Metal substrates activate NiFe(oxy)hydroxide catalysts for efficient oxygen evolution reaction in alkaline media

The amorphous NiFeOx(OH)y is synthesized on Fe, Ni, and Cu foam substrates to study the effects of the metal substrates on activity and stability for the electrochemical oxygen evolution reaction (OER) from water. The metal substrate for NiFeOx(OH)y catalyst does not merely perform the physical role of loading the catalyst, but actively participates in the activation process of the catalyst phase by controlling the charge transfer during the OER. The Ni foam substrate is found to be the best to make NiFeOx(OH)y/Ni foam the most active and the most stable electrode for OER in an alkaline medium due to its multiple functions. The nickel substrate forms the thinnest oxide layer on its surface to allow facile charge transfer, and stabilizes the M–Ox(OH)y structure of high oxidation degree of metals and balanced Ox/(OH)y responsible for excellent OER performance. The high intrinsic corrosion resistance of Ni and its ability to stabilize a thick layer of M–Ox(OH)y structure can also minimize the metal dissolution during the OER and provide superior long-term stability. Finally, oxidation of the Ni substrate itself results in more NiOOH phase formation to achieve an optimum NiFe composition.