title: Heterogenized Water Oxidation Catalysts Prepared by Immobilizing Kläui-Type Organometallic Precursors.
abstract: An efficient heterogenized water oxidation catalyst (2_TiO2 ) has been synthesized by immobilizing the Kläui-type organometallic precursor [Cp*Ir{P(O)(OH)2 }3 ]Na (2, Cp*=1,2,3,4,5-pentamethylcyclopentadienyl ligand) onto rutile TiO2 . Iridium is homogeneously distributed at the molecular and atomic/small cluster level in 2_TiO2 and 2'_TiO2 (solid catalyst recovered after the first catalytic run), respectively, as indicated by STEM-HAADF (scanning transmission electron microscopy - high angle annular dark field) studies. 2'_TiO2 exhibits TOF values up to 23.7 min(-1) in the oxidation of water to O2 driven by NaIO4 at nearly neutral pH, and a TON only limited by the amount of NaIO4 used, as indicated by multiple run experiments. Furthermore, while roughly 40 % leaching is observed during the first catalytic run, 2'_TiO2 does not undergo any further leaching even when in contact with strongly basic solutions and completely maintains its activity for thousands of cycles. NMR studies, in combination with ICP-OES (inductively coupled plasma optical emission spectrometry), indicate that the activation of 2_TiO2 occurs through the initial oxidative dissociation of PO4 (3-) , ultimately leading to active centers in which a 1:1 P/Ir ratio is present (derived from the removal of two PO4 (3-) units) likely missing the Cp* ligand.
authors.affiliation: Department of Chemistry, Biology and Biotechnology and CIRCC, University of Perugia, Via Elce di Sotto 8, 06123, Perugia, Italy.
authors.forename: Gabriele
authors.initials: G
authors.lastname: Pastori
authors.affiliation: Corporate Research and Development (CRD) Centre at SABIC-KAUST P.O. Box 4545-4700, Thuwal, 23955, Saudi Arabia.
authors.forename: Khaja
authors.initials: K
authors.lastname: Wahab
authors.affiliation: Department of Chemistry, Biology and Biotechnology and CIRCC, University of Perugia, Via Elce di Sotto 8, 06123, Perugia, Italy.
authors.forename: Alberto
authors.initials: A
authors.lastname: Bucci
authors.affiliation: Department of Chemistry, Biology and Biotechnology and CIRCC, University of Perugia, Via Elce di Sotto 8, 06123, Perugia, Italy.
authors.forename: Gianfranco
authors.initials: G
authors.lastname: Bellachioma
authors.affiliation: Department of Chemistry, Biology and Biotechnology and CIRCC, University of Perugia, Via Elce di Sotto 8, 06123, Perugia, Italy.
authors.forename: Cristiano
authors.initials: C
authors.lastname: Zuccaccia
authors.affiliation: Institute of Energy Technologies and Centre for Research in Nanoengineering, Universitat Politècnica de Catalunya, Diagonal 647, 08028, Barcelona, Spain.
authors.forename: Jordi
authors.initials: J
authors.lastname: Llorca
authors.affiliation: Corporate Research and Development (CRD) Centre at SABIC-KAUST P.O. Box 4545-4700, Thuwal, 23955, Saudi Arabia. IdrissH@SABIC.com.
authors.forename: Hicham
authors.initials: H
authors.lastname: Idriss
authors.affiliation: Department of Chemistry, Biology and Biotechnology and CIRCC, University of Perugia, Via Elce di Sotto 8, 06123, Perugia, Italy. alceo.macchioni@unipg.it.
authors.forename: Alceo
authors.identifier: http://orcid.org/0000-0001-7866-8332
authors.initials: A
authors.lastname: Macchioni
keywords: Kläui-type compounds; iridium; titanium dioxide; water oxidation; water splitting