*3.1. SEM and EDX*

Figure 1a–d shows SEM images of the G95 electrode and G70L25 electrode before and after cyclic voltammetry measurements. In Figure 1a, it can be seen that layers of graphene nanoplatelets are randomly stacked. Figure 1c shows that LSMCO is randomly contained between graphene nanoplatelets layers in the G70L25 the electrode. After cyclic voltammetry, both the G95 and G70L25 electrodes have white granules, as in Figure 1b,e. EDX analysis confirmed that carbon, platinum, and sulfur were found in the overall area, which are the primary materials of working and counter electrodes and electrolytes (H2SO4). In addition, white granules appear to be sulfur and Pt of counter electrodes as a result of the analysis. In reference [33], it is reported that, after the CV experiment, Pt particles generated on the working electrode surface and weight loss of the Pt electrode occurred in the H2SO4 electrolyte.

**Figure 1.** SEM images of as-prepared (**a**) electrode of G95 before cyclic voltammetry; (**b**) after cyclic voltammetry 5000 cycles; (**c**) SEM image of G95 with EDX mapping of C, S, and Pt; (**d**) electrode of G70L25 before cyclic voltammetry and (**e**) after cyclic voltammetry 5000 cycles; (**f**) SEM image of G70L25 with EDX mapping of C, S, and Pt.
