title: A Ru-Co hybrid material based on a molecular photosensitizer and a heterogeneous catalyst for light-driven water oxidation.
abstract: A novel approach to anchor a molecular photosensitizer onto a heterogeneous water oxidation catalyst via coordination bonds is presented. A photosensitizer (1) based on [Ru(bpy)3](2+) and decorated with two methylenediphosphonate (M2P) groups has been designed and synthesized for this purpose. The M2P groups in complex 1 allow for coordination of cobalt ions to afford a novel molecular-heterogeneous hybrid material P1. Scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) spectroscopy and X-ray photoelectron spectroscopy (XPS) were used to characterize P1 as an amorphous, non-uniform material that contains Ru and Co in a ratio of 1 : 2. A suspension of P1 in a buffered aqueous solution is active as a light-driven water oxidation catalyst in the presence of persulfate (S2O8(2-)) as electron acceptor. The yield of oxygen is higher when P1 is prepared in situ by mixing and illuminating 1 and Co(2+) in the presence of S2O8(2-). After oxygen evolution ceases, a second material P2 can be isolated from the reaction mixture. P2 is characterized by a lower Ru content than P1, and contains Co in a higher oxidation state. Interestingly, P2 as a freshly prepared suspension is also active for light-driven water oxidation. It is shown that 1 resides in the interior of P1 and P2, and is thus in a location where undesirable quenching pathways of the photo-excited state of 1 limit the oxygen production yields for both P1 and P2.
authors.affiliation: Molecular Biomimetics, Department of Chemistry - Ångström Laboratory, Uppsala University, P.O. Box 523, S-75120 Uppsala, Sweden. anders.thapper@kemi.uu.se.
authors.forename: Hong-Yan
authors.initials: HY
authors.lastname: Wang
authors.forename: Jia
authors.initials: J
authors.lastname: Liu
authors.forename: Jiefang
authors.initials: J
authors.lastname: Zhu
authors.forename: Stenbjörn
authors.initials: S
authors.lastname: Styring
authors.forename: Sascha
authors.initials: S
authors.lastname: Ott
authors.forename: Anders
authors.initials: A
authors.lastname: Thapper
mesh_terms: D015082:2,2'-Dipyridyl / Q000737:chemistry; D002384:Catalysis; D003035:Cobalt / Q000737:chemistry*; D056831:Coordination Complexes / Q000737:chemistry*; D008027:Light; D010084:Oxidation-Reduction; D017319:Photosensitizing Agents / Q000737:chemistry*; D012428:Ruthenium / Q000737:chemistry*; D014867:Water / Q000737:chemistry*
chemical_list: D056831:Coordination Complexes; D017319:Photosensitizing Agents; D014867:Water; D003035:Cobalt; D015082:2,2'-Dipyridyl; D012428:Ruthenium