Unraveling the Intrinsic Structures that Influence the Transport of Charges in TiO2 Electrodes

TiO2 is by far the most widely used semiconducting materials for electrodes in (photo)-electrochemical applications owing to its unique electrical and optical properties combined with the chemical and thermal stability as well as non-toxicity. The electronic processes, especially the transport of charges within the electrodes and interfacial charge transfer, are among the most concerned issues to achieve better solar energy utilization. Towards this end, many approaches, including the development of novel electrode configurations and tuning electronic structures have been devoted to facilitate these electronic processes. Despite the intensive studies, some intrinsic structural features in TiO2 nanostructures, which are usually hidden from the tangible materials characterization techniques, are far from being consciously concerned. In this review, in addition to briefly summarizing the recent progress in TiO2 nanostructures for (photo)-electrochemical applications, the intrinsic structural features in TiO2 nanostructures, together with the challenges and perspectives involving these features, are emphatically discussed. These intrinsic structural features are shown to have a profound influence on the transport of charges within the TiO2 electrodes and interfacial charge transfer, and thus it is proposed that the charge transport in TiO2 electrodes can be efficiently promoted by cognizing and making good use of the intrinsic structural features.