Hard ceramics exhibit robust mechanical properties, rendering them an essential choice for studying sustainable, supercapacitive electrode materials. In this report, we investigate the capacitive properties of boron carbide (B4C), a hard ceramic that exhibits excellent temperature and chemical resistance through the enhancement of sp2/sp3 hybridization via pulverization. The size-reduced B4C exhibited a nine-fold higher capacitive performance compared to larger particles, as confirmed by a significant difference in the carrier densities of Mott-Schottky plots. Further, the three-dimensional Bode plots were used to deconvolute the charge storage dynamic, in which the constant phase angle variation observed when different potentials were applied at lower frequencies indicated the formation of a double layer.