碳材料电化学腐蚀的质谱-电化学循环伏安(MSCV)法研究 Ⅱ.催化剂的影响

MSCV Studies of Carbon Electrooxidation Ⅱ. Influence of Catalyst

用MSCV法研究了Pt催化剂作用下,碳材料在pH 0.3～11.8范围内的阳极腐蚀.Pt催化剂明显加速了活性炭及乙炔黑的腐蚀速度,使这两种电极上CO_2开始析出的电位φ_s明显负移,以致均负于φ_(O_2/H_2O).因此两种碳电极无论作为阳极还是氧阴极工作时均会被腐蚀.Pt对乙炔黑的催化活性明显强于活性炭.对于活性炭,Pt并不改变CO_2的φ_s-pH及η_s-pH曲线的形状(η_s-CO_2开始析出的超电势)(即无论有无Pt它们均为折点在pH～7的折线).然而乙炔黑的情况更为复杂.Pt使CO_2的φ_s-pH及η_s-pH形状从折线变为直线;在CO_2的I_(M-φ)曲线上出现两个波.它们似与乙炔黑上两种表面氧化物相对应.

The corrosion of carbon materials in the presence of Pt catalyst was studied in pH 0.3～11.8 using mass spectrometric cyclic voltammetry (MSCV). The corrosion was found to be greatly accelarated by Pt for both active carbon and acetylene black as evidenced by a negative shift of the onset potential (φ_s) of CO_2 evolution which is more negative than the O_2/H_2O equilibrium potential. Both active carbon and acetylene black are corroded when they are used for either anodes or oxygen cathodes. In the case of active carbon Pt does not change the pH dependence of φ_s and the overpotential η_s of the onset of CO_2 evolution (they follow broken lines deflecting near pH = 7) while the situation is more complicated for acetylene black. The presence of Pt changes the φ_s-pH and η_s-pH from broken lines into straight lines. Moreover, there are two waves on the I_M-φ curves for CO_2 formation, probably indicating two types of oxides on the acetylene black surfaces.