title: Porous versus Compact Nanosized Fe(III)-Based Water Oxidation Catalyst for Photoanodes Functionalization.
abstract: Integrated absorber/electrocatalyst schemes are increasingly adopted in the design of photoelectrodes for photoelectrochemical cells because they can take advantage of separately optimized components. Such schemes also lead to the emergence of novel challenges, among which parasitic light absorption and the nature of the absorber/catalyst junction features prominently. By taking advantage of the versatility of pulsed-laser deposition technique, we fabricated a porous iron(III) oxide nanoparticle-assembled coating that is both transparent to visible light and active as an electrocatalyst for water oxidation. Compared to a compact morphology, the porous catalyst used to functionalize crystalline hematite photoanodes exhibits a superior photoresponse, resulting in a drastic lowering of the photocurrent overpotential (about 200 mV) and a concomitant 5-fold increase in photocurrents at 1.23 V versus reversible hydrogen electrode. Photoelectrochemical impedance spectroscopy indicated a large increase in trapped surface hole capacitance coupled with a decreased charge transfer resistance, consistent with the possible formation of an adaptive junction between the absorber and the porous nanostructured catalyst. The observed effect is among the most prominent reported for the coupling of an electrocatalyst with a thin layer absorber.
authors.affiliation: Department of Physics, University of Trento , I-38123, Povo, Trento, Italy.
authors.forename: Michele
authors.initials: M
authors.lastname: Orlandi
authors.affiliation: Department of Chemical and Pharmaceutical Sciences, University of Ferrara , Via Fossato di Mortara 17-19, 44100 Ferrara, Italy.
authors.forename: Nicola
authors.initials: N
authors.lastname: Dalle Carbonare
authors.affiliation: Department of Chemical and Pharmaceutical Sciences, University of Ferrara , Via Fossato di Mortara 17-19, 44100 Ferrara, Italy.
authors.forename: Stefano
authors.initials: S
authors.lastname: Caramori
authors.affiliation: Department of Chemical and Pharmaceutical Sciences, University of Ferrara , Via Fossato di Mortara 17-19, 44100 Ferrara, Italy.
authors.forename: Carlo A
authors.initials: CA
authors.lastname: Bignozzi
authors.affiliation: Department of Chemical and Pharmaceutical Sciences, University of Ferrara , Via Fossato di Mortara 17-19, 44100 Ferrara, Italy.
authors.forename: Serena
authors.initials: S
authors.lastname: Berardi
authors.affiliation: Department of Physics, University of Trento , I-38123, Povo, Trento, Italy.
authors.forename: Alberto
authors.initials: A
authors.lastname: Mazzi
authors.affiliation: Department of Physics, University of Trento , I-38123, Povo, Trento, Italy.
authors.forename: Zakaria
authors.initials: Z
authors.lastname: El Koura
authors.affiliation: Department of Physics, University of Trento , I-38123, Povo, Trento, Italy.
authors.forename: Nicola
authors.initials: N
authors.lastname: Bazzanella
authors.affiliation: Department of Physics, University of Mumbai , Vidyanagari, Santacruz (E), Mumbai 400 098, India.
authors.forename: Nainesh
authors.initials: N
authors.lastname: Patel
authors.affiliation: Department of Physics, University of Trento , I-38123, Povo, Trento, Italy.
authors.forename: Antonio
authors.initials: A
authors.lastname: Miotello
keywords: a-Fe2O3; adaptive junction; hematite; nanostructures; photoanodes; pulsed-laser deposition; water splitting