Effective promotion of oxygen reduction reaction activity by ‘Co’ doping in PrMnO3 at B-site

Abstract

In this work, rare-earth perovskites (PrMnO₃) prepared by sol-gel method were studied for their electrocatalytic activity. Substituting the B site of PrMnO₃ with Cobalt, a series of catalysts PCM-0.9, PCM-0.8, PCM-0.7, and PCM-0.6 were prepared having the composition PrCo_xMn_1-xO₃ with x = 0.1, 0.2, 0.3 and 0.4 respectively. The structural and morphological properties of the synthesized catalysts were evaluated by different characterization tools such as XRD, FESEM, TEM and XPS. From XRD analysis we confirmed that the prepared catalyst PCM-0.7 was having orthorhombic structure with particle size and d-spacing 4.3 nm, 2.71 respectively. 3D network like morphology with double triple layer was confirmed from FESEM analysis. TEM analysis showed particles with size ranges between 5 and 20 nm. The ORR (Oxygen Reduction Reaction) activity of the prepared catalysts was evaluated in an alkaline medium. PCM-0.7 was evaluated as the most active ORR catalyst among the synthesized catalysts, with onset potential, current density and half-wave potential is -0.07 V Vs Ag/AgCl, -5.69 mA/cm² and -0.21 V respectively. Furthermore, the PCM-0.7 catalyst's lower Tafel slope validates its enhanced catalytic activity. The electrocatalytic activities of the prepared catalysts depend on the percentage of cobalt doping at the B site of the perovskite, with PCM-0.7 showing the highest ORR performance and stability. X-ray photoelectron spectroscopy analysis demonstrated that the addition of Co enhanced the percentage of Mn⁴⁺ in the prepared catalysts. This work suggests a viable method for improving the ORR performance of rare earth-based perovskite through B- site cation substitution.