Elucidating O2 Reduction Reaction on 2D Monolayer LaMnO3 Perovskite

Abstract

O2 reduction reaction (ORR) is critical in energy conversion technologies such as proton exchange membrane fuel cells (PEMFCs) and metal-air batteries (MABs), and it is a fundamental reaction related to various disciplines such as energy conversion, material dissolution and renewable green energy technology. Despite extensive research, efficient and cost-effective catalysts remain a great challenge for scientists. Platinum-based catalysts, while effective, are prohibitively expensive and lack durability. In this work, we have computationally modeled a novel 2D monolayer LaMnO3 perovskite by cleaving (001) plane from the 3D LaMnO3 cubic perovskite. The 2D monolayer shows a high density of states along with overlapping energy bands at the Fermi level, indicating its potential use as a cathode material. Detailed ORR pathways, including both dissociative and associative reaction mechanisms have been explored on the surfaces of 2D monolayer LaMnO3. For all the intermediates occurring during ORR, the changes of Gibbs free energy (ΔG) were calculated by employing the PBE-D method. The 2D monolayer LaMnO3 demonstrated superior selectivity for the associative mechanism over the dissociative mechanism as described by the obtained free energy diagram or potential energy surface (PES) plot. We have also explored the charge transfer occurring during the reaction in both ORR mechanisms. Theoretical overpotential was calculated to be 0.85 V in the case of 2D monolayer LaMnO3. This theoretical/computational groundwork lays the foundation for future applications of the 2D monolayer LaMnO3 perovskite-based electro-catalysts, indicating their promise as Pt-free alternatives for fuel cell components.