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

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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.


a EIS spectra of the TNTAs/QDs, TNTAs/QDs/10 cycles ZnO, TNTAs/QDs/25 cycles TiO2, and TNTAs/QDs/30 cycles Al2O3 electrodes. b Mott-Schottky analysis of the TNTAs/QDs, TNTAs/QDs/10 cycles ZnO, TNTAs/QDs/25 cycles TiO2, and TNTAs/QDs/30 cycles Al2O3 electrodes
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Fig7: a EIS spectra of the TNTAs/QDs, TNTAs/QDs/10 cycles ZnO, TNTAs/QDs/25 cycles TiO2, and TNTAs/QDs/30 cycles Al2O3 electrodes. b Mott-Schottky analysis of the TNTAs/QDs, TNTAs/QDs/10 cycles ZnO, TNTAs/QDs/25 cycles TiO2, and TNTAs/QDs/30 cycles Al2O3 electrodes

Mentions: The effects of the passivation layer on the photoelectric properties can be summarized as follows: (1) to passivate the surface defects of the TNTAs/quantum dots, (2) to play a catalytic effect in order to promote charge transfer, (3) to build a heterojunction to reduce the interface impedance. In order to clarify the underlying mechanism, these photoelectrodes were examined by EIS and Mott-Schottky measurements [30], and the results are shown in Fig. 7.Fig. 7


Photoelectrochemical Performance of Quantum dot-Sensitized TiO 2 Nanotube Arrays: a Study of Surface Modification by Atomic Layer Deposition Coating
a EIS spectra of the TNTAs/QDs, TNTAs/QDs/10 cycles ZnO, TNTAs/QDs/25 cycles TiO2, and TNTAs/QDs/30 cycles Al2O3 electrodes. b Mott-Schottky analysis of the TNTAs/QDs, TNTAs/QDs/10 cycles ZnO, TNTAs/QDs/25 cycles TiO2, and TNTAs/QDs/30 cycles Al2O3 electrodes
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC5383911&req=5

Fig7: a EIS spectra of the TNTAs/QDs, TNTAs/QDs/10 cycles ZnO, TNTAs/QDs/25 cycles TiO2, and TNTAs/QDs/30 cycles Al2O3 electrodes. b Mott-Schottky analysis of the TNTAs/QDs, TNTAs/QDs/10 cycles ZnO, TNTAs/QDs/25 cycles TiO2, and TNTAs/QDs/30 cycles Al2O3 electrodes
Mentions: The effects of the passivation layer on the photoelectric properties can be summarized as follows: (1) to passivate the surface defects of the TNTAs/quantum dots, (2) to play a catalytic effect in order to promote charge transfer, (3) to build a heterojunction to reduce the interface impedance. In order to clarify the underlying mechanism, these photoelectrodes were examined by EIS and Mott-Schottky measurements [30], and the results are shown in Fig. 7.Fig. 7

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.