Water oxidation by lambda-MnO2: catalysis by the cubical Mn4O4 subcluster obtained by delithiation of spinel LiMn2O4

J Am Chem Soc. 2010 Aug 25;132(33):11467-9. doi: 10.1021/ja1055615.

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).

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Catalysis
  • Lithium / chemistry*
  • Manganese / chemistry*
  • Manganese Compounds / chemistry*
  • Models, Molecular
  • Nanostructures / chemistry
  • Oxidation-Reduction
  • Oxides / chemistry*
  • Particle Size
  • Surface Properties
  • Water / chemistry*

Substances

  • Manganese Compounds
  • Oxides
  • lithium manganese oxide
  • Water
  • Manganese
  • manganese oxide
  • Lithium
  • manganese dioxide