Low-Overpotential Electrochemical Water Oxidation Catalyzed by CuO Derived from 2 nm-Sized Cu₂(NO₃)(OH)₃ Nanoparticles Generated by Laser Ablation at the Air–Liquid Interface

A CuO-based water oxidation electrocatalyst that operates at a low overpotential without strong alkaline conditions was developed using a laser ablation process. A two-step laser ablation, laser ablation of Cu powder in liquid (LAL) followed by laser ablation at the air–liquid interface (LAAL), enabled the preparation of a mixture of 2 nm-sized orthorhombic (gerhardtite) and metastable monoclinic Cu2(NO3)(OH)3 colloidal nanoparticles. Electrodes in which the colloidal nanoparticles were deposited as a precursor on carbon paper (CP) formed the CuO-based catalyst after pre-electrolysis (LAAL-CuO/CP), and the electrodes catalyzed electrochemical water oxidation in 1.0 M Na2CO3 (pH 11.3) with a potential of ∼1.53 V versus RHE. This value was lower than the reference electrodes of Cu, Cu2O, and CuO/CP and is the lowest among previously reported Cu-based water oxidation electrocatalysts. A current density over 10 mA/cm2 was achieved at 1.77 V versus RHE in the 1.0 M Na2CO3 solution, which is competitive with best CuO catalyst.