Hierarchical Heterostructure of Amorphous CoFe@CoNi Hydroxides Composite on Nickel Foam as Efficient Electrocatalyst for Oxygen Evolution Reaction

Design of efficient and low-cost electrocatalysts for oxygen evolution reaction (OER) is of great importance for practical energy-related technologies such as hydrogen production. Herein, CoFe@CoNi hydroxides composite supported on nickel foam (NF) as electrocatalyst for OER was prepared via a two-step electrodeposition method. The CoFe@CoNi hydroxides composite has an amorphous structure with a hierarchical nanostructure where small nanosheets of CoNi hydroxide were decorated on the large nanosheet of CoFe hydroxide. The architecture provides abundant electrochemically active surface area with more exposed active sites as well as the small electron-transfer resistance at the interface to promote the catalytic activity for OER. In addition, the core-shell hierarchical nanostructure may further improve the catalytic activity by regulating the electronic structure due to the synergetic interaction of CoFe and CoNi hydroxides. It is noted that the deposition sequence is important to form hierarchical heterostructure, and no hierarchical structure can be obtained by depositing CoFe hydroxide on CoNi hydroxide due to the reconfiguration of the metal ions during the synthesis. CoFe@CoNi hydroxides composite shows efficient electrocatalytic activity toward OER with an overpotential of 0.227 V at a current density of 10 mA/cm(2) and a long-term durability in 1.0 M KOH.