A NiCo₂O₄@Ni–Co–Ci core–shell nanowire array as an efficient electrocatalyst for water oxidation at near-neutral pH

It is attractive but still remains challenging to develop efficient water oxidation electrocatalysts working in a carbonate (Ci) electrolyte. In this communication, we report that a Ni-Co-Ci layer can be developed on a NiCo₂O₄ nanowire array supported on carbon cloth (NiCo₂O₄/CC) via electrochemical surface derivation of NiCo₂O₄. The resulting NiCo₂O₄@Ni-Co-Ci core-shell nanowire array on carbon cloth (NiCo₂O₄@Ni-Co-Ci/CC) exhibits high activity toward water oxidation in 1.0 M KHCO₃ (K-Ci, pH = 8.3) with the overpotential requirement of 309 mV to drive 10 mA cm^-2. NiCo₂O₄@Ni-Co-Ci/CC also shows long-term electrochemical stability for 20 h and a high turnover frequency of 0.464 mol O₂ s^-1 at an overpotential of 600 mV.