Tuning PbS QDs deposited onto TiO2 nanotube arrays to improve photoelectrochemical performances.

The ability to anchor quantum dots (QDs) onto the inner channels of nanotube arrays affords the opportunity to engineer the electron and band structures for a variety of applications. During the successive ionic layer adsorption and reaction (SILAR) preparation, the deposition of PbS QDs had been tuned by adjusting the concentration ratio of sulfur and lead sources onto the TiO2 nanotube array (TNA) support formed via anodic ionization. The photoelectrochemical properties of the PbS QD sensitized TNAs were optimized. The sample microstructure and photoelectrochemical properties were analyzed with X-ray diffraction (XRD), transmission electron microscopy (TEM), field-emission scanning electron microscopy (FE-SEM), UV-visible diffuse reflectance spectroscopy (UV-vis DRs), photoluminescence (PL), current-voltage characteristics (J-V), electrochemical impedance spectroscopy (EIS), transient photovoltage plots and Mott-Schottky curves. The size and distribution of the PbS QDs were tuned by varying the concentration ratio of sulfur and lead sources during the SILAR process. The band gap structure, flat band potential, lifetime and transport of the photo-induced charge carriers were subsequently modified. With a S/Pb concentration ratio of 5, the samples demonstrated the best photoelectrochemical characteristics with a peak photocurrent density of 8.24mAcm-2 and a corresponding photoconversion efficiency of 7.80%.