Copper oxide was prepared with thermal decomposition of basic copper carbonate to complement the concentration of cupric ions for copper electrodeposition in a plating system with insoluble anode. Copper oxide particles with a structure of aggregated porous flakes had a wide size distribution ranging from 100 nm to 100 μm. Copper oxide exhibited a dissolution rate of about 15 s in 12.5 vol% H2SO4 solution. During copper electrodeposition, copper deposits with fine growth formed in the electrolyte with stable cupric concentration provided by rapid dissolution of copper oxide