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 μm, 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.