Core–Shell‐Structured NiS2@Ni‐Bi Nanoarray for Efficient Water Oxidation at Near‐Neutral pH

The development of high‐performance and cost‐effective water oxidation catalysts operating under mild conditions is attractive for the conversion of electricity into chemical fuels. In this communication, we report the in situ electrochemical development of a Ni‐Bi layer (5–8 nm thick) on a NiS2 nanoarray supported on carbon cloth (i.e., NiS2@Ni‐Bi/CC) for efficient water oxidation in 0.1 m potassium borate electrolyte at pH 9.2. As a durable 3 D catalyst electrode, core–shell‐structured NiS2@Ni‐Bi/CC shows excellent catalytic activity for water oxidation and approaches a geometrical catalytic current density of 20 mA cm−2 at an overpotential of 486 mV, with long‐term electrochemical stability for at least 24 h with a high turnover frequency of 0.28 mol O2 s−1 at an overpotential of 500 mV and nearly 100 % Faradic efficiency for oxygen evolution.