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Photoelectrochemical Performance of Quantum dot-Sensitized TiO 2 Nanotube Arrays: a Study of Surface Modification by Atomic Layer Deposition Coating

View Article: PubMed Central - PubMed

ABSTRACT

Although CdS and PbS quantum dot-sensitized TiO2 nanotube arrays (TNTAs/QDs) show photocatalytic activity in the visible-light region, the low internal quantum efficiency and the slow interfacial hole transfer rate limit their applications. This work modified the surface of the TNTAs/QDs photoelectrodes with metal-oxide overlayers by atomic layer deposition (ALD), such as coating Al2O3, TiO2, and ZnO. The ALD deposition of all these overlayers can apparently enhance the photoelectrochemical performance of the TNTAs/QDs. Under simulated solar illumination, the maximum photocurrent densities of the TNTAs/QDs with 10 cycles ZnO, 25 cycles TiO2, and 30 cycles Al2O3 overlayers are 5.0, 4.3, and 5.6 mA/cm2 at 1.0 V (vs. SCE), respectively. The photoelectrode with Al2O3 overlayer coating presents the superior performance, whose photocurrent density is 37 times and 1.6 times higher than those of the TNTAs and TNTAs/QDs, respectively. Systematic examination of the effects of various metal-oxide overlayers on the photoelectrochemical performance indicates that the enhancement by TiO2 and ZnO overcoatings can only ascribed to the decrease of the interfacial charge transfer impedance, besides which Al2O3 coating can passivate the surface states and facilitate the charge transfer kinetics. These results could be helpful to develop high-performance photoelectrodes in the photoelectrochemical applications.

No MeSH data available.


PEC properties of the TNTAs/QDs, TNTAs/QDs/10 cycles ZnO, TNTAs/QDs/25 cycles TiO2, and TNTAs/QDs/30 cycles Al2O3 electrodes with a surface area of 1 cm2. a LSV curves of the electrodes under simulated solar illumination. b Photoconversion efficiency derived from LSV curves. c Transient photoresponse under chopped light irradiation under a potential 0 V vs. SCE
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Fig6: PEC properties of the TNTAs/QDs, TNTAs/QDs/10 cycles ZnO, TNTAs/QDs/25 cycles TiO2, and TNTAs/QDs/30 cycles Al2O3 electrodes with a surface area of 1 cm2. a LSV curves of the electrodes under simulated solar illumination. b Photoconversion efficiency derived from LSV curves. c Transient photoresponse under chopped light irradiation under a potential 0 V vs. SCE

Mentions: The photoelectrochemical performance of the photoelectrodes with different cycle metal oxide passivation layers deposited on the TNTAs/QDs is shown in Fig. 6. Figure 6a is the LSV plots of the four electrodes, which is made negligible since the dark current density of all of the samples is less than 200 μA, which is negligible. Under the simulated solar irradiation, the photocurrent density of the pure TNTAs is 0.14 mA/cm2 at 1 V (vs. SCE). After quantum dot sensitization, the photocurrent density increases to 3.48 mA/cm2 under the same bias, which is 23 times higher than the photocurrent density of the unsensitized electrode. Under simulated solar illumination, the maximal photocurrent density of 10 cycles ZnO, 25 cycles TiO2, and 30 cycles Al2O3 overlayer coating on the TNTAs/QDs are 5.0, 4.3, and 5.6 mA/cm2, respectively. In comparison, photocurrent density of TNTAs/QDs/30 cycles Al2O3 is relatively maximal, which is 37 times higher than the photocurrent density of the TNTAs, and 1.6 times higher than the TNTAs/QDs. With the exception of TNTAs, the starting potentials of the photocurrent in all the samples are about −1.0 V (vs. SCE), indicating that the conduction band edge basically remains fixed.Fig. 6


Photoelectrochemical Performance of Quantum dot-Sensitized TiO 2 Nanotube Arrays: a Study of Surface Modification by Atomic Layer Deposition Coating
PEC properties of the TNTAs/QDs, TNTAs/QDs/10 cycles ZnO, TNTAs/QDs/25 cycles TiO2, and TNTAs/QDs/30 cycles Al2O3 electrodes with a surface area of 1 cm2. a LSV curves of the electrodes under simulated solar illumination. b Photoconversion efficiency derived from LSV curves. c Transient photoresponse under chopped light irradiation under a potential 0 V vs. SCE
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Fig6: PEC properties of the TNTAs/QDs, TNTAs/QDs/10 cycles ZnO, TNTAs/QDs/25 cycles TiO2, and TNTAs/QDs/30 cycles Al2O3 electrodes with a surface area of 1 cm2. a LSV curves of the electrodes under simulated solar illumination. b Photoconversion efficiency derived from LSV curves. c Transient photoresponse under chopped light irradiation under a potential 0 V vs. SCE
Mentions: The photoelectrochemical performance of the photoelectrodes with different cycle metal oxide passivation layers deposited on the TNTAs/QDs is shown in Fig. 6. Figure 6a is the LSV plots of the four electrodes, which is made negligible since the dark current density of all of the samples is less than 200 μA, which is negligible. Under the simulated solar irradiation, the photocurrent density of the pure TNTAs is 0.14 mA/cm2 at 1 V (vs. SCE). After quantum dot sensitization, the photocurrent density increases to 3.48 mA/cm2 under the same bias, which is 23 times higher than the photocurrent density of the unsensitized electrode. Under simulated solar illumination, the maximal photocurrent density of 10 cycles ZnO, 25 cycles TiO2, and 30 cycles Al2O3 overlayer coating on the TNTAs/QDs are 5.0, 4.3, and 5.6 mA/cm2, respectively. In comparison, photocurrent density of TNTAs/QDs/30 cycles Al2O3 is relatively maximal, which is 37 times higher than the photocurrent density of the TNTAs, and 1.6 times higher than the TNTAs/QDs. With the exception of TNTAs, the starting potentials of the photocurrent in all the samples are about −1.0 V (vs. SCE), indicating that the conduction band edge basically remains fixed.Fig. 6

View Article: PubMed Central - PubMed

ABSTRACT

Although CdS and PbS quantum dot-sensitized TiO2 nanotube arrays (TNTAs/QDs) show photocatalytic activity in the visible-light region, the low internal quantum efficiency and the slow interfacial hole transfer rate limit their applications. This work modified the surface of the TNTAs/QDs photoelectrodes with metal-oxide overlayers by atomic layer deposition (ALD), such as coating Al2O3, TiO2, and ZnO. The ALD deposition of all these overlayers can apparently enhance the photoelectrochemical performance of the TNTAs/QDs. Under simulated solar illumination, the maximum photocurrent densities of the TNTAs/QDs with 10 cycles ZnO, 25 cycles TiO2, and 30 cycles Al2O3 overlayers are 5.0, 4.3, and 5.6 mA/cm2 at 1.0 V (vs. SCE), respectively. The photoelectrode with Al2O3 overlayer coating presents the superior performance, whose photocurrent density is 37 times and 1.6 times higher than those of the TNTAs and TNTAs/QDs, respectively. Systematic examination of the effects of various metal-oxide overlayers on the photoelectrochemical performance indicates that the enhancement by TiO2 and ZnO overcoatings can only ascribed to the decrease of the interfacial charge transfer impedance, besides which Al2O3 coating can passivate the surface states and facilitate the charge transfer kinetics. These results could be helpful to develop high-performance photoelectrodes in the photoelectrochemical applications.

No MeSH data available.