Facile solvothermal synthesis of CaMn2O4 nanorods for electrochemical oxygen reduction

Electrocatalysts for the oxygen reduction reaction (ORR) are of pivotal importance in various fuel cells and metal-air batteries. In this study, we report a facile synthesis of one-dimensional (1D) CaMn2O4 nanostructures and their applications as cheap and active electrocatalysts for the ORR. Marokite CaMn2O4 nanorods with post-spinel phase were prepared by a solvothermal route at mild temperatures, using potassium manganese oxide hydrate and calcium nitrate as the precursors and ethanol as the solvent. The as-prepared nanorods adopted the orthorhombic structure and possessed diameters of 150-300 nm and lengths of 2-4 mu m, with preferentially exposed (023) planes on surfaces. In alkaline electrolytes, CaMn2O4 nanorods exhibited considerable catalytic performance and enabled an apparent quasi-four-electron transfer in the ORR, as evidenced by rotating disk electrode and rotating ring-disk electrode studies. The determined Tafel slop and the chronoamperometry stability of CaMn2O4 nanorod electrocatalysts were comparable to the counterpart Pt nanoparticles supported on carbon.