Preparation of high surface area Cu‐Au bimetallic nanostructured materials by co‐electrodeposition in a deep eutectic solvent

•Co-electrodeposition of Cu and Au bimetallic films has been conducted in a deep eutectic solvent.•Bimetallic Cu and Au nanostructures with variable morphology and composition are obtained.•Lead underpotential deposition on Cu-Au films has been used to assess the electroactive surface area.•Cu-Au films had an electroactive surface area five to 14 times higher than the geometric area.