Effects of Growth Temperature on Cupric Oxide Nanorod Photoelectrodes Using a Modified Chemical Bath Deposition

Abstract

In this study, vertically aligned CuO nanorods were grown on a fluorine-doped tin oxide (FTO) substrate by a modified chemical bath deposition process at various growth temperatures. Field emission gun scanning electron microscopy, X-ray diffraction and UVvisible spectroscopy were used to characterize the morphological, structural and optical properties of the CuO nanorods, respectively. The photoelectrochemical properties of CuO nanorods as a photoelectrode were also measured in aqueous electrolyte solution (1 M KOH) under 1-sun illumination conditions (1.5 AM filter, 100 mW/cm 2 ) with a three-electrode potentiostat. In this study, well aligned CuO nanorods were obtained with a high growth rate (as high as 113 nm/min). Furthermore, primarily (020) directional growth was determined from X-ray diffraction measurements, and a maximum photocurrent density of −1.02 mA/cm 2 at −0.6 V (vs. saturated calomel electrode) was obtained from the CuO nanorod photoelectrode grown in this experiment.Photoelectrochemical (PEC) cells are considered to be efficient solar energy converters. 1 PEC cells convert solar energy into storable clean energy as hydrogen is created from water. Accordingly, many studies have used solar energy in water splitting for the production of hydrogen. 1-7 Semiconductors such as TiO 2 , 1-3 SrTiO 3 , 4 BaTiO 4 , 5 and ZnO 6 have been investigated as photoelectrode candidates. These materials are stable inside electrolytes but cannot fully absorb visible light due to their large band gaps. An ideal semiconductor for a PEC cell should have a bandgap between 1.7 and 2.1 eV, which is larger than the theoretical minimum value of 1.23 eV needed for water splitting, 8 and should be economically available. Therefore, cupric oxide (CuO) is expected to be a promising photoelectrode candidate due to its narrow bandgap and abundance. 7,8 CuO is well regarded as a p-type semiconductor with a narrow bandgap (1.4-1.7 eV) and has been extensively studied due to its properties and applications in electronics, sensors, optics, batteries, field emission devices, superconductors and photocatalysts. 9-15 Many studies have been carried out to synthesize various CuO nanostructures because the properties of CuO depend on its structure and morphology. [16][17][18] In particular, one-dimensional (1-D) structures such as nanorods with large surface areas are attracting much attention because of the many advanced properties of such 1-D nanostructures. 19,20 In this regard, the vertical growth of the 1-D CuO nanostructure is relevant to CuO photoelectrodes.Many growth methods have been developed for the synthesis of CuO 1-D nanostructures, such as hydrothermal, 21,22 and arc-discharge processes, 23 thermal evaporation 24 and thermal oxidation using copper foil. 11,20 However, these conventional methods have challenges, including growth rate, cost efficiency and synthesis on a transparent conducting oxide (TCO) substrate. In this study, CuO nanorods were synthesized using a modified chemical bath deposition (M-CBD) method that hea...

Rod-like Nano-structures of Copper Oxide Prepared by Chemical Bath Deposition

“…It has many applications in sensors, batteries, superconductors, optics, photocatalysts, and field emission devices [3]. Copper oxide is also an important candidate for photovoltaic applications [4]. It is well-known that the physical and chemical properties of the CuO are significantly dependent on its microstructures and morphology [5].…”

“…Few articles have been published on the growth of rod-like shapes of copper oxide. In particular, Oh, et al studied the effect of growth time on the CuO nanorods using the CBD method [4]. In the work of Ha et al, Ni-doped CuO nanorods were grown on a CuO film using different nickel amounts via the modified CBD method [19].…”