Enhancing the electrocatalytic properties of LaMnO₃ by tuning surface oxygen deficiency through salt assisted combustion synthesis

In this work, we report a detailed investigation on the salt assisted combustion synthesis of LaMnO₃ perovskite catalyst for improving the electrochemical properties through agglomeration control and enhanced oxygen defects for fuel cell and battery applications. The main challenge in conventional solution combustion synthesis (SCS) is the nanoparticle agglomeration that masks the active sites in catalysts. Herein, we follow a salt assisted solution combustion synthesis route to synthesize LaMnO₃ perovskites (LaMnO₃-SA) with a lower level of agglomeration and investigate its application for oxygen electrocatalysis. Through an effective incorporation of salt in the redox combustion mixture, the surface area of the particles doubled along with an improved pore size and pore volume distribution. The surface analysis by x-ray photoelectron spectroscopy indicated the formation of more surface oxygen defects with the introduction of inert salt that helps the absorption of oxygenated species during electrochemical process. Remarkably, LaMnO₃-SA showed superior characteristics in terms of limiting current density, onset potential and half wave potential displaying enhanced bifunctionality towards oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). The mass activity of LaMnO₃-SA was almost double and kinetic current density was threefold the value at -0.25 V in comparison to the traditional SCS LaMnO₃. This work demonstrates that active sites accessible for oxygen electrocatalysis in solution combustion synthesis can be enhanced through the introduction of an inert salt during the synthesis.