Structure Properties Correlations on Nickel-Iron Oxide Catalysts Deposited by Atomic Layer Deposition for the Oxygen Evolution Reaction in Alkaline Media

Abstract

Thermal atomic layer deposition (ALD) is used for the first time to deposit iron-nickel oxides onto carbon nanotubes in a ternary process to produce a wide range of mixed oxide thin films. When using ferrocene (FeCp₂) and nickelocene (NiCp₂) with ozone (O₃) as metals and oxygen sources, respectively, a competition between the metal precursors and the growth modes is observed. Indeed, while ferrocene promotes a 2D-growth, nickelocene prefers a 3D-growth. Although both precursors are homoleptic metallocenes, they behave differently in the ALD of their respective metal oxide, leading to unexpected atomic ratios and films morphologies of the iron-nickel oxides. The 2Fe:1Ni sample displays the best performances in the electrochemical water oxidation (oxygen evolution reaction) exhibiting an overpotential of 267 mV at a current density of 10 mA cm⁻¹, a Tafel slope of 36.8 mV dec⁻¹, as well as a good stability after 15 h of continuous operation.