Biomass-derived carbons were synthesized through carbonization at 600 o C and subsequent KOH activation at 800 o C. The detailed synthesis procedure is discussed in the supporting information (section S1 and Figure ). The activated carbons show a microporous structure, as seen from the type-1 N2 sorption isotherms (Figure ). The sorption isotherms of garlic roots (GR) and garlic skin (GS) deviate from the ideal microporous behaviour at low relative pressure and continue to adsorb N2 above a relative pressure of 0.2. This indicates the presence of mesopores in addition to micropores in GR and GS. The activated carbons obtained from garlic powder (GP), garlic roots (GR), and garlic skin (GS) exhibit high BET surface areas of 2341 m 2 .g -1 , 2454 m 2 .g -1 , and 2582 m 2 .g -1 , respectively. Coke-derived supersorb carbon (S), coal-derived BPL carbon, and carbide-derived Y carbon exhibit surface areas of 2715 m 2 .g -1 , 1023 m 2 .g -1 , and 1109 m 2 .g -1 , respectively. A direct relation between surface area and pore volume is observed (Figure ). However, supersorb (S) activated carbon and garlic roots (GR) activated carbon flip positions with regards to their pore volumes. A maximum pore volume of 1.41 cm 3 .g -1 is obtained for GR activated carbon. The electrode densities of biomass-derived carbons are oppositely related with surface areas and follow the sequence: GR (0.19 g.cm -3 ) < GS (0.25 g.cm -3 ) < GP (0.28 g.cm -3 ) (Figure ). Commercial activated carbons exhibit higher electrode densities than biomass-derived carbons and follow the sequence: S (0.31 g.cm -3 ) < BPL (0.48 g.cm -3 ) = Y (0.48 g.cm -3 ). The micropore surface areas and micropore volumes of biomass-derived carbons (GP, GR, GS) are lower than commercial activated carbons (S, BPL, Y), as shown in table . Information about the surface structure and composition of activated carbons (ACs) was obtained from X-ray photoelectron spectroscopy (XPS). The survey scan of all ACs shows two main peaks at 284 eV and 532 eV, attributed to C1s and O1s (Figure ). The N1s peaks at 400 eV are not visible in the survey spectra while small peaks at around 1000 eV are due to oxygen auger electrons. The surface chemical state of each AC was obtained by deconvoluting the high resolution C1s and O1s spectra (Figure and Figure ). Three surface chemical states of carbon (C-C3 sp 2 , C-C4 sp , sp 2 /sp 3 C-Ox-Cy, x=1,2; y =1-3)) are identified in all the samples (Figure ). GS, S, BPL, and Y contain very small amounts of C-N bonds. The percentage (atomic %) of sp 2 -hybridized C-atoms is highest in GR (83.5 %) and follows the sequence GR > GS > Y > BPL > GP > S. The percentage of sp 3 -hybridized C-atoms follows the sequence S > GS > Y > BPL > GR > GP. The percentage of C-O follows the sequence S > BPL > GP > Y > GR > GS. Higher sp 2 character and presence of oxygen functionalities are desirable for improving the conductivity and pseudocapacitance, respectively. The percentage of OH functionality is highest in GR (4.0 %) and follows the sequence GR > GP > GS > S > BPL > Y. The elemental percentage of C, O, N, and other elements is given in table .