title: Improvement of the electron collection efficiency in porous hematite using a thin iron oxide underlayer: towards efficient all-iron based photoelectrodes.
abstract: Different approaches have been explored to increase the water oxidation activity of nanostructured hematite (α-Fe2O3) photoanodes, including doping with various elements, surface functionalization with both oxygen evolving catalysts (OEC) and functional overlayers and, more recently, the introduction of ultrathin oxide underlayers as tunneling back contacts. Inspired by this latter strategy, we present here a photoanode design with a nanometric spin-coated iron oxide underlayer coupled with a mesoporous hematite film deposited by electrophoresis. The electrodes equipped with the thin underlayer exhibit a four-fold improvement in photoactivity over the simple hematite porous film, reaching a stable photocurrent density of ca. 1 mA cm(-2) at 0.65 V versus the saturated calomel electrode (SCE) at pH 13.3 (NaOH 0.1 M) under air mass (AM) 1.5G illumination. A further improvement to 1.5 mA cm(-2) is observed after decoration of the hematite surface with a Fe(iii)-OEC. These results demonstrate that by combining different iron oxide morphologies, it is possible to improve the selectivity of the interfaces towards both electron collection at the back contact and hole transfer to the electrolyte, obtaining an efficient all-iron based photoelectrode entirely realized with simple wet solution scalable procedures.
authors.affiliation: Department of Chemical and Pharmaceutical Sciences, University of Ferrara, via Fossato di Mortara 17-27, 44121 Ferrara, Italy. cte@unife.it g4s@unife.it.
authors.forename: Nicola
authors.initials: N
authors.lastname: Dalle Carbonare
authors.forename: Stefano
authors.initials: S
authors.lastname: Carli
authors.forename: Roberto
authors.initials: R
authors.lastname: Argazzi
authors.forename: Michele
authors.initials: M
authors.lastname: Orlandi
authors.forename: Nicola
authors.initials: N
authors.lastname: Bazzanella
authors.forename: Antonio
authors.initials: A
authors.lastname: Miotello
authors.forename: Stefano
authors.initials: S
authors.lastname: Caramori
authors.forename: Carlo A
authors.initials: CA
authors.lastname: Bignozzi
mesh_terms: D004566:Electrodes; D004583:Electrons; D005290:Ferric Compounds / Q000737:chemistry*; D008855:Microscopy, Electron, Scanning; D010777:Photochemistry; D016062:Porosity
chemical_list: D005290:Ferric Compounds; C000499:ferric oxide