Transformation of CoFe₂O₄ spinel structure into active and robust CoFe alloy/N-doped carbon electrocatalyst for...

Electrochemical water splitting is an environmentally benign technology employed for H₂ production; however, it is critically hampered by the sluggish kinetics of the oxygen evolution reaction (OER) at the positive electrode. In this work, nitrogen-doped carbon-coated CoFe electrocatalysts were synthesized via a three-step route comprising (1) hydrothermal reaction, (2) in-situ polymerization of dopamine and (3) carbonization. The effect of carbonized polydopamine on the overall physicochemical properties and electrochemical activity of CoFe catalysts was systematically studied. By controlling and optimizing the ratio of CoFe₂O₄ and dopamine contents, a transformation of the CoFe₂O₄ structure to CoFe alloy was observed. It was found that CoFe/NC_30% (prepared with 30% dopamine) exhibits an excellent catalytic activity towards OER. A small overpotential of 340 mV was required to generate a current density of 10 mA cm^-2 in a 1.0 M KOH electrolyte. More importantly, the CoFe/NC_30% catalyst reflected exceptional durability for at least 24 h. This research sheds light on the development of affordable, highly efficient, and durable electrocatalysts for OER.