Rapid growth of amorphous cobalt-iron oxyhydroxide nanosheet arrays onto iron foam: Highly efficient and low-cost catalysts for oxygen evolution

The oxygen evolution reaction (OER) is a key process for metal-air batteries and water splitting technologies. The design and synthesis of efficient, durable, low-cost, and earth-abundant electrocatalysts for OER is of great urgency. To achieve the rapid synthesis of untrathin two-dimensional (2D) nanomaterials and improve their electrocatalytic performance, a new strategy has been developed to grow amorphous cobalt-iron nanosheet arrays directly onto the surface of the macroporous iron foam substrates. This method requires significantly shorter reaction times (about 5 min) at room temperature compared to the conventional high-temperature hydrothermal reaction which requires a few hours. The as-prepared cobalt-iron nanosheets acting as oxygen electrode exhibits high OER activity, which is capable of delivering current densities of 10 mA cm(-2) and 500 mA cm(-2) at over-potential of 208 mV and 298 mV, respectively. It also shows small Tafel slope and long-term durability in an alkaline electrolyte.