Fast and selective Cu 2 O nanorod growth into anodic alumina templates via electrodeposition HyungKuk Ju a , Jae Kwang Lee b , Jongmin Lee b , Jaeyoung Lee a, b, * a Electrochemical Reaction and Technology Laboratory (ERTL), School of Environmental Science and Engineering (SESE), Gwangju 500-712, Republic of Korea b Ertl center for Electrochemistry and Catalysis, Gwangju Institute of Science and Technology (GIST), Gwangju 500-712, Republic of Korea article info Article history: Received 13 December 2010 Received in revised form 5 April 2011 Accepted 25 April 2011 Available online 30 April 2011 Keywords: Fast growth Cu 2 O Electrodeposition Pottery-shaped layer Alumina template abstract The fast and selective growth of cuprous oxide (Cu 2 O) nanorods into anodic aluminum oxide (AAO) templates is achieved under optimized alkaline conditions via electrochemical deposition. The growth rate of Cu 2 O nanorods at room temperature reached 360 nm/min, the fastest rate reported to date. The synthesis of Cu 2 O nanorods by applying a constant current by using Cu 2 O nanotubes as a transition state is extensively discussed; a Pt pottery-shaped layer played a key role as a seed layer for the fast Cu 2 O growth. We report here the existence of regions of nanostructured Cu 2 O based on our studies and previous relevant works, which include potential-pH curves for Cu 2þ -lactate solutions. Ó 2011 Elsevier B.V. All rights reserved. 1. Introduction The synthesis of nanostructures, in the ranges of only a few hundred nanometers, such as nanowires, erods, and etubes, has generated great interest owing to their distinct properties and unique applications, as compared to bulk materials [1,2]. For such nano-objects, template-based approaches are one of the most common fabrication methods for mass production and alignment [3]. In particular, anodic aluminum oxide (AAO) templates have been widely employed in the production of nanostructures due to their relatively uniform pore distribution, as well as their thermal and chemical stability [4,5]. Electrochemical deposition is generally used for the growth of metals and conducting metal oxides because of the following advantages: (i) the thickness and morphology of the nanostructure can be precisely controlled by adjusting the electrochemical parameters, (ii) relatively uniform and compact deposits can be synthesized in template-based structures, (iii) higher deposition rates are obtained, and (iv) the equipment is inexpensive due to the non-requirements of either a high vacuum or a high reaction temperature [6,7]. Note that our previous studies have demonstrated the fabrication of nanostructures such as Ni [8,9], Bi 2 Te 3 [10], PbeCeO 2 [11] nanowires, and V 2 O 5 agglomeration [12]. Thus, it is expected that the preparation of nanosized mate- rials via electrodeposition into an AAO template can be a powerful fabrication method. Copper (I) oxide (Cu 2 O) is one of the best photovoltaic p-type semiconducting materials, with a direct band gap of ca. 2.0 eV [13]. Furthermore, Cu 2 O has been attracting considerable attention not only due to its potential applications for splitting water into H 2 and O 2 upon visible light irradiation, but also for its application in cost- effective solar cell production and non-toxic devices [14e16]. Recently, we have extensively reported the preparation of Cu 2 O nanowires or erods via electrodeposition into AAO templates [17e20]. The electrodeposition of Cu 2 O is available from an alkaline solution of copper lactate, according to the following reactions [20]: 2Cu 2þ þ 2e  /2Cu þ (1) 2Cu þ þ 2OH  /2CuðOHÞ s (2) 2CuðOHÞ s /Cu 2 O þ H 2 O (3) however, such reactions typically take place under optimized electrochemical preparative conditions, which includes the pres- ence of sufficient OH  ions (pH > 8) and a solution temperature of ca. 65  C. If the solution is unsuitable for this optimized condition, the formation of Cu metal could be the dominant reaction into the porous template [19,21]: * Corresponding author. Electrochemical Reaction and Technology Laboratory (ERTL), School of Environmental Science and Engineering (SESE), Gwangju 500-712, Republic of Korea. Tel.: þ82 62 715 2440; fax: þ82 62 715 2434. E-mail address: jaeyoung@gist.ac.kr (J. Lee). Contents lists available at ScienceDirect Current Applied Physics journal homepage: www.elsevier.com/locate/cap 1567-1739/$ e see front matter Ó 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.cap.2011.04.042 Current Applied Physics 12 (2012) 60e64