Unravelling Small-Polaron Transport in Metal Oxide Photoelectrodes

作者：Rettie Alexander J E; Chemelewski William D; Emin David; Mullins C Buddie^*

来源：Journal of Physical Chemistry Letters, 2016, 7(3): 471-479.

DOI：10.1021/acs.jpclett.5b02143

Transition-metal oxides are a promising class of semiconductors for the oxidation of water, a process that underpins both photoelectrochemical water splitting and carbon dioxide reduction. However, these materials are limited by very slow charge transport. This is because, unlike conventional semiconductors, material aspects of metal oxides favor the formation of slow-moving, self-trapped charge carriers: small polarons. In this Perspective, we seek to highlight the salient features of small-polaron transport in metal oxides, offer guidelines for their experimental characterization, and examine recent transport studies of two prototypical oxide photoanodes: tungsten-doped monoclinic bismuth vanadate (W:BiVO4) and titanium-doped hematite (Ti:alpha-Fe2O3). Analysis shows that conduction in both materials is well-described by the adiabatic small-polaron model, with electron drift mobility (distinct from the Hall mobility) values on the order of 10(-4) and 10(-2) cm(2) V-1 s(-1) respectively. Future directions to build a full picture of charge transport in this family of materials are discussed.

• 出版日期2016-2-4