活性炭表面性质对氧气扩散电极电催化性能的影响

 分别采用硝酸和空气氧化处理制得具有不同表面性质的粉末活性炭,并以此为催化层材料制成炭基氧气扩散电极,测定了不同电极的极化曲线和电化学阻抗谱. N2物理吸附和He程序升温脱附(He-TPD)研究表明,硝酸处理对活性炭孔结构的影响较小,但可使其表面含氧基团明显增加; 而空气氧化处理则会导致活性炭的中孔面积和孔容显著增大,但对表面含氧基团的影响较小. 极化曲线和电化学阻抗谱研究发现,当活性炭的孔结构相近时,电极的催化性能随着表面含氧基团的增多而急剧下降; 当活性炭表面含氧基团的量相近时,中孔孔容增大将导致电极催化性能的恶化. 与活性炭表面含氧基团相比,孔结构对氧气扩散电极的电化学性能具有更显著的影响.

Effects of Surface Nature of Activated Carbon on Electrocatalytic Performance of Oxygen Diffusion Electrodes

Activated carbon(AC) samples with different surface nature were prepared from a commercial activated carbon by treating in HNO_3 with different concentrations and calcining in air at different temperatures.The texture and surface oxygen groups of these samples were characterized by N_2 physisorption and He temperature-programmed desorption.The results show that HNO_3 treatment results in a minor effect on the texture of AC samples but a great increase in the amount of surface oxygen groups.Air oxidation treatment leads to a remarkable increase in the surface area and mesopore volume of AC samples but little change in the quantity of surface oxygen groups.The electrocatalytic activity of the gas diffusion electrodes using these AC samples as the catalyst layer material for the oxygen reduction was evaluated by means of polarization curve and electrochemical impedance spectroscopy.The electrocatalytic activity of the carbon-based oxygen diffusion electrode decreases with the increase of surface oxygen groups on AC samples with similar texture and gets worse with increasing surface area and volume of mesopores for the AC samples with equivalent quantity of surface oxygen groups.Compared with the surface oxygen groups,the texture of AC samples has greater effects on the electrocatalytic activity of the carbon-based oxygen diffusion electrode.