Maximal electrocatalytic activity of Sr-doped Nd1−xSrxMnO3 perovskite oxides (x = 0.1, 0.2, 0.3) towards ORR: for next-generation power systems

Abstract

By using the sol–gel method, a series of Nd_1−xSr_xMnO₃ perovskite oxides (x = 0.1, 0.2, 0.3), designated as NSM-0.9, NSM-0.8, and NSM-0.7, were prepared and characterized using analytical techniques including XRD, FESEM, TEM, EDS, and XPS. Our investigation revealed that NSM-0.7 (Nd_0.7Sr_0.3MnO₃) is the most effective electrocatalyst for the oxygen reduction reaction (ORR). Its superior electrocatalytic performance in a 0.1 M KOH solution, evaluated with RDE and RRDE techniques, was quantified by an onset potential (E_on) of 0.82 V vs. RHE, a half-wave potential (E_1/2) of 0.58 V vs. RHE, a limiting current density (J_L) of −5 mA cm⁻², which is the same as the current density of Pt/C, and a kinetic current density (J_k) of 0.41 mA cm⁻² at 1600 rpm. This material also favoured a highly efficient 4e⁻ pathway with the formation of a minimal amount of H₂O₂. NSM-0.7's superior catalytic performance is attributed to optimal Sr-doping at the perovskite's A-site, a process that significantly enhances its Mn valence and oxygen adsorption capacity. Furthermore, chronoamperometry confirmed that NSM-0.7 exhibits superior stability compared to the benchmark Pt/C catalyst, demonstrating that strategic A-site doping is a promising approach for improving conventional perovskite oxides for electrocatalytic applications.