Supporting information for Colloidal synthesis of 1T-WS2 and 2H-WS2 ...
Supporting information
for
Colloidal synthesis of 1T-WS2 and 2H-WS2 nanosheets: applications for photocatalytic hydrogen evolution. Benoit Mahler, Veronika Hoepfner, Kristine Liao, Geoffrey A. Ozin*.
I.
Additional STEM images of 1T-WS2 nanosheets: ..................................................................... 2
II. Crystal structure of distorted 1T-WS2: ........................................................................................ 4 III. Annealing effect on 1T-WS2 nanosheets: .................................................................................. 7 IV.
WS2 synthesis without oleic acid: ................................................................................................. 8
V.
WS2 synthesis with dodecanethiol (DDT): ................................................................................. 9
VI.
WS2 synthesis with DDT and HMDS: ........................................................................................ 10
VII. Additional photocatalysis experiments: ............................................................................... 12
S1
I. Additional STEM images of 1T-WS2 nanosheets:
Figure S1. STEM-HAADF images of different magnifications of the 1T-WS2 sample, highlighting the highly defected structure of the sheets.
S2
Figure S2. STEM-HAADF image of the 1T-WS2 sample showing the lamellar structure of the aggregate.
S3
II. Crystal structure of distorted 1T-WS2:
Figure S3. Proposed crystal structure of distorted 1T-WS2 using ReS2 as a prototype
Figure S4. Crystal structure of three distorted 1T-WS2 layers S4
Cif file of the distorted 1T-WS2 _audit_creation_method 'generated by CrystalMaker 8.1.7' _cell_length_a 6.4170(0) _cell_length_b 6.6700(0) _cell_length_c 6.4900(0) _cell_angle_alpha 121.1000(0) _cell_angle_beta 88.3800(0) _cell_angle_gamma 106.4700(0) _symmetry_space_group_name_H-M 'P -1' _symmetry_Int_Tables_number 2 _symmetry_cell_setting triclinic loop_ _symmetry_equiv_pos_as_xyz '+x,+y,+z' '-x,-y,-z' loop_ _atom_site_label _atom_site_type_symbol _atom_site_type_occupancy _atom_site_fract_x _atom_site_fract_y _atom_site_fract_z S1 S 1.0000 0.2174 0.2498 0.3676 S2 S 1.0000 0.2769 0.7705 0.3819 S3 S 1.0000 0.7562 0.2729 0.1178 S4 S 1.0000 0.6975 0.7526 0.1169 W1 W 1.0000 0.4925 0.0564 0.2477 W2 W 1.0000 0.5026 0.5112 0.2974
S5
Figure S5. Simulated powder X-ray diffractogram of distorted 1T-WS2.
S6
III. Annealing effect on 1T-WS2 nanosheets: The protocol is the same as described in experimental section, except that after injection, the reaction flask is annealed at 330 °C for 30minutes.
Figure S6. TEM images of WS2 nanosheets before annealing (left) and after 30 minutes annealing at 330 °C (right).
Figure S7. Diffractogram of the WS2 nanosheets before annealing (black) and after 30 minutes of annealing at 330 °C. Note the position of the diffraction peak at 32°.
S7
IV. WS2 synthesis without oleic acid: Protocol: 15mL oleylamine in a 100 mL three-neck flask is degassed for one hour under vacuum at 65 °C. The flask is then heated up to 320 °C under Argon atmosphere. Meanwhile, 50 mg of WCl6 (0.125 mmol) and 500 μL of isopropanol are mixed in a vial and sonicated until full dissolution. The vial is then flushed with nitrogen and 5 mL of oleylamine is added. Prior to injection, 240 μL of CS2 is swiftly introduced, inducing a temperature increase. The solution immediately begins to thicken and will solidify over time. The precursor mixture is injected drop wise into the hot oleylamine solution over a 30 minute interval using a syringe pump. After injection, the reaction mixture is left to cool down to room temperature. The WS2 nanosheets are then precipitated by adding 15 mL of hexane and 15 mL of isopropanol followed by centrifugation. The nanosheets are finally redispersed in 10 mL of hexane.
a)
c)
b)
d)
1200
I.(a.u.)
Counts (a.u.)
1000 800 600 400 200 0 40
38
36 34 B.E.(eV)
32
30
Figure S8. a) TEM image of WS2 nanosheets synthesized without oleic acid. b) Absorbance spectrum of the WS2 colloidal solution. c) Powder X-ray diffractogram of the WS2 nanosheets. d) X-ray photoelectron spectroscopy spectrum of the WS2 nanosheets for the W 4f core level peaks.
S8
V. WS2 synthesis with dodecanethiol (DDT): Protocol: 15mL oleylamine in a 100 mL three-neck flask is degassed for one hour under vacuum at 65 °C. The flask is then heated up to 320 °C under Argon atmosphere. Meanwhile, 50 mg of WCl6 (0.125 mmol) and 230μL of dodecanethiol are mixed in a vial and sonicated until full dissolution. The vial is then flushed with nitrogen and 5 mL of oleylamine is added. Prior to injection, 240 μL of CS2 is swiftly introduced, inducing a temperature increase. The solution immediately begins to thicken and will solidify over time. The precursor mixture is injected drop wise into the hot oleylamine solution over a 30 minute interval using a syringe pump. After injection, the reaction mixture is left to cool down to room temperature. The WS2 nanosheets are then precipitated by adding 15 mL of hexane and 15 mL of isopropanol followed by centrifugation. The nanosheets are finally redispersed in 10 mL of hexane.
a)
b)
c)
d)
700 600
I.(a.u.)
Counts (a.u.)
500 400 300 200 100 0 40
35 B.E.(eV)
30
Figure S9. a) TEM image of WS2 nanosheets synthetized with dodecanethiol. b) Absorbance spectrum of the WS2 colloidal solution. c) Powder X-ray diffractogram of the WS2 nanosheets. d) X-ray photoelectron spectroscopy spectrum of the WS2 nanosheets for the W 4f core level peaks.
S9
VI. WS2 synthesis with DDT and HMDS: Protocol: 15 mL oleylamine in a 100 mL three-neck flask is degassed for one hour under vacuum at 65 °C. The flask is then heated up to 320 °C under Argon atmosphere. Meanwhile, 50 mg of WCl6 (0.125 mmol) and 230 μL of dodecanethiol are mixed in a vial and sonicated until full dissolution. The vial is then flushed with nitrogen and 5 mL of oleylamine is added. Prior to injection, 240 μL of CS2 is swiftly introduced, inducing a temperature increase. The solution immediately begins to thicken and will solidify over time. Before injection of the precursors, 1mL of HMDS is added to the hot flask. The precursor mixture is injected drop wise into the hot oleylamine solution over a 30 minute interval using a syringe pump. After injection, the reaction mixture is left to cool down to room temperature. The WS2 nanosheets are then precipitated by adding 15mL of hexane and 15 mL of isopropanol followed by centrifugation. The nanosheets are finally redispersed in 10 mL of hexane.
a)
b)
c)
d)
700 600
I.(a.u.)
Counts (a.u.)
500 400 300 200 100 0 40
38
36 34 B.E.(eV)
32
30
Figure S10. a) TEM image of WS2 nanosheets synthetized with DDT and HMDS. b) Absorbance spectrum of the WS2 colloidal solution. c) Powder X-ray diffractogram of the WS2 nanosheets. d) X-ray photoelectron spectroscopy spectrum of the WS2 nanosheets for the W 4f core level peaks.
S10
WS2 monolayers WS2-HMDS nanoflowers WS2 without oleic acid WS2-DDT WS2 DDT-HMDS
1T 2H tungstate or W4f7/2 W4f5/2 W4f7/2 W4f5/2 W5p3/2 31.98 33.98 32.94 35.14 36.27 32.07 34.21 32.83 35.62 37.78 31.94 34.10 32.84 34.99 35.90 38.01 32.14 34.25 32.92 35.01 35.97 37.86 32.16 34.18 32.88 35.01 36.01 37.91
Table S1. XPS peak positions (in eV) obtained after deconvolution for the 5 samples described in the main text and in the Supporting Information.
WS2 monolayers WS2-HMDS nanoflowers WS2 without oleic acid WS2-DDT WS2 DDT-HMDS
1T (%) 36.1 10.1 29.7 61.1 40.4
2H (%) 7.4 82.6 61.6 29.4 13.4
Tungstate (%) 56.5 7.2 8.7 9.6 46.2
Table S2. Relative percentages of 1T-WS2, 2H-WS2 and tungsten oxide species obtained by integration of the W4f7/2 peak for the 5 samples described in the main text and in the Supporting Information.
S11
VII. Additional photocatalysis experiments:
800
H2 formation / mmol g1 h1
700 600 500 400 300 200 100 0 0.3wt%WS2-P25
1wt% WS2-P25
3wt% WS2-P25
Figure S11. Loading dependency of the photocatalytic activity of the TiO2/1T-WS2 composite (under illumination with a 150W Xe lamp equipped with an AM 1.5 filter).
60
P25 1wt WS2 on P25
H2 (mmol.g1)
50 40 30 20 10 0 0
5
10 15 time (h)
20
25
Figure S12. Photoproduction rates of hydrogen over time for the TiO2/1T-WS2 1% wt composite and pure P25-TiO2.
S12
1000
H2 formation rate / mmol g1 h1
AM 1.5 filter 495 nm cut off filter
100
10
1 2H-WS2/P25 (1wt%)
1T-WS2/P25 (3wt%)
Figure S13. Comparison between full spectrum photoactivity (blue) and visible light only (red) photoactivity for the TiO2/2H-WS2 and TiO2/1T-WS2 composites.
S13
for
Colloidal synthesis of 1T-WS2 and 2H-WS2 nanosheets: applications for photocatalytic hydrogen evolution. Benoit Mahler, Veronika Hoepfner, Kristine Liao, Geoffrey A. Ozin*.
I.
Additional STEM images of 1T-WS2 nanosheets: ..................................................................... 2
II. Crystal structure of distorted 1T-WS2: ........................................................................................ 4 III. Annealing effect on 1T-WS2 nanosheets: .................................................................................. 7 IV.
WS2 synthesis without oleic acid: ................................................................................................. 8
V.
WS2 synthesis with dodecanethiol (DDT): ................................................................................. 9
VI.
WS2 synthesis with DDT and HMDS: ........................................................................................ 10
VII. Additional photocatalysis experiments: ............................................................................... 12
S1
I. Additional STEM images of 1T-WS2 nanosheets:
Figure S1. STEM-HAADF images of different magnifications of the 1T-WS2 sample, highlighting the highly defected structure of the sheets.
S2
Figure S2. STEM-HAADF image of the 1T-WS2 sample showing the lamellar structure of the aggregate.
S3
II. Crystal structure of distorted 1T-WS2:
Figure S3. Proposed crystal structure of distorted 1T-WS2 using ReS2 as a prototype
Figure S4. Crystal structure of three distorted 1T-WS2 layers S4
Cif file of the distorted 1T-WS2 _audit_creation_method 'generated by CrystalMaker 8.1.7' _cell_length_a 6.4170(0) _cell_length_b 6.6700(0) _cell_length_c 6.4900(0) _cell_angle_alpha 121.1000(0) _cell_angle_beta 88.3800(0) _cell_angle_gamma 106.4700(0) _symmetry_space_group_name_H-M 'P -1' _symmetry_Int_Tables_number 2 _symmetry_cell_setting triclinic loop_ _symmetry_equiv_pos_as_xyz '+x,+y,+z' '-x,-y,-z' loop_ _atom_site_label _atom_site_type_symbol _atom_site_type_occupancy _atom_site_fract_x _atom_site_fract_y _atom_site_fract_z S1 S 1.0000 0.2174 0.2498 0.3676 S2 S 1.0000 0.2769 0.7705 0.3819 S3 S 1.0000 0.7562 0.2729 0.1178 S4 S 1.0000 0.6975 0.7526 0.1169 W1 W 1.0000 0.4925 0.0564 0.2477 W2 W 1.0000 0.5026 0.5112 0.2974
S5
Figure S5. Simulated powder X-ray diffractogram of distorted 1T-WS2.
S6
III. Annealing effect on 1T-WS2 nanosheets: The protocol is the same as described in experimental section, except that after injection, the reaction flask is annealed at 330 °C for 30minutes.
Figure S6. TEM images of WS2 nanosheets before annealing (left) and after 30 minutes annealing at 330 °C (right).
Figure S7. Diffractogram of the WS2 nanosheets before annealing (black) and after 30 minutes of annealing at 330 °C. Note the position of the diffraction peak at 32°.
S7
IV. WS2 synthesis without oleic acid: Protocol: 15mL oleylamine in a 100 mL three-neck flask is degassed for one hour under vacuum at 65 °C. The flask is then heated up to 320 °C under Argon atmosphere. Meanwhile, 50 mg of WCl6 (0.125 mmol) and 500 μL of isopropanol are mixed in a vial and sonicated until full dissolution. The vial is then flushed with nitrogen and 5 mL of oleylamine is added. Prior to injection, 240 μL of CS2 is swiftly introduced, inducing a temperature increase. The solution immediately begins to thicken and will solidify over time. The precursor mixture is injected drop wise into the hot oleylamine solution over a 30 minute interval using a syringe pump. After injection, the reaction mixture is left to cool down to room temperature. The WS2 nanosheets are then precipitated by adding 15 mL of hexane and 15 mL of isopropanol followed by centrifugation. The nanosheets are finally redispersed in 10 mL of hexane.
a)
c)
b)
d)
1200
I.(a.u.)
Counts (a.u.)
1000 800 600 400 200 0 40
38
36 34 B.E.(eV)
32
30
Figure S8. a) TEM image of WS2 nanosheets synthesized without oleic acid. b) Absorbance spectrum of the WS2 colloidal solution. c) Powder X-ray diffractogram of the WS2 nanosheets. d) X-ray photoelectron spectroscopy spectrum of the WS2 nanosheets for the W 4f core level peaks.
S8
V. WS2 synthesis with dodecanethiol (DDT): Protocol: 15mL oleylamine in a 100 mL three-neck flask is degassed for one hour under vacuum at 65 °C. The flask is then heated up to 320 °C under Argon atmosphere. Meanwhile, 50 mg of WCl6 (0.125 mmol) and 230μL of dodecanethiol are mixed in a vial and sonicated until full dissolution. The vial is then flushed with nitrogen and 5 mL of oleylamine is added. Prior to injection, 240 μL of CS2 is swiftly introduced, inducing a temperature increase. The solution immediately begins to thicken and will solidify over time. The precursor mixture is injected drop wise into the hot oleylamine solution over a 30 minute interval using a syringe pump. After injection, the reaction mixture is left to cool down to room temperature. The WS2 nanosheets are then precipitated by adding 15 mL of hexane and 15 mL of isopropanol followed by centrifugation. The nanosheets are finally redispersed in 10 mL of hexane.
a)
b)
c)
d)
700 600
I.(a.u.)
Counts (a.u.)
500 400 300 200 100 0 40
35 B.E.(eV)
30
Figure S9. a) TEM image of WS2 nanosheets synthetized with dodecanethiol. b) Absorbance spectrum of the WS2 colloidal solution. c) Powder X-ray diffractogram of the WS2 nanosheets. d) X-ray photoelectron spectroscopy spectrum of the WS2 nanosheets for the W 4f core level peaks.
S9
VI. WS2 synthesis with DDT and HMDS: Protocol: 15 mL oleylamine in a 100 mL three-neck flask is degassed for one hour under vacuum at 65 °C. The flask is then heated up to 320 °C under Argon atmosphere. Meanwhile, 50 mg of WCl6 (0.125 mmol) and 230 μL of dodecanethiol are mixed in a vial and sonicated until full dissolution. The vial is then flushed with nitrogen and 5 mL of oleylamine is added. Prior to injection, 240 μL of CS2 is swiftly introduced, inducing a temperature increase. The solution immediately begins to thicken and will solidify over time. Before injection of the precursors, 1mL of HMDS is added to the hot flask. The precursor mixture is injected drop wise into the hot oleylamine solution over a 30 minute interval using a syringe pump. After injection, the reaction mixture is left to cool down to room temperature. The WS2 nanosheets are then precipitated by adding 15mL of hexane and 15 mL of isopropanol followed by centrifugation. The nanosheets are finally redispersed in 10 mL of hexane.
a)
b)
c)
d)
700 600
I.(a.u.)
Counts (a.u.)
500 400 300 200 100 0 40
38
36 34 B.E.(eV)
32
30
Figure S10. a) TEM image of WS2 nanosheets synthetized with DDT and HMDS. b) Absorbance spectrum of the WS2 colloidal solution. c) Powder X-ray diffractogram of the WS2 nanosheets. d) X-ray photoelectron spectroscopy spectrum of the WS2 nanosheets for the W 4f core level peaks.
S10
WS2 monolayers WS2-HMDS nanoflowers WS2 without oleic acid WS2-DDT WS2 DDT-HMDS
1T 2H tungstate or W4f7/2 W4f5/2 W4f7/2 W4f5/2 W5p3/2 31.98 33.98 32.94 35.14 36.27 32.07 34.21 32.83 35.62 37.78 31.94 34.10 32.84 34.99 35.90 38.01 32.14 34.25 32.92 35.01 35.97 37.86 32.16 34.18 32.88 35.01 36.01 37.91
Table S1. XPS peak positions (in eV) obtained after deconvolution for the 5 samples described in the main text and in the Supporting Information.
WS2 monolayers WS2-HMDS nanoflowers WS2 without oleic acid WS2-DDT WS2 DDT-HMDS
1T (%) 36.1 10.1 29.7 61.1 40.4
2H (%) 7.4 82.6 61.6 29.4 13.4
Tungstate (%) 56.5 7.2 8.7 9.6 46.2
Table S2. Relative percentages of 1T-WS2, 2H-WS2 and tungsten oxide species obtained by integration of the W4f7/2 peak for the 5 samples described in the main text and in the Supporting Information.
S11
VII. Additional photocatalysis experiments:
800
H2 formation / mmol g1 h1
700 600 500 400 300 200 100 0 0.3wt%WS2-P25
1wt% WS2-P25
3wt% WS2-P25
Figure S11. Loading dependency of the photocatalytic activity of the TiO2/1T-WS2 composite (under illumination with a 150W Xe lamp equipped with an AM 1.5 filter).
60
P25 1wt WS2 on P25
H2 (mmol.g1)
50 40 30 20 10 0 0
5
10 15 time (h)
20
25
Figure S12. Photoproduction rates of hydrogen over time for the TiO2/1T-WS2 1% wt composite and pure P25-TiO2.
S12
1000
H2 formation rate / mmol g1 h1
AM 1.5 filter 495 nm cut off filter
100
10
1 2H-WS2/P25 (1wt%)
1T-WS2/P25 (3wt%)
Figure S13. Comparison between full spectrum photoactivity (blue) and visible light only (red) photoactivity for the TiO2/2H-WS2 and TiO2/1T-WS2 composites.
S13
