关键词: 碳材料, 溶液PH值, MSCV, 循环伏安法, 电化学, 质谱法, 乙炔黑, 活性炭, 电位, 氧化活性

The electrooxidation of active carbon and acetylene black was studied using MSCV (Mass Spectroscopic Cyclic Voltammetry) technique over pH 1-12. For both active carbon and acetylene black the pH dependences of φ~s and η ~s (the onset potential and overpotential of CO~2 formation), I~M (the mass intensity of CO~2 at a given potential) and φ ~I (the potential at a given mass intensity) are all broken lines deflecting near pH 7. These phenomena imply that the mechanism of carbon oxidation is different in acidic and basic media. Both η~s and Tafel slope b in the range of pH>7 were found higher than that in pH<7. Based on these observations it is postulated that in acidic media the O atom needed for CO~2 formation comes from the discharge of H~2O molecules and the oxidation of carbon to CO~2 is easier than in basic media where the O atom comes from the discharge of OH^-. There were also distinct differences between active carbon and acetylene black. φ~s was found 400-600mV lower than φⅲ (O~2/H~2O) for active carbon but close to or higher than φⅲ (O~2/H~2O0 for acetylene black. At the same time, I~M and b of the former were higher than the latter. The lower oxidation activity of acetylene black is attributed to its more highly ordered structure.

Key words: CYCLOVOLTAMGRAPH, ELECTROCHEMISTRY, MASS SPECTROGRAPHY, ACETYLENE BLACK, ACTIVE CARBON, ELECTRIC POTENTIAL