Regular-Hexahedron-Shaped Iron–Copper Bimetallic Oxides Engineered on Plasma-Treated Iron Foam for Enhanced Electrocatalytic Oxygen Evolution in an Alkaline Medium

Designing a highly efficient transition-metal-based electrocatalyst for the oxygen evolution reaction (OER) in an alkaline electrolyte by a green and low-cost protocol is still facing many challenges. Herein, a regular-hexahedron-shaped iron-copper oxide (CuFe₂O₄-Fe₂O₃) is engineered on plasma-treated iron foam (PFF) with a one-step hydrothermal process. Benefiting from the formed rich heterointerfaces, the obtained CuFe₂O₄-Fe₂O₃/PFF exhibits an outstanding OER activity and stability in the alkaline medium, and the overpotential for delivering a current density of 10 mA cm^-2 (<i>j</i>₁₀) is only 190 mV. Meanwhile, thanks to the micronized hexahedron profile, CuFe₂O₄-Fe₂O₃/PFF also shows an excellent electrocatalytic stability, and the OER activity decays only 8% after a 90 h OER test under a high current density (<i>j</i>₁₀₀). Furthermore, the theory calculation (DFT) indicates that Fe sites exposed on the heterointerface of CuFe₂O₄ and Fe₂O₃ are the main active centers for O₂ evolution in an alkaline medium.