In this study, the properties of graphene photocathodes were investigated using a modified Hummers’ method enhanced by ultrasonic and hot water treatments to synthesize graphene powder. This powder, serving as a precursor, was used to form graphene films on the glass substrates of the photocathode window via spin coating. Subsequently, annular Ni/Cr electrodes were fabricated by electron-beam evaporation, resulting in the assembly of the graphene photocathode. Comprehensive analyses of photocathodes subjected to various preparation and processing techniques were conducted using atomic force microscopy, spectrophotometry, four-point probing, and photoluminescence testing. The results indicate that both the increased dispersion concentration and subsequent temperature reduction treatments significantly enhanced the absorption rate of the photocathode. Importantly, high-temperature reduction not only improves the surface smoothness of the photocathode assembly but also maintains the integrity of its crystal structure, reducing defects. This contributes positively to enhancing the emission characteristics of the graphene photocathode.