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Title: Charge Transport at Ti-Doped Hematite (001)/Aqueous Interfaces

Solid-state transport and electrochemical properties of Ti-doped hematite (001) epitaxial thin films (6.0, 8.3, and 16.6 at% Ti) were probed to achieve a better understanding of doped hematite for photoelectrochemical (PEC) applications. Room temperature resistivity measurements predict a resistivity minimum near 10 at% Ti doping, which can be rationalized as maximizing charge compensating Fe2+ concentration and Fe3+ electron accepting percolation pathways simultaneously. Temperature dependent resistivity data are consistent with small polaron hopping, revealing an activation energy that is Ti concentration dependent and commensurate with previously reported values (≈ 0.11 eV). In contact with inert electrolyte, linear Mott-Schottky data at various pH values indicate that there is predominantly a single donor for Ti-doped hematite at 6.0 at% Ti and 16.6 at% Ti concentrations. Two slope Mott-Schottky data at pH extremes indicate the presence of a second donor or surface state in the 8.3 at% Ti-doped film, with an energy level ≈ 0.7 eV below the Fermi level. Mott-Schottky plots indicate pH and Ti concentration dependent flatband potentials of -0.4 to -1.1 V vs. Ag/AgCl, commensurate with previously reported data. Flatband potentials exhibited super-Nernstian pH dependence ranging from -69.1 to -101.0 mV/pH. Carrier concentration data indicate that the Fermi energy of themore » Ti-doped system is Ti concentration dependent, with a minimum of 0.15 eV near 10 at% Ti. These energy level data allow us to construct an energy band diagram for Ti-doped hematite electrode/electrolyte interfaces, and to determine a Ti-doping concentration t« less
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Publication Date:
OSTI Identifier:
Report Number(s):
47824; KC0302060
DOE Contract Number:
Resource Type:
Journal Article
Resource Relation:
Journal Name: Chemistry of Materials, 27(5):1665-1673
Research Org:
Pacific Northwest National Laboratory (PNNL), Richland, WA (US), Environmental Molecular Sciences Laboratory (EMSL)
Sponsoring Org:
Country of Publication:
United States
Environmental Molecular Sciences Laboratory