Deep-Eutectic-Solvent-Based Electrochemical Engineering: Efficient Synthesis of Selenium Nanorods from Cu₂Se

Selenium is a strategically important element that occurs at low concentrations in the Earth’s crust. Cuprous selenide (Cu 2 Se), enriched in selenium and commonly found in copper anode slime, also shows promise as a thermoelectric material, making it an attractive target for recovery. A room-temperature solid-state electrolysis route is reported for producing well-defined selenium nanorods from Cu 2 Se in a choline chloride–urea deep-eutectic solvent with concurrent copper recovery. The redox behavior of Cu 2 Se was elucidated via electrochemical analysis, and constant-potential electrolysis enabled controlled species separation, while constant-voltage electrolysis demonstrated the method’s scalability. Structural characterizations confirmed the formation of highly crystalline Se nanorods and high-purity Cu. This electrochemical approach enables phase-selective separation and nanostructure fabrication under ambient conditions without thermal input or additional reagents. The process offers a sustainable and scalable strategy for recovering critical elements from selenium-rich residues and producing functional selenium nanomaterials applicable in energy and electronics.