Platinum on nitrogen-doped Mn2O3–NiO as a bifunctional electrocatalyst for air cathodes

Abstract

Designing and developing oxygen electrode bifunctional electrocatalysts to be used in rechargeable metal-air batteries is crucial for their efficient operation. Herein, Mn<inf>2</inf>O<inf>3</inf>–NiO is synthesised by two different co-precipitation and solid-state reaction methods, and nitrogen is doped into these binary oxides. Subsequently, platinum (Pt) is grafted onto the binary oxide supports, undoped and N-doped, and materials’ structure, texture, surface morphology, and elemental composition/state are examined using XRD, N<inf>2</inf>-sorption, TEM, and XPS analysis, respectively. The as-prepared materials were further examined for bifunctional catalysis of oxygen reduction/evolution reactions (ORR/OER). The best-performing Pt/N–Mn<inf>2</inf>O<inf>3</inf>–NiO (S1) electrocatalyst showed Tafel slope values of 77 and 219 mV dec⁻¹ for ORR and OER, respectively, a number of electrons exchanged during ORR of 3.61 and a diffusion-limited current density of −4.86 mA cm⁻², and finally, the lowest ΔE of 0.92 V. Demonstrated catalytic activity along with the high stability observed during the accelerated stress test make Pt/N–Mn<inf>2</inf>O<inf>3</inf>–NiO a promising bifunctional ORR/OER electrocatalyst for rechargeable metal-air batteries.