SEM-EDS analysis of the post-electrolysis Ni foam revealed the presence of Mg and N on the electrode, as demonstrated in the EDS mapping shown in Figure . To determine the physical characteristics of the SEI layer, we conducted the experiment using a polished planar metal electrode as the cathode. The cell setup remained the same, with the only difference being the replacement of the 3 mm Ni foam with the planar electrode. This facilitated faster drying of the solvent and provided clearer imaging of the SEI structure. SEM images and EDS mapping as shown in Figure revealed the deposition of a thick SEI layer on the planar electrode. The mapping also showed a dense presence of Mg, further confirming that Mg deposition mediates the ammonia synthesis, supporting the direction of our hypothesized mechanism to a greater extent. These exsitu analysis findings collectively reinforce the conclusion that Mg was successfully deposited during electrolysis. Although in situ analysis to understand the interface would be valuable, it is outside the scope of this work.