Electrooxidation methods to produce pseudocapacitance-containing porous carbons

Surface oxygen groups play a key role on the performance of porous carbon electrodes for electrochemical capacitors in aqueous media. The electrooxidation method in NaCl electrolyte using a filter press cell and dimensionally stable anodes is proposed as a viable process for the generation of oxygen groups on porous carbon materials. The experimental set-up is so flexible that allows the easy modification of carbon materials with different configurations, i.e. cloths and granular, obtaining different degrees of oxidation for both conformations without the requirement of binders and conductivity promoters. After the electrooxidation method, the attained porosity is maintained between 90 and 75% of the initial values. The surface oxygen groups generated can increase the capacitance up to a 30% when compared to the pristine material. However, a severe oxidation is detrimental since it may decrease the conductivity and increase the resistance for ion mobility.We thank the Generalitat Valenciana and FEDER (PROMETEO/2009/047) and the Spanish Ministry of Economy and Competitiveness (Projects CTQ2012-31762 and MAT2010-15273) for financial support

Tailoring the surface chemistry of activated carbon cloth by electrochemical methods

This paper presents a systematic study of the effect of the electrochemical treatment (galvanostatic electrolysis in a filter-press electrochemical cell) on the surface chemistry and porous texture of commercial activated carbon cloth. The same treatments have been conducted over a granular activated carbon in order to clarify the effect of morphology. The influence of different electrochemical variables, such as the electrode polarity (anodic or cathodic), the applied current (between 0.2 and 1.0 A) and the type of electrolyte (HNO3 and NaCl) have also been analyzed. The anodic treatment of both activated carbons causes an increase in the amount of surface oxygen groups, whereas the cathodic treatment does not produce any relevant modification of the surface chemistry. The HNO3 electrolyte produced a lower generation of oxygen groups than the NaCl one, but differences in the achieved distribution of surface groups can be benefitial to selectively tune the surface chemistry. The porous texture seems to be unaltered after the electro-oxidation treatment. The validity of this method to introduce surface oxygen groups with a pseudocapacitive behavior has been corroborated by cyclic voltammetry. As a conclusion, the electrochemical treatment can be easily implemented to selectively and quantitatively modify the surface chemistry of activated carbons with different shapes and morphologies.The authors thank the MINECO and FEDER for financial support (MAT2010-15273 project). R.R.R. gratefully acknowledges funding from MINECO through "Juan de la Cierva" program (JCI-2012-12664)Tabti, Z.; Ruiz-Rosas, R.; Quijada Tomás, C.; Cazorla-Amorós, D.; Morallón, E. (2014). Tailoring the surface chemistry of activated carbon cloth by electrochemical methods. ACS Applied Materials and Interfaces. 6:11682-11691. https://doi.org/10.1021/am502475vS1168211691