New Synthetic Route, Characterization, and Electrocatalytic Activity of Nanosized Manganite

Abstract

Nanosized γ-MnOOH (manganite) has been synthesized by a new route via the reduction of KMnO4 with sucrose and MnSO4 in acidic medium under refluxing conditions for 4 and 6 h. Characterization of these manganite materials using XRD, FESEM, TEM, TGA, and IR were carried out. The obtained manganite samples using the new route were compared against a conventionally prepared one where synthesis involved the oxidation of MnSO4 with a H2O2 solution in a basic medium. Two new synthetic methods were developed, one involving addition of KMnO4 into a solution of both sucrose and MnSO4 while the other involved addition of KMnO4 solution into sucrose only followed by addition of MnSO4 (s). The latter method yielded smaller particles (up to 30 nm) than the former method (up to 80 nm) and the conventionally prepared manganite (up to 50 nm). The synthesized manganite materials exhibited promising characteristics when tested as electrocatalysts in the reduction of O2. The larger particles gave higher peak currents in CV. When incorporated in Yardney's medium-sized lithium-air battery, the larger particles gave higher specific capacity (up to 2.2 A·h/g), which corresponds to about a 38% increase in specific energy of the battery when compared to a battery where no manganite was incorporated.