Photoelectrochemical Response and Semiconductor Characters of Cu/Cu2O/CuO/TiO2 Nanotube Arrays Photocatalyst

Abstract

Abstract. The cocatalysts of various copper morphology modified TiO2 nanotube arrays (TNTs) were prepared by electrochemical deposition. The morphologies of the samples were investigated by SEM. The reductive and oxidative copper modification strongly reinforce TNTs photocurrent response in UV and visible light region, especially the later one shows higher catalytical activity in visible light from 610nm to 740nm. The reductive copper morphology consists of Cu and Cu2O, and oxidative one comprises Cu, Cu2O and CuO by photocurrent analysis. The flat band potentials calculated by Mott-Schottky curves move positive potential direction with the oxidation depth. IntroductionOne-dimensional TiO2 nanotube arrays (TNTs) due to their high aspect ratio and large surface to volume ratio, have displayed excellent charge-transfer and photochemical property in photocatalytical process [1][2][3][4][5][6]. However, only wavelength below 387 nm, about 5% of solar spectrum energy can be directly utilized due to its large band gap of 3.2 eV. TNTs modification by doping metals such as Au, Pt, Pd, Ag [7][8][9][10][11] or metal oxides such as ZnO, RuO2, WO3, has been a hot topic of research to improve the solar spectrum absorption efficiency while maintaining its excellent charge-transfer property. The metal ion or metal oxides enhances the photo-catalytic activity by reducing electron-hole pair recombination and/or reducing the band gap.Cu as a metal of relative abundance and low cost has attracted much attention due to enhancement of the photocatalytic activity [16][17][18][19][20][21][22][23]. It can prevent the recombination of photoexcited electrons and holes as co-catalysts and generate localized surface plasmon resonance(LSPR) effect which promotes the separation of electron-holes [17]. Momeni prepared highly ordered copper doped TiO2 nanotube arrays thin-film by in situ electrochemical method and the samples exhibited better photo-catalytic activity than the TNTs [19]. The energy band gaps (Eg) of its oxides Cu2O and CuO are narrower than TiO2, respectively 2.2 eV and 1.7eV, which can promote visible light absorption [20].Chen et al. have developed a novel core-shell heterostructured Cu/Cu2O nanowires as efficient visible light photocatalysts [21,22]. Multifunctional CuO nanowire/TiO2 nanotube arrays photoelectrode has been fabricated applying for photocatalysis [23]. However, very few studies on the photoelectrochemical performance of TNTs co-modification by elemental Cu and its oxides( CuO and Cu2O) have been reported.In this work, we prepared Cu/Cu2O/CuO/TNTs catalysts by electrochemical method successfully, and tested their photo electrochemical response in UV and visible light and semiconductor characters. Moreover, the mechanism of TNTs modification by Cu/Cu2O/CuO has been analyzed.