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

Abstract

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 nontoxicity. 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.

TiO2 nanotree films for the production of green H2 by solar water splitting: From microstructural and optical characteristics to the photocatalytic properties

“…This is consistent with the work of Chen et al, who showed that the charge mobility of small anatase nanorods (0.57 cm 2 V −1 s −1 ) [55] is much lower than that of large crystallites (20 cm 2 V −1 s −1 ) [9]. Further, we suspect that a larger number of grain boundaries in the nanotree TiO 2 , which act as diffusion centers [56], and a higher disorder may cause charge carrier traps and ohmic behavior. Finally, the intensity of reflected light increases with increasing T d mainly because of scattering.…”

In- and out-plane transport properties of chemical vapor deposited TiO2 anatase films

“…This large variety of techniques results in a wealth of morphological forms and crystalline phases. Concerning anatase TiO2 thin films, numerous studies demonstrated a broad resistivity range (from 10 10 Ω cm to 10 Ω cm [15][16][17][18]), in strong correlation with crystalline phases and/or morphology [15][16][19][20][21][22][23].…”

Toward the Intrinsic Superiority of Aligned One‐Dimensional TiO2 Nanostructures: the Role of Defect States in Electron Transport Process

“…[2,[5][6][7] Tremendous efforts have been devoted to develop TiO 2 nanostructure-based electrodes for efficient photoelectrochemical applications, [7][8][9] and among which, transport of electrons in TiO 2 electrodes is the most concerned issue. [10][11][12] According to the multiple trapping/detrapping framework, [13][14] electron transport through extended states would be slowed down by trapping/detrapping events. In the most widely adopted TiO 2 electrodes that made up of zero-dimensional nanoparticles, large surface area was obtained in this nanostructure; however, electron transport could be severely affected by electron scattering at grain boundaries and trapping/detrapping events.…”

“…Tremendous efforts have been devoted to develop TiO 2 nanostructure‐based electrodes for efficient photoelectrochemical applications, [7–9] and among which, transport of electrons in TiO 2 electrodes is the most concerned issue [10–12] . According to the multiple trapping/detrapping framework, [13–14] electron transport through extended states would be slowed down by trapping/detrapping events.…”