稀土助剂对氧电极性能的影响

Effect of rare earth additives on MnO_2/C air electrode

为了提高MnO2对氧气还原的催化活性,将硝酸锰和稀土硝酸盐(镧和铈)溶液浸渍到活性炭中,并在270℃下煅烧,制得氧电极催化剂,通过冷压方法制成气体扩散电极.用稳态极化测试了各个空气电极的电化学性能,结果表明铈的添加对MnO2的催化活性影响明显,硝酸铈添加10%时空气电极极化最小,在一般金属 空气电池的工作电流密度20～50mA·cm-2下,电位比单独MnO2催化剂可正移30～60mV,并且随着电流密度的增加,电位正移的越显著.采用交流阻抗测试了空气电极的阻抗特性,通过分析对阻抗图谱采用两个Nerstian阻抗的等效电路进行了拟和,得到相关动力学数据.数据显示添加稀土硝酸盐,减小了电化学极化阻抗和氧气扩散阻抗,提高了MnO2对氧气还原的催化活性.

Research was done in order to improve the electrocatalystic performance of MnO2.The catalyst was prepared from the carbon black impregnated with Mn(NO3)2 and rare earth nitrate, and heated at 270℃. The gas-diffusion electrode was obtained by cold-pressing. Electrochemical performance of the electrodes was studied by current-potential polarization curves. The result showed that Ce additives had better performance than La. When adding 10-percent content of Ce(NO3)3·6H2O can best improve the performance.Its polarization was the smallest. At the typical current density 20～50mA/cm^2 of an air-metal battery, this air electrode potential can be improved by 30～60mV. AC impedance properties of air electrode adding rare earth were investigated .The impedance spectra were analyzed using an equivalent circuit containing two Nerstian diffusion terms.The simulated data were also discussed.The rare earth additives can decrease the charge-transfer resistance and oxygen diffusion resistance,especially Ce.