title: Calcium manganese(IV) oxides: biomimetic and efficient catalysts for water oxidation.
abstract: CaMnO(3) and Ca(2)Mn(3)O(8) were synthesized and characterized by SEM, XRD, FTIR and BET. Both oxides showed oxygen evolution activity in the presence of oxone, cerium(IV) ammonium nitrate and H(2)O(2). Oxygen evolution from water during irradiation with visible light (λ > 400 nm) was also observed upon adding these manganese oxides to an aqueous solution containing tris(2,2'-bipyridyl) ruthenium(II), as photosensitizer, and chloro pentaammine cobalt(III) chloride, as electron acceptor, in an acetate buffer. The amounts of dissolved manganese and calcium from CaMnO(3) and Ca(2)Mn(3)O(8) in the oxygen evolving reactions were reported and compared with other (calcium) manganese oxides. Proposed mechanisms of oxygen evolution and proposed roles for the calcium ions are also considered.
authors.affiliation: Department of Chemistry, Institute for Advanced Studies in Basic Sciences (IASBS), Zanjan, 45137-66731, Iran. mmnajafpour@iasbs.ac.ir
authors.forename: Mohammad Mahdi
authors.initials: MM
authors.lastname: Najafpour
authors.forename: Babak
authors.initials: B
authors.lastname: Pashaei
authors.forename: Sara
authors.initials: S
authors.lastname: Nayeri
mesh_terms: D032701:Biomimetics; D002118:Calcium / Q000737:chemistry*; D002384:Catalysis; D002563:Cerium / Q000737:chemistry; D006861:Hydrogen Peroxide / Q000737:chemistry; D017895:Manganese Compounds / Q000737:chemistry*; D008855:Microscopy, Electron, Scanning; D009566:Nitrates / Q000737:chemistry; D016877:Oxidants / Q000737:chemistry; D010084:Oxidation-Reduction; D010087:Oxides / Q000737:chemistry*; D010100:Oxygen / Q000737:chemistry*; D033362:Powder Diffraction; D017550:Spectroscopy, Fourier Transform Infrared; D013464:Sulfuric Acids / Q000737:chemistry; D014867:Water / Q000737:chemistry; D014961:X-Ray Diffraction
chemical_list: D017895:Manganese Compounds; D009566:Nitrates; D016877:Oxidants; D010087:Oxides; D013464:Sulfuric Acids; C532772:cerium(IV) ammonium nitrate; D014867:Water; D002563:Cerium; C027424:manganese oxide; D006861:Hydrogen Peroxide; C048813:potassium peroxymonosulfuric acid; D010100:Oxygen; D002118:Calcium