A nickel-borate nanoarray: a highly active 3D oxygen-evolving catalyst electrode operating in near-neutral water.

The exploration of high-performance and cost-effective water oxidation catalysts operating under mild conditions is still urgent and challenging. In this communication, a nickel-borate nanoarray supported on carbon cloth (Ni-Bi/CC) has been fabricated through oxidative polarization of a nickel oxide nanoarray on CC (NiO/CC) in a borate electrolyte (pH 9.2). As a 3D electrode, this Ni-Bi/CC exhibits superior catalytic activity for water oxidation in 0.1 M potassium borate (K-Bi) solution, yielding a geometrical catalytic current density of 10 mA cm-2 at an overpotential of 470 mV. Notably, this electrode also demonstrates outstanding long-term electrochemical durability for 25 h with 100% Faradaic efficiency.