Binary\nTransition-Metal Oxide Hollow Nanoparticles for Oxygen Evolution Reaction

Abstract

Low-cost transition\nmetal oxides are actively explored as alternative materials to precious\nmetal-based electrocatalysts for the challenging multistep oxygen\nevolution reaction (OER). We utilized the Kirkendall effect allowing\nthe formation of hollow polycrystalline, highly disordered nanoparticles\n(NPs) to synthesize highly active binary metal oxide OER electrocatalysts\nin alkali media. Two synthetic strategies were applied to achieve\ncompositional control in binary transition metal oxide hollow NPs.\nThe first strategy is capitalized on the oxidation of transition-metal\nNP seeds in the presence of other transition-metal cations. Oxidation\nof Fe NPs treated with Ni (+2) cations allowed the synthesis of hollow\noxide NPs with a 1–4.7 Ni-to-Fe ratio via an oxidation-induced\ndoping mechanism. Hollow Fe–Ni oxide NPs also reached a current\ndensity of 10 mA/cm² at 0.30 V overpotential. The second\nstrategy is based on the direct oxidation of iron–cobalt alloy\nNPs which allows the synthesis of hollow Fe_<i>x</i>Co_{100–<i>x</i>}-oxide NPs where <i>x</i> can be tuned in the range between 36 and 100. Hollow Fe₃₆Co₆₄-oxide NPs also revealed the current density\nof 10 mA/cm² at 0.30 V overpotential in 0.1 M KOH.