Ternary Transition Metal Oxide Nanoparticles with Spinel Structure As Oxygen Reduction Reaction Electrocatalysts

Abstract

Electrocatalysts for the oxygen reduction reaction (ORR) has been developed to meet the requirements for renewable energy applications. Herein, we explore mixed valence transition-metal oxides with a spinel structure for this purpose. A simple and scalable method was employed for synthesis of four different types of spinel oxide nanocrystals (NiCo2O4, NiMn2O4, ZnCo2O4, and ZnMn2O4). This allowed for a systematic investigation of the influence of the composition of the catalysts (XY2O4, X=Ni, Zn and Y=Co, Mn) on ORR. Given the general spinel structure of XY2O4, we changed X (Ni, Zn) and Y (Co, Mo) systematically. The influence of different transition-metals on the morphology and electrocatalytic properties of the spinel oxides toward ORR were studied and compared using scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray photoelectron microscopy, and voltammetry. In general, cobalt-based spinel oxides exhibited significant electrocatalytic activity towards the ORR, with Ni-substituted spinel oxides outperforming their respective Zn-substituted congeners. These findings may have profound impact in the research field of renewable energy.