Efficient photoelectrochemical water splitting using CuO nanorod/Al2O3 heterostructure photoelectrodes with different Al layer thicknesses

In this study, an efficient water splitting technique was investigated with CuO nanorod/Al2O3 heterostructure photoelectrodes. Cupric oxide (CuO) nanorods were grown on a fluorine-doped tin oxide (FTO) glass substrate by using modified-chemical bath deposition. In addition, Al thin films were deposited on the CuO nanorods using thermal evaporation, and then, aluminum oxide (Al2O3) layers were formed in open air to create the CuO nanorod/Al2O3 structure. In this study, the morphological, optical and structural properties of CuO nanorod/Al2O3 photoelectrodes were analyzed according to the various thicknesses of the Al layers, and the effects of the thickness on the photoelectrochemical (PEC) properties were mainly discussed. We obtained a maximum photocurrent value of −2.26 mA/cm2 (−0.55 V vs. SCE) and a theoretical solar-to-hydrogen (STH) conversion efficiency of 1.61% using the Al 30-nm thick sample, which had the largest amount of the Al2O3 layer, as confirmed by X-ray photoelectron spectroscopy (XPS).