Magnesium cobalt silicate as a bifunctional catalyst for the O2 electrode and its application in Li–O2 cells

Abstract

Magnesium cobalt silicate (MgCoSiO₄) is investigated for the oxygen evolution reaction (OER). It is synthesized by a mixed solvothermal approach and characterized by physicochemical techniques. Cubic shaped particles of MgCoSiO₄ are observed in microscopy images. The catalytic activity of MgCoSiO₄ is studied in alkaline (KOH solution) and neutral (phosphate buffer solutions) media. The effects of the electrolyte concentration and loading level on OER are studied. Additionally, the oxygen reduction reaction (ORR) of MgCoSiO₄ is studied in aqueous and non-aqueous electrolytes. Oxygen follows the 4e⁻ and 1e⁻ reduction pathways in aqueous and non-aqueous electrolytes, respectively. Li–O₂ cells are assembled with MgCoSiO₄ as the oxygen electrode catalyst in non-aqueous electrolyte and subjected to charge–discharge cycling at several current densities. A discharge capacity of 7221 mA h g⁻¹ (8.272 mA h cm⁻²) was obtained at 0.3 mA cm⁻². The results suggest that MgCoSiO₄ is a good non-platinum based catalyst, which is useful for Li–O₂ cells.