Improved photoelectrochemical property of a nanocomposite NiO/CdS@ZnO photoanode for water splitting

Polygonal ZnO nanorods are synthesized with a hydrothermal technique and coated with an ultrathin CdS layer. A NiO cocatalyst layer is then deposited on the surface of the CdS coated ZnO and makes up a three-component nanostructured composite photoelectrode (NiO/CdS@ZnO). This composite photoelectrode shows an improved photoelectrochemical performance under Air Mass 1.5 (AM 1.5) simulated sunlight. It generates a photocurrent density of 950 mu A/cm(2) with a comparatively low potential -0.6 V vs. Ag/AgCl in a 0.5 M Na2S and Na2SO3 solution, which is 6.78 times as much as that of the as-grown ZnO nanorods. Furthermore, it is also an efficient photoanode to split pure water, producing a photocurrent density of 530 mu A/cm(2) at 0.5 V vs. Ag/AgCl in a 1 M Na2SO4 solution. In the composite, ZnO nanorods absorb UV light with a wide band gap, 3.2 eV, while CdS, with a narrow band gap (2.4 eV), utilizes the remaining visible light, furthermore, an ordered transfer of the charge carriers occurs in the component phases. The photoluminescence (PL) experiment results prove that the direct loading of NiO on ZnO results in an inactive material. However, both the CdS/ZnO and NiO/CdS@ZnO composites are active and the charge carrier separations in them are effectively improved than in the as-grown ZnO. (C) 2014 Elsevier B.V. All rights reserved.