1：Experimental Design and Method Selection:

The study involved cyclic voltammetry and potentiostatic electrodeposition to investigate the cathodic processes and deposit PbSe films. Theoretical models for underpotential deposition and compound formation were employed.

2：Sample Selection and Data Sources:

Choline chloride-based ionic liquids (ChCl-ethylene glycol and ChCl-urea eutectic mixtures) with precursors PbCl2 and SeO2 were used. Substrates included copper and nickel plates.

3：List of Experimental Equipment and Materials:

Equipment included a Zahner elektrik IM 6e potentiostat, glassy carbon, platinum, and nickel working electrodes, platinum mesh auxiliary electrode, silver wire quasi-reference electrode, SEM-EDX (SU8230, HITACHI), and XRD (Rigaku High Resolution SmartLab). Materials included choline chloride, ethylene glycol, urea, PbCl2, SeO2, alumina paste, abrasive paper, and nitric acid for pickling.

4：Experimental Procedures and Operational Workflow:

Ionic liquids were prepared by mixing ChCl with ethylene glycol or urea in a 1:2 molar ratio at 80-90°C, then adding precursors. Cyclic voltammetry was performed at 70°C with various scan rates and electrodes. Electrodeposition was done potentiostatically at 70°C for 0.5-4 hours. Substrates were polished and pickled before use. Films were characterized using SEM-EDX and XRD.

5：5-4 hours. Substrates were polished and pickled before use. Films were characterized using SEM-EDX and XRD. Data Analysis Methods:

5. Data Analysis Methods: Voltammograms were analyzed for peak potentials and currents. SEM-EDX provided morphology and composition, and XRD with Scherrer equation determined crystallite sizes.