Electrocatalytic Activity of Non-Stoichiometric Perovskites toward Oxygen Reduction Reaction in Alkaline Electrolytes

摘要

Perovskite La_xCa_(0.4)MnO_3 (x = 0.4, 0.5, 0.6) powder was prepared through a sol-gel method and characterized by X-ray diffraction (XRD), a gas adsorption technique (BET) and transmission electron microscopy (TEM). The electrocatalytic properties of La_xCa_(0.4)MnO_3C composites towards the oxygen reduction reaction (ORR) were studied using rotating ring-disk electrode (RRDE) techniques and Koutecky-Levich theory in both 1 M and 6 M KOH electrolytes. The results show better ORR activities for non-stoichiometric perovskites than that for stoichiometric La_(0.6)Ca_(0.4)MnO_3. The overall electron transfer numbers for these La_xCa_(0.4)MnO_3 composites are in the range of 3.2-3.7, and with decreasing values of x the electron transfer number increases and accordingly H_2O_2 production decreases. These results suggest that the existence of a Mn reduction/oxidation pair in Ca-doped nonstoichiometric perovskites could activate the ORR reaction sites, resulting in improved catalytic activity.