**2. Experimental methods**

### **2.1 Preparation and investigation of Zn-Ni Electrocatalyst for CO2 reduction reaction**

Zinc-nickel Alloys were coated on the low-carbon steel substrate by chronopotentiometry method at different electrochemical parameters. Then, Zn-Ni coatings were investigated in terms of microstructure, microcrack formation, and coating composition using SEM / EDX analysis and corrosion resistance by Autolab potentiostat (Model: PGSTAT128N) to obtain the coating with the best performance and quality. Besides, the coatings were analyzed using SEM/EDX analysis after CO2 reduction reaction for microstructure and coke formation, as well as gas efficiency by gas chromatography analyzer. Nickel chloride hexahydrate (NiCl2.6H2O), ammonium chloride (NH4Cl), and zinc chloride (ZnCl2) of raw materials were utilized for bath electrolyte preparation and ammonia solution (25%) for pH modification. All electrolytes were made using distilled water. The zinc and nickel alloy solutions were prepared in the laboratory to allow the study of the deposition at different bath solution temperatures. The pH of the solution was measured using a pH meter. Ammonia solution (25%) was used to raise the pH of the electrolyte to the needed level of pH 5. The solution was stirred using a glass rod and the pH measuring was taken applying a pH meter, continuously. Chronopotentiometry electrodeposition was applied at different bath solution temperatures of 25°C, 40°C, 60°C, and 70°C. There were three types of electrodes, low carbon steel (working electrode), Ag/ AgCl (reference electrode), and Pt mesh (counter electrode). The electrodeposition process was performed galvanostatically for each deposition temperature. The experimental setup for electrodeposition was performed as seen in **Figure 4**.

The deposited Zn-Ni coatings were analyzed on their compositional and microstructural properties applying SEM. The morphologies were observed and investigated for the electrodeposited zinc-nickel alloy samples at different temperatures of the bath solution. The material composition is determined by the SEM equipped with EDX which shows the composition information of the alloy coating. Linear polarization resistance (LPR) analysis was performed regarding the ASTM standard of G 96.– 90 (Reapproved 2001)e1.
