Optimization of Praseodymium-Based Perovskites as Electrocatalysts for Oxygen Reduction Reaction

Praseodymium-based perovskites Pr1-xSrxMnO3 (x = 0.1, 0.2, 0.3, 0.4), denoted as PSM-0.9, PSM-0.8, PSM-0.7, and PSM-0.6, respectively, are prepared by the sol-gel method. The structural properties and morphology of the as-prepared catalysts are studied with the help of XRD, SEM, TEM, and XPS. The prepared catalysts were tested for their oxygen reduction reaction (ORR) activities in an alkaline medium. Among the prepared catalysts, PSM-0.7, with the onset potential of -0.02 V, is found to be the most active ORR catalyst. The number of electron transfer, n= 4, for PSM-0.7, was calculated using the Koutechy-Levich plot acquired from a rotating disk electrode. Further, the lower Tafel slope of the PSM-0.7 catalyst justifies its higher catalytic activity. The higher catalytic activity of PSM-0.7 having moderate A-site Sr doping is ascribed to the oxygen vacancies and Mn4+ concentration, as confirmed by XPS analysis. The chronoamperometric results confirmed that the PSM-0.7 electrocatalyst has higher durability and methanol-tolerant ability compared to commercial Pt/C.