La1－xSrxNi1－yFeyO3型钙钛矿双功能氧电极的电化学性能研究

采用溶胶-凝胶法制备了一系列La_1－xSr_xNi_1－yFe_yO₃ (x＝0, 0.1, 0.2, 0.5; y＝0～1.0)型的钙钛矿催化剂, 以活性碳为载体, PTFE乳液为粘接剂制备双功能氧电极. 对催化剂进行了XRD结构分析以及SEM分析和BET比表面积测量. 采用三电极体系测试了氧电极的稳态极化曲线和电化学交流阻抗谱并对其阴极极化和阳极极化的交流阻抗谱图进行分析. 通过等效电路的拟合研究了该系列双功能氧电极氧还原反应的工作机理. 实验表明对于LaNiO₃化合物, B位掺杂可显著提高催化剂的电催化性能; 电极氧还原反应的极化主要由电荷转移反应和Nernstian扩散过程造成. 通过各个电极对于催化分解H₂O₂的分解速率常数的测定得知, Ni离子对于催化H₂O₂分解反应的活性大于Fe离子, 继续在对于氧还原反应和氧析出反应都具有较高电催化活性的LaNi_0.8Fe_0.2O₃催化剂上进行A位掺杂Sr离子后显著提高了催化剂分解H₂O₂的催化活性, 主要是因为氧空位的增多和金属离子d电子含量的降低有利于催化分解H₂O₂的活性的提高, 但由于氧空位的增多导致催化剂电导率的降低, 所以其电催化活性降低了. 通过多圈循环伏安扫描的测试, 催化剂LaNi_0.8Fe_0.2O₃有很好的稳定性.

Study on the Electrochemical Properties of La1-xSrxNi1-yFeyO3 Bifunctional Oxygen Electrodes

A series of novel La_1－xSr_xNi_1－yFe_yO₃ (x＝0, 0.1, 0.2, 0.5; y＝0～1.0) perovskite oxides were prepared by sol-gel method and characterized by XRD, SEM and BET measurement. The activity of PTFE bonded bifunctional oxygen electrodes made by the perovskite-type catalyst dispersed on active carbon was investigated using steady polarization curves and electrochemical impedance spectroscopy (EIS) method. The impedance spectra of both cathodic and anodic polarization were analyzed. The electrochemical parameters of the oxygen reduction reaction were obtained by fitting the experimental impedance data to an equivalent circuit containing two Nernstian diffusion terms. The results show that the oxygen reduction activity was improved by doping Fe^3＋ ions on site B of LaNiO₃ oxides. But doping Sr^2＋ ions on site A could impair the effect because the ordering level of oxygen vacancy and electrode resistance were increased. The decomposition reaction rate of H₂O₂ catalyzed by perovskite catalysts was examined. The data showed that the catalytic activity of Ni ion was higher than that of Fe ion and when doped with Sr ion the catalytic activity of decomposition reaction rate of H₂O₂ was increased. The results of CV multi-cycle examination showed that LaNi_0.8Fe_0.2O₃ had a good electrochemical stability.