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Free keywords:
Cost effectiveness, Durability, Electrocatalysts, Ion exchange, Metal-air batteries, Oxygen, Oxygen evolution reaction, Positive ions, Transition metal oxides, Transition metals, Acidic solutions, Atom arrangement, Cation exchanges, Electrocatalytic performance, Hydroxyl groups, Oxygen evolution activity, Oxygen evolution reaction (oer), Particulate morphology, Sodium compounds
Abstract:
Cost-effective electrocatalysts with high activity and long durability for the oxygen evolution reaction (OER) are key to water splitting and rechargeable metal-air batteries. Here, we report the development of a superior OER electrocatalyst with outstanding activity, favorable durability, and stable particulate morphology based on an ex situ ultra-fast cation exchange strategy that can result in fine tuning of the atom arrangement inside the oxide lattice, thus optimizing the electrocatalytic performance. O3-phase NaCo0.8Fe0.2O2 (O-NCF) is selected as the starting material, and the sodium in the oxide lattice is rapidly exchanged (several minutes) with hydronium ions (H3O+) in an acidic solution. The as-derived structure fine-tuned sample displays excellent OER performances in alkaline media with an ultra-low overpotential of only 234 mV at 10 mA cm-2 in oxide-based electrocatalysts and an ultra-small Tafel slope of 34 mV dec-1. The exchange of H3O+ with Na+ does not affect the oxidation state of cobalt and iron cations inside the oxide lattice, while protons in the inserted H3O+ promote the formation of the hydroxyl group to improve activity. As a general strategy, such cation exchange strategy can also be applied to many other layered sodium transition metal oxides. © The Royal Society of Chemistry.
