ic9b00327_si_001.pdf (392.58 kB)
Mössbauerite as Iron-Only Layered Oxyhydroxide Catalyst for WO3 Photoanodes
journal contribution
posted on 2019-07-16, 17:36 authored by Michael Ertl, Zili Ma, Thomas Thersleff, Pengbo Lyu, Sven Huettner, Petr Nachtigall, Josef Breu, Adam SlabonMössbauerite,
a trivalent iron-only layered oxyhydroxide, has been recently identified
as an electrocatalyst for water oxidation. We investigated the material
as potential cocatalyst for photoelectrochemical water oxidation on
semiconductor photoanodes. The band edge positions of mössbauerite
were determined for the first time with a combination of Mott–Schottky
analysis and UV–vis diffuse reflectance spectroscopy. The positive
value of the Mott–Schottky slope and the flatband potential
of 0.34 V vs reversible hydrogen electrode (RHE) identifies the material
as an n-type semiconductor, but bare mössbauerite does not
produce noticeable photocurrent during water oxidation. Type-II heterojunction
formation by facile drop-casting with WO3 thin films yielded
photoanodes with amended charge carrier separation and photocurrents
up to 1.22 mA cm–2 at 1.23 V vs RHE. Mössbauerite
is capable of increasing the charge carrier separation at lower potential
and improving the photocurrent during photoelectrochemical water oxidation.
The rise in photocurrent of the mössbauerite-functionalized
WO3 photoanode thus originates from improved charge carrier
separation and augmented hole collection efficiency. Our results highlight
the potential of mössbauerite as a second-phase catalyst for
semiconductor electrodes.