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.This publication was made possible by NPRP grant ( NPRP8-145-2-066 ) from the Qatar National Research Fund (a member of Qatar Foundation) . The statements made herein are solely the responsibility of the author(s). The authors also wish to gratefully acknowledge the Gas Processing Centre (GPC) for carrying out XPS analysis, Center of Advanced Materials(CAM) for XRD facility and the Central Laboratory Unit (CLU) at Qatar University for services related to electron microscopy. The authors would also like to acknowledge QEERI Core Labs for their support related to the TEM characterization.Scopu