title: Electron collection in host-guest nanostructured hematite photoanodes for water splitting: the influence of scaffold doping density.
abstract: Nanostructuring has proven to be a successful strategy in overcoming the trade-off between light absorption and hole transport to the solid/electrolyte interface in hematite photoanodes for water splitting. The suggestion that poor electron (majority carrier) collection hinders the performance of nanostructured hematite electrodes has led to the emergence of host-guest architectures in which the absorber layer is deposited onto a transparent high-surface-area electron collector. To date, however, state of the art nanostructured hematite electrodes still outperform their host-guest counterparts, and a quantitative evaluation of the benefits of the host-guest architecture is still lacking. In this paper, we examine the impact of host-guest architectures by comparing nanostructured tin-doped hematite electrodes with hematite nanoparticle layers coated onto two types of conducting macroporous SnO2 scaffolds. Analysis of the external quantum efficiency spectra for substrate (SI) and electrolyte side (EI) illumination reveals that the electron diffusion length in the host-guest electrodes based on an undoped SnO2 scaffold is increased substantially relative to the nanostructured hematite electrode without a supporting scaffold. Nevertheless, electron collection is still incomplete for EI illumination. By contrast, an electron collection efficiency of 100% is achieved by fabricating the scaffold using antimony-doped SnO2, showing that the scaffold conductivity is crucial for the device performance.
authors.affiliation: Department of Chemistry and Center for NanoScience (CeNS), Ludwig-Maximilians-Universität München , Butenandtstr. 5-11, D-81377 Munich, Germany.
authors.forename: Ilina
authors.initials: I
authors.lastname: Kondofersky
authors.forename: Halina K
authors.initials: HK
authors.lastname: Dunn
authors.forename: Alexander
authors.initials: A
authors.lastname: Müller
authors.forename: Benjamin
authors.initials: B
authors.lastname: Mandlmeier
authors.forename: Johann M
authors.initials: JM
authors.lastname: Feckl
authors.forename: Dina
authors.initials: D
authors.lastname: Fattakhova-Rohlfing
authors.forename: Christina
authors.initials: C
authors.lastname: Scheu
authors.forename: Laurence M
authors.initials: LM
authors.lastname: Peter
authors.forename: Thomas
authors.initials: T
authors.lastname: Bein
keywords: antimony-doped SnO2; effective electron diffusion length; host−guest; iron oxide; photoelectrochemical water splitting