Electrochemical behavior of the carbon black Vulcan XC-72R: Influence of the surface chemistry

The effect of chemical surface oxidation of the carbon black Vulcan XC-72R on the capacitance, tolerance to corrosion and electrochemical activity toward the hydrogen evolution reaction (HER) has been studied in 0.1 M NaHCO3. Acid treatments with HNO3 or a HNO3H2SO4 mixture resulted in a progressive introduction of oxygen-containing groups which led to a strong increase of the capacitance and a higher tendency to carbon corrosion. In contrast, an inhibition of the hydrogen evolution current (at potentials more negative than −1.0 V) was observed for oxidized samples in comparison to the un-treated material. HER was also tested in the presence of dissolved CO2 to study the influence of the surface chemistry on the CO2 electroreduction. An inhibition of the H2 evolution current was evidenced in the CO2 saturated electrolyte due to the adsorption of species from CO2 reduction. A strong hydrogen current decrease (65-78%), and thus a higher tendency to adsorb (CO2)red species, was obtained on the original Vulcan and the HNO3-treated samples, in comparison to the carbon oxidized with HNO3H2SO4 (15%), which could be related to the highest content of basic groups of the last carbon.