sun*, and Liqiang Jing*

SI-Figures: Figure S1 XRD patterns (A) and UV-vis spectra (B) of different TiO2 samples prepared by varying the concentration of HCl solution used from 0 to 3.0 M. TX indicates the resulting TiO2 unless stated elsewhere, in which T means TiO2 and X is the concentration of used HCl solution. EDX spectroscopy. 100

A

UV-vis DRS ( % )

Intensity (a.u.)

T3.0 T2.5 T2.0 T1.5 T1.0 T0

20

30

40

50

60

2 theta (degree)

70

80

B

80 60

T0 T1.0 T1.5 T2.0 T2.5 T3.0

40 20 0 300

350

400

450

500

550

600

Wavelength (nm)

1

Ti2p

O1s

T3.0

T3.0

T2.5 T2.0 T1.5 T1.0

Intensity (a. u.)

Intensity (a.u.)

Figure S2 XPS spectra of Ti2p (A), O1s (B), and Cl2p (C) of different TiO2 samples.

T2.5 T2.0 T1.5 T1.0

T0

452

456

460

464

T0

468

526

528

530

532

534

536

Binding energy (eV)

Binding energy (eV)

Cl2p

Intensity (a. u.)

T3.0 T2.5 T2.0 T1.5 T1.0 T0

196

198

200

202

204

206

Binding energy (eV)

2

Figure S3 XRD patterns (A) and SEM images (B) of different TiO2 films. A

Intensity (a.u.)

T3.0

T2.5

T1.5 T0

20

30

40

50

60

70

80

2 theta (degree)

Figure S4 I-t curves of T0 and T2.5 samples under illumination. Potentials are measured against an Ag/AgCl (saturated KCl solution) reference electrode in an oxygen-free 0.5 M NaClO4 (A) and Na2SO4 (B) solution. 8

A

in NaClO4

6

T2.5

4 T0

2 0

0

600

1200 1800 2400 3000 3600

Time (s)

Current density (mA / cm2)

Current density (mA/cm2)

8

B

in Na2SO4 T2.5

6 4

T0

2 0

0

600

1200 1800 2400 3000 3600

Time (s)

3

Figure S5 XRD patterns (A), SPS responses in different atmospheres (B), and I-V curves (C) of rutile TiO2 (T0-800) prepared by calcining T0 at 800 ºC. To compare, the T0 is also included here. 

T0-800

Photovoltage (a.u.)

Intensity (a.u.)

A

100% O2 20% O2 N2



T0-800

B

T0

20

30

40

50

60

70

80

2 theta (degree)

Current density (mA / cm2)

3.0

300

350

400

450

500

Wavelength (nm)

C

2.5 2.0

T0 T0-800

1.5 1.0 0.5 0.0 -0.4

0.0

0.4

0.8

1.2

1.6

Potential (V) vs Ag / AgCl

4

Figure S6 XRD patterns (A), XPS spectra of Cl2p (B), SPS responses in different atmospheres (C), and I-V curves (D) of TiO2-Cl-free nanorod (T2.5-treated) treated by the twice hydrothermal process. To compare, the T2.5 is also included here. Potentials are measured against an Ag/AgCl (saturated KCl solution) reference electrode in an oxygen-free 0.5 M NaClO4 solution. The SPS responses in different atmospheres of T2.5 is as taken as the inset. Cl2p

B

T2.5-Cl-free

T2.5

Intensity (a.u.)

Intensity (a.u.)

A

T2.5-Cl free

T2.5

10

20

30

40

50

60

70

196

80

198

Photovoltage (a.u.)

Photovoltage (a.u.)

T2.5 N2 air O2

300

350

400

450

500

Wavelength / nm

O2 Air N2

300

350

400

450

T2.5-Cl-free 500

Wavelength (nm)

550

600

Current density (mA/cm2)

8

C

200

202

204

206

1.2

1.6

Binding energy (eV)

2 theta (degree)

7

D

6

T2.5 T2.5-Cl-free

5 4 3 2 1 0 -0.4

0.0

0.4

0.8

Potential (V) vs Ag / AgCl

5

Figure S7 XRD patterns (A), SPS responses in different atmospheres (B), and I-V curves (C) of H3BO3-modified T2.5 (B-T2.5). Potentials are measured against an Ag/AgCl (saturated KCl solution) reference electrode in an oxygen-free 0.5 M NaClO4 solution. To compare, the T2.5 is also included here. A

B-T2.5

B-T2.5

Photovoltage (a.u.)

Intensity / a.u.

B O2 air N2

T2.5

20

30

40

50

60

70

80

2 theta / degree

Current density (mA / cm2)

8

300

350

400

450

500

Wavelength / nm

C

6

T2.5 H3BO3-modified T2.5

4 2 0 -0.4

0.0

0.4

0.8

1.2

1.6

Potential (V) vs Ag / AgCl

6

Figure S8 XRD patterns (A), DRS spectra (B), Cl2p XPS spectra (C), SPS responses of T0-0.5NaCl in different atmosphere (D), I-V curves (E) and produced O2 amount (F) of different chloride-functionalized anatase TiO2 (T0-XNaCl), in which X indicates the mass of the NaCl added during the modification process. Potentials are measured against an Ag/AgCl (saturated KCl solution) reference electrode in an oxygen-free 0.5 M NaClO4 solution. A

100 B

T0-0.7NaCl T0-0.5NaCl T0-0.3NaCl

UV-vis DRS ( % )

Intensity / a.u.

T0-1.0NaCl

80 60 40 20

T0

20

30

40

50

60

T0 T0-0.3NaCl T0-0.5NaCl T0-0.7NaCl T0-1.0NaCl

0 300

70

350

2 theta (degree)

Cl2p

C

T0-0.3NaCl

T0

200

202

204

300

206

350

O2detector reading (a.u.)

Current density (mA / cm2)

E 3

2

0 -0.4

T0-0.5NaCl T0-0.3NaCl T0-0.7NaCl T0-1.0NaCl T0

0.0

0.4

0.8

550

600

400

450

500

550

600

Wavelength (nm)

Binding energy (eV)

1

500

N2 air O2

Photovoltage (a.u.)

Intensity (a.u.)

T0-0.5NaCl

198

450

D

T0-1.0NaCl T0-0.7NaCl

196

400

Wavelength / nm

1.2

Potential (V) vs Ag / AgCl

1.6

F

80

T0 T0-0.3NaCl T0-0.5NaCl T0-0.7NaCl T0-1.0NaCl

70 60 50 0

200

400

600

800

1000 1200

Time (s)

7

Figure S9 I-V curves (A) and O2 evolution (B) of T2.5-Cl-free. Potentials are measured against an Ag/AgCl (saturated KCl solution) reference electrode in an oxygen-free 0.5 M NaClO4 solution and an oxygen-free 0.5 M NaClO4 / 0.01 M NaCl solution.

14 12 10 8 6 4 2 0

0.0

64

A

with NaCl without NaCl

O2 detector reading (a.u.)

Current density (mA / cm2)

16

0.5

1.0

1.5

Potential (V) vs Ag / AgCl

B

without NaCl with NaCl

60 56 52 48 0

100

200

300

400

500

600

Time (s)

Figure S10 I-V curves under illumination (solid lines) and in the dark (dash lines). Potentials are measured against an Ag / AgCl (saturated KCl) reference electrode in a nitrogen purged 0.5M NaClO4 (aq) solution. (a) T2.5, (b) T2.5-Cl-free, (c) 0.0045M Methanol-T2.5-Cl-free, (d) 0.009M Methanol-T2.5-Cl-free.

Current density (mA/cm2)

14 12 10

d a c b

8 6 4 2 0 -0.4

0.0

0.4

0.8

1.2

1.6

Potential (V) vs Ag / AgCl

8

Figure S11 I-V curves under illumination (solid lines) and in the dark (dash lines) (A) Potentials are measured against an Ag / AgCl (saturated KCl) reference electrode in a nitrogen purged 0.5M NaClO4 (aq) solution,(a) T2.5, (b) T2.5-Cl-free, (c) 2×10-3 Co-P-T2.5-Cl-free, (d) 5×10-3 Co-P-T2.5-Cl-free, (e) 8×10-3 Co-P-T2.5-Cl-free. IPCE value of T0 and T2.5 under 365nm wavelength illumination (B). A

8 6

7 a d c e b

6.72

5

4 2 e d c

0 -0.4

B

6

IPCE (%)

Current density (mA / cm2)

10

0.0

0.4

0.8

1.2

Potential vs Ag / AgCl (V)

b

a

1.6

4 3

2.66

2 1 0

T0

T2.5

Samples

9