Na<sub>0.86</sub>Co<sub>0.95</sub>Fe<sub>0.05</sub>O<sub>2</sub> Layered Oxide As Highly Efficient Water Oxidation Electrocatalyst in Alkaline Media

Electrochemical energy storage and conversion technologies, such as water-splitting devices, rechargeable metal-air batteries, and regenerative fuel cells, are promising alternatives to traditional nonrenewable energy systems. Given the sluggish oxygen evolution reaction (OER) in the above renewable-energy technologies, the development of efficient OER electrocatalysts with high performance is of great importance. Here, we demonstrate a layer-structured oxide Na<sub>0.86</sub>Co<sub>0.95</sub>Fe<sub>0.05</sub>O<sub>2</sub> (NCF0.05) as a novel electrocatalyst for efficient water oxidation in alkaline media. NCF0.05 shows enhanced performance, including lower overpotential, lower Tafel slope and better stability than the parent Na<sub>0.86</sub>CoO<sub>2</sub> (NC). Especially, the OER performance of NCF0.05 is comparable to the state-of-the-art IrO<sub>2</sub> catalyst. This enhanced catalytic activity of NCF0.05 may be ascribed to the unusual synergistic interplay between Fe and Co. A possible dual-metal-site mechanism was also proposed for OER on NCF0.05.