New Insights into the Electron-Collection Efficiency Improvement of CdS-Sensitized TiO Nanorod Photoelectrodes by Interfacial Seed-Layer Mediation.

Titanium dioxide (TiO) nanorods (NRs) are widely used as photoanodes in photoelectrochemical (PEC) solar fuel production because of their remarkable photoactivity and stability. In addition, TiO NR electrode materials can be decorated with active CdS quantum dots (QDs) to expand the sunlight photon capture. The overall photoelectric conversion efficiency for TiO NR or QD-sensitized TiO NR electrode materials in PEC is typically dominated by their interfacial electron transfer (ET) properties. To understand the key factors affecting the ET, the anatase TiO seed layer was added into the interface between the rutile TiO NRs and fluorine-doped tin oxide (FTO) substrate. This seed layer enhanced the photocatalytic performance of both the TiO NR and CdS QD-sensitized TiO NR photoanodes in PEC. Time-resolved photoluminescence spectroscopy and PEC analyses, including Mott-Schottky, electrochemical impedance spectroscopy, and photovoltage ( V) measurements, were used to study the charge-carrier dynamics at the interfaces between the FTO, TiO, and CdS QD. Analysis of the results showed that band alignment at the anatase/rutile junction between the TiO and FTO promoted electron-collection efficiency ( e) at the FTO/TiO interface and ET rate constant ( k) at the TiO/CdS QD interface. Furthermore, 34% enhancement of the efficiency in hydrogen (H) generation demonstrated the potential of the TiO seed-layer-mediated TiO/CdS QD NR photoanode in the application of PEC solar fuel production. The current work represents new insights into the mechanism of ET in TiO and TiO/CdS QD NR, which is very useful for the development of photoelectrode materials in solar energy conversions.