Controlled electropolishing of copper foils at elevated temperature

•Electrochemical polishing of copper foils at elevated temperature in H3PO4 electrolytes.•Copper foils electropolished at 65°C in 2.17M H3PO4 exhibited a lower surface roughness.•New prospects for the preparation of copper foils before the growth of high quality graphene layers. We have studied the electrochemical polishing of copper foils at elevated temperature, in H3PO4 electrolytes of various concentrations. Atomic force microscopy, surface reflectance measurements as well as optical microscopy and scanning electron microscopy (including electron backscattering diffraction) have been used throughout this study to characterize the surface of the electropolished foils. We have found that copper foils electropolished at 65°C in 2.17M H3PO4, exhibited a lower surface roughness and a higher percent specular reflection, comparing with values obtained after classical electropolishing in concentrated H3PO4 at room temperature or comparing with values obtained after chemical-mechanical polishing. This work could open up new prospects for the preparation of copper foils before the growth of high quality graphene layers.