Characterization and Electrocatalytic Behavior of Layered Li₂MnO₃ and Its Acid-Treated Form

The material H[H 0.18 Li 0.15 Mn 0.67 ]O 1.90, obtained by the delithiation of layered Li 2 MnO 3 using acid, gives a 2-fold increase in oxygen reduction ability versus Li 2 MnO 3 . Using elemental analysis by the ICP technique, average oxidation state determination, acid−base titrations, and thermal analysis, we determined the chemical composition of the proton-exchanged material to be H[H 0.18 Li 0.15 Mn 0.67 ]O 1.90 . Rietveld refinement shows that the structure of the delithiated material is a monoclinic distortion of the P 3 structure resulting in the C 2/ m space group with cell parameters a =5.049(2) Å, b = 8.707(2) Å, c = 4.903(1) Å, β = 109.17(2)°. The BET surface area for the materials increases from 18 to 57 m 2 /g upon delithiation. Application of H[H 0.18 Li 0.15 Mn 0.67 ]O 1.90 as an electrocatalyst in a lithium-air cell gives a specific discharge capacity of 1618 mA h g - 1 .