Valence state modulation of Mn/FePO4 nanostructures for the oxygen reduction reaction

Abstract

The oxygen reduction reaction (ORR) is the limiting factor in many renewable technologies, for example, metal–air batteries and fuel cells, that have received a lot of scientific attention. Herein, we first prepared Mn-doped FePO₄ nanoparticles encased in phosphorus incorporated reduced graphene oxide (PhG) sheets. The electrocatalyst gets a significant boost in ORR activity via adjustment of the Mn valence state when the as-prepared m-MnFePO₄@PhG is modified by the chemical reduction method. The optimized r-MnFePO₄@PhG shows an impressive half-wave potential (E_1/2) of 0.73 V vs. RHE and limiting current density (J_L) of 5.16 mA cm⁻² at 0.1 V (1600 rpm) which reach close to those of Pt/C (20 wt%) (E_1/2 = 0.77 V and J_L = 5.51 mA cm⁻²). Moreover, the catalyst exhibits strong methanol tolerance and retains 94.7% of the original current density after ∼14 h of testing under alkaline conditions.