1

Electronic Supplementary Information

Metal-Free 2D/2D Heterostructured Photocatalyst of Black Phosphorus/Covalent Triazine-Based Frameworks for Water Splitting and Pollutant Degradation†

Yun Zheng,*a, b, c Yilin Chen,*a Lvting Wang,a Mingyue Tan,a Yingying Xiao,a Bifen Gaoa and

Bizhou Lina

aFujian Key Laboratory of Photoelectric Functional Materials, College of Materials Science

and Engineering, Huaqiao University, Xiamen, Fujian 361021, P. R. China.

E-mail: zheng-yun@hqu.edu.cn; ylchen@hqu.edu.cnbInstitute of Luminescent Materials and Information Display, College of Materials Science and

Engineering, Huaqiao University, Xiamen, 361021, P.R. China.cState Key Laboratory of Photocatalysis on Energy and Environment, College of Chemistry,

Fuzhou University, Fuzhou, Fujian 350116, P. R. China

Electronic Supplementary Material (ESI) for Sustainable Energy & Fuels.This journal is © The Royal Society of Chemistry 2020

2

Experimental

Chemicals

Trifluoromethanesulfonic acid, terephthalonitrile and red phosphorus were purchased from

Aladdin. Ammonia (27.0 wt%), methanol, chloroform, dichloromethane, toluene, acetone,

N-methyl-2-pyrrolidone (NMP), ethanol, rhodamine B (RhB), H2PtCl6·6H2O, triethanolamine,

melamine, KBr, N,N'-dimethyformamide and Na2SO4 were obtained from China Sinopharm

Chemical reagent Co. Ltd. Sn powder and SnI4 were obtained from Alfa Aesar. All regents

were used as received without further purification.

Preparation of black phosphorus

Bulk BP crystal was prepared via a low-pressure transport route according to the

literature.[S1] 0.5 g red phosphorus, 20 mg Sn powder, and 10 mg SnI4 were sealed in

an evacuated Pyrex tube. The tube was heated at 650 °C for 300 min with a ramping

rate of ca. 1.35 °C/min and then the temperature was reduced to 500 °C with a

cooling rate of 0.33 °C/min, followed by a natural cooling process. The crystals was

then collected and washed with hot toluene and acetone for several times to remove

the residual mineralizer. The product was vacuum dried and grounded into powders.

Few-layered BP nanosheets were prepared by exfoliation of BP powders (10 mg) in

NMP (20 mL) via a sonication for 8 h.

Characterization

The scanning emission microscope (SEM) measurements were performed using

Hitachi S4800 Field Emission Scanning Electron Microscope. Transmission electron

microscopy (TEM) was recorded using a FEI TECTFAIG2F20 instrument. N2 adsorption-

desorption isotherms of samples were obtained using a Quantochrome autosorb iQ

instrument at 77 K. X-ray diffraction (XRD) measurements were carried out on a

SmartLa X-ray diffraction analyzer with Cu Ka1 radiation (λ=1.5406 Å). Fourier

transform infrared (FT-IR) spectra were collected with a NICOLET iS 50 FT-IR

spectrometer, and the samples were mixed with KBr at a concentration of ca. 0.2 wt%.

X-ray photoelectron spectroscopy (XPS) was performed on a Thermo ScientificTM K-

AlphaTM+ spectrometer equipped with a monochromatic Al Kα X-ray source (1486.6

eV) operating at 100 W. Samples were analyzed under vacuum (P < 10−8 mbar) with a

pass energy of 150 eV (survey scans) or 25 eV (high-resolution scans). All peaks were

3

calibrated with C1s peak binding energy at 284.8 eV for adventitious carbon. The

UV-Vis diffuse reflectance spectra (DRS) were recorded on a Shimadzu UV-2550 UV-

Vis-NIR system. Fluorescence measurements were conducted on an Edinburgh FLS920

steady state and time resolved fluorescence spectrometer. The absolute quantum

yields (QY) of the samples were determined with an integrating sphere by collecting

the fluorescence from 400 to 720 nm.

Ultraviolet photoelectron spectroscopy (UPS) measurements were performed with an

unfiltered HeI (21.22 eV) gas discharge lamp and a gold (Au) calibration. A typical UPS

spectrum usually has two intersections with baseline, from which the width of binding energy (∆E)

is determined. The width value of He I UPS spectra (21.22 eV) is used as the standard. The valence

band energy (Ev) of a semiconductor can be calculated by subtracting the width of the He I UPS

spectra from the determined width of binding energy (Ev= ∆E - 21.22 eV). The calculated value in

eV can be converted to potentials in volts according to the reference standard for which 0 V versus

RHE (reversible hydrogen electrode) equals to –4.44 eV versus vacuum level.

Photocatalytic hydrogen evolution measurement

Photocatalytic H2 evolution arrays were performed in a Pyrex top-irradiation reaction

vessel linked to a glass closed gas system. Catalyst powder (50 mg) was dispersed in

an aqueous solution (100 mL) containing triethanolamine (10 vol.%) via sonication for

5 min. The mixture was evacuated for several times to remove air completely, and

then illuminated under a 300 W Xe-lamp with a 400 nm long pass cut-off filter. The

temperature of the reaction solution was kept at 5 °C by a flow of cooling water. The

generated gases were analyzed by gas chromatography equipped with a thermal

conductive detector with Argon as the carrier gas. 3 wt.% Pt was loaded on the

surface of photocatalyst by the in-situ photodeposition approach using H2PtCl6·6H2O.

The apparent quantum yield (AQY) for H2 evolution was measured as follow [S2, S3]:

Conditions: LED lamps with λ = 420 nm. The irradiation area was controlled as 3×3

cm2. Where, Ne, M, Np and NA is the amount of reaction electrons, the amount of H2

molecules, the incident photons and Avogadro constant, respectively. In addition, c is

the speed of light, h is the Planck constant, S is the irradiation area, t is the

4

photoreaction time, P is the intensity of the irradiation and λ is the wavelength of the

light.

Photocatalytic degradation of RhB

Catalyst powder (20 mg) was dispersed in RhB solution (10-5 mol/L, 40 mL) and stirred

in the dark for ca. 30 min at room temperature. The mixture was irradiated under a

300 W Xe-lamp with cut-off filter to produce visible light irradiation (λ>400 nm). At

given irradiation time intervals, specimens (4 mL) were taken from the dispersion,

and centrifuged at 10000 rpm for 10 min to separate the catalyst particles. The

concentration of aqueous RhB was determined using a SHIMADZU UV-1780 UV-vis

spectrophotometer at 554 nm by measuring its absorbance.

The apparent rate constant of RhB degradation was calculated according to the

following equation:

k=ln(C0/C)/t (1)

Photoelectrochemical measurement

Photoelectrochemical tests were performed with a Biologic VSP-300 electrochemical

system in a conventional three electrode cell. Pt plate and Ag/AgCl electrode were

used as the counter electrode and reference electrode, respectively. The working

electrode was prepared on indium-tin oxide glass. Catalyst powder (5 mg) was

dispersed in N,N'-dimethyformamide (1 mL) via sonication for 12 h to get a slurry

mixture, and then spread onto clean indium-tin oxide glass (with the active area of

0.25 cm2). After natural drying, the uncoated part of the electrode was isolated with

epoxy resin. The electrolyte was 0.2 mol/L Na2SO4 aqueous solution (pH 6.8), and the

light source is a 300 W Xe-lamp.

5

(a) (b)

Fig. S1 SEM images of CTF.

(b)(a)

(c) (d)

Fig. S2 (a, b) TEM and (c, d) HRTEM images of CTF.

6

0.0 0.5 1.0 1.5 2.0 2.5 3.00

1000

2000

3000

4000

O

N

Cou

nts

Energy / keV

C

Fig. S3 TEM-EDX spectra of CTF.

Table S1 Quantification results of CTF based on TEM-EDX analysis.Element Weight (%) Atomic (%) Uncert. (%) Correction k-Factor

C(K) 82.58 84.97 0.84 0.28 3.601

N(K) 14.22 12.55 0.43 0.28 3.466

O(K) 3.18 2.46 0.15 0.51 1.889

(b)(a)

Fig. S4 SEM images of BP.

7

(b)(a)

(c) (d)

Fig. S5 SEM images of BP/CTF hybrid.

(b)(a)

(c) (d)

d (021)=0.336 nm

d (041)=0.225 nm

(e) (f)

(d)(c)

BP CTF

d (040)= 0.262 nm

(d)

CTFBP CTF

CTF BP

Fig. S6 (a-c) TEM and (d-f) HRTEM images of BP/CTF hybrid.

8

Energy / keV

Cou

nts

Fig. S7 SEM-EDX spectra of BP/CTF hybrid.

Table S2 Elemental composition of BP/CTF hybird based on SEM-EDX analysis.Element Weight (%) Atomic (%)

C(K) 70.92 78.25

N(K) 8.73 8.26

O(K) 11.96 9.90

P(K) 8.39 3.59

Total 100.00 100.0

9

0.0 0.5 1.0 1.5 2.0 2.5 3.00

2000

4000

6000

8000

10000

12000

O

P

N

Cou

nts

Energy / keV

C

Fig. S8 TEM-EDX spectra of BP/CTF hybrid.

Table S3 Quantification results of BP/CTF hybrid based on TEM-EDX analysis.Element Weight (%) Atomic (%) Uncert. (%) Correction k-Factor

C(K) 66.47 78.43 0.31 0.28 3.601

N(K) 9.28 9.39 0.12 0.28 3.466

O(K) 2.54 2.25 0.05 0.51 1.889

P(K) 21.69 9.92 0.09 0.9 1.067

10

0.0 0.2 0.4 0.6 0.8 1.0

0

20

40

60

80

V /

cm3 g

-1

P/ P0

3% BP/CTF CTF BP

Fig. S9 N2-sorption isotherms of BP/CTF hybrid, CTF and BP.

Table S4 Physicochemical properties of CTF, BP powders and BP/CTF.Entry Catalysts BET surface

area (m2 g-1)Pore volume (cm3 g-1)

Average pore size determined by BJH method (nm)

Most probable pore size (nm)

1 3% BP/CTF

14 0.13 12.3 3.8

2 CTF 8 0.05 12.3 3.8

3 BP powders

6 0.02 9.7 -

11

400 450 500 550 600

Inte

nsity

/ a.

u.

/ nm

CTF 1% BP/CTF 3% BP/CTF 5% BP/CTF 10% BP/CTF BP

Fig. S10 PL spectra of BP/CTF hybrids.

Table S5 The PL QY and kRhB of the samples.Sample PL QY(%) kRhB (min-1)

CTF 1.33 0.016

1% BP/CTF 0.84 0.129

3% BP/CTF 0.55 0.155

5% BP/CTF 0.36 0.135

10% BP/CTF 0.29 0.104

BP 0.41 0.005

Table S6 The fitted fluorescence decay components of CTF, BP/CTF, and BP samples.Sample τ1 (ns) τ2 (ns) a1 (%) a2 (%) τav (ns) X2 (%)

CTF 0.8779 23.9119 95.13 4.87 2.00 95.77

1% BP/CTF 0.7793 0.7793 50.00 50.00 0.78 94.38

3% BP/CTF 0.7037 0.7037 49.99 50.01 0.70 95.63

BP 0.6949 0.6949 49.98 50.02 0.69 94.74

12

0 5 10 15 200

50

100

150

200

4 th3 rd 2 nd 1 st

Prod

uced

H2 /

m

ol

t / hFig. S11 Cycle stability of 3% BP/CTF for photocatalytic H2 evolution.

300 400 500 6000.0

0.2

0.4

0.6

0.8

1.0

Abs

.

/ nm

0 min 5 min 10 min 15 min 20 min 25 min 30 min 35 min 40 min

(a)

300 400 500 6000.0

0.2

0.4

0.6

0.8

1.0

Abs

.

/ nm

0 min 5 min 10 min 15 min 20 min 25 min 30 min 35 min 40 min

(b)

300 400 500 6000.0

0.2

0.4

0.6

0.8

1.0

Abs

.

/ nm

0 min 5 min 10 min 15 min 20 min 25 min 30 min 35 min 40 min

(c)

300 400 500 6000.0

0.2

0.4

0.6

0.8

1.0

Abs

.

/ nm

0 min 5 min 10 min 15 min 20 min 25 min 30 min 35 min 40 min

(d)

Fig. S12 UV-vis absorption spectra of the RhB pollutant solutions under visible light irradiation (>400 nm) at different irradiation time intervals for (a) 3% BP/CTF, (b) CTF, (c)

BP and (d) no catalyst.

13

-5 0 5 10 15 20 25 300.0

0.2

0.4

0.6

0.8

1.0 (a)

Time / min

C/C 0

No catalyst 3% BP/CTF-dark P25 3% BP/TiO2

bulk g-CN CdS 3% BP/CTF

0 5 10 15 200

1

2

3 CTF BP 1% BP/CTF 3% BP/CTF 5% BP/CTF 10% BP/CTF

ln(C

0/C)

Time / min

(b)

Fig. S13 (a) Photocatalytic activities of RhB degradation for different photocatalysts and blank test. (b) Apparent reaction rate constants of RhB degradation for different

photocatalysts.

14

20 40 60 80

3% BP/CTF-after

3% BP/CTF-before

(a)

Inte

nsity

/ a.

u.

2 theta / degree

4000 3500 3000 2500 2000 1500 1000 500

(b)3% BP/CTF-after

3% BP/CTF-before

T% /

a.u.

Wavenumber / cm-1

Fig. S14 (a) XRD patterns and (b) FT-IR spectra of 3% BP/CTF before and after photocatalytic reactions.

15

600 500 400 300 200 100 0

3% BP/CTF-after

(a)O1s

N1s

C1s

Binding Energy / eV

Inte

nsity

/ a.

u.

3% BP/CN-before

P2p

138 136 134 132 130 128

3% BP/CTF-after

3% BP/CTF-before

Inte

nsity

/ a.

u.

(b)

Binding Energy / eV

133.8130.3

129.4P2p

290 288 286 284 282

288.4

Inte

nsity

/ a.

u.

3% BP/CTF-before

287.2

284.8(c) C1s

Binding Energy / eV

3% BP/CTF-after

402 400 398 396

Inte

nsity

/ a.

u.

3% BP/CTF-after

400.0

398.8(d) N1s

Binding Energy / eV

3% BP/CTF-before

Fig. S15 XPS spectra of (a) survey, (b) P 2p, (c) C 1s, and (d) N 1s of 3% BP/CTF before and after photocatalytic reactions.

Table S7 XPS analysis of 3% BP/CTF sample before and after photocatalytic degradation of RhB.

Atomic (%)

NameBinding

energy (eV)Assignment

CTF BP

3%

BP/CTF-

before

3%

BP/CTF-

after

P2p 129.4 P2p3/2 - 50.86 7.74 6.98

P2p Scan A 130.3 P2p1/2 - 18.08 3.35 2.89

P2p Scan B 133.8PxOy, P-OH

or P-H2O- 31.06 5.62 5.16

C1s 284.8 C-C - - - -

C1s Scan A 287.2 C-N 47.48 - 26.75 29.07

C1s Scan B 288.4 C-P - 11.74 13.33

N1s 398.8 C=N-C 34.90 - 28.59 25.21

N1s Scan A 400.0 C≡N 17.62 - 16.21 17.36

16

(b)(a)

Fig. S16 SEM images of BP/CTF hybrid after photocatalytic reactions.

25 20 15 10 5 0

17.1921.81 6.63 6.06

UP

S in

tens

ity /

a.u.

Binding energy / eV

CTF 3% BP/CTF BP

21.21

1.20

Fig. S17 Valence band UPS cutoff spectra of samples.

17

2.0 2.5 3.0 3.5 4.00.0

0.5

1.0

1.5

2.0 CTF 1% BP/CTF 3% BP/CTF 5% BP/CTF 10% BP/CTF

(ah

)1/2

h/ eV

(a)

1.0 1.5 2.0 2.5 3.0 3.5 4.00

5

10

15

1.39

BP

(ah

)2

h/ eV

(b)

Fig. S18 (a) The plots of (αhν)1/2 vs. photon energy (hν) for CTF and BP/CTF hybrids. (b) The plots of (αhν)2 vs. photon energy (hν) for BP.

References[S1] H. Wang, X. Yang, W. Shao, S. Chen, J. Xie, X. Zhang, J. Wang and Y. Xie, J. Am. Chem. Soc., 2015,

137, 11376-11382.

[S2] K. Maeda, K. Teramura, D. Lu, T. Takata, N. Saito, Y. Inoue and K. Domen, Nature, 2006, 440,

295-295.

[S3] H. Ou, C. Tang, Y. Zhang, A. M. Asiri, M. M. Titirici and X. Wang, J. Catal., 2019, 375, 104-112.