Fabrication of unique three-dimensional CdS nanosheets/TiO2 nanosheets hierarchical heterostructure as photoelectrode for enhancing photoelectrochemical performance

Abstract

TiO2 is a promising photovoltaic material, but its inherent problems such as wide bandgap and rapid electron-hole recombination limit its application. To address these deficiencies, a unique three-dimensional (3D) CdS nanosheet (NS)/TiO2 NS hierarchical heterostructure as photoelectrode was fabricated by using triethanolamine (TEA) as surface regulator via hydrothermal method. Under the effect of TEA, the morphology of CdS can evolve form nanoparticle to NS, and the hierarchical film composed of CdS NSs and TiO2 NSs owned the optimal morphology characteristics due to its larger surface area, more active sites and adequate interspace. Benefiting from the morphological advantages, the light-harvesting ability of CdS NS/TiO2 NS composite was greatly improved. Meanwhile, the unique surface heterojunctions between the {001} and {101} facets of TiO2 NSs and the high-quality CdS/TiO2 heterojunctions effectively facilitated the separation and transport of photo-generated electron-hole pairs, prolonged the lifetime of photo-generated carriers and increased the electron density. Based on these favorable factors, the photoelectrochemical (PEC) performance of CdS NS/TiO2 NS hierarchical films exhibited the remarkable enhancements. The photocurrent density of CdS NS/TiO2 NS composite film under optimal reaction conditions reached to 9.35 mA cm−2, which was approximately 45 times greater than that of pure TiO2 NS film (0.21 mA cm−2). In addition, the detailed analysis of the effects of reaction time and temperature on sample morphology and properties was presented.