Rapid synthesis of nickel–iron-oxide (NiFeO_x) solid-solution nano-rods thin films on nickel foam as advanced electrocatalyst for sustained water oxidation

The development of earth-rich, noble-metal-free, and highly electroactive catalysts to accelerate the oxygen evolution reaction (OER) is a formidable challenge for the establishment of water-splitting technologies. Here, a solid-solution nickel-iron oxide (NiFeO_x) electrocatalyst is readily grown on a Ni-foam (NF) substrate by a rapid and economical aerosol-assisted chemical vapor deposition process. In particular, the NiFeO_x thin film fabricated in 40 min acquires a distinctive nanorod structure and proves to be stable and efficient for OER in alkaline solutions. It is shown that the catalyst needs a low over-potential of 226 mV to reach the typical current density of 10 mA/cm², and it can approach a remarkable current density level of 1000 mA/cm² by taking a slightly higher over-potential of 139 mV. The small Tafel slope of 64 mv.dec⁻¹ and splendid electrochemical stability of 40 h at high current densities outperform many known FeNi-based anodes as well as commercial IrO₂ and RuO₂. The unique structure of the thin film offers many electroactive sites and a high surface area in combination with an improved electrical conductivity of NF, which is believed to play an imperative role in the excellent activity of the catalyst. The cost-effective and simple strategy to fabricate NiFeO_x nano-fibrous is very attractive for the development of electrocatalysts for water splitting.