Interfacial Charge Dynamics of in2S3-Decorated TiO2 Nanowires

Ultrafast laser spectroscopy such as time-resolved photoluminescence is a powerful tool to retrieve dynamical information on the early steps of charge carrier transfer. In the past few years, considerable efforts have been devoted to studying interfacial charge dynamics of semiconductor heterostructures and realizing their implications in the photocatalytic processes. On the other hand, electrochemical impedance spectroscopy has demonstrated practical capability of revealing the reaction kinetics at the electrode/electrolyte interface, which is important for estimating the electrode efficiency for electrochemical reactions. Here we present the interfacial charge dynamics for In2S3-decorated TiO2 nanowires, which represent a typical TiO2-based type-II heterostructure system that has been widely used for photoelectrochemical water splitting. Because of the band alignment, the photoexcited electrons would preferentially transfer from In2S3 to TiO2, while the photogenerated holes were transported in an opposite direction from TiO2 to In2S3. Time-resolved up-conversion photoluminescence and electrochemical impedance spectroscopy were utilized to monitor the generation of charge carriers, the subsequent relaxation and recombination processes as well as their further involvement in the water splitting reaction. A temporal scheme which depicts the carrier lifetime at each of the above deactivation pathways was established to fully understand the fate of charge carriers within the In2S3-decorated TiO2 samples. The in-depth understanding of charge carrier dynamics can boost insights into the factors dictating the overall carrier utilization efficiency, which is imperative to the intelligent design of optimalsemiconductor nanostructures for photoelectrochemicalapplications.