Highly Efficient Solar Water Splitting from Transferred TiO2 Nanotube Arrays.
We report a synergistic effect of flame and chemical reduction methods to maximize the efficiency of solar water splitting in transferred TiO2 nanotube (TNT) arrays on a transparent conducting oxide (TCO) substrate. The flame reduction method (>1000 °C) leads to few oxygen vacancies in the anatase TNT arrays, but it exhibits unique advantages for excellent interfacial characteristics between transferred TNT arrays and TCO substrates, which subsequently induce a cathodic on-set potential shift and sharp photocurrent evolution. By contrast, the employed chemical reduction method for TNT arrays/TCO gives rise to an abrupt increase in photocurrent density, which results from the efficient formation of oxygen vacancies in the anatase TiO2 phase, but a decrease in charge transport efficiency with increasing chemical reduction time. We show that flame reduction followed by chemical reduction could significantly improve the saturation photocurrent density and interfacial property of TNT arrays/TCO photoanodes simultaneously without mechanical fracture via the synergistic effects of coreducing methods.
Department of Materials Science & Engineering and Energy Systems Research, Ajou University , Suwon, 443-749, Korea.|Department of Mechanical Engineering, Stanford University , California 94305, United States.
In Sun
IS
Cho
Department of Chemical Engineering, Pohang University of Science and Technology , San31, Nam-gu, Pohang, Kyoungbuk, Korea.
Jongmin
J
Choi
Department of Chemical and Biomolecular Engineering, Yonsei University , 50 Yonsei-ro, Seodaemun-gu, Seoul 120-749, Republic of Korea.
Kan
K
Zhang
Department of Chemical and Biomolecular Engineering, Yonsei University , 50 Yonsei-ro, Seodaemun-gu, Seoul 120-749, Republic of Korea.
Sung June
SJ
Kim
Department of Chemical and Biomolecular Engineering, Yonsei University , 50 Yonsei-ro, Seodaemun-gu, Seoul 120-749, Republic of Korea.
Myung Jin
MJ
Jeong
Department of Mechanical Engineering, Stanford University , California 94305, United States.
Lili
L
Cai
Department of Chemical Engineering, Pohang University of Science and Technology , San31, Nam-gu, Pohang, Kyoungbuk, Korea.
Taiho
T
Park
Department of Mechanical Engineering, Stanford University , California 94305, United States.
Xiaolin
X
Zheng
Department of Chemical and Biomolecular Engineering, Yonsei University , 50 Yonsei-ro, Seodaemun-gu, Seoul 120-749, Republic of Korea.
Jong Hyeok
JH
Park
TiO2 nanotubes; chemical reduction; flame reduction; photoelectrochemical water splitting; synergistic effects; transfer