title: Molecular Mixed-Metal Manganese Oxido Cubanes as Precursors to Heterogeneous Oxygen Evolution Catalysts.
abstract: Well-defined mixed-metal [CoMn3 O4 ] and [NiMn3 O4 ] cubane complexes were synthesized and used as precursors for heterogeneous oxygen evolution reaction (OER) electrocatalysts. The discrete clusters were dropcasted onto glassy carbon (GC) and indium tin oxide (ITO) electrodes, and the OER activities of the resulting films were evaluated. The catalytic surfaces were analyzed by various techniques to gain insight into the structure-function relationships of the electrocatalysts' heterometallic composition. Depending on preparation conditions, the Co-Mn oxide was found to change metal composition during catalysis, while the Ni-Mn oxides maintained the NiMn3 ratio. XAS studies provided structural insights indicating that the electrocatalysts are different from the molecular precursors, but that the original NiMn3 O4 cubane-like geometry was maintained in the absence of thermal treatment (2-Ni). In contrast, the thermally generated 3-Ni develops an oxide-like extended structure. Both 2-Ni and 3-Ni undergo structural changes upon electrolysis, but they do not convert into the same material. The observed structural motifs in these heterogeneous electrocatalysts are reminiscent of the biological oxygen-evolving complex in Photosystem II, including the MMn3 O4 cubane moiety. The reported studies demonstrate the use of discrete heterometallic oxide clusters as precursors for heterogeneous water oxidation catalysts of novel composition and the distinct behavior of two sets of mixed metal oxides.
authors.affiliation: Division of Chemistry and Chemical Engineering, California Institute of Technology, 1200 East California Boulevard, MC 127-72, Pasadena, California 91125 (USA).
authors.forename: Sandy
authors.initials: S
authors.lastname: Suseno
authors.affiliation: Joint Center for Artificial Photosynthesis, Pasadena, California 91125 (USA).
authors.forename: Charles C L
authors.initials: CC
authors.lastname: McCrory
authors.affiliation: Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (USA).
authors.forename: Rosalie
authors.initials: R
authors.lastname: Tran
authors.affiliation: Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (USA).
authors.forename: Sheraz
authors.initials: S
authors.lastname: Gul
authors.affiliation: Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (USA).
authors.forename: Junko
authors.initials: J
authors.lastname: Yano
authors.affiliation: Division of Chemistry and Chemical Engineering, California Institute of Technology, 1200 East California Boulevard, MC 127-72, Pasadena, California 91125 (USA). agapie@caltech.edu.
authors.forename: Theodor
authors.initials: T
authors.lastname: Agapie
mesh_terms: D002384:Catalysis; D004566:Electrodes; D007477:Ions / Q000737:chemistry; D017895:Manganese Compounds / Q000737:chemistry*; D008670:Metals / Q000737:chemistry*; D010084:Oxidation-Reduction; D010087:Oxides / Q000737:chemistry*; D010100:Oxygen / Q000737:chemistry*
chemical_list: D007477:Ions; D017895:Manganese Compounds; D008670:Metals; D010087:Oxides; C027424:manganese oxide; D010100:Oxygen
keywords: cubanes; electrocatalysis; manganese; metal oxides; oxygen evolution reaction