jp305221v_si_001.pdf (684.91 kB)
Effect of Tin Doping on α-Fe2O3 Photoanodes for Water Splitting
journal contribution
posted on 2012-07-26, 00:00 authored by Christopher D. Bohn, Amit K. Agrawal, Erich C. Walter, Mark D. Vaudin, Andrew
A. Herzing, Paul M. Haney, A. Alec Talin, Veronika A. SzalaiSputter-deposited films of α-Fe2O3 of
thickness 600 nm were investigated as photoanodes for solar water
splitting and found to have photocurrents as high as 0.8 mA/cm2 at 1.23 V vs the reversible hydrogen electrode (RHE). Sputter-deposited
films, relative to nanostructured samples produced by hydrothermal
synthesis,, permit facile characterization of the role
and placement of dopants. The Sn dopant concentration in the α-Fe2O3 varies as a function of distance from the fluorine-doped
tin oxide (FTO) interface and was quantified using secondary ion mass
spectrometry (SIMS) to give a mole fraction of cations of approximately
0.02% at the electrolyte interface. Additional techniques for determining
dopant density, including energy dispersive X-ray spectroscopy (EDS),
electron energy loss spectroscopy (EELS), electrochemical impedance
spectroscopy (EIS), and conductivity measurements, are compared and
discussed. Based on this multifaceted data set, we conclude that not
all dopants present in the α-Fe2O3 are
active. Dopant activation, rather than just increasing surface area
or dopant concentration, is critical for improving metal oxide performance
in water splitting. A more complete understanding of dopant activation
will lead to further improvements in the design and response of nanostructured
photoanodes.