Adsorption complexes of copper and copper oxide in the deep eutectic solvent 2:1 urea-choline chloride

► Neat 2:1 urea-choline chloride has low concentrations of urea anions. ► Binding of the urea anion to CuO is significantly greater than binding with the neutral urea. ► The significant increase in anion binding could drive the formation of the anion in solution. ► This DES becomes more aggressive in the presence of the urea anion leading to etching of metallic Cu. ► Binding trends of the chloride anion is opposite that of the urea neutral preferring Cu to CuO.