Abstract
•Developed a novel electropolishing process for analyzing the (111)-oriented NT-Cu foils.•Ultrasonic irradiation and gas aeration synergistically enhance mass transfer efficiency.•Optimized H₃PO₄–H₂SO₄ electrolyte achieves mirror-smooth, defect-free surfaces.•DOE-based statistical model establishes correlations between EP parameters and surface roughness.•Identifies a salt-film–controlled dissolution mechanism unique to (111)-oriented NT-Cu.
Nanotwinned copper (NT-Cu) has emerged as a promising material for advanced electronic and electrochemical applications due to its superior mechanical, electrical, and electrocatalytic properties. In this study, an advanced electropolishing (EP) process incorporating the novel gas aeration and ultrasonic irradiation into the EP system with optimized operation parameters is conducted to control the surface roughness and uniformity of the (111)-oriented NT-Cu foils for future applications. Through the design of experiments (DOEs) strategy, the key parameters, including inter-electrode gap, electrolyte composition, and mass transport enhancement strategy, have been systematically evaluated to establish a statistical model correlating these parameters with the outcomes. The results demonstrate that a combination of ultrasonic irradiation and aeration enhances mass transport significantly, leading to improved surface planarity and reduced roughness. Furthermore, an optimal electrolyte formulation of phosphoric and sulfuric acid ratios has been identified to achieve the defect-free surfaces. The findings in this work provide the advanced EP methodology for the (111)-oriented NT-Cu foils which are particularly important in the semiconductor, electronic, electrocatalytic, and energy storage fields.
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