Carbon-based electrodes are promising for flow batteries. While cerium redox reactions on carbon materials have been investigated, further studies are of necessity to improve the fundamental understanding of the impact of surface functionalization on reaction kinetics. An electrochemical study of the cerium redox reaction on glassy carbon (GC) electrode, as a standard carbon-based material, provides insights into the mechanism and underlying factors. Thus, an in situ electrochemical treatment is proposed to activate GC, and its influence on the kinetic parameters is demonstrated. Furthermore, a comprehensive investigation on reaction kinetics of cerium is conducted on activated GC, where the impact of sulfuric acid and methanesulfonic acid supporting electrolytes is studied. Moreover, the results reflect the contributions of different cerium complexes on electron transfer and diffusion processes.