S1 Enhancement of Solar Hydrogen Generation by Synergistic ...
Supporting Information
Enhancement of Solar Hydrogen Generation by Synergistic Interaction of La2Ti2O7 Photocatalyst with Plasmonic Gold Nanoparticles and Reduced Graphene Oxide Nanosheets Fanke Meng, Scott K. Cushing, Jiangtian Li, Shimeng Hao and Nianqiang Wu* F. K. Meng, Dr. J. T. Li, S. M. Hao, Prof. N. Q. Wu Department of Mechanical and Aerospace Engineering West Virginia University Morgantown, WV 26506-6106, USA. Fax: +1-304-293-6689 Email: [email protected] S. K. Cushing Department of Physics and Astronomy West Virginia University Morgantown, WV 26506-6315, USA.
Experimental Methods
1 Materials Synthesis La2Ti2O7 (LTO) nanosheets were synthesized following our previous publications [S1,S2]. To deposit the Pt nanoparticle on the LTO sheets, 0.05 g of Pt(NH3)4Cl2 (Sigma–Aldrich) and 0.5 g of La2Ti2O7 nanosheets were mixed with 20 mL of deionized water (DI) to form a homogenous suspension in a 50 mL of beaker, and then held at room temperature under stirring for 24 h. The white powder was obtained by centrifuging and subsequent drying at 80 ⁰C overnight. The white powder was then heated in air at 400 ⁰C for 3 h. The color of the powder became grey. The grey powder was finally reduced in a H2 flow at 500 ⁰C for 1 h to obtain the Pt-loaded La2Ti2O7 (Pt-LTO) nanosheets.
Au@Pt-La2Ti2O7 (LTO) nanosheets were synthesized as follows. 0.5 g of Pt-LTO nanosheets was mixed with 0.05 g of HAuCl4 (Alfa. Inc) in 10 mL of DI water to form a suspension. The suspension was centrifuged to get the fluffy powder, dried at 80 ⁰C overnight, and subsequently heated in air at 400 ⁰C for 3 h. The powder was reduced in a H2 flow at 500 ⁰C for 1 h, which resulted in the Au nanoparticle loaded nanosheet (Au@Pt-LTO).
Graphene oxide (GO) was synthesized with the Hummer method [S3].
Au@Pt-La2Ti2O7 (LTO) nanosheets coupled with rGO was synthesized as follows. 0.5 g of Au@Pt-LTO nanosheets were mixed with 0.0125 g of GO (2.5 wt.%) in 15 g of DI water to form a suspension and stirred rigorously in an ultrasonic bath for 20 s. 15 ml of ethanol was then added into the suspension and stirred for 1 min. The suspension was then transferred and sealed in a Teflon-lined pressure vessel in a pre-heated oven (200 ⁰C) for 24 h. After the pressure vessel was cooled to room temperature, the resulting powder was washed with DI water 5 times, and then dried on a hotplate at 80 ⁰C overnight. This resulted in the Au@Pt-LTO/rGO sample.
Pt-loaded N-doped La2Ti2O7 (NLTO) nanosheets were prepared by heating 0.5 g of Pt-loaded La2Ti2O7 nanosheets in a NH3 flow at 600 ⁰C for 3h. This resulted in the Pt-NLTO sample
Au and Pt-loaded N-doped La2Ti2O7 nanosheets were prepared by heating 0.5 g of Au and Pt-loaded La2Ti2O7 nanosheets in a NH3 flow at 600 ⁰C for 3h. This resulted in the Au@Pt-NLTO sample
S1
Supporting Information Au and Pt-loaded, N-doped La2Ti2O7 nanosheets coupled with rGO was synthesized with hydrothermal method. 0.5 g Au and Pt-loaded, N-doped La2Ti2O7 nanosheets was mixed with the GO sheets as described previously and subject to the hydrothermal processing. This resulted in the Au@Pt-NLTO/rGO sample
2 Materials characterization The detail materials characterization methods were reported in our previous literatures [S1,S2,S4]. The particle morphology was observed with a scanning electron microscope (SEM, JEOL 7600F) and a transmission electron microscope (TEM, JEOL, JEM 2100). The crystal structures of materials were characterized by a high-resolution TEM (HRTEM) and X-ray diffraction (XRD, X’ Pert Pro PW3040-Pro, Panalytical Inc.) with Cu Kα radiation. The chemical structure was determined by X-ray photoelectron spectroscopy (XPS, PHI 5000 Versa Probe system, Physical Electronics) with a reference to the C 1s peak at 284.8 eV. The light absorption spectra of the samples were acquired by an ultraviolet-visible spectrometer (UV-Vis, Lambda 750, PerkinElmer Inc.). The specific surface areas of the samples were measured by Brunauer, Emmett and Teller (BET, Micromeritics ASAP 2020).
3. Photocatalysis A commercial solar light simulator (300 W, Newport, Intensity: 40-50 mW/cm2) equipped with a monochromic shutter and an AM 1.5G filter was used as the light source for photocatalysis. To perform the photocatalytic H2 generation, 10 mg of photocatalyst powder was suspended in a 20 mL of solution (10 mL of DI and 10 mL of ethanol) in a 100 mL of quart flask. The suspension was bubbled with a N2 flow (99.9 %, Air Gas Inc.) for 10 min. After bubbling, the flask was sealed and illuminated under the simulated solar light with a light window of 2.0 cm2 for different time intervals. Finally, 5 mL of the gas sample was collected from the flask for chromatography measurement (GC, Shimadzu 2014).
4. Photoelectrochemical Measurement 4.1 Preparation of photoeletrodes 0.1 g of photocatalyst powder was mixed with 0.5 mL of terpineol (~95%, Sigma-Aldrich) under stirring overnight to form a homogenous suspension. The suspension was pasted onto a fluorine-doped tin oxide (FTO) substrate (Hartford, TEC 15) with doctor blading method. The pasted FTO photoelectrode was then dried on a hot plate in air, subsequently heated in N2 at 550 °C for 2 h. Finally, a copper wire was connected to the FTO substrate with the silver colloid paste and the sealed with epoxy glue.
4.2 Electrochemical measurement A three-electrode photoelectrochemical cell (PEC) was constructed and measured with a Gamry electrochemical station (Reference 3000™). The Pt plate, AgAgCl and photoelectrodes acted as the counter electrode, the reference electrode and the working electrode, respectively. 1 M NaOH (>98.0%, Sigma-Aldrich) aqueous solution was employed as the electrolyte (pH=13.6,) and bubbled with a N2 flow for 30 min prior to photoelectrochemical testing. The light source for the PEC was the same as that used in photocatalytic water splitting. The plot of photocurrent density (J) with the applied potential (V) was obtained. The potential (vs. AgAgCl) was converted to the reversible hydrogen electrode (RHE) according to the Nernst equation:
ERHE E 0.05916 pH E0
(S1)
Where ERHE is the potential vs. RHE, E0= 0.1976 V at 25 °C, and E is the measured potential vs. AgAgCl. The on-off J-V curves were obtained under a bias of -0.25 V vs. RHE.
The incident photo-to-electron conversion efficiency (IPCE) plots were measured with the photocurrents at different wavelengths of incident light under a bias of -0.25 V vs. RHE. The IPCE was calculated as follows:
IPCE 1240 J / I light Where
(S2)
I light is the light intensity at a wavelength of λ. λ was varied from 250 nm to 700 nm with an interval of 25 nm.
S2
Supporting Information Mott-Schottky (M-S) plots were used to estimate the flat-band potential [S5]: 𝑆𝑙𝑜𝑝 = 𝜀𝜀
2
(S3)
2 0 𝐴 𝑒𝑁𝐷
𝐼𝑛𝑡𝑒𝑟𝑐𝑒𝑝𝑡 =
𝑘𝐵 𝑇 𝑒
+ 𝑉𝑓𝑏
(S4)
Where ε, ε0, A, e, kB, ND and Vfb are dielectric constant of the semiconductor, permittivity of free space, electrode area, Boltzmann constant, charge density and flat-band potential, respectively. The charge recombination behavior was quantified according to the normalized transient photocurrent
D ( It Ist ) / ( Iin Ist )
(S5)
Where D is a normalized parameter [S4, S6], It and Ist are the time-dependent current density and final current density in dark, respectively. Iin is the initial photocurrent. In the plot of lnD–t, the transient time constant (τ) is determined when lnD=-1 [S4, S6].
S3
Supporting Information
Figure S1. TEM images of the sample (a) Au@Pt-NLTO and (b) Au@Pt-LTO/rGO.
Figure S2. XPS spectra of (a) Pt 4f, (b) Au 4f, and (c) N 1s peaks for Au@Pt-NLTO/rGO (curve 1), Au@Pt-NLTO (curve 2), Pt-NLTO (curve 3), and Au@Pt-LTO/rGO (curve 4).
Figure S3. XRD patterns for Au@Pt-NLTO/rGO (curve 1), Au@Pt-NLTO (curve 2), Pt-NLTO (curve 3), and Au@Pt-LTO/rGO (curve 4).
S4
Supporting Information
Figure S4. (a,b) UV-VIS absorption spectra, (c) J-V curves plotting the photocurrent density as a function of the applied potential and (d) IPCE spectra for LTO and NLTO with and without Au nanoparticles.
Figure S5. Hydrogen generation rate over three cycles for Au@Pt-NLTO/rGO, Au@Pt-NLTO, Pt-NLTO, and Au@Pt-LTO/rGO.
S5
Supporting Information
Figure S6. Mott-Schottky plots of the samples in the dark (hollow) and under irradiation of simulated solar light (solid).
Figure S7. Transient photocurrent measurement obtained from the photoelectrodes.
S6
Supporting Information
Figure S8. Plasmonic energy transfer mechanisms. (a) During direct electron transfer (DET), hot plasmonic electronics photo-excited in the Au can overcome the Schottky barrier. The transferred electrons are then trapped, leading to an increase in the photocurrent in the semiconductor at the absorption peak of the plasmon. (b) During plasmon induced resonant energy transfer (PIRET), the plasmonic dipole relaxes by nonradiatively exciting an electron hole pair in the semiconductor. Since the process does not require electron transfer, it can occur through an insulating barrier with a strength that decays with increasing separation distance. For the semiconductor and plasmon to interact through the near field the two spectrums must overlap energetically. Therefore the enhancement can be approximated by the overlap between the semiconductor and plasmon absorption (the plasmon absorption is approximately equal to its fluorescence in the samples measured [S7]). For further information on the plasmonic energy transfer mechanisms refer to references S8-S10.
Figure S9. (a) Increase in spectral utilization between the Pt-NLTO and Au@Pt-NLTO/rGO samples. (b) The increase in the IPCE is seen to be identical to that shown in the main text Figure 4. This is expected as the addition of rGO only increases lifetime, and not the spectral utilization. Therefore the plasmonic energy transfer mechanism is PIRET for both Au@Pt-NLTO and Au@Pt-NLTO/rGO samples.
S7
Supporting Information Table S1. The contents of Pt, Au and N in four samples. Sample
Pt (at. %)
Au (at. %)
N (at. %)
Au@Pt-NLTO/rGO
1.55
2.12
1.99
Au@Pt-NLTO
1.71
2.21
2.08
Pt-NLTO
1.65
0
2.13
Au@Pt-LTO/rGO
1.61
2.05
0
Table S2. The photocatalytic hydrogen generation rates and BET surface areas of four samples. Sample
Surface areas
H2 (μM·g-1·h-1)
H2 (μM·m-2·h-1)
(m2·g-1)
Au@Pt-NLTO/rGO
163.4
44.65
3.66
Au@Pt-NLTO
101.1
38.54
2.62
Pt-NLTO
65.3
40.25
1.62
Au@Pt-LTO/rGO
44.2
43.53
1.02
Table S3. Flat-band potentials of four samples. Sample
Vfb in dark (V)
Vfb under illumination (V)
Au@Pt-NLTO/rGO
-0.53
-0.72
Au@Pt-NLTO
-0.50
-0.71
Pt-NLTO
-0.52
-0.57
Au@Pt-LTO/rGO
-0.27
-0.37
S8
Supporting Information References [S1] Meng, F. K.; Li, J. T.; Hong, Z. L.; Zhi, M. J.; Sakla, A.; Xiang, C. C.; Wu, N. Q., Catal. Today, 2013, 199, 48-52. [S2] Meng, F. K.; Hong, Z. L.; Arndt, J.; Li, M.; Zhi, M. J.; Yang, F.; Wu, N. Q., Nano Res. 2012, 5, 213-221. [S3] Hummers, W. S.; Offeman, R. E. J. Am. Chem. Soc., 1958, 80, 1339. [S4] Meng, F.K., Li, J. T., Cushing, S. K., Zhi, M. J., Wu, N. Q., J. Am. Chem. Soc., 2013, 135, 10286-10289. [S5] Gelderman, K., Lee, L., Donne, S. W., J. Chem. Edu., 2007, 84, 685-688. [S6] Tafalla, D., Salvador, P. Benito, R. M. J. Electrochem. Soc., 1990, 137, 1810-1815. [S7] Zuloaga, J., Nordlander, P. Nano Lett. ,2011, 11, 1280-1283. [S8] Li, J. T., Cushing, S. K., Zheng, P., Meng, F. K., Chu, D., Wu, N. Q., Nature Comm., 2013, 4, 2651 [S9] Cushing, S. K., Li, J. T., Meng, F. K., Senty, T. R., Suri, S., Zhi, M. J., Li, M., Bristow, A. D., Wu, N. Q., J. Am. Chem. Soc., 2012, 134, 15033−15041. [S10] Li, J. T., Cushing, S. K., Bright, J., Meng, F. K., Senty, T. R., Zheng, P., Bristow, A. D., Wu, N. Q., ACS Catal., 2013, 3, 47-51.
S9
Enhancement of Solar Hydrogen Generation by Synergistic Interaction of La2Ti2O7 Photocatalyst with Plasmonic Gold Nanoparticles and Reduced Graphene Oxide Nanosheets Fanke Meng, Scott K. Cushing, Jiangtian Li, Shimeng Hao and Nianqiang Wu* F. K. Meng, Dr. J. T. Li, S. M. Hao, Prof. N. Q. Wu Department of Mechanical and Aerospace Engineering West Virginia University Morgantown, WV 26506-6106, USA. Fax: +1-304-293-6689 Email: [email protected] S. K. Cushing Department of Physics and Astronomy West Virginia University Morgantown, WV 26506-6315, USA.
Experimental Methods
1 Materials Synthesis La2Ti2O7 (LTO) nanosheets were synthesized following our previous publications [S1,S2]. To deposit the Pt nanoparticle on the LTO sheets, 0.05 g of Pt(NH3)4Cl2 (Sigma–Aldrich) and 0.5 g of La2Ti2O7 nanosheets were mixed with 20 mL of deionized water (DI) to form a homogenous suspension in a 50 mL of beaker, and then held at room temperature under stirring for 24 h. The white powder was obtained by centrifuging and subsequent drying at 80 ⁰C overnight. The white powder was then heated in air at 400 ⁰C for 3 h. The color of the powder became grey. The grey powder was finally reduced in a H2 flow at 500 ⁰C for 1 h to obtain the Pt-loaded La2Ti2O7 (Pt-LTO) nanosheets.
Au@Pt-La2Ti2O7 (LTO) nanosheets were synthesized as follows. 0.5 g of Pt-LTO nanosheets was mixed with 0.05 g of HAuCl4 (Alfa. Inc) in 10 mL of DI water to form a suspension. The suspension was centrifuged to get the fluffy powder, dried at 80 ⁰C overnight, and subsequently heated in air at 400 ⁰C for 3 h. The powder was reduced in a H2 flow at 500 ⁰C for 1 h, which resulted in the Au nanoparticle loaded nanosheet (Au@Pt-LTO).
Graphene oxide (GO) was synthesized with the Hummer method [S3].
Au@Pt-La2Ti2O7 (LTO) nanosheets coupled with rGO was synthesized as follows. 0.5 g of Au@Pt-LTO nanosheets were mixed with 0.0125 g of GO (2.5 wt.%) in 15 g of DI water to form a suspension and stirred rigorously in an ultrasonic bath for 20 s. 15 ml of ethanol was then added into the suspension and stirred for 1 min. The suspension was then transferred and sealed in a Teflon-lined pressure vessel in a pre-heated oven (200 ⁰C) for 24 h. After the pressure vessel was cooled to room temperature, the resulting powder was washed with DI water 5 times, and then dried on a hotplate at 80 ⁰C overnight. This resulted in the Au@Pt-LTO/rGO sample.
Pt-loaded N-doped La2Ti2O7 (NLTO) nanosheets were prepared by heating 0.5 g of Pt-loaded La2Ti2O7 nanosheets in a NH3 flow at 600 ⁰C for 3h. This resulted in the Pt-NLTO sample
Au and Pt-loaded N-doped La2Ti2O7 nanosheets were prepared by heating 0.5 g of Au and Pt-loaded La2Ti2O7 nanosheets in a NH3 flow at 600 ⁰C for 3h. This resulted in the Au@Pt-NLTO sample
S1
Supporting Information Au and Pt-loaded, N-doped La2Ti2O7 nanosheets coupled with rGO was synthesized with hydrothermal method. 0.5 g Au and Pt-loaded, N-doped La2Ti2O7 nanosheets was mixed with the GO sheets as described previously and subject to the hydrothermal processing. This resulted in the Au@Pt-NLTO/rGO sample
2 Materials characterization The detail materials characterization methods were reported in our previous literatures [S1,S2,S4]. The particle morphology was observed with a scanning electron microscope (SEM, JEOL 7600F) and a transmission electron microscope (TEM, JEOL, JEM 2100). The crystal structures of materials were characterized by a high-resolution TEM (HRTEM) and X-ray diffraction (XRD, X’ Pert Pro PW3040-Pro, Panalytical Inc.) with Cu Kα radiation. The chemical structure was determined by X-ray photoelectron spectroscopy (XPS, PHI 5000 Versa Probe system, Physical Electronics) with a reference to the C 1s peak at 284.8 eV. The light absorption spectra of the samples were acquired by an ultraviolet-visible spectrometer (UV-Vis, Lambda 750, PerkinElmer Inc.). The specific surface areas of the samples were measured by Brunauer, Emmett and Teller (BET, Micromeritics ASAP 2020).
3. Photocatalysis A commercial solar light simulator (300 W, Newport, Intensity: 40-50 mW/cm2) equipped with a monochromic shutter and an AM 1.5G filter was used as the light source for photocatalysis. To perform the photocatalytic H2 generation, 10 mg of photocatalyst powder was suspended in a 20 mL of solution (10 mL of DI and 10 mL of ethanol) in a 100 mL of quart flask. The suspension was bubbled with a N2 flow (99.9 %, Air Gas Inc.) for 10 min. After bubbling, the flask was sealed and illuminated under the simulated solar light with a light window of 2.0 cm2 for different time intervals. Finally, 5 mL of the gas sample was collected from the flask for chromatography measurement (GC, Shimadzu 2014).
4. Photoelectrochemical Measurement 4.1 Preparation of photoeletrodes 0.1 g of photocatalyst powder was mixed with 0.5 mL of terpineol (~95%, Sigma-Aldrich) under stirring overnight to form a homogenous suspension. The suspension was pasted onto a fluorine-doped tin oxide (FTO) substrate (Hartford, TEC 15) with doctor blading method. The pasted FTO photoelectrode was then dried on a hot plate in air, subsequently heated in N2 at 550 °C for 2 h. Finally, a copper wire was connected to the FTO substrate with the silver colloid paste and the sealed with epoxy glue.
4.2 Electrochemical measurement A three-electrode photoelectrochemical cell (PEC) was constructed and measured with a Gamry electrochemical station (Reference 3000™). The Pt plate, AgAgCl and photoelectrodes acted as the counter electrode, the reference electrode and the working electrode, respectively. 1 M NaOH (>98.0%, Sigma-Aldrich) aqueous solution was employed as the electrolyte (pH=13.6,) and bubbled with a N2 flow for 30 min prior to photoelectrochemical testing. The light source for the PEC was the same as that used in photocatalytic water splitting. The plot of photocurrent density (J) with the applied potential (V) was obtained. The potential (vs. AgAgCl) was converted to the reversible hydrogen electrode (RHE) according to the Nernst equation:
ERHE E 0.05916 pH E0
(S1)
Where ERHE is the potential vs. RHE, E0= 0.1976 V at 25 °C, and E is the measured potential vs. AgAgCl. The on-off J-V curves were obtained under a bias of -0.25 V vs. RHE.
The incident photo-to-electron conversion efficiency (IPCE) plots were measured with the photocurrents at different wavelengths of incident light under a bias of -0.25 V vs. RHE. The IPCE was calculated as follows:
IPCE 1240 J / I light Where
(S2)
I light is the light intensity at a wavelength of λ. λ was varied from 250 nm to 700 nm with an interval of 25 nm.
S2
Supporting Information Mott-Schottky (M-S) plots were used to estimate the flat-band potential [S5]: 𝑆𝑙𝑜𝑝 = 𝜀𝜀
2
(S3)
2 0 𝐴 𝑒𝑁𝐷
𝐼𝑛𝑡𝑒𝑟𝑐𝑒𝑝𝑡 =
𝑘𝐵 𝑇 𝑒
+ 𝑉𝑓𝑏
(S4)
Where ε, ε0, A, e, kB, ND and Vfb are dielectric constant of the semiconductor, permittivity of free space, electrode area, Boltzmann constant, charge density and flat-band potential, respectively. The charge recombination behavior was quantified according to the normalized transient photocurrent
D ( It Ist ) / ( Iin Ist )
(S5)
Where D is a normalized parameter [S4, S6], It and Ist are the time-dependent current density and final current density in dark, respectively. Iin is the initial photocurrent. In the plot of lnD–t, the transient time constant (τ) is determined when lnD=-1 [S4, S6].
S3
Supporting Information
Figure S1. TEM images of the sample (a) Au@Pt-NLTO and (b) Au@Pt-LTO/rGO.
Figure S2. XPS spectra of (a) Pt 4f, (b) Au 4f, and (c) N 1s peaks for Au@Pt-NLTO/rGO (curve 1), Au@Pt-NLTO (curve 2), Pt-NLTO (curve 3), and Au@Pt-LTO/rGO (curve 4).
Figure S3. XRD patterns for Au@Pt-NLTO/rGO (curve 1), Au@Pt-NLTO (curve 2), Pt-NLTO (curve 3), and Au@Pt-LTO/rGO (curve 4).
S4
Supporting Information
Figure S4. (a,b) UV-VIS absorption spectra, (c) J-V curves plotting the photocurrent density as a function of the applied potential and (d) IPCE spectra for LTO and NLTO with and without Au nanoparticles.
Figure S5. Hydrogen generation rate over three cycles for Au@Pt-NLTO/rGO, Au@Pt-NLTO, Pt-NLTO, and Au@Pt-LTO/rGO.
S5
Supporting Information
Figure S6. Mott-Schottky plots of the samples in the dark (hollow) and under irradiation of simulated solar light (solid).
Figure S7. Transient photocurrent measurement obtained from the photoelectrodes.
S6
Supporting Information
Figure S8. Plasmonic energy transfer mechanisms. (a) During direct electron transfer (DET), hot plasmonic electronics photo-excited in the Au can overcome the Schottky barrier. The transferred electrons are then trapped, leading to an increase in the photocurrent in the semiconductor at the absorption peak of the plasmon. (b) During plasmon induced resonant energy transfer (PIRET), the plasmonic dipole relaxes by nonradiatively exciting an electron hole pair in the semiconductor. Since the process does not require electron transfer, it can occur through an insulating barrier with a strength that decays with increasing separation distance. For the semiconductor and plasmon to interact through the near field the two spectrums must overlap energetically. Therefore the enhancement can be approximated by the overlap between the semiconductor and plasmon absorption (the plasmon absorption is approximately equal to its fluorescence in the samples measured [S7]). For further information on the plasmonic energy transfer mechanisms refer to references S8-S10.
Figure S9. (a) Increase in spectral utilization between the Pt-NLTO and Au@Pt-NLTO/rGO samples. (b) The increase in the IPCE is seen to be identical to that shown in the main text Figure 4. This is expected as the addition of rGO only increases lifetime, and not the spectral utilization. Therefore the plasmonic energy transfer mechanism is PIRET for both Au@Pt-NLTO and Au@Pt-NLTO/rGO samples.
S7
Supporting Information Table S1. The contents of Pt, Au and N in four samples. Sample
Pt (at. %)
Au (at. %)
N (at. %)
Au@Pt-NLTO/rGO
1.55
2.12
1.99
Au@Pt-NLTO
1.71
2.21
2.08
Pt-NLTO
1.65
0
2.13
Au@Pt-LTO/rGO
1.61
2.05
0
Table S2. The photocatalytic hydrogen generation rates and BET surface areas of four samples. Sample
Surface areas
H2 (μM·g-1·h-1)
H2 (μM·m-2·h-1)
(m2·g-1)
Au@Pt-NLTO/rGO
163.4
44.65
3.66
Au@Pt-NLTO
101.1
38.54
2.62
Pt-NLTO
65.3
40.25
1.62
Au@Pt-LTO/rGO
44.2
43.53
1.02
Table S3. Flat-band potentials of four samples. Sample
Vfb in dark (V)
Vfb under illumination (V)
Au@Pt-NLTO/rGO
-0.53
-0.72
Au@Pt-NLTO
-0.50
-0.71
Pt-NLTO
-0.52
-0.57
Au@Pt-LTO/rGO
-0.27
-0.37
S8
Supporting Information References [S1] Meng, F. K.; Li, J. T.; Hong, Z. L.; Zhi, M. J.; Sakla, A.; Xiang, C. C.; Wu, N. Q., Catal. Today, 2013, 199, 48-52. [S2] Meng, F. K.; Hong, Z. L.; Arndt, J.; Li, M.; Zhi, M. J.; Yang, F.; Wu, N. Q., Nano Res. 2012, 5, 213-221. [S3] Hummers, W. S.; Offeman, R. E. J. Am. Chem. Soc., 1958, 80, 1339. [S4] Meng, F.K., Li, J. T., Cushing, S. K., Zhi, M. J., Wu, N. Q., J. Am. Chem. Soc., 2013, 135, 10286-10289. [S5] Gelderman, K., Lee, L., Donne, S. W., J. Chem. Edu., 2007, 84, 685-688. [S6] Tafalla, D., Salvador, P. Benito, R. M. J. Electrochem. Soc., 1990, 137, 1810-1815. [S7] Zuloaga, J., Nordlander, P. Nano Lett. ,2011, 11, 1280-1283. [S8] Li, J. T., Cushing, S. K., Zheng, P., Meng, F. K., Chu, D., Wu, N. Q., Nature Comm., 2013, 4, 2651 [S9] Cushing, S. K., Li, J. T., Meng, F. K., Senty, T. R., Suri, S., Zhi, M. J., Li, M., Bristow, A. D., Wu, N. Q., J. Am. Chem. Soc., 2012, 134, 15033−15041. [S10] Li, J. T., Cushing, S. K., Bright, J., Meng, F. K., Senty, T. R., Zheng, P., Bristow, A. D., Wu, N. Q., ACS Catal., 2013, 3, 47-51.
S9
