Microporous carbon materials having a negligible contribution of mesopores have been synthesized by cyclic oxidation/desorption of grape seeds char using air, ozone and HNO3 as oxidant agents. By adequate selection of the operating conditions (oxidation procedure and number of cycles) it is possible to tune the volume and pore size distribution of carbon materials and therefore determine the influence of carbon textural properties on the electrochemical behaviour of carbon-carbon symmetric supercapacitors operating in different aqueous electrolytes. The results confirm that although energy density can be improved using neutral electrolytes in reason of their higher stability potential window compared to acidic or basic ones, it is important to adapt the textural properties of the carbon materials to improve the ions diffusion inside 2 the porosity for assuring the charging of the double layer at high current densities to reach high power densities. 1. Introduction Electric double-layer capacitors (EDLC), often known as "supercapacitors", have recently received much attention in high power electrochemical technology research. The behavior of double-layer charging at the distributed interface of high specific surface materials-such as activated carbon (AC) powders, carbon nanotubes (CNT)or carbon gels, fullerenes, etc.-has been widely studied [1]. The energy storage mechanism in supercapacitor is based on an electrostatic attraction between charges along the double layer formed at the electrode/electrolyte interface. Since this phenomenon is controlled by the surface area of the interface, ACs are the most extensively used electrode materials for EDLC.In addition to their high specific surface area (SSA), ACs have other advantages such as availability, easy process ability and relatively low cost of most of precursors and production technologies [2, 3]. To usethese materials as electrodes for supercapacitors certain conditions are needed, such as a high conductivity ensuring a high power density, and an adequate pore size distribution (PSD), mainly with an average pore size smaller than 1nm. Moreover, a large quantity of surface functionalities can be a source of additional capacitance, called pseudo-capacitance, as some particular functionalities could undergo fast redox reactions with the electrolyte when working in aqueous solutions such as H2SO4 or KOH [4]. When a supercapacitor is connected to a voltage source, the surface of the electrodes is charged and attracts the ions of opposite charge. The ions are stored at the surface of

This work studies the influence of the operating conditions used in the pyrolysis of grape seeds on the morphology and textural properties of the chars resulting. Flash and conventional (283 Kmin-1 heating rate) pyrolysis have been used within a wide range of temperature (300-1000 ºC). The effect of a pretreatment for oil extraction has also been studied. The porous structure of the chars was characterized by adsorption of N2 at 77 K, Ar at 77 K and 87 K, and CO2 at 273 K and mercury intrusion porosimetry. The morphology was analyzed by scanning electron microscopy. All the materials prepared revealed an essentially microporous structure, with a poor or even negligible contribution of mesopores. Increasing pyrolysis temperature led to higher specific surface areas and lower pore size. The highest specific surface area values occurred within 700-800 ºC, reaching up to 500 m 2 g-1 with pore sizes in the 0.4-1.1 nm range. No significant morphological changes were observed upon carbonization so that the resulting chars were granular materials of similar size than the starting grape seeds. The hollow core structure of the chars, with most of the material allocated at the periphery of 2 the granules can help to overcome the mass transfer limitations of most common (solid or massive) granular activated carbons. The chars showed a good mechanical strength during attrition tests. These chars can be potential candidates for the preparation of granular carbons molecular sieve or activated carbons raw materials.

h i g h l i g h t sNovel method of activation by cycles permits good control of porosity development. S BET values above 1000 m 2 /g can be obtained with burn-off values lower than 40%. The low burn-off helps to maintain granular morphology of the activated carbons.Carbons with unique hollow core structure and wall thickness of 250 lm are produced.The activated carbons showed a good mechanical strength during attrition test. a r t i c l e i n f o t r a c tActivation of grape seeds char upon cyclic oxygen chemisorption-desorption permits a controlled development of porosity versus burn-off using air as a cheap activation agent. In this work the influence of chemisorption and desorption temperature and the number of cycles is investigated. A fast increase of BET surface area (S BET ) is obtained in the two first cycles; that increase becomes then lower although the S BET continues increasing upon the successive cycles. Regarding the Dubinin-Astakhov surface area (S DA ) a slow increase was observed from cycle to cycle. The activation process led to the development of both micro and mesoporosity. Under the optimum conditions for surface area development, i.e. an oxidation temperature of 275°C and desorption temperatures between 850 and 950°C, values of 1129-1256 and 1339-1219 m 2 /g were obtained for S BET and S DA , respectively. Porosity was found to increase mainly during the desorption stage, although chemisorption also led to some surface area development. SEM characterization showed that the activated carbon maintained the granular morphology of the seeds even after 10 cycles showing the egg-shell structure of the precursor with longer and deeper cracks at the outer surface. The activated carbons showed a good mechanical strength during attrition tests.