title: Iridium Oxide Coatings with Templated Porosity as Highly Active Oxygen Evolution Catalysts: Structure-Activity Relationships.
abstract: Iridium oxide is the catalytic material with the highest stability in the oxygen evolution reaction (OER) performed under acidic conditions. However, its high cost and limited availability demand that IrO2 is utilized as efficiently as possible. We report the synthesis and OER performance of highly active mesoporous IrO2 catalysts with optimized surface area, intrinsic activity, and pore accessibility. Catalytic layers with controlled pore size were obtained by soft-templating with micelles formed from amphiphilic block copolymers poly(ethylene oxide)-b-poly(butadiene)-b-poly(ethylene oxide). A systematic study on the influence of the calcination temperature and film thickness on the morphology, phase composition, accessible surface area, and OER activity reveals that the catalytic performance is controlled by at least two independent factors, that is, accessible surface area and intrinsic activity per accessible site. Catalysts with lower crystallinity show higher intrinsic activity. The catalyst surface area increases linearly with film thickness. As a result of the templated mesopores, the pore surface remains fully active and accessible even for thick IrO2 films. Even the most active multilayer catalyst does not show signs of transport limitations at current densities as high as 75 mA cm(-2) .
authors.affiliation: Department of Chemistry, Technische Universität Berlin, Strasse des 17. Juni 124, 10623 Berlin (Germany).
authors.forename: Michael
authors.initials: M
authors.lastname: Bernicke
authors.affiliation: Division 6.8 Surface Analysis and Interfacial Chemistry, BAM Federal Institute for Materials Research and Testing, Unter den Eichen 44-46, 12203 Berlin (Germany).
authors.forename: Erik
authors.initials: E
authors.lastname: Ortel
authors.affiliation: Department of Chemistry, Technische Universität Berlin, Strasse des 17. Juni 124, 10623 Berlin (Germany).
authors.forename: Tobias
authors.initials: T
authors.lastname: Reier
authors.affiliation: Department of Chemistry, Technische Universität Berlin, Strasse des 17. Juni 124, 10623 Berlin (Germany).
authors.forename: Arno
authors.initials: A
authors.lastname: Bergmann
authors.affiliation: Department of Chemistry, Technische Universität Berlin, Strasse des 17. Juni 124, 10623 Berlin (Germany).
authors.forename: Jorge
authors.initials: J
authors.lastname: Ferreira de Araujo
authors.affiliation: Department of Chemistry, Technische Universität Berlin, Strasse des 17. Juni 124, 10623 Berlin (Germany).
authors.forename: Peter
authors.initials: P
authors.lastname: Strasser
authors.affiliation: Department of Chemistry, Technische Universität Berlin, Strasse des 17. Juni 124, 10623 Berlin (Germany). ralph.kraehnert@tu-berlin.de.
authors.forename: Ralph
authors.initials: R
authors.lastname: Kraehnert
mesh_terms: D004563:Electrochemistry; D007495:Iridium / Q000737:chemistry*; D010100:Oxygen / Q000737:chemistry*; D011108:Polymers / Q000737:chemistry; D016062:Porosity; D013329:Structure-Activity Relationship; D013499:Surface Properties; D014835:Volatilization
chemical_list: D011108:Polymers; C044458:iridium oxide; D007495:Iridium; D010100:Oxygen
keywords: electrochemistry; iridium; structure-activity relationships; template synthesis; water splitting