201. Water oxidation by lambda-MnO2: catalysis by the cubical Mn4O4 subcluster obtained by delithiation of spinel LiMn2O4
- Author
-
Martha Greenblatt, David M. Robinson, G. Charles Dismukes, and Yong Bok Go
- Subjects
Models, Molecular ,Surface Properties ,Inorganic chemistry ,chemistry.chemical_element ,engineering.material ,Lithium ,Biochemistry ,Catalysis ,chemistry.chemical_compound ,Colloid and Surface Chemistry ,Nitric acid ,Oxidizing agent ,Particle Size ,Manganese ,Spinel ,Water ,Oxides ,General Chemistry ,Persulfate ,Nanocrystalline material ,Nanostructures ,chemistry ,Manganese Compounds ,engineering ,Particle size ,Oxidation-Reduction - Abstract
Nanocrystalline spinel LiMn(2)O(4) has been prepared and treatment of LiMn(2)O(4) with dilute nitric acid solution resulted in the delithiation of the framework, while maintaining the spinel structure, lambda-MnO(2). LiMn(2)O(4) is not a catalyst for water oxidation. Upon removal of the lithium, the cubical Mn(4)O(4) cores become active sites for oxidizing water to molecular oxygen, which was investigated with the photochemical [Ru(2+)(2,2'-bpy)(3)]/persulfate system at pH 5.8. The nanosize lambda-MnO(2) obtained from the nanocrystalline LiMn(2)O(4), which was synthesized by the citrate route, shows a significantly higher water oxidation catalytic activity (Turnover Frequency: 3 x 10(-5) mol O(2)/s/mol Mn) than that obtained via solid state reaction with micrometer and irregular particle sizes (Turnover Frequency: 5 x 10(-6) mol O(2)/s/mol Mn).
- Published
- 2010